Observational Study
Copyright ©The Author(s) 2022. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Clin Cases. Jul 16, 2022; 10(20): 6876-6889
Published online Jul 16, 2022. doi: 10.12998/wjcc.v10.i20.6876
Comparative study of surface electromyography of masticatory muscles in patients with different types of bruxism
Kai-Wen Lan, Liu-Lin Jiang, Ying Yan
Kai-Wen Lan, Liu-Lin Jiang, Ying Yan, Hospital of Stomatology, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Stomatology, Guanghua School of Stomatology, Guangzhou 510080, Guangdong Province, China
Author contributions: Lan KW, Jiang LL, and Yan Y made contributions to conception and design of the project; Lan KW collected the data; Jiang LL participated in the data analysis; Lan KW drafted the initial manuscript; Lan KW, Jiang LL, and Yan Y revised the manuscript and approved the final version.
Institutional review board statement: The study was approved by the medical ethics committee of Hospital of Stomatology, Sun Yat-sen University (No. KQEC-2020-77-01).
Clinical trial registration statement: The study was registered in the Chinese Clinical Trials Registry (No. ChiCTR2100041699).
Informed consent statement: All study participants provided informed written consent prior to study enrollment.
Conflict-of-interest statement: All authors own a patent (No. ZL 202120549626.3, CN) describing the design of the muscle balance occlusal splint, as well as its treatment application for temporomandibular joint disorder and centric bruxism. The patent is licensed to Hospital of Stomatology, Sun Yat-sen University. Dr. Jiang and Dr. Yan own a patent (No. ZL 201620908577.7, CN) describing the design of the maxillary buccal-pterygoid splint, as well as its treatment application for eccentric bruxism. The patent is licensed to Hospital of Stomatology, Sun Yat-sen University.
Data sharing statement: The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.
STROBE statement: The authors have read the STROBE Statement—checklist of items, and the manuscript was prepared and revised according to the STROBE Statement—checklist of items.
Open-Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: https://creativecommons.org/Licenses/by-nc/4.0/
Corresponding author: Ying Yan, MSc, Chief Doctor, Hospital of Stomatology, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Stomatology, Guanghua School of Stomatology, No. 56 Lingyuan West Road, Yuexiu District, Guangzhou 510080, Guangdong Province, China. yanying2@mail.sysu.edu.cn
Received: March 10, 2022
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
Abstract
BACKGROUND

Bruxism is a rhythmic masticatory muscle activity that occurs involuntarily in a non-physiologically functional state. There is a lack of research classifying the functional status of masticatory muscles in patients with different mandibular movement types (centric clenching or eccentric grinding) of bruxism.

AIM

To assess the differences of the masticatory muscle activity in patients with different types of bruxism.

METHODS

A total of 21 subjects with centric bruxism (CB) and 21 subjects with eccentric bruxism (ECB) were screened from college students according to a questionnaire and their tooth wear features. Sixteen subjects with no bruxism were also recruited. The surface electromyography (EMG) signals of the temporalis anterior (TA) and superficial masseter muscle (MM) were measured in different mandibular positions and during the chewing task. The EMG amplitude and chewing cycle duration parameters were then analyzed.

RESULTS

The CB group showed fewer 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 a longer chewing cycle. The ECB group showed more TA maximal motor units and higher MM activity on the non-working side in unilateral chewing.

CONCLUSION

CB mainly affects the MM, and patients with CB show reduced masticatory muscle contraction efficiency and chewing cycle efficiency. ECB mainly affects the TA, and patients with ECB show enhanced contraction of non-functional lateral muscle bundles.

Keywords: Bruxism; Electromyography; Masticatory muscles; Mastication; Tooth wear; Classification

Core Tip: Bruxism can be divided into types by the nature of the mandibular movement: Centric bruxism is dominated by centric clenching movements and eccentric bruxism by eccentric grinding movements. This study found that eccentric bruxism mainly involved the temporalis anterior on the working side and the masseter muscle on the non-working side, with the temporalis anterior predominating, and the patients showed enhanced contraction of non-functional lateral muscles; centric bruxism mainly involved the temporalis anterior and the masseter muscle bilaterally, of which the masseter muscle was predominant, and the patients showed reduced masticatory muscle contraction efficiency and chewing cycle efficiency.