TMJ osteoarthritis/osteoarthrosis and dentofacial morphology in Japanese females

Degenerative bony changes in the temporal component of the temporomandibular joint - review of the literature

Temporomandibular joint (TMJ) changes are quite frequent in adults, but not all changes are degenerative. A high prevalence of bone alterations in the TMJs was reported by different research groups. Disturbed remodeling of bony articulating structures occurs because of overloading masticatory forces or because the mechanical loading in the area out-weighs the adaptive capacity of the TMJ structures. Although most of the degenerative TMJ alterations are identified at the level of the condylar process, a complete evaluation of the degenerative modifications encountered in the temporal TMJ region should not be forgotten as they are important for a comprehensive assessment and further management of the clinical situation. Several research groups have described osseous remodeling in the temporal component of the TMJ. Evidence is scarce for degenerative modifications at the level of the articular eminence and thickening of the roof of the glenoid fossa has been associated with osteoarthritis.

Temporomandibular Disorder Signs, Occlusal Support, and Craniofacial Structure Changes Among the Elderly Vietnamese

Objective

The aim of study was to determine the association between signs of temporomandibular disorders (TMD), occlusal support, and alterations in the craniofacial structure of elderly Vietnamese by using cephalometric analysis.

Methods

The cross-sectional study consisted of 244 participants aged 65-74 years. Participants were examined for signs of TMD, including limited mouth opening, temporomandibular joint (TMJ) crepitus, TMJ tenderness, and muscle tenderness. Dentition was divided into four occlusal support zones based on occluding pairs of posterior teeth by using Eichner's classification: Class A = 4 support zones; Class B = 1-3 support zones or only contact in anterior teeth; Class C = 0 support zones. Fifteen angular and seven linear parameters were used for sagittal craniofacial skeleton analysis.

Results

10.3% of participants had limited mouth opening, 49.6% TMJ crepitus, 16.3% TMJ tenderness, and 24.2% muscle tenderness; 45.5% had Class A occlusal support, 38.5% Class B, and 16.0% Class C. Those with Class C had significantly smaller ramus inclination, articular angle, and angles formed by the mandibular plane and shorter facial height compared to Class A and Class B (P < .001). TMD signs were significantly associated with: angles formed by mandibular plane, gonial angle, cranial base angle, effective mandibular length, and anterior facial height (P < .05).

Conclusions

The alteration of craniofacial structures was significantly associated with TMD signs among elderly Vietnamese. The higher number of lost occlusal support zones, the more significant the changes to craniofacial structures.

Childhood intelligence and early tooth wear patterns

OBJECTIVE

The aim of this study is to explore the relationships between early dental wear patterns and preschool IQ (Intelligence Quotient, by Stanford-Binet) of the child to illuminate the historic relationship of mental queries and bruxism.

METHODS

The dental study participants were 864 Euro-American preschool and school children whose IQs were tested for school maturity purposes at the age of 4 years, followed by dental data in a cross-sectional manner at the mean age of 7.8 years. Worn dentitions were classified as "symmetric" or "right-" and "left-sided," based on the faceting of the teeth.

RESULTS

In general, the relationships of tooth wear and intelligence were scarce, reflecting social background factors. Statistically significant results between asymmetric wear and gender groups suggest that direction of jaw function has a role in the regulation of processes responsible for individual mental performance in childhood.

DISCUSSION

Increased left-side tooth wear and early advantage in the intelligence test in girls is intriguing due to the fact that they reach maturity earlier than boys in verbal articulation, controlled in most cases by the limited area on the left side of the brain.

Relationship between the unilateral TMJ osteoarthritis/osteoarthrosis, mandibular asymmetry and the EMG activity of the masticatory muscles: a retrospective study

The purpose of this retrospective study was to investigate the relationship between the unilateral temporomandibular joint (TMJ) osteoarthritis/osteoarthrosis (OA), mandibular asymmetry and electromyographic (EMG) activity of the masticatory muscles. Twenty-two Japanese women (aged 23.2 +/- 5.4 years) and 10 Japanese men (aged 22.4 +/- 2.8 years) exhibiting unilateral TMJ OA were included in this study. Two angular and seven linear measurements were obtained for the analysis of the skeletal hard tissues. The cephalometric measurement values (CV) were normalized using the CV ratio for the evaluation of the degree of mandibular asymmetry. The EMG was recorded during maximal voluntary clenching efforts for 10 s in the intercuspal position. The average values of integral EMG (iEMG) of three trials were normalized using the iEMG ratio for the evaluation of the functional balance of the masticatory muscles. The mandibular midline was shifted to the TMJ OA side with a median value of 9.85 mm. The CV ratio of the ramus height of the TMJ OA side was significantly smaller than that of the non-OA side. For the masseter muscle, the iEMG ratio of the TMJ OA side was significantly larger than that of the non-OA side (P < 0.05). These results suggest that unilateral TMJ OA is related to the dentofacial morphology, thus resulting in a mandibular midline shift to the affected side and it is associated with a masticatory muscle imbalance.

Relationship of TMJ osteoarthritis / osteoarthrosis to head posture and dentofacial morphology

OBJECTIVE

The purpose of this study was to test the hypothesis that there is a relationship between the temporomandibular joint (TMJ) osteoarthritis/osteoarthrosis (OA), head posture and dentofacial morphology.

DESIGN

Case-control study.

SUBJECTS AND METHODS

The subjects consisted of 34 Japanese females with TMJ OA (aged 24.7 +/- 6.1 years) and a control group of 25 healthy Japanese females (aged 23.6 +/- 1.3 years). Six cranio-cervical angular measurements were constructed for head posture analysis. Nine angular and three linear measurements were constructed for the skeletal hard tissue analysis. Five angular and one linear measurements were constructed for the dental hard tissue analysis. Unpaired t-tests were used to compare the mean differences of head posture measurements and dentofacial cephalometric measurements between the TMJ OA and the control group.

RESULTS

The TMJ OA group had significantly larger cranio-cervical angles (p < 0.05) and had more posteriorly rotated mandibles (p < 0.0001) than those in the control group. They also had a significantly shorter posterior facial height (p < 0.0001). The TMJ OA group had more retroclined lower incisors (p < 0.05).

CONCLUSION

These results suggest that an association may exist between TMJ OA, head posture and dentofacial morphology.