Association between malocclusion and symptom of TMD

Abstract

Background: The first supposition of a possible relationship between occlusion and TMJ (temporomandibular joint) function was suggested by Costen, who hypothesized that changes in dental condition (loss of vertical dimension) can lead to symptoms of temporomandibular disorders (TMD). Symptoms of temporomandibular disorders are more common in women, with a female-to-male ratio ranging from 2:1 to 8:1. Temporomandibular disorders occur in 25-38% of the general population. The reason for conducting this study is that no research has been conducted in Mongolia on the relationship between malocclusion and TMJ. Aim: This study aimed to investigate the association between malocclusion and temporomandibular disorders. Materials and Methods: The study was conducted using a case-control design, and patients requiring orthodontic treatment who visited the Orthodontics Department of the Center Hospital of the Dentistry, Mongolian National University of Medical Sciences were included in the case group, while relatively healthy individuals with normal occlusion who had not undergone orthodontic treatment were included in the control group. The sample size for each case and control group was calculated to be 20 people, for a total of 40 people aged 20-30. The need for orthodontic treatment was determined by the IOTN index (Index of Orthodontic Treatment Need). Relatively healthy occlusion was defined according to Andrew’s six keys. The condition of the temporomandibular joint was determined using a questionnaire and physical examination. Results: The mean age of the study participants was 24.4±3.7 years in the malocclusion group and 26.0±3.6 years in the control group, 45% (n=8) of the malocclusion group were male and 40% (n=9) of the control group were male. The indicators of malocclusion, such as increased overjet, decreased overjet, increased overbite and mouth breathing were statistically significantly different between the malocclusion group and the control group (p<0.05). Logistic regression analysis showed that CII (OR=11.66, p=0.007) and CIII (OR=16.33, p=0.017) occlusion, increased overbite (OR=6.87, p=0.025) and mouth breathing (OR=4.22, p=0.042) had an impact on the occurrence of TMJ noise in both vertical and horizontal directions. Conclusions: 1. Among the study participants, Angle’s Class I accounted for 50% (the highest percentage), while Angle’s Class III accounted for 20% (the lowest percentage). But Angle’s Class II accounted for 30%. 2. Symptoms of temporomandibular joint disorder were statistically significantly higher in the case group (p<0.05). 3. People with Angle’s Class II and Class III were 11-16 times more likely to develop temporomandibular joint (TMJ) noise, a symptom of TMD, compared to people with normal occlusion.