jaw abnormality jaw abnormality a jaw abnormality is a disorder in the formation, shape and/or size of the jaw. in general abnormalities arise within the jaw when there is a disturbance or fault in the fusion of the mandibular processes. the mandible in particular has the most differential typical growth anomalies than any other bone in the human skeleton. this is due to variants in the complex symmetrical growth pattern which formulates the mandible. jaw abnormalityspecialtyoral & maxillofacial surgery the mandible in particular plays a significant role in appearance as it is the only moving part of the facial skeleton. this has a large impact upon an individual's ability to speak, masticate and also influence their overall aesthetic and expressive features of the face. in turn the maxilla faces the same issues if any abnormalities in size or position were to occur. the obvious functional disabilities that arise from jaw abnormalities are very much physically seen as previously stated, but when considering these individuals it must be kept in mind that these conditions may well affect them psychologically; making them feel as though they are handicapped. it is also of the utmost importance when correcting these mandibular anomalies that the teeth result in a good occlusion with the opposing dentition of the maxilla. if this is not done satisfactorily occlusal instability may be created leading to a plethora of other issues. in order to correct mandibular anomalies it is common for a complex treatment plan which would involve surgical intervention and orthodontic input. signs and symptoms individuals with jaw abnormalities have both functional and aesthetic impairment. misalignment of teeth creates difficulties in head and neck functions related to chewing, swallowing, breathing, speech articulation and lip closure/posture. affected individuals may also experience tmj pain and dysfunction, which negatively affect the quality of life. a proportion of affected individuals also have psychological problems. diagnosis diagnosis of a jaw deformity is a structured process, linking the undertaking of a history, physical examination of the patient, and appraisal of diagnostic studies. this process may involve more than a single discipline of dentistry – in addition to orthodontic and surgical needs, some patients may also require periodontal, endodontic, complex restorative, and prosthetic considerations. it involves the chief presenting complaint of the patient, which allows the clinician to understand the patient's perception of the problem – what they think the problem is and what they would like corrected. the patient may find eating difficult or may have problems with speech or the appearance of the teeth or face. however, patients may be hesitant to discuss dissatisfaction with their appearance because they may feel that it is more acceptable to present a functional problem to the clinician. for this reason it is important to reassure patients that their aesthetic problems and the effects of these are perfectly valid concerns. in children, psychological development can be affected due to teasing if they have abnormal appearance of teeth or face. correction of the abnormality can be extremely beneficial to the patient. the benefits can manifest themselves in many ways including improved peer relationships and social confidence. motivation on the patient's part is necessary if they are going to undergo lengthy orthodontic treatment and major surgery. in addition, they need to be well informed so that they may give valid consent. in terms of history, the family history and perhaps obstetric history may be relevant, especially when features of a syndrome are present.: 200 a medical and dental history is obtained for completeness. the medical history includes questions on the general health of the patient, to assess contraindications to treatment of jaw abnormality. special emphasis is placed on diseases and medication which cause altered metabolism, that may affect growth and tissue reactions. allergies are checked (specifically nickel allergies), so that treatment appliances with nickel-containing materials like stainless steel can be replaced with other materials to avoid the risk of allergic reactions. questions on family history are also relevant, as malocclusions, growth and development may be expressions of genetic patterns. the dental history investigates if the patient has had any previous dental trauma, or past dental experiences, which can serve as a gauge to patient compliance with treatment. examination the assessment of facial form includes the evaluation of facial soft tissue and dentition. as the human skeleton is not visibly perceptible, bone deformity is inferred and evaluated by facial appearance and dentition. to obtain a 3d assessment of the patient, the skeletal pattern must be measured in different planes: anterior-posterior, vertical, and transverse. this allows for an accurate assessment of the size, position, orientation, shape, and symmetry of the jaws. the anterior-posterior skeletal pattern measures the relationship of the lower jaw to the upper jaw. this is judged with the patient seated upright, head in a neutral horizontal position, and teeth in gentle occlusion. it can be classified into the following classes: class i: the ideal relationship whereby the upper jaw lies 2-4mm in front of the lower jaw class ii: upper jaw lies more than 4mm in front of the lower jaw class iii: upper jaw lies less than 2mm in front of the lower jaw, or in more severe cases, the lower jaw may be in front of the upper jaw. the vertical dimension can be measured by facial thirds, with ideal facial aesthetics showing equality between each vertical third. the face is divided into thirds – hairline to glabella; glabella to subnasale; and subnasale to the lowest part of the chin. two other clinical indicators can be assessed when analysing vertical dimensions, namely the frankfort mandibular planes angle (fmpa) and the lower facial height (lfh) – both of which are each recorded as either average, increased, or decreased. fmpa: this is estimated by the point of intersection between the lower border of the mandible and the frankfort horizontal plane. lfh: the face is divided into thirds, and the proportion of the lower third of the face is compared to the rest. the transverse relationship is a measure of jaw or facial asymmetry. it checks for the alignment of the soft tissue nasion, the middle part of the upper lip at the vermillion border, and the chin point. if present, it is necessary to distinguish between a false and true asymmetry. a false asymmetry arises due to occlusal interferences, which results in a lateral displacement of the mandible, producing a cross-bite in the anterior/buccal region. elimination of the displacement will return the mandible to a centric position. on the other hand, a true asymmetry indicates unequal facial growth on the left or right side of the jaws. elimination of any occlusal cross-bites is not only difficult, but unlikely to improve the facial asymmetry. the assessment of the transverse components of the facial width is best described by the "rule of fifths", which sagittally divides the face into five equal parts: each transverse fifth should be an eye distance in width. the middle fifth is marked by the inner canthus of both eyes. the medial three-fifths of the face is marked from the outer canthus of the eye frames the outer two-fifths of the face is measured from the lateral canthus to lateral helix of the ear, which represents the width of the ears. tests it is insufficient to derive at a diagnosis of jaw deformity solely based on the clinical examination. hence, additional information is gathered from diagnostic tests, which may include dental model analyses and radiographic imaging studies. dental model analyses - study models for analysis can be made by taking dental impressions, or by 3d intra-oral scanning. they allow for the appraisal of shape and size of jaws and teeth. this can be valuable for the long-term evaluation of development and for the follow up of treatment results. depending on the type of jaw abnormality, a face bow record for transfer on to the articulator, can sometimes be appropriate for the patient. radiographs - radiographic investigations should be based on individual needs and used in conjunction to the clinical examination. as with all other dental radiographs, the benefit gained for the patient with the radiograph must be weighed against the radiation dosage of taking it. in the assessment of jaw abnormalities, the most common radiographs taken used to be the dental panoramic tomography and lateral cephalometry. with the advancement in technology, the use of 3d imaging e.g. cone beam computed tomography (cbct) has gained popularity for the use of radiographic examinations of facial bones for purpose of planning complex orthognathic surgery, especially involving significant facial asymmetry. a 3d facial construction model can be utilised in more complex malocclusion to help plan management. classification size micrognathia mandibular micrognathia is the condition when lower jaw is smaller than normal. failure of the ramus to develop will give rise to micrognathia. micrognathia can be classified as either congenital or acquired. clinical appearance of some patients with congenital type of mandibular micrognathia can have a severe retrusion of the chin but by actual measurements, the mandible maybe be found to be within the normal limits of variation. this maybe because a posterior placing of the condylar head with regard to the skull or to a steep mandibular angle resulting in an evident jaw retrusion. the acquired type of micrognathia occurs after birth and usually is an effect of a disturbance to temporomandibular joint. growth of mandible depends on the normally developing condyles and the muscle function for example, trauma or infection that affect mastoid, middle ear or the joint will result in ankylosis of temporomandibular joint leading to mandibular micrognathia. macronagthia macronagthia is a condition of abnormally large jaws. the jaw size is usually proportion to the increase in skeleton size. it is usually due to excessive growth of the mandible and can have features including reverse maxillary to mandibular relationship, reverse overjet or absence of overbite. it can also be clinically presented when the glenoid fossa and condylar head is more anteriorly placed, causing mandibular prognathism. macronagthism can be associated with other medical conditions :- 1. paget's disease where there is overgrowth of the maxilla, cranium and mandible 2. acromegaly, an endocrine disease, can present with enlargement of bones with growth potential such as the mandible, thickened soft tissues and facial features and spade-like hands macrogenia or microgenia macrogenia and microgenia occur when there is a normal skeletal relationship but the chin, skeletal and soft tissue components, failed to develop in proportion to the skeletal base, resulting in marked protrusive (macrogenia) or retrusive (microgenia) facial profile. microgenia can be presented when there is inadequate bone depth at the apex of lower anteriors or the base of mandible and vice versa. position transverse a transverse jaw position is known as laterognathia. this term describes a lateral bite in the lower jaw and is often associated with a unilateral crossbite at an early age this can lead to bone development of an asymmetrical mandibular ramus resulting in asymmetry in the whole of the lower face. treatment of laterognathism is either possible with orthodontic tooth movement or a surgical relocation of the lower jaw. vertical one of the ways in which a jaw can develop abnormally is in the vertical dimension. abnormal growth can occur in the maxilla and the mandible. the jaw is usually loosely used to refer to the mandible (considered the lower jaw). however, the maxilla is also a jaw and should thus be referred to in this respect as well. the vertical jaw abnormalities relating to the mandible are in relation to excessive vertical growth and excessive horizontal growth, measured by the maxillary-mandibular plane angle (mmpa). the vertical jaw abnormalities relating to the maxilla are in relation to excessive downward displacement (edd) and insufficient downward displacement (idd). these terms used to previously be known as vertical maxillary excess and deficiency. this nomenclature changed because excess and deficiency typically refer to size. whereas when assessing this clinically, one would measure the distance between the central incisors and the upper lip, which, in fact, denotes position rather than size. therefore, in order to ‘harmonize with geometry’, edd and idd are now used widely. vertical and horizontal mandibular excess: simply put, excessive vertical growth is the term used for when the mandible is considered ‘too far down. whereas in excessive horizontal growth the opposite applies, where the mandible is growing