Evaluation of disc position in edentulous patients with complete dentures

Comparison of TMJ vibration frequencies under different joint conditions

OBJECTIVE

To compare 10 Hz wide segments of the 0 to 1000 Hz frequency distributions of vibrations recorded from five stages of internally deranged and asymptomatic temporomandibular joints (TMJs).

METHODS

TMJ vibrations were recorded from 236 patients with five stages of TMJ dysfunction: (1) reducing partial disc displacement (PDDR, n=39); (2) acute reducing complete disc displacement (A-DDR, n=39); (3) chronic reducing complete disc displacement (C-DDR, n=55); (4) un-adapted, non-reducing, complete disc displacement (DDUA, n=57); and (5) well adapted, non-reducing, complete disc displacement (DDWA, n=46). A totally asymptomatic control group with quiet TMJs (AQ, n=43) and a group with vibrating TMJs (AWV, n=93), but otherwise asymptomatic were also recorded. Frequency distributions were calculated for each group using discrete Fourier transform methods in 10 Hz increments (0-10 Hz, 10-20 Hz,…, 990-1000 Hz). The 10 Hz segments were compared between the seven groups using Student's t test with Bonferroni adjustment.

RESULTS

There were significant differences (P<0.05) in all 21 comparisons for the three segments between 80 Hz and 110 Hz, in 20 of 21 comparisons between 180 and 200 Hz, in 19 of 21 comparisons between 110 and 180 Hz and between 50 and 80 Hz.

DISCUSSION

The segments of the frequency distributions from 80 to 110 Hz provided the best differentiation between all seven groups.

Influence of defective complete dentures renewal on TMD; an MRI and clinical controlled prospective study

BACKGROUND

The influence of complete denture occlusion on temporomandibular disorder (TMD) is controversial. Some studies found that defective occlusion contributes to the development of TMD, while others found no correlation.

OBJECTIVE

This prospective controlled study evaluated the relationship between renewal of old defective complete dentures and TMD as evidenced both by clinical examination and magnetic resonance imaging (MRI) findings.

MATERIALS AND METHODS

The study included 25 complete denture patients with signs and symptoms of TMD and 21 asymptomatic controls. Clicking was a common finding in all symptomatic joints. All selected participants needed complete denture renewal. MRI and clinical assessment following research diagnostic criteria for TMD guidelines (RDC/TMD) were carried out at baseline and 2 years after new complete denture insertion. Temporomandibular joint (TMJ) pain, muscle pain, clicking and movement limitation were the assessed signs and symptoms. MRIs were conducted to evaluate the TMJs for disc displacement, disc morphology and joint effusion.

RESULTS

Complete denture renewal significantly improved the signs and symptoms of TMD in symptomatic group (p < 0.01). Only in the symptomatic group, treatment resulted in a significant increase in joints displaying superior (normal) disc position (symptomatic p < 0.001; asymptomatic p = 0.157). New dentures did not affect disc morphology in both groups (p = 0.5 for both groups) but significantly reduced joint effusion in the symptomatic group (symptomatic p < 0.001; asymptomatic p = 0.5). Relationship between clinical and MRI findings was not one to one.

CONCLUSIONS

New complete dentures had a positive impact on TMD signs and symptoms, disc position and joint effusion but not on disc morphology.

Distribution of temporomandibular joint vibration transfer to the opposite side

A vibration produced when a displaced temporomandibular disc reduces during opening can transfer some of its energy from the ipsilateral joint to the contralateral joint. The objective of this study was to measure what percentage of the ipsilateral vibration is transferred to the contralateral joint. The study included the temporomandibular joint (TMJ) vibrations of 144 (informed consent) subjects, (113 F, 31 M), with reducing displaced discs (DDR). Vibrations from 165 joints were recorded bilaterally with BioJVA (BioResearch Associates, Inc. Milwaukee, WI). In each case, any contralateral vibration was analyzed to verify that it was caused by the ipsilateral joint. The contralateral amplitude was divided by the ipsilateral amplitude and multiplied by 100 to produce a percentage of transfer. The percentage values (0-100%) were used to create a Relative Frequency Histogram with 20 classes (1-5%, 6-10%, 11-15%, etc.). The Relative Frequency Histogram graph revealed a three-mounded distribution of the percentage of transfer. One mound fell between 5 and 34 percent, one between 35 and 69 percent and the third between 70 and 98 percent. The appearance of a three-mounded distribution suggests that there may be three different failure modes leading to TMJ intemal derangements. Alternatively, it may be that failure of the disc's stabilizing ligaments leads to three different internal derangement conditions that are in some way distinct. The evidence of apparent tri-modality in this vibration data distribution suggests that there may be three different failure modes of disc displacement with reduction (e.g., anterior, anteromedial, and medio-lateral disc displacement). If so, identifying them could allow for a more detailed description of DDR. Therefore, further investigation of this 'tri-modal' distribution should be undertaken.

Test-retest reliability of MRI-based disk position diagnosis of the temporomandibular joint

This study evaluated the test-retest reliability for determining the temporomandibular joint (TMJ) disk position, diagnosed using magnetic resonance imaging (MRI). These assessments were done as a base-line measurement for a prospective cohort study, which examines the risk factors for precipitation and progression of temporomandibular disorders. Fifteen subjects (mean age, 24.2 ± 0.94 years; male/female = 8/7) were recruited from the students of Okayama University Dental School. Sagittal MR TMJ images were taken with a 1.5-T MR scanner (Magneton Vision, Siemens) in close and maximal open positions twice at about 1-week (6-11 days) interval. The images were displayed using 200% magnification on a computer screen with a commercially available image software package (OSIRIS, UIN/HCUG). Three calibrated examiners diagnosed the disk positions using the standardized criteria. The disk position of each joint was classified as normal, anterior disk displacement with or without reduction, and others. The first and second disk position diagnoses were compared, and the test-retest reliability level was calculated using the kappa index. The second disk position diagnosis was consistent with the first in 27 out of 30 joints. The calculated kappa value representing the test-retest reliability level between the first and second disk position diagnosis was 0.812. These results indicated that the test-retest reliability of MRI-based diagnosis of TMJ disk positions at about 1-week interval was substantially high, even though they were not completely consistent.