with larger sample sizes are needed. there is some evidence that some people who use nighttime biofeedback to reduce nighttime clenching experience a reduction in tmd. occlusal adjustment this is the adjustment or reorganizing of the existing occlusion, carried out in the belief that this will redistribute forces evenly across the dental arches or achieve a more favorable position of the condyles in the fossae, which is purported to lessen tooth wear, bruxism and tmd, but this is controversial. these techniques are sometimes termed "occlusal rehabilitation" or "occlusal equilibration". at its simplest, an occlusal adjustment involves selective grinding (with a dental drill) of the enamel of the occlusal surfaces of teeth, with the aim of allowing the upper teeth to fit with the lower teeth in a more harmonious way. however, there is much disagreement between proponents of these techniques on most of the aspects involved, including the indications and the exact goals. occlusal adjustment can also be very complex, involving orthodontics, restorative dentistry or even orthognathic surgery. some have criticized these occlusal reorganizations as having no evidence base, and irreversibly damaging the dentition on top of the damage already caused by bruxism. a "middle ground" view of these techniques is that occlusal adjustment in most cases of tmd is neither desirable nor helpful as a first-line treatment, and furthermore, with few exceptions, any adjustments should be reversible. however, most dentists consider this unnecessary overtreatment, with no evidence of benefit. specifically, orthodontics and orthognathic surgery are not considered by most to be appropriate treatments for tmd. a systematic review investigating all the scientific studies carried out on occlusal adjustments in tmd concluded the following: "there is an absence of evidence of effectiveness for occlusal adjustment. based on these data occlusal adjustment cannot be recommended for the treatment or prevention of tmd. these conclusions were based largely on the fact that, despite many different scientific studies investigating this measure as a therapy, overall no statistically significant differences can be demonstrated between treatment with occlusal adjustment and treatment with placebo. the reviewers also stated that there are ethical implications if occlusal adjustment was found to be ineffective in preventing tmd. orthodontic treatment, as described earlier, is sometimes listed as a possible predisposing factor in the development of tmd. on the other hand, orthodontic treatment is also often carried out in the belief that it may treat or prevent tmd. another systematic review investigating the relationship between orthodontics and tmd concluded the following: "there is no evidence to support or refute the use of orthodontic treatment for the treatment of tmd. in addition, there are no data which identify a link between active orthodontic intervention and the causation of tmd. based on the lack of data, orthodontic treatment cannot be recommended for the treatment or prevention of tmd." a common scenario where a newly placed dental restoration (e.g. a crown or a filling) is incorrectly contoured, and creates a premature contact in the bite. this may localize all the force of the bite onto one tooth, and cause inflammation of the periodontal ligament and reversible increase in tooth mobility. the tooth may become tender to bite on. here, the "occlusal adjustment" has already taken place inadvertently, and the adjustment aims to return to the pre-existing occlusion. this should be distinguished from attempts to deliberately reorganize the native occlusion. surgery main article: surgery for temporomandibular joint dysfunction attempts in the last decade to develop surgical treatments based on mri and cat scans now receive less attention. these techniques are reserved for the most difficult cases where other therapeutic modalities have failed. the american society of maxillofacial surgeons recommends a conservative/non-surgical approach first. only 20% of patients need to proceed to surgery. examples of surgical procedures that are used in tmd, some more commonly than others, include arthrocentesis arthroscopy, meniscectomy, disc repositioning, condylotomy or joint replacement. invasive surgical procedures in tmd may cause symptoms to worsen. meniscectomy, also termed discectomy refers to surgical removal of the articular disc. this is rarely carried out in tmd, it may have some benefits for pain, but dysfunction may persist and overall it leads to degeneration or remodeling of the tmj. acupuncture acupuncture is sometimes used for tmd. there is limited evidence that acupuncture is an effective symptomatic treatment for tmd. a short-term reduction in muscular pain of muscular origin can usually be observed after acupuncture in tmd, and this is more than is seen with placebo. there are no reported adverse events of acupuncture when used for tmd, and some suggest that acupuncture is best employed as an adjuvant to other treatments in tmd. however, some suggest that acupuncture may be no more effective than sham acupuncture, that many of the studies investigating acupuncture and tmd have significant risk of bias, and that the long term efficacy of acupuncture for tmd is unknown. chiropractic chiropractic adjustments (also termed manipulations or mobilizations) are sometimes used in the belief that this will treat tmd. related conditions that are also claimed to be treatable by chiropractic include tension headaches and neck pain. some sources suggest that there is some evidence of efficacy of chiropractic treatment in tmd, but the sources cited for these statements were case reports and a case series of only 9 participants. one review concluded "inconclusive evidence in a favorable direction regarding mobilization and massage for tmd". overall, although there is general agreement that chiropractic may be of comparable benefit to other manual therapies for lower back pain, there is no credible evidence of efficacy in other conditions, including tmd. however, there is some evidence of possible adverse effects from cervical (neck) vertebral manipulation, which sometimes may be serious. prognosis it has been suggested that the natural history of tmd is benign and self-limiting, with symptoms slowly improving and resolving over time. the prognosis is therefore good. however, the persistent pain symptoms, psychological discomfort, physical disability and functional limitations may detriment quality of life. it has been suggested that tmd does not cause permanent damage and does not progress to arthritis in later life,: 174–175 however, degenerative disorders of the tmj such as osteoarthritis are included within the spectrum of tmds in some classifications. epidemiology tmd mostly affects people in the 20 – 40 age group, and the average age is 33.9 years. people with tmd tend to be younger adults, who are otherwise healthy. within the catchall umbrella of tmd, there are peaks for disc displacements at age 30, and for inflammatory-degenerative joint disorders at age 50. about 75% of the general population may have at least one abnormal sign associated with the tmj (e.g. clicking), and about 33% have at least one symptom of tmd. however, only in 3.6–7% will this be of sufficient severity to trigger the individual to seek medical advice. for unknown reasons, females are more likely to be affected than males, in a ratio of about 2:1, although others report this ratio to be as high as 9:1. females are more likely to request treatment for tmd, and their symptoms are less likely to resolve. females with tmd are more likely to be nulliparous than females without tmd. it has also been reported that female caucasians are more likely to be affected by tmd, and at an earlier age, than female african americans. according to the most recent analyses of epidemiologic data using the rdc/tmd diagnostic criteria, of all tmd cases, group i (muscle disorders) accounts for 45.3%, group ii (disc displacements) 41.1%, and group iii (joint disorders) 30.1% (individuals may have diagnoses from more than one group). using the rdc/tmd criteria, tmd has a prevalence in the general population of 9.7% for group i, 11.4% for group iia, and 2.6% for group iiia. history temporomandibular disorders were described as early as ancient egypt. an older name for the condition is "costen's syndrome", eponymously referring to james b. costen. costen was an otolaryngologist, and although he was not the first physician to describe tmd, he wrote extensively on the topic, starting in 1934, and was the first to approach the disorder in an integrated and systematic way. costen hypothesized that malocclusion caused tmd, and placed emphasis on ear symptoms, such as tinnitus, otaglia, impaired hearing, and even dizziness. specifically, costen believed that the cause of tmd was mandibular over-closure, recommending a treatment revolving around building up the bite. the eponym "costen syndrome" became commonly used shortly after his initial work, but in modern times it has been dropped, partially because occlusal factors are now thought to play little, if any, role in the development of tmd, and also because ear problems are now thought to be less associated with tmd. other historically important terms that were used for tmd include "tmj disease" or "tmj syndrome", which are now rarely used.