Abstract
ObjectiveThe study was designed to investigate if alteration of different orofacial afferent inputs would have different effects on oral fine motor control and to test the hypothesis that reduced afferent inputs will increase the variability of bite force values and jaw muscle activity, and repeated training with splitting of food morsel in conditions with reduced afferent inputs would decrease the variability and lead to optimization of bite force values and jaw muscle activity.Material methodsForty-five healthy volunteers participated in a single experimental session and were equally divided into incisal, mucosal, and block anesthesia groups. The participants performed six series (with ten trials) of a standardized hold and split task after the intervention with local anesthesia was made in the respective groups. The hold and split forces along with the corresponding jaw muscle activity were recorded and compared to a reference group.ResultsThe hold force and the electromyographic (EMG) activity of the masseter muscles during the hold phase were significantly higher in the incisal and block anesthesia group, as compared to the reference group (P < 0.001). However, there was no significant effect of groups on the split force (P = 0.975) but a significant decrease in the EMG activity of right masseter in mucosal anesthesia group as compared to the reference group (P = 0.006). The results also revealed that there was no significant effect of local anesthesia on the variability of the hold and split force (P < 0.677). However, there was a significant decrease in the variability of EMG activity of the jaw closing muscles in the block anesthesia group as compared to the reference group (P < 0.041), during the hold phase and a significant increase in the variability of EMG activity of right masseter in the mucosal anesthesia group (P = 0.021) along with a significant increase in the EMG activity of anterior temporalis muscle in the incisal anesthesia group, compared to the reference group (P = 0.018), during the split phase.ConclusionsThe results of the present study indicated that altering different orofacial afferent inputs may have different effects on some aspects of oral fine motor control. Further, inhibition of afferent inputs from the orofacial or periodontal mechanoreceptors did not increase the variability of bite force values and jaw muscle activity; indicating that the relative precision of the oral fine motor task was not compromised inspite of the anesthesia. The results also suggest the propensity of optimization of bite force values and jaw muscle activity due to repeated splitting of the food morsels, inspite of alteration of sensory inputs.Clinical relevanceSkill acquisition following a change in oral sensory environment is crucial for understanding how humans learn and re-learn oral motor behaviors and the kind of adaptation that takes place after successful oral rehabilitation procedures.
Highlights
Over the past couple of decades, there has been extensive focus on understanding the peripheral and neural mechanisms of mastication [1,2,3]
The results suggest the propensity of optimization of bite force values and jaw muscle activity due to repeated splitting of the food morsels, inspite of alteration of sensory inputs
Reduced/no afferent inputs from the orofacial/periodontal mechanoreceptors (PMRs) did not increase the variability of bite force values and jaw muscle activity; contrary to our hypothesis
Summary
Over the past couple of decades, there has been extensive focus on understanding the peripheral and neural mechanisms of mastication [1,2,3]. Previous studies have suggested that one important class of receptors for sensorimotor regulation and oral fine motor control are the periodontal mechanoreceptors (PMRs) [5,6,7]. The PMRs provide important information regarding temporal, spatial, and intensive aspects of force acting on the tooth, during the initial tooth food contact [7,8,9,10,11,12]. This ability for spatially controlling the jaw is disrupted during periodontal anesthesia [5]. It was suggested that early afferent information about the tooth food contact would contribute to the regulation of the spatial (three-dimensional) control of the jaws
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