Optimization of jaw muscle activity and fine motor control during repeated biting tasks

Objective: To investigate if repeated holding and splitting of food morsel change the variability of force and jaw muscle activity in participants with natural dentition. Methods: Twenty healthy volunteers (mean age = 26.2 +/- 3.9 years) participated in a single session divided into six series. Each series consisted of ten trials of a standardized behavioural task (total 60 trials) involving holding and splitting a flat-faced tablet (8 mm, 180 mg) placed on a bite force transducer with the anterior teeth. The hold and split forces along with the electromyographic (EMG) activity of the left and right masseter (MAT. and MAR), left anterior temporalis (TAL) and digastric (DIG) muscles were recorded. A series (ten trials) of natural biting tasks was also performed before and after the six series of the behavioural task. Results: The mean hold force (P < 0.001) but not the mean split force (P = 0.590) showed significant effect of number of series. No significant effect of series was seen on the variability of hold and split force and the EMG activity except for the variability of EMG activity for MAL during the hold phase (P = 0.021) and DIG during the split phase (P < 0.001). The behavioural task had no effect on the EMG activity of the natural biting task. Conclusion: There was no evident optimization of jaw motor function in terms of reduction in the variability of bite force values and muscle activity, when this simple task was repeated up to sixty times in participants with normal intact periodontium. (C) 2014 Elsevier Ltd. All rights reserved.