The etiologies of most chronic temporomandibular joint disorders are unknown. However, an association between habitual chewing on a particular side and chronic temporomandibular joint disorders has been reported. The aim of this study was to investigate the differences between sides (affected vs unaffected) of biodynamic factors (including lateral dental guidance determined by dental anatomy) or condylar path angles (determined by temporomandibular joint morphology) and chewing function (physiological alternate chewing vs single habitual chewing side). The study scope was to investigate possible etiological factors to improve the understanding of temporomandibular joint disorders. The null hypothesis was that no difference would be found between sides that are or are not affected by chronic temporomandibular joint disorders in chewing function or in levels of dental or temporomandibular joint remodeling. This cross-sectional, double-blind study involved 24 adults with substantial, chronic, unilateral symptoms diagnosed as temporomandibular joint disorders. Chewing function, temporomandibular joint remodeling (using axiography) and dental anatomy (lateral guidance angles using kinesiography) were assessed. Habitual chewing on one particular side was observed in 17 of 24 participants; significantly more (n=15) chewed on the affected side than on the unaffected side (P=0.002 in a two-tailed Fisher's exact test; risk estimate=4.5; 95% CI 1.326-15.277). The condylar path (CP) angle was steeper on the affected side than on the unaffected side (mean (standard deviation)=50.52° (9.98°) versus 45.50° (7.98°); P=0.002 in a two-tailed t-test). The lateral guidance (LG) angles were flatter on the affected side in all 24 participants. Our results suggest that habitual chewing on one side may be associated with increasing condylar path, with flattening lateral guidance angles, and also with chronic temporomandibular joint disorder on the habitual chewing side.

Background/Objectives: Interincisive midline deviation is frequent. Determining the cause (dental versus skeletal) is crucial for treatment planning. This study assessed the null hypothesis that neither clinical dental midline shift nor the temporomandibular disorder (TMD)-affected side correlate with maxillary/mandibular asymmetry. Methods: Thirty-eight CBCT scans were analyzed: thirty-five (92.1%) females, three (7.9%) males; mean (SD) age 34.6 (11.9) years old. Tomographic images were acquired using the i-CAT^® Imaging System; mandibular/maxillary measurements were obtained with the Planmeca Romexis^® software v.6.This is an ancillary study of a clinical trial (NCT02144233) that included chronic pain (TMD diagnosis; DC/TMD criteria), fully dentate, and stable normo-occlusion participants. Results: We found sixteen (42.1%) dental midline deviations to the right and thirteen (34.2%) to the left. In the study population, the right side was more developed: a hemimandible length of 119.4 (5.7) mm versus 118.6 (5.3) mm for the right and left sides, respectively (95% CI 0.21 to 1.51), p = 0.01. Conclusions: Neither the dental midline shift side nor the affected side predicted a less developed hemimandible.

Results from clinical trials on chronic pain associated with temporomandibular disorders (TMDs) have been traditionally presented as differences in the means of pain intensity scores between the treatment and control group. However, this formulation does not permit any quantification of the treatment effect but is limited to assessing whether a statistically significant difference exists between groups. To address this limitation, a new analysis of our original trial of physiologically oriented occlusal equilibration (POOE) and jaw pain was carried out using a dichotomous outcome: therapy success or therapy failure. All participants in the trial were suffering from moderate to severe chronic jaw pain related to muscular or arthrogenous TMDs, refractory to other conservative or minimally invasive treatments. Participants were randomly assigned to POOE (n=39) or placebo therapy (n=38) groups. POOE was designed to eliminate premature contacts, to obtain balanced occlusion, and to recover physiological alternate mastication function. Adjusted odds ratios were calculated using unconditional logistic regression models in which the independent variable is the treatment received (either POOE or placebo) and the dependent variables are the group differences in change in pain outcomes after 3 and 6 months. The odds of success in pain reduction of POOE compared with those of placebo therapy were calculated. Success was defined as a decrease in pain scores of ≥2 points, while decreases of <2 points, as well as unmodified or increased pain scores were labeled as failure. To measure strong effects of the treatment, in an additional analysis, success was redefined as a decrease in pain of ≥4 points and any other effect as failure. Globally, participants receiving POOE were 2 to 10 times more likely to experience a decrease in jaw pain than patients receiving placebo treatments. The success or failure analysis determined the effectiveness, in terms of mitigation of jaw pain, of occlusal equilibration in the treatment of TMD after 3 and 6 months compared with placebo therapy.

Background/Objectives: Interincisive midline deviation is frequent. Determining the cause (dental versus skeletal) is crucial for treatment planning. This study assessed the null hypothesis that neither clinical midline shift nor temporomandibular disorder (TMD)-affected side correlate with maxillary/mandibular asymmetry. Methods: Tomographic images were acquired using the i-CAT Imaging System; mandibular/maxillary measurements were obtained with the Planmeca Romexis software. This is an ancillary study of a clinical trial (NCT02144233) that included chronic pain (TMD diagnosis; DC/TMD criteria), fully dentate and stable normo-occlusion participants. Results: Thirty-eight CBCT scans were analyzed: 35 (92.1%) females, 3 (7.9%) males. Mean age 34.6 (11.9) years old. Sixteen (42.1%) midline deviations to the right and 13 (34.2%) to the left. In the study population the right side was more developed: hemimandible length 119.4 (5.7) mm versus 118.6 (5.3) mm, right and left sides, respectively (95% CI 0.21 to 1.51), p=0.01. Conclusions: Neither midline shift side nor affected side predicted a less developed hemimandible.