Occlus-o-guide versus Andresen activator appliance : neuromuscular evaluation

Aim: To evaluate electromyographic (EMG) neuromuscular changes of the anterior temporalis and masseter muscles during functional therapy with Occlus-o-Guide and Andresen activator appliances. Materials and methods: Eighty-two patients aged 8-12 years with Class II malocclusion and deep bite were enrolled. Fifty subjects were treated with Occlus-o-Guide and 32 with an Andresen activator. EMG recordings were performed at appliance insertion (T0), after 6 months (T1), and after 12 months (T2). The percent overlapping coefficient (POC)of the anterior temporalis muscles (POC-ATM) and masseter muscles (POC-MM) was analyzed as an index of muscular symmetry. Normalized maximum voluntary contraction was also evaluated, calculated as the percentage ratio between clenching on teeth and clenching on cotton rolls. Intergroups comparisons were performed using the Mann-Whitney test. Results and conclusions: Without the appliances in situ, POC-ATM and PON-MM values remained consistently ≥85%. With the appliances in place, maximum muscular inhibition was observed at T0, followed by progressive recovery toward orthological muscular balance up to T2. At T0, POC-MM was significantly lower in the Andresen activator group compared with the Occlus-o-Guide group (p=0.02), whereas this difference was no longer significant at T2 (p=0.11). the Andresen activator induced a greater initial neuromuscular imbalance associated with a progressive evolution toward orthological muscular balance.