Temporomandibular joint osteoarthrosis. Correlation of clinical and arthroscopic findings with degree of molar support

[Case report of an osteoarthritic temporomandibular joint patient whose posterior open bite was successfully restored by occlusal bonding method]

PATIENT

The patient was a 50-year-old woman who complained of left temporomandibular joint pain during mastication and wide mouth opening. The diagnosis of this patient was bilateral osteoarthritis in temporomandibular joint; therefore maxillary full-arch stabilization appliance (SA) was delivered. In response, the TMD signs and symptoms were alleviated. However she subsequently complained of dysfunction of mastication due to anterior and posterior open bite. Sometime thereafter, after applying SA and provisional adhesion onlay, occlusal reconstruction was performed by means of porcelain direct-bonding onlay.

DISCUSSION

After 6 years follow-up, there were no failure finding on the porcelain direct-bonding onlay, no occlusal alteration, and no complaint of TMD signs and symptoms.

CONCLUSION

This direct-bonding adhesion prosthetic approach contributed not only to prevent aggravation of osteoarthritis but also to elevate QOL of this patient.

Disc derangements of the temporomandibular joint

Disc-related derangement of the temporomandibular joint is common and epidemiological research has found that about 20% of the population may be affected. Although very few of these people have the more prominent symptoms, recent data indicate that the numbers who need treatment is increasing. The two clinical variants of disc derangement, reciprocal clicking and closed lock, have long been recognized, but the association between them and their aetiology and pathogenesis is still unclear. As a consequence, there is still uncertainty on how to treat the conditions, and this is even more evident when surgery is involved. This paper describes new tissue research related to disc derangement. A simplified scheme is presented and implications for surgical treatment are discussed.

Anatomical modifications of the temporomandibular joint during ageing

It is essential to know the normal and pathological changes of ageing in the temporomandibular joint (TMJ) because of the frequency of pathology in this joint and the increased duration of life in current populations. A study was done on 70 TMJs harvested from 35 subjects older than 75 years. These joints were studied macroscopically, radiologically and histologically. Degenerative pathology of the TMJ affected more than 50% of the subjects studied and the disc was perforated in 7%. Ageing of the TMJ without any degenerative pathology is marked by radiographic signs which are not specific to the TMJ (cortical thinning, demineralisation). Histologically, amyloid degeneration was present in nearly 50% of TMJs studied.

Occlusal and TMJ loads in subjects with experimentally shortened dental arches

To determine whether shortened dental arches (SDAs) cause functional overloading of the teeth and the temporomandibular joints, which has been implicated in periodontal diseases and temporomandibular disorders, we investigated the influences of SDA on occlusal and joint loads. Bite force and masticatory muscle electromyograms were recorded in five dentate subjects who clenched maximally on intra-oral appliances, creating symmetrical SDAs experimentally. Muscular forces estimated from the recorded electromyograms were fed into a finite element jaw model for calculating bite forces and joint loads. Comparison between the measured and the calculated bite forces ensured that the joint loads were representative. The bite force on each tooth increased with missing molar occlusions, while joint loads decreased. The bite force per root surface area was always greatest on the most posterior tooth, and these values were most constant. The findings provide no evidence that SDA causes overloading of the joints and the teeth, which suggests that neuromuscular regulatory systems are controlling maximum clenching strength under various occlusal conditions.

Factors affecting degeneration in human temporomandibular joints as assessed histologically

The influence of sex, age, tooth loss, and articular disc position on temporomandibular joint (TMJ) degeneration was evaluated in specimens collected at autopsy from 15 women and 38 men ranging in age from 15 to 92 yr. The position of the articular discs was classified as normal or abnormal, tooth loss was both counted and categorized. Degenerative changes of the articular tissues were assessed histologically and quantified, taking into account both the severity of structural alterations and their extension along the articular surface. This was recorded separately in the condyle, disc, and temporal component, three latero-medial joint regions, and putative load-bearing and non-load-bearing surfaces. Analysis of covariance with repeated measures served for testing contributing factors. It showed that the effects of sex and the number of missing teeth were insignificant, whereas age up to about 55-60 yr and reduction of dental arch length proved to be the most important factors. Load-bearing seemed to play a significant role mainly at younger ages, and the effect of disc position was significant, when internal derangement was combined with reduction of dental arch length. Thus, rising severity of TMJ degenerative changes appears to be associated primarily with increasing age. In addition, it may also depend on mechanical factors, in particular loss of molar support and, to a minor degree, abnormal disc position.

Need for occlusal therapy and prosthodontic treatment in the management of temporomandibular disorders. Part II: Tooth loss and prosthodontic treatment

The second part of this review, evaluating the literature on the relationship between dental occlusion and temporomandibular disorders (TMDs), focuses on the aetiological importance of tooth loss and the place of prosthodontic replacement in the treatment of TMD. Loss of teeth and lack of posterior occlusal support seem to have little influence on the development of TMD, which calls into question the use of prosthodontic restoration as prevention or treatment for TMD. In addition, there are practically no studies assessing the benefit of instrumental analysis in diagnosis or comparing the outcome of prosthodontic treatment with simple reversible methods in the management of TMD. There is a trend in the current literature to abandon any treatment, including positioning appliances and prosthodontic measures, to 'recapture the disk' in patients with disk displacements because of the favourable, long-term results achieved after using more simple methods. It is concluded that prosthetic therapy in TMD patients is not appropriate for initial TMD treatment and should only be carried out on prosthodontic indications after reversible treatment has alleviated pain and dysfunction.

The shortened dental arch concept and its implications for oral health care

The minimum number of teeth needed to satisfy functional demands has been the subject of several studies. However, since functional demands--and consequently the number of teeth needed--can vary from individual to individual, this minimum number cannot be defined exactly. In general, occlusion of a complete dental arch is preferable. However, this goal might be neither attainable, for general, dental or financial reasons, nor necessary. Many studies demonstrate that shortened dental arches comprising the anterior and premolar regions can meet the requirements of a functional dentition. Consequently, when priorities have to be set, restorative therapy should be aimed at preserving the most strategic parts of the dental arch: the anterior and premolar regions. This also implies that in cases of a shortened dental arch, the prompt replacement of absent posterior molars by free-end removable partial dentures leads to overtreatment and discomfort. The shortened dental arch concept is based on circumstantial evidence: it does not contradict current theories of occlusion and fits well with a problem-solving approach. The concept offers some important advantages and may be considered a strategy to reduce the need for complex restorative treatment in the posterior regions of the mouth.