Published online Jul 16, 2022. doi: 10.12998/wjcc.v10.i20.6876
Peer-review started: March 10, 2022
First decision: April 13, 2022
Revised: April 22, 2022
Accepted: May 21, 2022
Article in press: May 21, 2022
Published online: July 16, 2022
Processing time: 116 Days and 15.8 Hours
Bruxism is a rhythmic masticatory muscle activity that occurs involuntarily in a non-physiologically functional state. Previous studies have classified bruxism mainly according to its phase of occurrence. However, this classification does not provide targeted guidance for the treatment of bruxism. Bruxism can also be classified according to the type of mandibular movement: Centric bruxism (CB), which is dominated by centric clenching movements, and eccentric bruxism (ECB), which is dominated by eccentric grinding movements. There is a dearth of research classifying the functional status of masticatory muscles in patients with different mandibular movement types of bruxism.
This study analyzed the differences in the functional status of the masticatory muscles affected by different types of bruxism (CB and ECB), thus illustrating the need for diagnostic classification and corresponding treatment for patients with different types of bruxism.
To reflect the mainly involved types of masticatory muscle and the functional status of the masticatory muscle in patients with different types of bruxism.
A total of 21 CB subjects and 21 ECB subjects were screened from college students according to a questionnaire and their tooth wear features. Sixteen non-bruxism subjects were also recruited. The surface electromyography signals of the temporalis anterior (TA) and superficial masseter muscle (MM) were measured in different mandibular positions and during the chewing task. The electromyography amplitude and chewing cycle duration parameters were then analyzed.
The CB group showed a reduced number of muscle maximal motor units, with the MM being more pronounced, a higher proportion of muscle contractions to be recruited for the same load of chewing activity, and the longer chewing cycle duration. The ECB group showed an increased number of TA maximal motor units, and higher MM activity on the non-working side the in unilateral chewing. This study provides a myoelectrophysiological basis for the diagnostic classification of bruxism based on the type of mandibular movement. Since the subjects selected for this study were college students, the effect of bruxism on populations containing people at other age levels is not clear.
CB mainly affects the MM, and the patients show reduced masticatory muscle contraction efficiency and chewing cycle efficiency. ECB mainly affects the TA, and the patients show enhanced contraction of non-functional lateral muscle bundles.
The effects of different types of bruxism on people of other ages should be explored in further study to provide a comprehensive picture of the effects of bruxism on masticatory muscle function.