Effect of occlusal appliance wear on mastication in Down syndrome

Objectives: Untreated facial dysmorphology affects mandibular stability in persons with Down Syndrome (DS). Wearing an occlusal appliance can improve mandibular stability. The aim of this study is to estimate the effect of occlusal appliances on electromyographic (EMG) masticatory parameters in persons with DS. Material and methods: 8 subjects with DS chewed four food products of different hardness during 3 sessions: before treatment, wearing an occlusal appliance and wearing a placebo appliance. EMG recordings of anterior temporalis and masseter muscles were recorded simultaneously during chewing. Oral Assesment of Down's Syndrome questionnaire (OADS), photographs, and registration of the number of functional occlusal units were collected during the 3 sessions. Subjects wore the appliances from 2 weeks to 2 months before recording sessions. During this period, an appliance diary was completed. Results were compared to a control population of dentate adults. Results: There was no significant effect of occlusal appliance wear on masticatory EMG parameters in persons with DS. Occlusal appliance wear had an effect on mandibular rest posture and increased the number of functional occlusal units. Subjects tolerated occlusal appliances better than placebo. Mean muscular work was lower in subjects with DS than in controls. Masticatory sequences lasted longer in persons with DS, the number of cycles was increased and total work was equal compared to controls. No adaptation to increased food hardness was found in persons with DS. Conclusion: This study demonstrated no significant effect of short-term occlusal appliance wear on masticatory EMG parameters in persons with DS. The recordings are to be continued after a longer period of wear and with muscular re-education in order to complete evaluation of the effect of occlusal appliance wear on mastication in persons with DS.