Effect of osseointegrated implants on the coordination of masticatory muscles: a pilot study

The neuromuscular network of masticatory function is, in part, coordinated with afferent information provided by the periodontal ligament (PDL). Osseointegrated implant-supported prostheses lack this PDL-derived proprioceptive feedback mechanism.

This pilot study was designed to address the hypothesis that implant patients acquire different patterns of functional coordination. Patients with implant-supported prostheses were characterized in regard to masticatory muscle tenderness and fatigue as well as changes in the coordinated activities of masticatory muscles during chewing and maximal occluding force. Results were compared with those of patients with natural teeth and interpreted to assess the functional outcome of implant therapy.

Fifty-seven volunteers (25 partially edentulous patients restored with implantsupported fixed prostheses; 32 control patients) were evaluated. A comprehensive set of clinical examinations was performed, including occlusal analysis and examination of masticatory muscle and TMJ. EMG recordings of 5 volunteers from each group were further evaluated. EMG activities of the masseter and anterior temporalis were recorded during habitual chewing and voluntary maximal occluding force.

There were essentially no differences in the clinical evaluations between volunteers in the implant and control groups and no significant alterations in the masticatory muscle coordination for habitual chewing. During the maximal occluding force measurement, EMG recordings revealed a unique masticatory muscle coordination pattern in the implant group with a tendency to activate the working and nonworking side muscles simultaneously.

Patients with implant-supported prostheses appeared to be well adapted to perform habitual masticatory functions. However, during a nonhabitual function such as maximal occluding force, our pilot data revealed a less coordinated masticatory muscle activity in the implant patients.