Malocclusion Complexity in Patients with Myofascial Pain with or without Mouth-Opening Limitation: A Case-Control Study

BACKGROUND: This study is aimed at determining the association between myofascial pain with or without mouth-opening limitation and malocclusion complexity. METHODS: A prospective, cross-sectional, case-control study was conducted. The Research Diagnostic Criteria were used to evaluate the presence of myofascial pain, chronic pain, and depression. The Index of Complexity, Outcome, and Need (ICON) was applied to quantify malocclusion complexity. A total of 96 patients with myofascial pain were grouped into two: subjects without mouth-opening limitation (n = 76, group A) and subjects with mouth-opening limitation (group B, n = 20). Both groups were compared with 231 controls (group C). A Chi-squared test and a multinomial logistic regression (p ≤ 0.05) were used to identify associations between the variables. RESULTS: Statistically significant associations were found between myofascial pain and the variables gender, malocclusion complexity, and depression (p ≤ 0.05). Age was not significantly associated (p = 0.327). Concerning malocclusion complexity, 77.9% of the controls were distributed in the first three ICON levels; however, 76.5% of group A subjects and 90% of group B were in the last three (p < 0.001). The multinomial logistic regression showed a significant association between malocclusion complexity in group A (p < 0.05) and an association between depression and group B (p < 0.05). Group B had the highest grades of chronic pain. CONCLUSIONS: Females had greater risk of myofascial pain without mouth-opening limitation. As the complexity of the malocclusion increases, so do the odds of presenting myofascial pain without mouth-opening limitation. Myofascial pain with mouth-opening limitation frequently coexists with depression and chronic pain.