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## **Meet the editors**

Assoc. Prof. Dr. Yusuf Emes, Born in Istanbul in 1974. He graduated from Istanbul University Faculty of Dentistry in 1997 and completed his PhD degree in Istanbul University faculty of Dentistry Department of Oral and Maxillofacial Surgery in 2005. He has papers published in international and national scientific journals, including research articles on implantology, oroantral fistulas,

odontogenic cysts, and temporomandibular disorders. Dr. Emes is currently working as a full-time academic staff in Istanbul University faculty of Dentistry Department of Oral and Maxillofacial Surgery.

Buket Aybar, DDS, PhD, was born in 1971. She graduated from Istanbul University, Faculty of Dentistry, in 1992 and completed her PhD degree on Oral and Maxillofacial Surgery in Istanbul University in 1997. Dr. Aybar is currently a full-time professor in Istanbul University, Faculty of Dentistry Department of Oral and Maxillofacial Surgery. She has teaching responsibilities

in graduate and postgraduate programs. Her clinical practice includes mainly dentoalveolar surgery.

Her topics of interest are biomaterials science and cell culture studies. She has many articles in international and national scientific journals and chapters in books; she also has participated in several scientific projects supported by Istanbul University Research fund.

Assoc. Prof. Dr. Gühan Dergin was born in 1973 in Izmit. He graduated from Marmara University Faculty of Dentistry in 1999. He completed his specialty of OMFS surgery in Marmara University Faculty of Dentistry and obtained his PhD degree in 2006. In 2005, he was invited as a visiting doctor in the Oral and Maxillofacial Surgery Department of the University of North Carolina, USA,

where he went on a scholarship. Dr. Dergin still continues his academic career as an associate professor in Marmara University Faculty of Dentistry. He has many articles in international and national scientific journals and chapters in books.

Contents

**Preface VII**

**and Treatment 17** Serdar Gözler

Rolando Vernal

Karasu

Chapter 1 **Introductory Chapter: Optimizing the Management Outcomes in Patients with Temporomandibular Disorder 3**

**Section 2 Pathological Conditions of the Temporomandibular Joint 15**

Chapter 2 **Myofascial Pain Dysfunction Syndrome: Etiology, Diagnosis,**

Chapter 3 **Internal Derangements of the Temporomandibular Joint:**

Chapter 4 **Osteoarthritis of the Temporomandibular Joint: Clinical and**

**Based on T Regulatory Lymphocytes 69**

Chapter 5 **Benign Tumors of Temporomandibular Joint 99**

**Imagenological Diagnosis, Pathogenic Role of the Immuno-Inflammatory Response, and Immunotherapeutic Strategies**

Gustavo Monasterio, Francisca Castillo, Daniel Betancur, Arnoldo Hernández, Guillermo Flores, Walter Díaz, Marcela Hernández and

Mehmet Emre Yurttutan, Ayşegül Tüzüner Öncül and Hakan Alpay

**Diagnosis and Management 47** Ufuk Tatli and Vladimir Machon

Buket Aybar, Yusuf Emes and Guhan Dergin

**Section 1 Introduction 1**

## Contents

## **Preface XI**

#### **X** Contents

### **Section 3 Evaluation and Management 125**

Chapter 6 **JVA, Mastication and Digital Occlusal Analysis in Diagnosis and Treatment of Temporomandibular Disorders 127** Serdar Gözler

Preface

Dental practitioners face a large number of patients seeking help for pain and loss of func‐ tion in their temporomandibular joint and related structures. This book consists of eight chapters by authors who would like to share their experiences and researches on pathologi‐ cal conditions related to the temporomandibular joint. The chapters mainly focus on disor‐ ders, diseases, and entities while shedding light on the diagnostic methods and management modalities. We would like to thank Mr. Edi Lipović for his support in prepar‐ ing this book, which we hope will be a reference material to both clinicians and researchers.

> **Yusuf Emes, DDS, PhD** Associate Professor

**Buket Aybar, DDS, PhD**

**Gühan Dergin, DDS, PhD**

Istanbul, Turkey

Istanbul, Turkey

Istanbul, Turkey

Professor

Istanbul University Faculty of Dentistry Department of Oral and Maxillofacial Surgery

Istanbul University Faculty of Dentistry Department of Oral and Maxillofacial Surgery

Marmara University Faculty of Dentistry Department of Oral and Maxillofacial Surgery

## Preface

**Section 3 Evaluation and Management 125**

**Clinical Orthodontics 161**

Serdar Gözler

**VI** Contents

Chapter 6 **JVA, Mastication and Digital Occlusal Analysis in Diagnosis and Treatment of Temporomandibular Disorders 127**

Chapter 7 **Temporomandibular Joint Pathology and Its Indication in**

Chapter 8 **Surgical Approaches to the Temporomandibular Joint 185** Mohammad Esmaeelinejad and Maryam Sohrabi

Bakr M. Rabie, Jeremy Ho and Qianfeng Li

Dental practitioners face a large number of patients seeking help for pain and loss of func‐ tion in their temporomandibular joint and related structures. This book consists of eight chapters by authors who would like to share their experiences and researches on pathologi‐ cal conditions related to the temporomandibular joint. The chapters mainly focus on disor‐ ders, diseases, and entities while shedding light on the diagnostic methods and management modalities. We would like to thank Mr. Edi Lipović for his support in prepar‐ ing this book, which we hope will be a reference material to both clinicians and researchers.

#### **Yusuf Emes, DDS, PhD**

Associate Professor Istanbul University Faculty of Dentistry Department of Oral and Maxillofacial Surgery Istanbul, Turkey

#### **Buket Aybar, DDS, PhD**

Professor Istanbul University Faculty of Dentistry Department of Oral and Maxillofacial Surgery Istanbul, Turkey

#### **Gühan Dergin, DDS, PhD**

Marmara University Faculty of Dentistry Department of Oral and Maxillofacial Surgery Istanbul, Turkey

**Section 1**

**Introduction**

**Section 1**

## **Introduction**

**Chapter 1**

**Provisional chapter**

**Introductory Chapter: Optimizing the Management**

**Introductory Chapter: Optimizing the Management**

Being one of the most controversial topics in dentistry, treatment of temporomandibular disorders (TMDs) requires the clinician to determine the patients' needs and try to help the patient based on the most recent scientific evidence. TMDs are today commonly considered as a collection of various conditions of the temporomandibular joint (TMJ) or the masticatory muscles, which have different etiologies and mechanisms but presenting with similar symptoms [1]. Temporomandibular joint (TMJ) is affected by musculoskeletal disorders of the neck and masticatory system [2], and it is important for the clinical practitioner to tell the difference between the complaint originating from a musculoskeletal disorder and a complaint caused by an intra-articular disorder. By making this discernment, the patient can receive the optimal

management and is protected from going under unnecessary surgical interventions.

There are several classification systems for the TMDs. The most recent and the most commonly used classification is the research diagnostic criteria for temporomandibular disorders (RDC-TMD) [3]. The most common intra-articular disorders are known to be reducing and

Anterior disc displacement is a condition in which the disc is positioned anteriorly to the mandibular condyle. If the disc reduces on opening, this is called anterior disc displacement with reduction. If the disc does not reduce on opening, then this is called anterior disc displacement without reduction (irreductible disc displacement) which is closely related to acute

> © 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2018 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

DOI: 10.5772/intechopen.73537

**Outcomes in Patients with Temporomandibular**

**Outcomes in Patients with Temporomandibular**

Buket Aybar, Yusuf Emes and Guhan Dergin

Buket Aybar, Yusuf Emes and Guhan Dergin

Additional information is available at the end of the chapter

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.73537

nonreducing anterior disc displacements.

**Disorder**

**1. Introduction**

closed lock [1, 4].

**Disorder**

#### **Introductory Chapter: Optimizing the Management Outcomes in Patients with Temporomandibular Disorder Introductory Chapter: Optimizing the Management Outcomes in Patients with Temporomandibular Disorder**

DOI: 10.5772/intechopen.73537

Buket Aybar, Yusuf Emes and Guhan Dergin Buket Aybar, Yusuf Emes and Guhan Dergin

Additional information is available at the end of the chapter Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.73537

## **1. Introduction**

Being one of the most controversial topics in dentistry, treatment of temporomandibular disorders (TMDs) requires the clinician to determine the patients' needs and try to help the patient based on the most recent scientific evidence. TMDs are today commonly considered as a collection of various conditions of the temporomandibular joint (TMJ) or the masticatory muscles, which have different etiologies and mechanisms but presenting with similar symptoms [1]. Temporomandibular joint (TMJ) is affected by musculoskeletal disorders of the neck and masticatory system [2], and it is important for the clinical practitioner to tell the difference between the complaint originating from a musculoskeletal disorder and a complaint caused by an intra-articular disorder. By making this discernment, the patient can receive the optimal management and is protected from going under unnecessary surgical interventions.

There are several classification systems for the TMDs. The most recent and the most commonly used classification is the research diagnostic criteria for temporomandibular disorders (RDC-TMD) [3]. The most common intra-articular disorders are known to be reducing and nonreducing anterior disc displacements.

Anterior disc displacement is a condition in which the disc is positioned anteriorly to the mandibular condyle. If the disc reduces on opening, this is called anterior disc displacement with reduction. If the disc does not reduce on opening, then this is called anterior disc displacement without reduction (irreductible disc displacement) which is closely related to acute closed lock [1, 4].

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Anteriorly displaced discs are common findings in the asymptomatic patients too. Studies by Larheim et al. [5] and Davant et al. [6] reported that magnetic resonance imaging (MRI) shows that about one third of the asymptomatic patients have displaced discs. It is also known that anteriorly displaced discs are most of the time displaced medially too [7], and it is important to evaluate the patient's complaints and try to resolve the symptoms which are joint sounds, pain, and limited mouth opening. Chronic disc displacement can lead to the adhesion of the disc to the articular fossa. Pain in the TMJ is present in the 10% of the adult population and found more often in women [8]. However, it must be kept in mind that prior to initiating the treatment of a TMD patient, any possibilities of benign and malign tumors, developmental disorders, and fractures should be out-ruled.

are all parts of the treatment [1, 13]. Biting the food using incisors should be avoided, and bit-

Introductory Chapter: Optimizing the Management Outcomes in Patients…

http://dx.doi.org/10.5772/intechopen.73537

5

Self-management is another important part of the management process. Self-massage is the initial self-management therapy, which is found to be very helpful in pain management especially in patients with masticatory muscle-originated pain [14, 15]. In myofascial pain massaging, the trigger points especially lead to improvement in pain even though it is temporary,

Another self-management method is the application of moist heat or application of ice especially in cases of local myalgia and myofascial pain [1]. As a simple method, 20 minutes of hot

Another method that can be used is the application of a hot pack to the tender site for 20 minutes three times a day. Heat relaxes the muscles and provides increased blood flow to the muscles. Also when cold is applied, as a reaction in order to increase the heat in the coldapplied muscle, the brain increases the blood flow to the muscle by vasodilatation providing an improvement in pain. Most of the studies on cold application are about acute pain, so there

Pharmacological therapy is a part of TMD management. Nonsteroidal anti-inflammatory drugs (NSAIDs), analgesics, muscle relaxants, anxiolytic drugs, local anesthetics, antidepres-

Analgesics and NSAIDs form an important part of the pharmacological treatment of the osteoarthritic TMJ. The American College of Rheumatology guidelines recommend the use of paracetamol as the first medication of choice for the osteoarthritic hip and knee [17–19]. The use of paracetamol is also recommended for the management of osteoarthritis by some authors; however, they conclude that paracetamol is effective in osteoarthritis only at very high, near toxicity level doses. Ibuprofen and naproxen are recommended agents in osteoarthritis of the TMJ, but in the management of chronic pain, cox-2 inhibitors such as celecoxib or meloxicam should be preferred, not only for their effectiveness in chronic pain but also for less gastrointestinal effects, for they may require a prolonged

NSAIDs provide anti-inflammatory effects and analgesia for the TMD patients with osteoarthritis, capsulitis, synovitis, myositis, and pain related to reducing and nonreducing disc

Naproxen, ibuprofen, and diclofenac are the most often used NSAIDs [22]. Mejersjo and Wenneberg [23] have studied the effects of diclofenac 50 mg, given orally 3 ×1 in patients with TMJ arthritis. Their findings at the end of 3 months produced results similar to efficacy

ing on the effected side is recommended in case of joint pain [1].

bath is found to be effective in decreasing muscle pain.

sants, and corticosteroids are indicated in TMD treatment.

**2. Nonsteroidal anti-inflammatory drugs**

use in chronic pain [20].

displacements [21].

of occlusal appliances.

and the massage must be continued to keep the benefits obtained from it [13].

is little data on the application of cold for the management of chronic pain [16].

If the overloading of the TMJ continues (parafunctional habits, bruxism) remodeling, mechanism is triggered. When overloading exceeds the limits of remodeling, degenerative process of the articular surfaces may begin leading to the osteoarthritis of the TMJ [9].

General consensus in treatment is that the most conservative and the most reversible method should be the initial treatment of choice. This is because temporomandibular disorders have a tendency of improving over time, and clinical experience shows that sometimes conservative treatments are as effective as invasive methods in relieving the patient's symptoms [10].

When a patient is referred to a dentist for a complaint of temporomandibular disorder, oral history must be taken, and the patient should initially be examined for medical pathologies of the head and neck, including intraoral examination to search for a pain of dentoalveolar origin, type of occlusion, and any indicator of parafunctional habits such as bruxism. Imaging studies should be performed if necessary. The patients should also be evaluated for neurological and psychological conditions and should be referred to a specialist if necessary [11].

Management of the TMD patient may require a multidisciplinary approach. Physical therapy, cognitive behavioral intervention, educating the patients on self-care, and sometimes referring the patient to a psychologist or psychiatrist are all parts of the management. However, in most of the cases, a dental practitioner can begin the initial management. Using a step-by-step approach, a wide range of treatment modalities may be applied alone or in combination with each other. When conservative methods are ineffective in treating the patient, more invasive methods are applied, and open surgery may be indicated in patients not responding to other treatments. The practitioner should know that duration of symptoms is an important factor in the treatment success even in open surgery; earlier interventions have a higher chance for success [12].

Being an important aspect of the management of the patients with TMD, patient education requires full compliance of the patient because the treatment may fail due to the non-cooperative behavior of the patient.

The patient should be informed not to contact the teeth during rest (preventing clenching at daytime), being aware of parafunctional habits such as nail biting, lip-cheek chewing, and jaw protrusion [1].

The patient must be informed that he/she should have a soft diet and should limit the range of mouth opening. Slow chewing, decreasing the amount of daily tea, and coffee consumption are all parts of the treatment [1, 13]. Biting the food using incisors should be avoided, and biting on the effected side is recommended in case of joint pain [1].

Self-management is another important part of the management process. Self-massage is the initial self-management therapy, which is found to be very helpful in pain management especially in patients with masticatory muscle-originated pain [14, 15]. In myofascial pain massaging, the trigger points especially lead to improvement in pain even though it is temporary, and the massage must be continued to keep the benefits obtained from it [13].

Another self-management method is the application of moist heat or application of ice especially in cases of local myalgia and myofascial pain [1]. As a simple method, 20 minutes of hot bath is found to be effective in decreasing muscle pain.

Another method that can be used is the application of a hot pack to the tender site for 20 minutes three times a day. Heat relaxes the muscles and provides increased blood flow to the muscles. Also when cold is applied, as a reaction in order to increase the heat in the coldapplied muscle, the brain increases the blood flow to the muscle by vasodilatation providing an improvement in pain. Most of the studies on cold application are about acute pain, so there is little data on the application of cold for the management of chronic pain [16].

Pharmacological therapy is a part of TMD management. Nonsteroidal anti-inflammatory drugs (NSAIDs), analgesics, muscle relaxants, anxiolytic drugs, local anesthetics, antidepressants, and corticosteroids are indicated in TMD treatment.

## **2. Nonsteroidal anti-inflammatory drugs**

Anteriorly displaced discs are common findings in the asymptomatic patients too. Studies by Larheim et al. [5] and Davant et al. [6] reported that magnetic resonance imaging (MRI) shows that about one third of the asymptomatic patients have displaced discs. It is also known that anteriorly displaced discs are most of the time displaced medially too [7], and it is important to evaluate the patient's complaints and try to resolve the symptoms which are joint sounds, pain, and limited mouth opening. Chronic disc displacement can lead to the adhesion of the disc to the articular fossa. Pain in the TMJ is present in the 10% of the adult population and found more often in women [8]. However, it must be kept in mind that prior to initiating the treatment of a TMD patient, any possibilities of benign and malign tumors, developmental

If the overloading of the TMJ continues (parafunctional habits, bruxism) remodeling, mechanism is triggered. When overloading exceeds the limits of remodeling, degenerative process

General consensus in treatment is that the most conservative and the most reversible method should be the initial treatment of choice. This is because temporomandibular disorders have a tendency of improving over time, and clinical experience shows that sometimes conservative treatments are as effective as invasive methods in relieving the patient's symptoms [10]. When a patient is referred to a dentist for a complaint of temporomandibular disorder, oral history must be taken, and the patient should initially be examined for medical pathologies of the head and neck, including intraoral examination to search for a pain of dentoalveolar origin, type of occlusion, and any indicator of parafunctional habits such as bruxism. Imaging studies should be performed if necessary. The patients should also be evaluated for neurological and psychological conditions and should be referred to a specialist if necessary [11].

Management of the TMD patient may require a multidisciplinary approach. Physical therapy, cognitive behavioral intervention, educating the patients on self-care, and sometimes referring the patient to a psychologist or psychiatrist are all parts of the management. However, in most of the cases, a dental practitioner can begin the initial management. Using a step-by-step approach, a wide range of treatment modalities may be applied alone or in combination with each other. When conservative methods are ineffective in treating the patient, more invasive methods are applied, and open surgery may be indicated in patients not responding to other treatments. The practitioner should know that duration of symptoms is an important factor in the treatment suc-

Being an important aspect of the management of the patients with TMD, patient education requires full compliance of the patient because the treatment may fail due to the non-cooper-

The patient should be informed not to contact the teeth during rest (preventing clenching at daytime), being aware of parafunctional habits such as nail biting, lip-cheek chewing, and jaw

The patient must be informed that he/she should have a soft diet and should limit the range of mouth opening. Slow chewing, decreasing the amount of daily tea, and coffee consumption

cess even in open surgery; earlier interventions have a higher chance for success [12].

of the articular surfaces may begin leading to the osteoarthritis of the TMJ [9].

disorders, and fractures should be out-ruled.

4 Temporomandibular Joint Pathology - Current Approaches and Understanding

ative behavior of the patient.

protrusion [1].

Analgesics and NSAIDs form an important part of the pharmacological treatment of the osteoarthritic TMJ. The American College of Rheumatology guidelines recommend the use of paracetamol as the first medication of choice for the osteoarthritic hip and knee [17–19]. The use of paracetamol is also recommended for the management of osteoarthritis by some authors; however, they conclude that paracetamol is effective in osteoarthritis only at very high, near toxicity level doses. Ibuprofen and naproxen are recommended agents in osteoarthritis of the TMJ, but in the management of chronic pain, cox-2 inhibitors such as celecoxib or meloxicam should be preferred, not only for their effectiveness in chronic pain but also for less gastrointestinal effects, for they may require a prolonged use in chronic pain [20].

NSAIDs provide anti-inflammatory effects and analgesia for the TMD patients with osteoarthritis, capsulitis, synovitis, myositis, and pain related to reducing and nonreducing disc displacements [21].

Naproxen, ibuprofen, and diclofenac are the most often used NSAIDs [22]. Mejersjo and Wenneberg [23] have studied the effects of diclofenac 50 mg, given orally 3 ×1 in patients with TMJ arthritis. Their findings at the end of 3 months produced results similar to efficacy of occlusal appliances.

Anti-inflammatory properties of corticosteroids are greater than that of NSAIDs. Because the long term systemic use of corticosteroids may lead to complications such as Cushing's syndrome, diabetes, and osteoporosis, they must be used only for a short time [24]. Anxiolytics is also recommended for a limited period of use because of their potential for dependency. Their sedative and muscle relaxant properties help reduce the effects of masticatory parafunctional habits such as bruxism. They help patients cope with stress, which is an important etiologic factor of TMD, stress-induced muscular hyperactivity, and dysfunction [22, 25]. A recent animal study has shown that the benzodiazepines also have effects on the biochemical content of the TMJ [26].

Occlusal splints are the most commonly used treatment modality in the management of TMDs. Occlusal splints help in relieving the muscle hyperactivity originating from bruxism. Occlusal appliances also provide relief from occlusal overload to the TMJ and inhibit strain [38].

Introductory Chapter: Optimizing the Management Outcomes in Patients…

http://dx.doi.org/10.5772/intechopen.73537

7

Casares et al. have [39] measured the effects of occlusal splints on intra-articular pressure using a pressure transducer, and they have concluded that stabilization splints significantly reduced the intra-articular pressure in the upper joint compartment. They have also reported

Conti et al. [40] have reported that even though behavioral treatment improves symptoms in patients with myofascial pain in short term, occlusal splints may accelerate the process, helping the patients to get positive results earlier. Another study even has hinted that occlusal

First described for the temporomandibular joint by Nitzan et al. [42], arthrocentesis is simply the irrigation of the superior TMJ compartment using two needles and is considered to be an efficient process with low morbidity rate [43]. When applied for the treatment of TMJ osteoarthritis, this process removes degradation products and inflammatory mediators from the joint [44, 45]. However, Laskin [44] has stated that intra-articular lavage may also remove the favorable agents such as hyaluronic acid from the intra-articular space too. TMJ arthrocentesis

Two needles are used for irrigation and outflow of the irrigation solution, which is in most cases ringers lactate solution [9]. The amount of ringer's solution is a subject of debate and

The current understanding in the management of TMDs positions arthrocentesis after the initial conservative treatment modalities. When the conservative treatment fails, then arthrocentesis is indicated. However, some studies have evaluated the outcomes of arthrocentesis as an initial treatment. Vos et al. [50] have studied 80 patients in which 40 patients had arthrocentesis as an initial treatment, and the other 40 received conservative treatment as control. They have reported a more rapid improvement in symptoms following arthrocentesis, whereas the conservative treatment group showed a more gradual improvement. Their study has also shown that both methods produced similar results at the end of 26 weeks. However, they have discussed that this might be partially due to conservative treatment being dependent on patient compliance, whereas arthrocentesis is not, which may affect the outcome of the study. Machon et al. [45] have reported arthrocentesis to be more effective when combined

Arthrocentesis may be performed in combination with the injection of various agents such as sodium hyaluronate [51] and corticosteroids (It has been previously reported that corticosteroids have positive effects on pain and function when injected intra-articularly) [52, 53]. For this reason, corticosteroid injection alone or in combination with arthrocentesis is used for treatment of the internal derangements of the TMJ. However, the injection of corticosteroids into the TMJ is still controversial due to reported complications such as bone necrosis, destruction of the cartilage, and progression of the degenerative disease [54–56]. These complications are reported to be mostly due to multiple injections or high-dose injections, and

splints may be helping improve the psychological status of the TMD patients [41].

may inhibit pain and increase the range of mandibular motion [42, 46, 47].

varies between 60 ml [48] and 200 ml [49] in the literature.

with splint therapy.

single injections are considered to be safe [57].

better joint function as an outcome of splint treatment.

Usually used in combination with NSAIDs, centrally acting muscle relaxants help relax the masticatory muscles, and the patients may also benefit from their sedative properties [22]. The aim of using the muscle relaxants in the TMD patient is not only to manage acute muscle pain but also to decrease muscle activity for a limited period [27, 28].

The mechanism via which the muscle relaxants help the TMD patients is not totally clear. The prescribed doses are not high enough when taken orally to relax masticatory muscles locally. So, it is believed that their sedative and stress-reducing effects are more effective in helping the TMD patient [27].

Chlorzoxazone, cyclobenzaprine, methocarbamol, and diazepam are the most commonly used centrally acting muscle relaxants. All of these drugs have sedating effects, so the patients should preferably take them at bedtime [29].

Tizanidine is a spasmolytic agent, and there is so far only one clinical trial studying its effectiveness in the TMDs. Alencar et al. [30] have reported that tizanidine and cyclobenzaprine have effects similar to placebo on myofascial pain patients.

Even though there is little scientific evidence to support the efficacy of opioid analgesics in TMDs, they are usually prescribed together with non-opioid analgesics, in the management of TMJ pain. However, they must be used with caution for their tendency to create dependence in the patients. Opioid analgesics should be used only for short periods such as 2–3 weeks [22].

Hydrocodone is an opioid analgesic used in combination with a non-opioid analgesic or a NSAID in order to manage moderate to severe pain [31]. However, hydrocodone is not very effective in chronic pain cases. Codeine, morphine, oxycodone, hydromorphone, and fentanyl are also among the opioid analgesics preferred in the management of pain. The use of opioid analgesics is considered safe in some forms of noncancer pain as long as patients are selected carefully, well monitored for adverse effects, and onset of dependence [32].

However, it is still a subject of debate, which kind of opioids to use in the management of TMJ pain. Opioids are classified as short-acting and long-acting opioids. Short-acting opioids have the advantage of rapid onset of pain relief; however, they have a higher risk of drug-related adverse effects [33]. Long-acting opioids also help improve pain, and there is less reported drug-related adverse effects in patients [34]. However, Argoff and Silvershein [35] have not found any differences between the two types of drugs for efficacy.

Currently, due to lack of enough randomized controlled clinical trials on the clinical efficiency of pharmacological agents on TMD-related pain, it must be kept in mind that the pharmacological treatment in TMD patients is mostly empirical [36, 37].

Occlusal splints are the most commonly used treatment modality in the management of TMDs. Occlusal splints help in relieving the muscle hyperactivity originating from bruxism. Occlusal appliances also provide relief from occlusal overload to the TMJ and inhibit strain [38].

Anti-inflammatory properties of corticosteroids are greater than that of NSAIDs. Because the long term systemic use of corticosteroids may lead to complications such as Cushing's syndrome, diabetes, and osteoporosis, they must be used only for a short time [24]. Anxiolytics is also recommended for a limited period of use because of their potential for dependency. Their sedative and muscle relaxant properties help reduce the effects of masticatory parafunctional habits such as bruxism. They help patients cope with stress, which is an important etiologic factor of TMD, stress-induced muscular hyperactivity, and dysfunction [22, 25]. A recent animal study has shown that the benzodiazepines also have effects on the biochemical content of the TMJ [26]. Usually used in combination with NSAIDs, centrally acting muscle relaxants help relax the masticatory muscles, and the patients may also benefit from their sedative properties [22]. The aim of using the muscle relaxants in the TMD patient is not only to manage acute muscle pain

The mechanism via which the muscle relaxants help the TMD patients is not totally clear. The prescribed doses are not high enough when taken orally to relax masticatory muscles locally. So, it is believed that their sedative and stress-reducing effects are more effective in helping

Chlorzoxazone, cyclobenzaprine, methocarbamol, and diazepam are the most commonly used centrally acting muscle relaxants. All of these drugs have sedating effects, so the patients

Tizanidine is a spasmolytic agent, and there is so far only one clinical trial studying its effectiveness in the TMDs. Alencar et al. [30] have reported that tizanidine and cyclobenzaprine

Even though there is little scientific evidence to support the efficacy of opioid analgesics in TMDs, they are usually prescribed together with non-opioid analgesics, in the management of TMJ pain. However, they must be used with caution for their tendency to create dependence in the patients. Opioid analgesics should be used only for short periods such as 2–3 weeks [22]. Hydrocodone is an opioid analgesic used in combination with a non-opioid analgesic or a NSAID in order to manage moderate to severe pain [31]. However, hydrocodone is not very effective in chronic pain cases. Codeine, morphine, oxycodone, hydromorphone, and fentanyl are also among the opioid analgesics preferred in the management of pain. The use of opioid analgesics is considered safe in some forms of noncancer pain as long as patients are selected

However, it is still a subject of debate, which kind of opioids to use in the management of TMJ pain. Opioids are classified as short-acting and long-acting opioids. Short-acting opioids have the advantage of rapid onset of pain relief; however, they have a higher risk of drug-related adverse effects [33]. Long-acting opioids also help improve pain, and there is less reported drug-related adverse effects in patients [34]. However, Argoff and Silvershein [35] have not

Currently, due to lack of enough randomized controlled clinical trials on the clinical efficiency of pharmacological agents on TMD-related pain, it must be kept in mind that the pharmaco-

but also to decrease muscle activity for a limited period [27, 28].

6 Temporomandibular Joint Pathology - Current Approaches and Understanding

the TMD patient [27].

should preferably take them at bedtime [29].

have effects similar to placebo on myofascial pain patients.

carefully, well monitored for adverse effects, and onset of dependence [32].

found any differences between the two types of drugs for efficacy.

logical treatment in TMD patients is mostly empirical [36, 37].

Casares et al. have [39] measured the effects of occlusal splints on intra-articular pressure using a pressure transducer, and they have concluded that stabilization splints significantly reduced the intra-articular pressure in the upper joint compartment. They have also reported better joint function as an outcome of splint treatment.

Conti et al. [40] have reported that even though behavioral treatment improves symptoms in patients with myofascial pain in short term, occlusal splints may accelerate the process, helping the patients to get positive results earlier. Another study even has hinted that occlusal splints may be helping improve the psychological status of the TMD patients [41].

First described for the temporomandibular joint by Nitzan et al. [42], arthrocentesis is simply the irrigation of the superior TMJ compartment using two needles and is considered to be an efficient process with low morbidity rate [43]. When applied for the treatment of TMJ osteoarthritis, this process removes degradation products and inflammatory mediators from the joint [44, 45]. However, Laskin [44] has stated that intra-articular lavage may also remove the favorable agents such as hyaluronic acid from the intra-articular space too. TMJ arthrocentesis may inhibit pain and increase the range of mandibular motion [42, 46, 47].

Two needles are used for irrigation and outflow of the irrigation solution, which is in most cases ringers lactate solution [9]. The amount of ringer's solution is a subject of debate and varies between 60 ml [48] and 200 ml [49] in the literature.

The current understanding in the management of TMDs positions arthrocentesis after the initial conservative treatment modalities. When the conservative treatment fails, then arthrocentesis is indicated. However, some studies have evaluated the outcomes of arthrocentesis as an initial treatment. Vos et al. [50] have studied 80 patients in which 40 patients had arthrocentesis as an initial treatment, and the other 40 received conservative treatment as control. They have reported a more rapid improvement in symptoms following arthrocentesis, whereas the conservative treatment group showed a more gradual improvement. Their study has also shown that both methods produced similar results at the end of 26 weeks. However, they have discussed that this might be partially due to conservative treatment being dependent on patient compliance, whereas arthrocentesis is not, which may affect the outcome of the study. Machon et al. [45] have reported arthrocentesis to be more effective when combined with splint therapy.

Arthrocentesis may be performed in combination with the injection of various agents such as sodium hyaluronate [51] and corticosteroids (It has been previously reported that corticosteroids have positive effects on pain and function when injected intra-articularly) [52, 53]. For this reason, corticosteroid injection alone or in combination with arthrocentesis is used for treatment of the internal derangements of the TMJ. However, the injection of corticosteroids into the TMJ is still controversial due to reported complications such as bone necrosis, destruction of the cartilage, and progression of the degenerative disease [54–56]. These complications are reported to be mostly due to multiple injections or high-dose injections, and single injections are considered to be safe [57].

Sodium chlorate injections are also commonly used in the TMDs [58–61]. They are either used in single injections or multiple injections, and multiple arthrocenteses followed by multiple injections of sodium hyaluronate have been found to be beneficial in patients with internal derangement [62, 63].

**Author details**

, Yusuf Emes1

\*Address all correspondence to<EMAIL_ADDRESS>
Sussex: Blackwell; 2010. pp. 1175-1197

(1939). 1993;**124**(10):115-121

Winter;**28**(1):6-27

Sep;**51**(6):469-472

1993;**51**(9):974-979

**8**(3):291-305

Endodontics. 1992;**73**(3):364-368

\* and Guhan Dergin2

1 Faculty of Dentistry, Department of Oral and Maxillofacial Surgery, Istanbul University,

Introductory Chapter: Optimizing the Management Outcomes in Patients…

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9

2 Faculty of Dentistry, Department of Oral and Maxillofacial Surgery, Marmara University,

[1] McNeill C, Rudd PA. Diagnosis and non-surgical management of orofacial pain. In: Andersson L, Kahnberg K, Pogrel MA, editors. Oral and Maxillofacial Surgery. West

[2] Lipton JA, Ship JA, Larach-Robinson D. Estimated prevalence and distribution of reported orofacial pain in the United States. Journal of the American Dental Association

[3] Schiffman E, Ohrbach R, Truelove E, Look J, Anderson G, Goulet JP, et al. Diagnostic criteria for Temporomandibular disorders (DC/TMD) for clinical and research applications: Recommendations of the international RDC/TMD consortium network\* and orofacial pain special interest group. Journal of Oral & Facial Pain and Headache. 2014

[4] Sidebottom AJ. How do I manage restricted mouth opening secondary to problems with the temporomandibular joint? The British Journal of Oral & Maxillofacial Surgery. 2013

[5] Larheim TA, Westesson PL, Sano T. Temporomandibular joint disk displacement: Comparison in asymptomatic volunteers and patients. Radiology. 2001;**218**(2):428-432

[6] Davant TSI, Greene CS, Perry HT, Lautenschlager EP. A quantitative computer-assisted analysis of the disc displacement in patients with internal derangement using sagittal view and magnetic resonance imaging. Journal of Oral and Maxillofacial Surgery.

[7] Kurita K, Westesson PL, Tasaki MM, Liedberg J. Temporomandibular joint: Diagnosis of medial and lateral disc displacement with anterioposterior arthrography. Correlations with cryosections. Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and

[8] LeResche L. Epidemiology of temporomandibular disorders: Implications for the investigation of etiologic factors. Critical Reviews in Oral Biology and Medicine. 1997;

Buket Aybar<sup>1</sup>

Turkey

Turkey

**References**

However, Manfredini et al. [51] have stated that a single dose of sodium hyaluronate injection following single arthrocentesis produced benefits similar to multiple interventions.

Emes et al. [64] have compared the effects of arthrocentesis to tenoxicam injection alone and reported no differences between the groups. However, their groups consisted of patients who did not respond to a previous arthrocentesis.

Sipahi et al. [48] have injected morphine and tramadol following arthrocentesis into the TMJs of patients with TMJ pain and have concluded that injection of morphine has significantly increased pain relief for 6 months. They have had similar pain relief with tramadol too, but this relief period was shorter in tramadol when compared to morphine.

Arthroscopy of the TMJ is an invasive surgical technique, which is used for the diagnosis and treatment of internal derangements of the TMJ [9]. It also has a low risk of degenerative articular change in the long term, which makes it a safe procedure (has lower complications than open surgery and less invasive than open surgery) [65]. However, it is not beneficial in examining the lower joint compartment. When there is a degenerative process affecting the lower joint compartment, usually an open surgery is indicated. Arthroscopy and arthrocentesis have similar benefits in TMDs, but arthroscopy is the technique of choice in the diagnosis and management of rheumatoid disorders affecting the TMJ [66]. It can also be used for techniques other than simple lysis and lavage; for example, Murakami et al. [67] have reported that arthroscopic lateral release of the capsule and anterior discal release were more effective than arthrocentesis in increasing the range of mouth opening.

Several studies show that the majority of TMDs can be managed by nonsurgical methods. When these methods fail to help the patient with his/her symptoms, then invasive techniques, such as arthrocentesis and arthroscopy, or open joint surgery are indicated [68]. Open procedures are used in order to reposition the anteriorly displaced disc, remove the anteriorly displaced disc, or remove and replace it (by temporalis flap, auricular cartilage, or an alloplastic material) [69, 70]. Several studies conclude that, in the treatment of the internal derangement of TMJ, open surgery is more effective in decreasing pain when compared to arthroscopic surgery [69, 70–73].

## **3. Conclusion**

The treatment of the TMD patient is challenging for the clinician because of the complex pathophysiology of the disorder, and deciding the optimal method for these patients is a difficult task. Our current treatment modalities all have some degree of placebo properties, and due to lack of randomized controlled clinical trials with placebo, our treatment protocols may fall within the boundaries of empirical treatment. In most cases, optimal treatment is the treatment targeting the patient's individual needs, a step-by-step approach, avoiding aggressive, radical surgical protocols as much as possible, will be beneficial for the patient and increase the successful outcomes of our treatment.

## **Author details**

Sodium chlorate injections are also commonly used in the TMDs [58–61]. They are either used in single injections or multiple injections, and multiple arthrocenteses followed by multiple injections of sodium hyaluronate have been found to be beneficial in patients with internal

However, Manfredini et al. [51] have stated that a single dose of sodium hyaluronate injection

Emes et al. [64] have compared the effects of arthrocentesis to tenoxicam injection alone and reported no differences between the groups. However, their groups consisted of patients who

Sipahi et al. [48] have injected morphine and tramadol following arthrocentesis into the TMJs of patients with TMJ pain and have concluded that injection of morphine has significantly increased pain relief for 6 months. They have had similar pain relief with tramadol too, but

Arthroscopy of the TMJ is an invasive surgical technique, which is used for the diagnosis and treatment of internal derangements of the TMJ [9]. It also has a low risk of degenerative articular change in the long term, which makes it a safe procedure (has lower complications than open surgery and less invasive than open surgery) [65]. However, it is not beneficial in examining the lower joint compartment. When there is a degenerative process affecting the lower joint compartment, usually an open surgery is indicated. Arthroscopy and arthrocentesis have similar benefits in TMDs, but arthroscopy is the technique of choice in the diagnosis and management of rheumatoid disorders affecting the TMJ [66]. It can also be used for techniques other than simple lysis and lavage; for example, Murakami et al. [67] have reported that arthroscopic lateral release of the capsule and anterior discal release were more effective

Several studies show that the majority of TMDs can be managed by nonsurgical methods. When these methods fail to help the patient with his/her symptoms, then invasive techniques, such as arthrocentesis and arthroscopy, or open joint surgery are indicated [68]. Open procedures are used in order to reposition the anteriorly displaced disc, remove the anteriorly displaced disc, or remove and replace it (by temporalis flap, auricular cartilage, or an alloplastic material) [69, 70]. Several studies conclude that, in the treatment of the internal derangement of TMJ, open surgery is more effective in decreasing pain when compared to arthroscopic surgery [69, 70–73].

The treatment of the TMD patient is challenging for the clinician because of the complex pathophysiology of the disorder, and deciding the optimal method for these patients is a difficult task. Our current treatment modalities all have some degree of placebo properties, and due to lack of randomized controlled clinical trials with placebo, our treatment protocols may fall within the boundaries of empirical treatment. In most cases, optimal treatment is the treatment targeting the patient's individual needs, a step-by-step approach, avoiding aggressive, radical surgical protocols as much as possible, will be beneficial for the patient and increase

following single arthrocentesis produced benefits similar to multiple interventions.

this relief period was shorter in tramadol when compared to morphine.

than arthrocentesis in increasing the range of mouth opening.

derangement [62, 63].

**3. Conclusion**

the successful outcomes of our treatment.

did not respond to a previous arthrocentesis.

8 Temporomandibular Joint Pathology - Current Approaches and Understanding

Buket Aybar<sup>1</sup> , Yusuf Emes1 \* and Guhan Dergin2

\*Address all correspondence to<EMAIL_ADDRESS>
1 Faculty of Dentistry, Department of Oral and Maxillofacial Surgery, Istanbul University, Turkey

2 Faculty of Dentistry, Department of Oral and Maxillofacial Surgery, Marmara University, Turkey

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**Section 2**

**Pathological Conditions of the**

**Temporomandibular Joint**

## **Pathological Conditions of the Temporomandibular Joint**

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14 Temporomandibular Joint Pathology - Current Approaches and Understanding

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Mosby; 1985

**Chapter 2**

**Provisional chapter**

**Myofascial Pain Dysfunction Syndrome: Etiology,**

**Myofascial Pain Dysfunction Syndrome: Etiology,**

DOI: 10.5772/intechopen.72529

Myofascial pain dysfunction syndrome (MPDS) is a stomatognathic system disturbance, which consists of pain, jaw movement irregularities, and muscle spasm. Hyperexcitation of peripheral sensory neurons causes a reaction of induction in the motor neuron and then spasms of the masticatory muscles follow. Long-term spasm causes muscular pain and irregular mandibular motion. Pain is the most important inducer and therefore must be managed firstly in order to manage the muscle spasms. Symptomatic treatment approaches may be useful, but after symptom elimination, etiologically based treatment must be provided to the patient. The neurophysiology of the stomatognathic system must be well understood to determine a proper treatment for the MPDS condition. Both symptomatic and etiological treatment methods have been proposed by differing authors as potential solutions for MPDS. Occlusal splints are a commonly used treatment for relieving MPDS symptoms. Alternatively, some forms of occlusal adjustment (not all) have been shown to be an effective, permanent treatment course for myofascial pain dysfunction syndrome. This chapter describes the neural controls over the stomatognathic system and how that system can neurologically promote the MPDS disease state. It then details the computer-guided MPDS occlusal adjustment treatment known as disclusion time reduction that has been shown in many published studies to be a highly effective

> © 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution,

© 2018 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

and reproduction in any medium, provided the original work is properly cited.

In the year 1996, the National institute of Health (NIH, USA) held a conference from which the NIH issued a pamphlet of clinical guidelines regarding temporomandibular disorders (TMD).

**Keywords:** MPDS, muscle pain dysfunction syndrome, TMD, stomatognathic system

**Diagnosis, and Treatment**

**Diagnosis, and Treatment**

http://dx.doi.org/10.5772/intechopen.72529

Additional information is available at the end of the chapter

myofascial pain dysfunction syndrome (MPDS) therapy.

problems, masticatory muscle problems

Additional information is available at the end of the chapter

Serdar Gözler

**Abstract**

**1. Introduction**

Serdar Gözler

**Provisional chapter**

## **Myofascial Pain Dysfunction Syndrome: Etiology, Diagnosis, and Treatment Diagnosis, and Treatment**

**Myofascial Pain Dysfunction Syndrome: Etiology,**

DOI: 10.5772/intechopen.72529

#### Serdar Gözler Additional information is available at the end of the chapter

Serdar Gözler

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.72529

#### **Abstract**

Myofascial pain dysfunction syndrome (MPDS) is a stomatognathic system disturbance, which consists of pain, jaw movement irregularities, and muscle spasm. Hyperexcitation of peripheral sensory neurons causes a reaction of induction in the motor neuron and then spasms of the masticatory muscles follow. Long-term spasm causes muscular pain and irregular mandibular motion. Pain is the most important inducer and therefore must be managed firstly in order to manage the muscle spasms. Symptomatic treatment approaches may be useful, but after symptom elimination, etiologically based treatment must be provided to the patient. The neurophysiology of the stomatognathic system must be well understood to determine a proper treatment for the MPDS condition. Both symptomatic and etiological treatment methods have been proposed by differing authors as potential solutions for MPDS. Occlusal splints are a commonly used treatment for relieving MPDS symptoms. Alternatively, some forms of occlusal adjustment (not all) have been shown to be an effective, permanent treatment course for myofascial pain dysfunction syndrome. This chapter describes the neural controls over the stomatognathic system and how that system can neurologically promote the MPDS disease state. It then details the computer-guided MPDS occlusal adjustment treatment known as disclusion time reduction that has been shown in many published studies to be a highly effective myofascial pain dysfunction syndrome (MPDS) therapy.

**Keywords:** MPDS, muscle pain dysfunction syndrome, TMD, stomatognathic system problems, masticatory muscle problems

## **1. Introduction**

In the year 1996, the National institute of Health (NIH, USA) held a conference from which the NIH issued a pamphlet of clinical guidelines regarding temporomandibular disorders (TMD).

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

In the NIH report as well as from the National Institute of Dental Research (NIDR) (NIH publication no. 94-3487), no distinction was made between temporomandibular disorders and myofascial pain dysfunction syndrome (MPDS). All potential etiological factors, clinical symptoms, the diagnoses and the treatment recommendations fell under the single term, "Temporomandibular Disorders" [1]. There was no clear distinction made between TMJ internal derangements and myofascial pain dysfunction syndrome. Additionally, the final report did not recommend any definitive treatment for temporomandibular disorders. Although the NIH meeting attendees claimed to have solved the "TMJ problem," no consensus was reached making the conference a complete disappointment. However, later in 1999, Dr. Peter Dawson opposed the conference results in an article that was cosponsored by American Equilibration Society (AES, Chicago, IL, USA) [2]. After further numerous arguments, no consensus was found regarding the etiology or treatments that should be applied in TMD cases.

ligament laxity affects the movements of the joint structures in the glenoid fossa and often

Myofascial Pain Dysfunction Syndrome: Etiology, Diagnosis, and Treatment

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19

Myofascial pain dysfunction syndrome (MPDS) is one particular type of temporomandibular disorder (TMD) [12]. Historically, clinicians and researchers have subclassified TMDs into either intracapsular disorders or masticatory muscle disorders (such as local myalgia, myofascial pain, centrally mediated myalgia, myospasm, myositis, myofibrotic contracture, and masticatory muscle neoplastic disease). TMJ internal derangement may not be involved with MPDS. However, when a temporomandibular joint irregularity occurs along with the symptoms of MPDS, the complete problematic condition should be considered as temporomandibular joint disease [17, 18]. All masticatory organs participating in oral function may or may not be involved in MPDS. Before discussing about the etiologic factors and treatment techniques related to MPDS, it is

Muscular pain is a typical and a decisive symptom of MPDS. Functional disorders that occur in the stomatognathic system are a cause of pain. If the functional disorders are not successfully treated, pain may be present for years. Pain minimization during function is the result of

The most important stomatognathic function is chewing. There is a great relationship between impairment of chewing function and painful muscle problems [13, 16, 17, 19–24]. During the chewing function, tooth contact occurs at the extreme end of the chewing cycle when occlusal force is applied to crush the food bolus. In this way, the resultant chewed food is readied for swallowing. For the chewed food product to be effectively prepared for swallowing, all related functions must occur in a harmonious order. Hence, the duration of chewing, the control of the mandibular movements, the masticatory muscle contractions, the level of force applied during the bolus crush, temporomandibular joint movements, the tooth-tooth interactions, and the neural feedback mechanisms all must interact synergistically (**Figure 1**).

The relationship between muscle malfunction and MPDS is a two-sided problem, where each affects the other. Muscle malfunction triggers MPDS, while MPDS causes impairment of masticatory movements. Stomatognathic system functions are the best diagnostic indicator of dysfunction. The main purpose of the stomatognathic system is to perform the best chewing possible, which requires a very well-coordinated system. As proper chewing evolves within the developmental period of human growth, it becomes optimal during the adult years. Deciduous, mixed, and permanent dentitions have their own chewing patterns [25], with the chewing pattern being closely linked to a person's dental condition [24]. However, corruption

As is the case with other body functions, the chewing pattern results from a complex integration of the neural and the myofascial structures. The resultant product of chewing is chewed food that is readied for swallowing. The most effective determining factor of a good chewing pattern is the dental occlusion [28], whereby the structural posture, the stretching of muscles and the chewing process itself are improved by upper and lower tooth contact. However, changes to the dental occlusion from tooth loss, orthodontic tooth movement, restorative dentistry, or mechanical trauma, all of which can alter the neurologic input significantly, may be the most important etiological factor leading to the impairment of chewing mechanism [19].

of the chewing pattern indicates the beginnings of myofascial distortion [26, 27].

necessary to properly understand the neural mechanisms of masticatory system.

occurs without patient awareness of the problem's existence.

the protective mechanisms within the stomatognathic system.

Of note is that 4 years before the release of the NIH report in 1991, Dr. Robert Barry Kerstein from Tufts University School of Dental Medicine in Boston Massachusetts had developed a T-Scan I time-based coronoplasty procedure, which focused on reducing excursive movement disclusion times [3]. According to this study, the length of disclusion time was correlated to high levels of masseter and temporalis excursive muscle activity levels [3] that were of diagnostic importance when evaluating differing etiologic factors of chronic MPDS [2]. These early studies were the beginning of a series of studies about this topic [3, 4]. As Dawson noted in his article, there had been found an evidence-based relationship between occlusion and MPDS. Often MPDS symptoms affected the chewing system mechanics because the symptoms had a close association with the dental occlusion and its relationship to the central nervous system (CNS).

Myofascial pain dysfunction syndrome is a common term that is used in other medical branches outside of Dentistry [5–7]. But in the last few decades, this term has been used in Dental Medicine to describe orofacial chronic pain [8, 9], often abbreviated in the literature as MPDS [3]. MPDS is a functional disease related to the masticatory muscles, the neural structures and the temporomandibular joint structures. MPDS syndrome can be a very uncomfortable condition for a patient. The patient can barely move their mandible, and often there is pain in the face and head area. Sometimes, the pain may extend to neck and dorsal area. Most typical symptoms are acute hypercontraction (spasm) of the muscles, and laxity of the TM joint ligaments. The symptoms of the MPDS are explained in detail later in this chapter [5, 10–12].

Etiologically, the MPDS muscle and TM joint symptoms have been linked primarily to the occlusion [2, 3, 13, 14]. Muscle spasm is caused by occlusal surface friction and prolonged disclusion time overcompressing the posterior tooth PDLs causing hyperfunction and ischemia in the muscles. This leads to muscle fatigue and then poor mandibular movements. This is what leads to deterioration of the movements.

Muscle spasm is usually caused by occlusal surface friction and prolonged disclusion time [15] overcompressing the posterior tooth periodontal ligament mechanoreceptors causing hyperfunction and ischemia in the muscles. This leads to muscle fatigue and then poor mandibular movements [16].

The deterioration of mandibular movements can be accelerated by deterioration of the occlusion. A filling, crown, or a bridge will always cause the occlusion to deteriorate. Alternatively, ligament laxity affects the movements of the joint structures in the glenoid fossa and often occurs without patient awareness of the problem's existence.

In the NIH report as well as from the National Institute of Dental Research (NIDR) (NIH publication no. 94-3487), no distinction was made between temporomandibular disorders and myofascial pain dysfunction syndrome (MPDS). All potential etiological factors, clinical symptoms, the diagnoses and the treatment recommendations fell under the single term, "Temporomandibular Disorders" [1]. There was no clear distinction made between TMJ internal derangements and myofascial pain dysfunction syndrome. Additionally, the final report did not recommend any definitive treatment for temporomandibular disorders. Although the NIH meeting attendees claimed to have solved the "TMJ problem," no consensus was reached making the conference a complete disappointment. However, later in 1999, Dr. Peter Dawson opposed the conference results in an article that was cosponsored by American Equilibration Society (AES, Chicago, IL, USA) [2]. After further numerous arguments, no consensus was

18 Temporomandibular Joint Pathology - Current Approaches and Understanding

found regarding the etiology or treatments that should be applied in TMD cases.

what leads to deterioration of the movements.

dibular movements [16].

Of note is that 4 years before the release of the NIH report in 1991, Dr. Robert Barry Kerstein from Tufts University School of Dental Medicine in Boston Massachusetts had developed a T-Scan I time-based coronoplasty procedure, which focused on reducing excursive movement disclusion times [3]. According to this study, the length of disclusion time was correlated to high levels of masseter and temporalis excursive muscle activity levels [3] that were of diagnostic importance when evaluating differing etiologic factors of chronic MPDS [2]. These early studies were the beginning of a series of studies about this topic [3, 4]. As Dawson noted in his article, there had been found an evidence-based relationship between occlusion and MPDS. Often MPDS symptoms affected the chewing system mechanics because the symptoms had a close association with the dental occlusion and its relationship to the central nervous system (CNS). Myofascial pain dysfunction syndrome is a common term that is used in other medical branches outside of Dentistry [5–7]. But in the last few decades, this term has been used in Dental Medicine to describe orofacial chronic pain [8, 9], often abbreviated in the literature as MPDS [3]. MPDS is a functional disease related to the masticatory muscles, the neural structures and the temporomandibular joint structures. MPDS syndrome can be a very uncomfortable condition for a patient. The patient can barely move their mandible, and often there is pain in the face and head area. Sometimes, the pain may extend to neck and dorsal area. Most typical symptoms are acute hypercontraction (spasm) of the muscles, and laxity of the TM joint ligaments. The symptoms of the MPDS are explained in detail later in this chapter [5, 10–12]. Etiologically, the MPDS muscle and TM joint symptoms have been linked primarily to the occlusion [2, 3, 13, 14]. Muscle spasm is caused by occlusal surface friction and prolonged disclusion time overcompressing the posterior tooth PDLs causing hyperfunction and ischemia in the muscles. This leads to muscle fatigue and then poor mandibular movements. This is

Muscle spasm is usually caused by occlusal surface friction and prolonged disclusion time [15] overcompressing the posterior tooth periodontal ligament mechanoreceptors causing hyperfunction and ischemia in the muscles. This leads to muscle fatigue and then poor man-

The deterioration of mandibular movements can be accelerated by deterioration of the occlusion. A filling, crown, or a bridge will always cause the occlusion to deteriorate. Alternatively, Myofascial pain dysfunction syndrome (MPDS) is one particular type of temporomandibular disorder (TMD) [12]. Historically, clinicians and researchers have subclassified TMDs into either intracapsular disorders or masticatory muscle disorders (such as local myalgia, myofascial pain, centrally mediated myalgia, myospasm, myositis, myofibrotic contracture, and masticatory muscle neoplastic disease). TMJ internal derangement may not be involved with MPDS. However, when a temporomandibular joint irregularity occurs along with the symptoms of MPDS, the complete problematic condition should be considered as temporomandibular joint disease [17, 18]. All masticatory organs participating in oral function may or may not be involved in MPDS.

Before discussing about the etiologic factors and treatment techniques related to MPDS, it is necessary to properly understand the neural mechanisms of masticatory system.

Muscular pain is a typical and a decisive symptom of MPDS. Functional disorders that occur in the stomatognathic system are a cause of pain. If the functional disorders are not successfully treated, pain may be present for years. Pain minimization during function is the result of the protective mechanisms within the stomatognathic system.

The most important stomatognathic function is chewing. There is a great relationship between impairment of chewing function and painful muscle problems [13, 16, 17, 19–24]. During the chewing function, tooth contact occurs at the extreme end of the chewing cycle when occlusal force is applied to crush the food bolus. In this way, the resultant chewed food is readied for swallowing. For the chewed food product to be effectively prepared for swallowing, all related functions must occur in a harmonious order. Hence, the duration of chewing, the control of the mandibular movements, the masticatory muscle contractions, the level of force applied during the bolus crush, temporomandibular joint movements, the tooth-tooth interactions, and the neural feedback mechanisms all must interact synergistically (**Figure 1**).

The relationship between muscle malfunction and MPDS is a two-sided problem, where each affects the other. Muscle malfunction triggers MPDS, while MPDS causes impairment of masticatory movements. Stomatognathic system functions are the best diagnostic indicator of dysfunction. The main purpose of the stomatognathic system is to perform the best chewing possible, which requires a very well-coordinated system. As proper chewing evolves within the developmental period of human growth, it becomes optimal during the adult years. Deciduous, mixed, and permanent dentitions have their own chewing patterns [25], with the chewing pattern being closely linked to a person's dental condition [24]. However, corruption of the chewing pattern indicates the beginnings of myofascial distortion [26, 27].

As is the case with other body functions, the chewing pattern results from a complex integration of the neural and the myofascial structures. The resultant product of chewing is chewed food that is readied for swallowing. The most effective determining factor of a good chewing pattern is the dental occlusion [28], whereby the structural posture, the stretching of muscles and the chewing process itself are improved by upper and lower tooth contact. However, changes to the dental occlusion from tooth loss, orthodontic tooth movement, restorative dentistry, or mechanical trauma, all of which can alter the neurologic input significantly, may be the most important etiological factor leading to the impairment of chewing mechanism [19].

in and around the teeth that hypercontract the elevator muscles. Along with muscle spasm, painful trigger points can also be a component of the MPDS condition. Some trigger points may be classified as latent [5, 6, 31, 32], in that they only occur when a muscle is pressed upon. The neuronal mechanism is a determining factor in the development of MPDS. The central nervous system (CNS) controls all activities of the masticatory system including the contraction of masticatory muscles, the sequence of contractions, the level of contraction, the posture of mandible, the mandibular movements, and the resultant occlusal force, all of which are influenced by the occlusal relationship of upper and lower teeth [33]. The control mechanism of the nervous system is based on environmental neural data input. Every function of the masticatory system has a characteristic pattern that occurs within certain physiologic limits. Any overreaching from a physiologic limit can lead to a symptom of a particular problem. For example, any deviation in the opening (or closing) movement of the mandible is often the result of a muscle spasm that occurs during the opening movement. Limited mouth opening mouth (or S-shaped masticatory movement) is also an indication there is a problem within the stomatognathic system. Functional movements that designed by central nervous system (CNS) are outside of their physiologic limits. Many pathological conditions can also be produced by the central nervous system (CNS). If there is a strong but problematic feedback mechanism present in stomatognathic system, certain pathological conditions may increase in frequency and intensity, unless the pathology is not removed. Every type of nonphysiological

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movement has its own specific characteristics.

stomatognathic system pathology.

**3. Central nervous system and the stomatognathic system**

The neural system mechanics must be very well understood to ascertain the etiology of a

**Figure 2.** A resting EMG recording of the masseter and temporalis muscles. Note, there is slight electrical activity

providing tension to these muscles when holding the mandible in the rest position.

**Figure 1.** A normal mastication pattern in three planes as recorded by a Jaw Tracker (3-D Electrognathograph, BioResearch Assoc., Milwaukee, WI, USA). Excellent chewing ability evolves in the developing human from youth into the adult years. An ideal chewing pattern requires harmony between all the masticatory functional organs.

Nervous system mechanoreceptors in and around the teeth transmit neural information to the central nervous system (CNS) regarding the nature of the masticatory function. This neural feedback mechanism is designed to protect the physiologic borders of the chewing pattern and controls the masticatory system mechanics. Neural sensors collect all the necessary neural input during chewing function as it is a sensory process. However, the mandibular functional and parafunctional movements are controlled by the motor function of the neural system. The neuromuscular mechanism of stomatognathic system collects the neural input that controls mandibular motion [29, 30].

#### **2. Neuronal mechanism of masticatory system**

Myofascial pain dysfunction syndrome (MPDS) can be used as general definition for one type musculoskeletal human disease state that consists of specific muscular symptoms. In a patient with temporomandibular disorders, MPDS often results from the hypercontraction of the masticatory elevator muscles. Spasm of one or more elevator muscles is a serious problem, which may cause pain, muscle tenderness, limitation of mandibular movements, and induce changes in the temporomandibular joint structural alignment. Muscle spasm usually emanates through the central nervous system (CNS) from the neural mechanoreceptors located in and around the teeth that hypercontract the elevator muscles. Along with muscle spasm, painful trigger points can also be a component of the MPDS condition. Some trigger points may be classified as latent [5, 6, 31, 32], in that they only occur when a muscle is pressed upon.

The neuronal mechanism is a determining factor in the development of MPDS. The central nervous system (CNS) controls all activities of the masticatory system including the contraction of masticatory muscles, the sequence of contractions, the level of contraction, the posture of mandible, the mandibular movements, and the resultant occlusal force, all of which are influenced by the occlusal relationship of upper and lower teeth [33]. The control mechanism of the nervous system is based on environmental neural data input. Every function of the masticatory system has a characteristic pattern that occurs within certain physiologic limits. Any overreaching from a physiologic limit can lead to a symptom of a particular problem. For example, any deviation in the opening (or closing) movement of the mandible is often the result of a muscle spasm that occurs during the opening movement. Limited mouth opening mouth (or S-shaped masticatory movement) is also an indication there is a problem within the stomatognathic system. Functional movements that designed by central nervous system (CNS) are outside of their physiologic limits. Many pathological conditions can also be produced by the central nervous system (CNS). If there is a strong but problematic feedback mechanism present in stomatognathic system, certain pathological conditions may increase in frequency and intensity, unless the pathology is not removed. Every type of nonphysiological movement has its own specific characteristics.

## **3. Central nervous system and the stomatognathic system**

Nervous system mechanoreceptors in and around the teeth transmit neural information to the central nervous system (CNS) regarding the nature of the masticatory function. This neural feedback mechanism is designed to protect the physiologic borders of the chewing pattern and controls the masticatory system mechanics. Neural sensors collect all the necessary neural input during chewing function as it is a sensory process. However, the mandibular functional and parafunctional movements are controlled by the motor function of the neural system. The neuromuscular mechanism of stomatognathic system collects the neural input

**Figure 1.** A normal mastication pattern in three planes as recorded by a Jaw Tracker (3-D Electrognathograph, BioResearch Assoc., Milwaukee, WI, USA). Excellent chewing ability evolves in the developing human from youth into

the adult years. An ideal chewing pattern requires harmony between all the masticatory functional organs.

Myofascial pain dysfunction syndrome (MPDS) can be used as general definition for one type musculoskeletal human disease state that consists of specific muscular symptoms. In a patient with temporomandibular disorders, MPDS often results from the hypercontraction of the masticatory elevator muscles. Spasm of one or more elevator muscles is a serious problem, which may cause pain, muscle tenderness, limitation of mandibular movements, and induce changes in the temporomandibular joint structural alignment. Muscle spasm usually emanates through the central nervous system (CNS) from the neural mechanoreceptors located

that controls mandibular motion [29, 30].

**2. Neuronal mechanism of masticatory system**

20 Temporomandibular Joint Pathology - Current Approaches and Understanding

The neural system mechanics must be very well understood to ascertain the etiology of a stomatognathic system pathology.

**Figure 2.** A resting EMG recording of the masseter and temporalis muscles. Note, there is slight electrical activity providing tension to these muscles when holding the mandible in the rest position.

The stomatognathic system neural network is comprised of three basic parts:

Sensory input collection is an ongoing function of the neural system that can be conscious or unconscious. There is a continuous data stream entering the CNS from the peripheral nervous system (PNS), which gathers environmental data that send impulses to the masticatory muscle fibers to establish postural tonus activity. This occurs even when there is no function, such that there is a slight tension in the muscles when at rest (**Figure 2**).

Therefore, the electrical potential difference exists on both sides of the membrane. A change in the electrical activity within the cell membrane plays an important role in the character of

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All masticatory system functions are governed by the central nervous system (CNS). In order to coordinate what function occurs, and when, how much, and how it should occur physiologically, the CNS gathers information about the environment in which the function is to take place. There is a continuous flow of information between the sensory and motor neurons within the stomatognathic system and the central nervous system (CNS). Physiologically, proper oral functions like mastication, swallowing, and speaking need a rhythmic process whereby all parts of the masticatory system are coordinated so that the activity of the jaw muscles, the tongue, the cheeks, and the lips work synergistically to

For controlling and managing oral function, the central nervous system (CNS) must initially sense the environmental data. This data collection process is provided to the CNS by the mechano and sensory receptors of the peripheral nervous structures (PNS). Data collected from these receptors are transferred to the other levels of central nervous system (CNS). These receptors are specialized neurons for gathering the environmental sensory data related to the many sensorimotor functions, involving the coordinated contraction and inhibition of the musculature located around the mouth, at the tongue, larynx, pharynx, and esophagus bilaterally [34]. Moreover, according to the localization of the function, there are many differing types of receptors present in the mouth. The data received from receptors are transferred electrochemically to differing levels of the central nervous system (CNS). In this way, the peripheral neural control modulates the output of the central pattern generator and associated motor neurons, so that most effective occlusal forces are developed during chewing,

Transmission of the peripheral neural data is provided to the CNS by a neuron's axons and dendrites. Dendrites receive the potential from the previous neuron. If a nerve cell is stimulated, the transmembrane voltage is necessarily changed. The stimulation may be excitatory or inhibitory. If the membrane stimulus is insufficient to cause the transmembrane potential to reach the threshold, then the membrane will not activate. If the excitatory stimulus is strong enough, the transmembrane potential reaches the threshold, and the membrane produces a characteristic electric impulse, known as the *nerve impulse*. This is the basic principle of the

**6. Neural receptors in the stomatognathic area: the collection of**

**peripheral data and the neural response**

There are two basic neurologic components of mastication:

sensory conduction.

achieve correct function.

• the central pattern generator (and the)

without overly damaging the masticatory organs.

stimulus and transmission of a neuron.

• the peripheral control mechanisms

## **4. Neurons and myocites (muscle cells)**

The human body consists of billions of similarly constructed cells that contain the cytoplasm, a nucleus, some chromosomes, some mitochondria, and some ribosomes. But some cells are different from the ordinary cells, despite that they also have cytoplasm, a nucleus, and ribosomes, but also contain neurons. Neurons and muscle cells are an excitable type of cell because they can receive electrical impulses and transfer the environmental neurologic data biochemically. These special cells are known as inducible cells.

The functional unit of the motor system, the motor unit, is composed of a motor neuron and a group of muscle fibers with similar, if not identical, structural and functional properties. These are inducible cells known as neurons and myocites (muscle cell).

## **5. Membrane potential difference and the firing of a neuron**

There is a static electrical balance between the outside and inside of a cell membrane. This steady state is called the "resting membrane potential," which does not change unless there exists a stimulus. This steady-state electrical potential difference between the outside and inside of a cell membrane is between −50 mV and −100 mV. A stimulus changes this steady state to an action state, whereby the resting potential difference is turned into an action potential difference. The main cause of the potential difference results from the existence of anions and cations on both sides of the cell membrane. Outside the membrane are positively charged natrium cations. Positively charged natrium ions attach to negatively charged chlorine ions (Cl−) that are outside of the membrane. However, despite the presence of negative ions (such as chlorine and HCO3 ), the outer side of the membrane remains positively charged. Alternatively, the inside of the membrane is negatively charged because positively charged potassium (K+) ions diffuse "down" its steep concentration gradient to move out of a cell via leakage channels. This K+ ion movement to outside of the cell membrane makes the outside more positively charged than inside the cell membrane. Outside the positive ions side at the edge of the membrane, with the inside negative ions located at the inner edge of the membrane. Therefore, the electrical potential difference exists on both sides of the membrane. A change in the electrical activity within the cell membrane plays an important role in the character of sensory conduction.

## **6. Neural receptors in the stomatognathic area: the collection of peripheral data and the neural response**

All masticatory system functions are governed by the central nervous system (CNS). In order to coordinate what function occurs, and when, how much, and how it should occur physiologically, the CNS gathers information about the environment in which the function is to take place. There is a continuous flow of information between the sensory and motor neurons within the stomatognathic system and the central nervous system (CNS). Physiologically, proper oral functions like mastication, swallowing, and speaking need a rhythmic process whereby all parts of the masticatory system are coordinated so that the activity of the jaw muscles, the tongue, the cheeks, and the lips work synergistically to achieve correct function.

There are two basic neurologic components of mastication:

The stomatognathic system neural network is comprised of three basic parts:

22 Temporomandibular Joint Pathology - Current Approaches and Understanding

such that there is a slight tension in the muscles when at rest (**Figure 2**).

biochemically. These special cells are known as inducible cells.

These are inducible cells known as neurons and myocites (muscle cell).

**5. Membrane potential difference and the firing of a neuron**

**4. Neurons and myocites (muscle cells)**

ions (such as chlorine and HCO3

Sensory input collection is an ongoing function of the neural system that can be conscious or unconscious. There is a continuous data stream entering the CNS from the peripheral nervous system (PNS), which gathers environmental data that send impulses to the masticatory muscle fibers to establish postural tonus activity. This occurs even when there is no function,

The human body consists of billions of similarly constructed cells that contain the cytoplasm, a nucleus, some chromosomes, some mitochondria, and some ribosomes. But some cells are different from the ordinary cells, despite that they also have cytoplasm, a nucleus, and ribosomes, but also contain neurons. Neurons and muscle cells are an excitable type of cell because they can receive electrical impulses and transfer the environmental neurologic data

The functional unit of the motor system, the motor unit, is composed of a motor neuron and a group of muscle fibers with similar, if not identical, structural and functional properties.

There is a static electrical balance between the outside and inside of a cell membrane. This steady state is called the "resting membrane potential," which does not change unless there exists a stimulus. This steady-state electrical potential difference between the outside and inside of a cell membrane is between −50 mV and −100 mV. A stimulus changes this steady state to an action state, whereby the resting potential difference is turned into an action potential difference. The main cause of the potential difference results from the existence of anions and cations on both sides of the cell membrane. Outside the membrane are positively charged natrium cations. Positively charged natrium ions attach to negatively charged chlorine ions (Cl−) that are outside of the membrane. However, despite the presence of negative

Alternatively, the inside of the membrane is negatively charged because positively charged potassium (K+) ions diffuse "down" its steep concentration gradient to move out of a cell via leakage channels. This K+ ion movement to outside of the cell membrane makes the outside more positively charged than inside the cell membrane. Outside the positive ions side at the edge of the membrane, with the inside negative ions located at the inner edge of the membrane.

), the outer side of the membrane remains positively charged.

**1.** Perception of the sensory inputs. **2.** Evaluation of the gathered inputs.

**3.** Reaction to the inputs.

For controlling and managing oral function, the central nervous system (CNS) must initially sense the environmental data. This data collection process is provided to the CNS by the mechano and sensory receptors of the peripheral nervous structures (PNS). Data collected from these receptors are transferred to the other levels of central nervous system (CNS). These receptors are specialized neurons for gathering the environmental sensory data related to the many sensorimotor functions, involving the coordinated contraction and inhibition of the musculature located around the mouth, at the tongue, larynx, pharynx, and esophagus bilaterally [34]. Moreover, according to the localization of the function, there are many differing types of receptors present in the mouth. The data received from receptors are transferred electrochemically to differing levels of the central nervous system (CNS). In this way, the peripheral neural control modulates the output of the central pattern generator and associated motor neurons, so that most effective occlusal forces are developed during chewing, without overly damaging the masticatory organs.

Transmission of the peripheral neural data is provided to the CNS by a neuron's axons and dendrites. Dendrites receive the potential from the previous neuron. If a nerve cell is stimulated, the transmembrane voltage is necessarily changed. The stimulation may be excitatory or inhibitory. If the membrane stimulus is insufficient to cause the transmembrane potential to reach the threshold, then the membrane will not activate. If the excitatory stimulus is strong enough, the transmembrane potential reaches the threshold, and the membrane produces a characteristic electric impulse, known as the *nerve impulse*. This is the basic principle of the stimulus and transmission of a neuron.

**Figure 3.** A very tiny premature contact that is not removed for a long time will have a sufficient excitatory level for instigating a nerve impulse. When the total sum level of stimulus reaches the threshold level, an action potential can emerge. This is known as the All-or-None principle.

Touch sensory activity (Touch) is the critical neurologic control for the stomatognathic sys-

**Figure 4.** Spasm of the elevator muscles and limited maximum mouth opening of less than 25 mm indicates this women exhibits significant muscular dysfunction. This critical distance of healthy limited opening in men is 35–40 mm.

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• The transfer of the sensory response into the CNS and then back out to the muscles.

Mandibular functional movement sensory detection and the associated reflex responses are shaped by information gathered from the periodontal ligament mechanoreceptors in response to tooth compressions during chewing and from the temperature and touch receptors present in the pulp, the gingival tissues, and the mucobuccal tissues. One of the most important neural receptors is the pulpal mechanoreceptors, which together with periodontal mechanoreceptors carry tooth loading information to the CNS. These receptors transmit the intensity of force acting on a tooth as it contacts its opposing tooth counterpart, the changes of the force velocity at occlusal impact, a tooth's movement direction during chewing, and the hardness of the food bolus. Moreover, the periodontal ligaments are also extremely important structures because their mechanoreceptors within the PDL are highly concentrated [34–38]. Receptors in the periodontal ligaments control and guide all functional and parafunctional movements because they relay information about the magnitude of tooth loads, which is described by the

Several studies have indicated that the extracellular matrix collagens of the periodontal ligament have a high turnover and remodeling rate that are much higher than collagen turnover observed in the gingiva, skin, and bone [39]. The periodontal ligaments themselves are basically striated muscles with muscle spindles located within the fibers of the ligaments. These ligament fiber muscle spindles gather stretching and compression information when teeth are

Periodontal mechanoreceptors respond to the forces that are applied to teeth. They have been studied in histological and electrophysiological investigations that illustrated periodontal mechanoreceptors signal information about the degree of tooth loads because they have special

tem's functional and parafunctional movements. Neural receptors perform two important tasks:

mean firing rate response of loaded periodontal receptors [34].

under tooth movement within the PDL space.

• The gathering of sensory information

The membrane potential may reach the threshold by a short, strong stimulus, or by *a longer, weaker stimulus*. A very tiny premature contact that is not removed and is clinically present for a long time will have a sufficient excitatory level for starting a nerve impulse (**Figure 3**). This is the result of nerve cell's All-or-None principle. Premature contacts can lead to pain, which then leads to the formation of a stronger stimulus. The CNS sends a nociceptive warning to the muscles to move the mandible toward the opposite arch side as a reflex action to lessen the pain. If the premature contact on one side was not removed, spasm on the other side tends to persist. Aggregating stimuli will increase the spasms, which may be a major etiological cause of myofascial pain dysfunction syndrome [14] (**Figure 3**).

A sudden nociceptive stimulus can cause a special type escape reflex known as the "jaw jerk reflex." The jaw-jerk myotatic reflex is activated by the sudden stretching of the jaw-closing muscles spindles. The jaw jerk reflex is one of the most important neuronal patterns as it may or may not be nociceptive. The repetition of nociceptive stimuli that causes a reflex action early on during the development of dysfunction may after awhile cease to exist. This adaptation to the stimulus initiates the failure of the CNS to continue to respond to the stimulus.  This worsening can lead to reduced mandibular vertical opening (**Figure 4**).

Information from the peripheral nervous system (PNS) tissues outside the CNS is continuously transferred into the CNS onto higher centers in the brain stem and cortex for interpretation and evaluation. All human functional and parafunctional movements are based on five major sensory systems:

**Figure 4.** Spasm of the elevator muscles and limited maximum mouth opening of less than 25 mm indicates this women exhibits significant muscular dysfunction. This critical distance of healthy limited opening in men is 35–40 mm.

Touch sensory activity (Touch) is the critical neurologic control for the stomatognathic system's functional and parafunctional movements.

Neural receptors perform two important tasks:

• The gathering of sensory information

The membrane potential may reach the threshold by a short, strong stimulus, or by *a longer, weaker stimulus*. A very tiny premature contact that is not removed and is clinically present for a long time will have a sufficient excitatory level for starting a nerve impulse (**Figure 3**). This is the result of nerve cell's All-or-None principle. Premature contacts can lead to pain, which then leads to the formation of a stronger stimulus. The CNS sends a nociceptive warning to the muscles to move the mandible toward the opposite arch side as a reflex action to lessen the pain. If the premature contact on one side was not removed, spasm on the other side tends to persist. Aggregating stimuli will increase the spasms, which may be a major etiological cause

**Figure 3.** A very tiny premature contact that is not removed for a long time will have a sufficient excitatory level for instigating a nerve impulse. When the total sum level of stimulus reaches the threshold level, an action potential can

A sudden nociceptive stimulus can cause a special type escape reflex known as the "jaw jerk reflex." The jaw-jerk myotatic reflex is activated by the sudden stretching of the jaw-closing muscles spindles. The jaw jerk reflex is one of the most important neuronal patterns as it may or may not be nociceptive. The repetition of nociceptive stimuli that causes a reflex action early on during the development of dysfunction may after awhile cease to exist. This adaptation to the stimulus initiates the failure of the CNS to continue to respond to the stimulus.  This worsening can lead to reduced mandibular vertical opening (**Figure 4**). Information from the peripheral nervous system (PNS) tissues outside the CNS is continuously transferred into the CNS onto higher centers in the brain stem and cortex for interpretation and evaluation. All human functional and parafunctional movements are based on five

of myofascial pain dysfunction syndrome [14] (**Figure 3**).

24 Temporomandibular Joint Pathology - Current Approaches and Understanding

emerge. This is known as the All-or-None principle.

major sensory systems:

• Olfaction

• Taste • Vision • Hearing • Touch

• The transfer of the sensory response into the CNS and then back out to the muscles.

Mandibular functional movement sensory detection and the associated reflex responses are shaped by information gathered from the periodontal ligament mechanoreceptors in response to tooth compressions during chewing and from the temperature and touch receptors present in the pulp, the gingival tissues, and the mucobuccal tissues. One of the most important neural receptors is the pulpal mechanoreceptors, which together with periodontal mechanoreceptors carry tooth loading information to the CNS. These receptors transmit the intensity of force acting on a tooth as it contacts its opposing tooth counterpart, the changes of the force velocity at occlusal impact, a tooth's movement direction during chewing, and the hardness of the food bolus. Moreover, the periodontal ligaments are also extremely important structures because their mechanoreceptors within the PDL are highly concentrated [34–38]. Receptors in the periodontal ligaments control and guide all functional and parafunctional movements because they relay information about the magnitude of tooth loads, which is described by the mean firing rate response of loaded periodontal receptors [34].

Several studies have indicated that the extracellular matrix collagens of the periodontal ligament have a high turnover and remodeling rate that are much higher than collagen turnover observed in the gingiva, skin, and bone [39]. The periodontal ligaments themselves are basically striated muscles with muscle spindles located within the fibers of the ligaments. These ligament fiber muscle spindles gather stretching and compression information when teeth are under tooth movement within the PDL space.

Periodontal mechanoreceptors respond to the forces that are applied to teeth. They have been studied in histological and electrophysiological investigations that illustrated periodontal mechanoreceptors signal information about the degree of tooth loads because they have special force-encoding properties, which provides for functional control of human mastication. Microneurography recordings from single nerve fibers revealed that human periodontal receptors adapt slowly to maintained tooth loads. Most receptors are broadly tuned to the direction of force application, while about half respond to forces that are applied to more than one tooth at a time. Populations of periodontal receptors reliably encode information about both how the teeth are stimulated, and the direction that forces are applied to the individual teeth.

A protective reflex is not continuous because the reflex stimulus is defined in the memory, and after few cycles, it does not cause the repeated reflex. Development of the multicellular structures in the nervous system evolves a specialized apparatus that detects and reacts to external stimuli, when combined together with the evolution of specific transduction proteins, and enables the CNS to accurately differentiate between innocuous and noxious stimuli. This early warning system, which is further elaborated, develops the capacity to increase its sensitivity following an exposure to an injurious stimulus, which is known as nociceptive sensitization. In mammals, the early warning protective pain that occurs in response to noxious stimuli (nociceptive pain) is mediated by specialized, high-threshold primary sensory

Myofascial Pain Dysfunction Syndrome: Etiology, Diagnosis, and Treatment

http://dx.doi.org/10.5772/intechopen.72529

27

Pain management is one of the most important therapeutic interventions. Chronic pain is the main reason that patients seek out health care, while also being the most common reason for disability and addiction, and being the highest driver of health care costs. Most often, myopain conditions are the pain source. As such, it has been reported that in the United States, more than 100 million adults suffer from myofascial pain dysfunction syndrome. In dentistry, MPDS is defined as one type of masticatory system problem [32]. However, myofascial pain (MFP) is the most common cause of persistent regional back pain, headaches, and facial pain [10].

Myofascial pain is pain that arises from the muscles or the related fascia. The trigger point concept has been a widely studied aspect of myofascial pain dysfunction syndrome. Many hypotheses of how trigger points evolve are based on the opinions of experienced clinicians who treat and research trigger points. Trigger points are most often discussed as a component of myofascial pain syndromes where widespread or regional muscular pain is associated with hyperalgesia, psychological disturbance, and significant restriction of daily function [44]. Trigger points are 2–5 mm diameter points of increased hypersensitivity in palpable bands of the skeletal muscle, tendons, and ligaments with decreasing hypersensitivity as one palpates the band further away from the trigger point. As stated before, trigger points may be active or latent. An active trigger point causes spontaneous pain at rest, with an increase in pain on contraction or stretching of the involved muscle. There is often restricted muscular range of motion. Any pain on motion may cause "pseudo-muscle weakness" due to pin reflex inhibition. A latent trigger point is a focal area of tenderness and tightness in a muscle that does not result in spontaneous pain, but must be palpated to elicit the pain. However, a latent trigger

point may restrict the range of motion and result in weakness of the muscle involved.

been previously described by R. Bennett as follows [5]:

**4.** A restricted range of motion in the muscle involved,

**2.** Patient complaint from trigger point palpation,

approximately 5 s in duration.

**1.** A focal point of tenderness to palpation of the muscle involved,

**5.** Pain is accompanied by pseudo-weakness of the muscle involved,

**3.** Palpation reveals an induration of the adjacent muscle (the "taut band"),

The characteristic symptoms of a myofascial pain dysfunction syndrome trigger points have

**6.** Referred pain can result with continuous applied pressure on the trigger point that lasts

neurons (nociceptors) [43].

Another important receptor type is "periodontal ligament integrins" [40], which are cell-surface receptors that connect cells to the collagen-rich and mechanically stressed periodontal ligament microenvironment. Mutations in integrin subunits have been found to cause clinical disorders in man that correlate well with mice, in which the same integrins are deleted [40]. Integrins are able to transduce signals intracellularly following ligand binding ("outsidein" signaling). However, unlike most other cell receptors, integrins can shift between highand low-affinity conformations for ligand binding, whereby the signal direction is reversed ("inside-out" signaling). Depending on the cell type, integrins can be either basally activated, as is the case with most adherent cells that are attached to a basement membrane, or they can be basally inactive, like platelets or leukocytes that freely circulate until activated to undergo platelet aggregation or mediate an inflammatory response [41].

Ultimately, all the collected load data from the pulp, the periodontal ligament receptors, and the mucosa are transmitted to the CNS via the trigeminal nerve (V) ganglions. Ganglions are the neurologic distribution center for both the afferent and efferent neural pathways.

Basically, there are two important ganglions involved in craniofacial area with neuroanatomic ties to the stomatognathic system:

#### **6.1. Pain: an alarm system for protection of the body**

Living organisms need to be able to sense their immediate environment if they are to withdraw from or avoid potentially hazardous situations.  Sudden, strange matter that is perceived during chewing leads to the formation of this reflex. However, shortly after the identification of a hard substance, the central nervous system (CNS) reduces the reflex level to normal levels. Sometimes, the jaw jerk reflex may occur as a nociceptive reaction. For example, touching the pulp meter to the tooth surface can lead to a typical jaw jerk reflex.

Reflexes are involuntary and relatively stereotyped responses to specific stimuli. Stimulated receptors send afferent impulses to the central nervous system (CNS), which are then transmitted through efferent nerve fibers to the cells, muscles, and organs that carry out the *reflex response*. The entire pathway is known as the *reflex arc* [42]. The afferent impulses generated at the receptors are conveyed via fast-twitch Ia fibers to the spinal alpha motor neuron. Their α<sup>1</sup> process impulses excite the agonistic muscle of an opposing muscle pair. Despite the monosynaptic nature of intrinsic reflexes, extrinsic reflexes are polysynaptic, where there are both afferent and efferent arms within the chain of spinal interneurons.

A protective reflex is not continuous because the reflex stimulus is defined in the memory, and after few cycles, it does not cause the repeated reflex. Development of the multicellular structures in the nervous system evolves a specialized apparatus that detects and reacts to external stimuli, when combined together with the evolution of specific transduction proteins, and enables the CNS to accurately differentiate between innocuous and noxious stimuli. This early warning system, which is further elaborated, develops the capacity to increase its sensitivity following an exposure to an injurious stimulus, which is known as nociceptive sensitization. In mammals, the early warning protective pain that occurs in response to noxious stimuli (nociceptive pain) is mediated by specialized, high-threshold primary sensory neurons (nociceptors) [43].

Pain management is one of the most important therapeutic interventions. Chronic pain is the main reason that patients seek out health care, while also being the most common reason for disability and addiction, and being the highest driver of health care costs. Most often, myopain conditions are the pain source. As such, it has been reported that in the United States, more than 100 million adults suffer from myofascial pain dysfunction syndrome. In dentistry, MPDS is defined as one type of masticatory system problem [32]. However, myofascial pain (MFP) is the most common cause of persistent regional back pain, headaches, and facial pain [10].

Myofascial pain is pain that arises from the muscles or the related fascia. The trigger point concept has been a widely studied aspect of myofascial pain dysfunction syndrome. Many hypotheses of how trigger points evolve are based on the opinions of experienced clinicians who treat and research trigger points. Trigger points are most often discussed as a component of myofascial pain syndromes where widespread or regional muscular pain is associated with hyperalgesia, psychological disturbance, and significant restriction of daily function [44]. Trigger points are 2–5 mm diameter points of increased hypersensitivity in palpable bands of the skeletal muscle, tendons, and ligaments with decreasing hypersensitivity as one palpates the band further away from the trigger point. As stated before, trigger points may be active or latent. An active trigger point causes spontaneous pain at rest, with an increase in pain on contraction or stretching of the involved muscle. There is often restricted muscular range of motion. Any pain on motion may cause "pseudo-muscle weakness" due to pin reflex inhibition. A latent trigger point is a focal area of tenderness and tightness in a muscle that does not result in spontaneous pain, but must be palpated to elicit the pain. However, a latent trigger point may restrict the range of motion and result in weakness of the muscle involved.

The characteristic symptoms of a myofascial pain dysfunction syndrome trigger points have been previously described by R. Bennett as follows [5]:

force-encoding properties, which provides for functional control of human mastication. Microneurography recordings from single nerve fibers revealed that human periodontal receptors adapt slowly to maintained tooth loads. Most receptors are broadly tuned to the direction of force application, while about half respond to forces that are applied to more than one tooth at a time. Populations of periodontal receptors reliably encode information about both how the

Another important receptor type is "periodontal ligament integrins" [40], which are cell-surface receptors that connect cells to the collagen-rich and mechanically stressed periodontal ligament microenvironment. Mutations in integrin subunits have been found to cause clinical disorders in man that correlate well with mice, in which the same integrins are deleted [40]. Integrins are able to transduce signals intracellularly following ligand binding ("outsidein" signaling). However, unlike most other cell receptors, integrins can shift between highand low-affinity conformations for ligand binding, whereby the signal direction is reversed ("inside-out" signaling). Depending on the cell type, integrins can be either basally activated, as is the case with most adherent cells that are attached to a basement membrane, or they can be basally inactive, like platelets or leukocytes that freely circulate until activated to undergo

Ultimately, all the collected load data from the pulp, the periodontal ligament receptors, and the mucosa are transmitted to the CNS via the trigeminal nerve (V) ganglions. Ganglions are

Basically, there are two important ganglions involved in craniofacial area with neuroana-

Living organisms need to be able to sense their immediate environment if they are to withdraw from or avoid potentially hazardous situations.  Sudden, strange matter that is perceived during chewing leads to the formation of this reflex. However, shortly after the identification of a hard substance, the central nervous system (CNS) reduces the reflex level to normal levels. Sometimes, the jaw jerk reflex may occur as a nociceptive reaction. For example, touching the

Reflexes are involuntary and relatively stereotyped responses to specific stimuli. Stimulated receptors send afferent impulses to the central nervous system (CNS), which are then transmitted through efferent nerve fibers to the cells, muscles, and organs that carry out the *reflex response*. The entire pathway is known as the *reflex arc* [42]. The afferent impulses generated at the receptors are conveyed via fast-twitch Ia fibers to the spinal alpha motor neuron. Their α<sup>1</sup> process impulses excite the agonistic muscle of an opposing muscle pair. Despite the monosynaptic nature of intrinsic reflexes, extrinsic reflexes are polysynaptic, where there are both

the neurologic distribution center for both the afferent and efferent neural pathways.