Occlusal contact area and temporomandibular joint symptoms

Influence of filler loading on the two-body wear of a dental composite

The purpose of the study was to explore the fundamental wear behaviour of a dental composite with different filler loadings under two-body wear conditions. The parent resin and filler components were mixed according to different weight ratios to produce experimental composites with filler loadings ranging from 20 to 87.5% by weight. A two-body wear test was conducted on the experimental composites using a wear-testing machine. The machine was designed to simulate the impact of the direct cyclic masticatory loading that occurs in the occlusal contact area in vivo. The results showed that there was little increase in the rate of wear with filler loadings below 60 wt%, but a sharp increase between 80 and 87.5 wt% in filler loading. Wide striations and bulk loss of material were apparent on the wear surfaces at higher filler loadings. Coefficients of friction increased with filler loading and followed the increase in rate of wear loss closely. It was concluded that, under two-body wear conditions, addition of high levels of filler particles into the resin matrix could reduce the wear resistance of dental composites. This finding may help when designing future dental composites for use in particular clinical settings.

Unilateral temporomandibular disorder and asymmetry of occlusal contacts

STATEMENT OF PROBLEM

The relationship between temporomandibular disorders and occlusal tooth contacts is unclear and controversial.

PURPOSE

This study assessed whether unilateral temporomandibular disorders were associated with the absence of bilateral symmetry in the number of occlusal contacts.

MATERIAL AND METHODS

Fifteen university dental students who had complete natural dentition and normal occlusion and exhibited unilateral signs and symptoms of temporomandibular disorders were compared to 15 age- and sex-matched healthy control subjects. All participants met specific inclusion and exclusion criteria. Occlusal contacts were recorded in the intercuspal position with wax registrations. Dental impressions were made and poured in type I stone. Contacts were classified according to location and intensity. Four experienced dentists using an established protocol made all measurements. Assessment of the reliability of the occlusal registration procedure showed a small (<4%) within-subject variability. Statistical analysis was based on the binomial distribution and nonparametric tests (P < .05).

RESULTS

Subjects with unilateral temporomandibular disorders had greater bilateral difference in the number of contacts than controls. The median (95% confidence interval) difference was 3 (2 to 4) and 2 (1 to 2), respectively. In unilateral temporomandibular disorder subjects, the number of occlusal contacts was greater on the side with, rather than without, disorder (median number 20 vs. 16). The median (95% confidence interval) difference between sides with and without unilateral temporomandibular disorders was 3 (2 to 4) for all contacts and 2 (1 to 3) for contacts on the posterior teeth.

CONCLUSION

Within the population of this study, a weak association was found between unilateral temporomandibular disorders and asymmetry in the number of occlusal contacts.

Facial pain and temporomandibular disorders: an epidemiological study of the Northern Finland 1966 Birth Cohort

Recent clinical studies have shown an association between temporomandibular disorders (TMD) and facial pain. The aim of this epidemiological study was to investigate the prevalence of facial pain and TMD, their relation to each other, and also their relation to previous traumas, occlusal factors and pain in other areas of the body. The study is a part of the Well-Being and Health Research of the Northern Finland Birth Cohort 1966 using questionnaires where data on facial pain, TMD symptoms, occlusal divergencies, traumas in the face and other pain areas of the body were registered. Data were obtained from 5696 subjects born in the year 1966 in northern Finland. Twelve percent of the men and 18% of the women had suffered from facial pain during the last year. The most often reported symptom of TMD was clicking of the temporomandibular joints (TMJs) (21% in men, 28% in women), while prevalence of more severe symptoms was 13% or under. Facial pain was related to symptoms of TMD, as well as to traumas in the face or TMJs, distal occlusion and other pain areas (neck, shoulders, arms, lower back, jaws, tooth). The results suggest that facial pain is a usual symptom in adult population, and has an association with TMD, as well as with other musculoskeletal pain symptoms. Traumas to face and TMJs, certain occlusal factors and dental pathology may have a remarkable role in the etiology.

Role of temporomandibular disorders (TMD) in facial pain: occlusion, muscle and TMJ pain

Temporomandibular disorders (TMD) which comprise myogenic and arthralgic components have been reported to predispose subjects to headache and facial pain. The aim of this study was to evaluate the role of these components in patients with facial pain and to investigate the influence of treatment of TMD on pain of these patients. The subject group consisted of 25 patients suffering from facial pain. The clinical stomatognathic examination was performed before conservative treatment of TMD, and one-two weeks, three months and one year after treatment. The severity of TMD was assessed using the anamnestic (AI) and clinical dysfunction (DI) indices of Helkimo. The intensity of pain was evaluated on a numerical rating scale (NRS). According to clinical findings the patients were classified to following diagnostic subgroups: TMD myo (mainly myogenic), TMD arthro (mainly arthrogenous) and TMD comb (both myogenic and arthrogenous components involved). Fifteen patients were classified in the TMD myo group, nine in the TMD comb group and one in the TMD arthro group. The DI index decreased significantly one-two weeks after treatment and remained at this level at three month and one year follow-up examinations. At the first examination the TMD myo group had the highest level of NRS index, which decreased significantly during the time of follow-up, while no significant changes were found in other groups. Bruxism reported by the patient had a positive correlation with the amount of painful muscles on the right side at first examination. The results show that facial pain combined with TMD may be mostly of myogenic origin, and myogenic pain seems to have most favorable response to conservative treatment of TMD.

Two-body in vitro wear study of some current dental composites and amalgams

STATEMENT OF PROBLEM

Wear resistance of restorative materials is a major concern in clinical practice for restorations involving occlusion. The relatively poor wear resistance of dental composites in stress-bearing posterior situations has restricted even wider clinical application of this type of restorative material.

PURPOSE

This in vitro study compared the relative wear resistance of a selection of current dental composites and amalgams under cyclic loading to explore the wear mechanisms operating on these materials and to assess their relative potential clinical wear resistance under variable masticatory loads.

MATERIAL AND METHODS

A 2-body in vitro wear test was undertaken on a selection of 2 Ultrafine Compact-Filled composites, 1 microfilled composite, and 3 dental amalgams. An alternating sine curve load (0.5 to 15 N) was applied to the wear surface through a rotating countersample with a purpose-built system to simulate the variable loading pattern that occurs during mastication.

RESULTS

Under conditions simulating the repetitive cyclic loading pattern that may occur intraorally in high stress occlusal contact situations, the Ultrafine Compact-Filled composites exhibited a delamination wear pattern and had a significantly lower wear resistance than the amalgams. By comparison, the microfilled composite (Silux Plus) displayed an improved wear resistance that was superior to some amalgams. Dispersalloy had the best wear resistance among the materials selected.

CONCLUSION

The wear of Ultrafine Compact-Filled composite and microfilled composite differed and reflect different operative wear mechanisms. For amalgams, the size, shape, and composition of the particles had an effect on the wear resistance of the materials.

Liaison psychiatry and psychology in dentistry

Dentists are trained to provide treatment for patients with straightforward problems that respond to routine therapy and do not recur. However, patients may present to dentists and complain solely of physical symptoms such as toothache, headache, and facial pain: only after much inappropriate treatment these symptoms are revealed to be due to emotional disturbance. The dentist may spend hours investigating such patients, in some of whom dental pathology may be present, but the symptoms and ensuing disability cannot be satisfactorily explained as a result. There are other patients who are preoccupied by physical symptoms or by their appearance. In others, anxiety may manifest itself as a phobia, or a dysmorphic concern about certain aspects of their appearance. This article reviews the role of liaison psychiatry and psychology in dentistry.

Age-related changes in the human mandibular condyle: a morphologic, radiologic, and histologic study

PURPOSE

This study determined the osteoarthrotic changes in the human mandibular condyle in relation to aging and the loss of dental occlusal contacts.

MATERIALS AND METHODS

Thirty-four condyles obtained at autopsy were studied morphologically, radiologically, and histologically.

RESULTS

With advancing age, the articular surface of the mandibular condyle morphologically showed severe degenerative changes. The condyles with these changes tended to be from the side of the mandible with minimal areas of occlusal contact. Radiographically, an irregularity of the cortical bone plate was most commonly seen in the fifth and sixth decades, whereas a polygonal or flattened structure was mainly observed after the seventh decade.

CONCLUSION

The histologic findings suggest that a decrease in the cellular components with advancing age may play a critical role in the development of degenerative changes.