Changes in rabbit jaw-muscle activity parameters in response to reduced masticatory load

Abstract

SUMMARYMechanical food properties influence the neuromuscular activity of jaw-closing muscles during mastication. It is, however, unknown how the activity profiles of the jaw muscles are influenced by long-term alterations in masticatory load. In order to elucidate the effect of reduced masticatory load on the daily habitual activity profiles of three functionally different jaw muscles, the electromyograms of the masseter, temporalis and digastric muscles were recorded telemetrically in 16 male rabbits between seven and 20 weeks of age. Starting at eight weeks of age the experimental animals were fed significantly softer pellets than the control animals. Daily muscle activity was quantified by the relative duration of muscle use (duty time), burst number and burst length in relation to multiple activity levels. The daily duty time and burst number of the masseter muscle were significantly lower in the experimental group than in the control group at 5% and 10% of the maximum activity during the two weeks following the change in food hardness. By contrast, altered food hardness did not significantly influence the activity characteristics of the temporalis and digastric muscles. The findings suggest that a reduction in masticatory load decreases the neuromuscular activity of the jaw-closing muscles that are primarily responsible for force generation during mastication. This decrease is most pronounced in the weeks immediately following the change in food hardness and is limited to the activity levels that reflect muscle contractions during chewing. These findings support the conclusion that the masticatory system manifests few dietspecific long-term changes in the activity profiles of jaw muscles.

Effects of low occlusal loading on the neuromuscular behavioral development of cortically-elicited jaw movements in growing rats

“…Moreover, the duty time of the peak EMG exceeding 5% appeared to represent overall usage of muscle activity, whereas activity exceeding 50% was representative of forceful muscle recruitment in a previous stud 14 . During training with low occlusal loading, the amount of low muscle activity increased due to a slow-to-fast transition of the myosin heavy chain isoform, which resulted in a small amount of powerful muscle contractions 14,47 . Thus, it is likely that in our study low occlusal loading induced by a soft diet did not affect the overall daily activity at lower activity levels; however, an increased amount of low muscle activity in uenced higher activity levels, especially in forceful muscle constriction.…”

“…It has been reported that altering the masticatory load does not affect the burst length at any activity level 14 . Moreover, the duration of muscle contraction is mainly achieved by modulating the response from the masticatory CPGs, which results in a relatively constant frequency of burst length in a muscle 36,47 . Therefore, it is likely that the A-CMA stimulation induces excitatory activation of jaw muscles via masticatory CPGs, yielding a stable duration of burst length during stimulation of muscle contractions.…”

The effect of fixation plate use on bone healing during the reconstruction of mandibular defects

“…In this study, DFIA was used as a primary indicator to demonstrate the recovery rate of each rabbit2122. As shown in Fig.…”

Masticatory biomechanics in the rabbit: a multi-body dynamics analysis

“…Numerous studies have investigated the form and function of the rabbit feeding apparatus, leading to detailed descriptions of the anatomical structure of individual masticatory muscles [32,33], along with estimation of their sarcomere lengths [34,35]. Muscle activations have been recorded via electromyography (EMG) during consumption of various foods [32,34,[36][37][38][39], and when the cortical masticatory area and trigeminal motor nucleus are electrically stimulated [40][41][42][43]. EMG has also been used to analyse the function of the masticatory muscles in juvenile rabbits during growth [44,45], whereas radiotelemetric devices have measured their daily burst activities [46,47].…”