Motor Behavior During First Chewing Cycle

Objective: Unaffected periodontal mechanoreceptors surrounding the roots of natural teeth have shown to be important to optimize positioning of food and adjustment of force vectors during precision biting. The aim of this study was to describe the motor behavior during the first cycle of a natural chewing task in subjects with a natural dentition and to evaluate the role of unaffected sensory information from the periodontal mechanoreceptors in this behavior.
Method: Subjects with natural dentition, bimaxillary tooth-supported fixed prosthesis (TSP) or bimaxillary implant-supported fixed prosthesis (ISP) (10-11 in each group, mean age 70 (range 61-83)) chewed a hazelnut while the vertical and lateral jaw movements, electromyographic activity from the masseter and temporal muscles and sound from the external auditory meatus were recorded for verifying fracture of the hazelnut. Data during the first chewing cycle were analyzed.
Result: The amplitude of the vertical mandibular movement and duration of jaw opening did not differ between the groups, indicating a similar behavior during this part of the chewing cycle. However, the total time used to fracture the hazelnut was longer for the TSP and ISP groups (0.64s and 0.76s) compared to the natural group (0.50s). 30% of the subjects in the natural group, 70% of the TSP and 80% of the ISP groups exhibited slippage of the hazelnut during jaw closure. The TSP and ISP groups had significantly narrower motion patterns (0.15 and 0.19 in total lateral/vertical movement) compared to the natural group (0.27).
Conclusion: Subjects with tooth- or implant-supported fixed prosthesis in both jaws show an altered behavior, including inadequate control of the hazelnut, during the first chewing cycle compared to subjects with natural dentition. We suggest that these differences can be explained by impairment or absence of sensory signals from periodontal mechanoreceptors in the bridge and implant group respectively.