Effets du port continu de coquilles correctrices Invisalign® sur l’articulation temporo-mandibulaire et les muscles du complexe facial

INTRODUCTION: The temporomandibular joint (TMJ) is a complex articulation susceptible to pain due to dysfunctions. The etiology of temporomandibular disorders (TMD) is still unclear and whether orthodontic therapy is a risk factor is a question that has long been discussed. At the present time, there is no published data that objectively measured the effects of aligners regarding the TMJ and the orofacial muscles. This prospective clinical study aims to evaluate the effects of continuous wear of Invisalign® aligners on the TMJ and the orofacial muscles. MATERIALS & METHODS: The study included 43 adolescents and adults aged 13 to 51 years old (25 females and 18 males) who were randomly selected from the Orthodontic Clinic at the University of Montreal. Two of them were excluded due to poor compliance and discontinuation of orthodontic treatment. The effects over time of Invisalign® aligners on the TMJ and the muscles of the orofacial complex were assessed using the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD). The number of masticatory muscle contractions was measured with sleep electromyograph (EMG) recordings and the frequency of tooth grinding or clenching was reported with self-administered questionnaires. Repeated measurements were taken at the following time points:  at baseline evaluation (T1), 2 weeks (T2), and 6 months (T3) after the start of the treatment. Repeated measures ANOVA and Brunner-Langer method for numerical values and Cochran-Mantel-Haenszel test for nominal data were used with the significance level set at 5 %.  RESULTS & DISCUSSION: The number of masticatory muscle contractions per hour (index) and their mean duration were not statistically different between the three nights with the EMG recordings (Brunner Langer, p > 0.05). However, 67 % of the participants reported tooth grinding or clenching at night at T2 and 64 % at T3 compared to 39 % at T1, which was a significant increase (Cochran-Mantel-Haenszel, p = 0.0112). Forty-four percent of the patients reported tooth grinding or clenching during daytime at T1, whereas a significant higher percentage of 66 % reported the same at T2 and 61 % at T3 (Cochran-Mantel-Haenszel, p = 0.0294). At T1, 12 % of subjects indicated that they woke up with muscle soreness compared to 29 % at T2, which was a significant increase (Cochran-Mantel-Haenszel, p = 0.0347). At T2, there was a significant reduction in the maximum movement amplitude of the lower jaw in all directions (repeated measures ANOVA, p < 0.05).  In addition, there was a significant increase in the number of painful sites and in the intensity of pain upon palpation of the TMJ and orofacial muscles with the RDC/TMD assessment compared to T1 and T3 (Brunner Langer, p < 0.05). CONCLUSION: This study revealed no effect of Invisalign® aligners on the number of masticatory muscle contractions measured using EMG recordings during sleep over time, but a significant increase of reported tooth grinding or clenching of teeth at T2 and T3. At T2, there was a significant increase of symptoms in the TMJ and orofacial muscles, but these symptoms returned to baseline levels over time.

Keyphrases: Invisalign®, ATM, Muscles, Orthodontics, TMJ, Muscles, Pain, Tooth grinding, Clenching