Impact of clear aligner (Invisalign®) treatment and occlusal changes on the masticatory function and temporomandibular disorders: A cross-sectional study

BACKGROUND: Clear aligner treatment (CAT) may induce masticatory muscle tenderness and trigger temporomandibular disorders (TMD). Considering that CAT may interfere with the masticatory system, it is important to understand the relationship between CAT and occlusal changes. OBJECTIVES: This study aimed to analyze occlusal changes during CAT and assess the influence of postorthodontic occlusion on masticatory performance. A secondary objective was to determine whether the case complexity, the facial biotype and malocclusion were associated with occlusal alterations, masticatory performance, or the onset of TMD signs and symptoms during CAT. MATERIAL AND METHODS: Forty-two individuals who underwent and completed CAT were evaluated at 3 time points: before treatment (T0); at the end of treatment (T1); and 3 months after treatment, during which time clear aligners (CAs) were used only at night (T2). Temporomandibular disorders were assessed using Axis I of the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) at T0, T1 and T2. Masticatory performance was evaluated at T1 and T2 using a two-colored chewing gum test and colorimetric analysis. Occlusal area and anterior and posterior occlusal contacts were evaluated digitally. Non-parametric statistical tests were used, with the significance level set at p < 0.05. RESULTS: The occlusal area decreased significantly from T0 to T1 (p = 0.016). At T1, normodivergent individuals had significantly more anterior contacts than hyperdivergent patients (p = 0.013). Masticatory performance increased with the number of posterior occlusal contacts (p < 0.05), and individuals with Class I molar relationship had more anterior contacts than Class II patients (p = 0.004). At T2, Class III individuals showed higher values than Class II patients (p = 0.011). CONCLUSIONS: The number of occlusal contacts and occlusal contact area decreased during treatment. Nighttime use of CAs slightly enhanced occlusal contact recovery. Complex cases presented more posterior contacts at T0; simple cases presented a greater occlusal area at the end of CAT. Class I individuals presented more anterior contacts at T0. These movements increased the anterior contacts in Class III molar cases at the end of treatment and 3 months later. No significant differences in masticatory performance were found according to the molar relationship, the facial biotype or the case complexity; no TMD signs and symptoms were found during or after CAT.