Influence of Jaw Clenching and Tooth Grinding on Bilateral Sternocleidomastoid EMG Activity

Abstract

This study compares the effect of tooth clenching and grinding on sternocleidomastoid electromyographic (EMG) activity during different laterotrusive jaw posture tasks. The study included 28 healthy subjects with natural dentition and bilateral molar support, 14 with bilateral canine guidance and 14 with bilateral group function. Bipolar surface electrodes were located on the left and right sternocleidomastoid muscles. EMG activity was recorded during the following tasks: A. eccentric grinding from intercuspal position to the right lateral edge-to-edge contact position; B. clenching in right edge-to-edge lateral contact position; C. concentric grinding from right lateral edge-to-edge contact position to intercuspal position. On the working side, activity in the task C was significantly higher than in tasks A and B in subjects with canine guidance, whereas no significant differences were observed between tasks in subjects with group function. On the nonworking side, activity was significantly lower during task A than in tasks B and C, in both occlusal schemes (mixed model with unstructured covariance matrix). When comparing by side, EMG activity was significantly lower during task B on the working side than on the nonworking side. However, there were no significant differences during tasks A and C. The EMG activity was significantly lower with canine guidance than group function on the working side during tasks A, B, and C, and on the nonworking side during tasks B and C. These results could explain muscular symptoms in the sternocleidomastoid muscles if the subject is experiencing parafunctional habits while awake and/or during sleep that exceed the individual’s adaptation capability.

Additional information

Notes on contributors

Karen Rodríguez

Dr. Karen Rodriguez received her D.D.S. degree in 2008 from the University of Chile. Dr. Rodriguez is currently a staff member of the Oral Physiology Laboratory, Biomedical Sciences Institute, Faculty of Medicine, University of Chile. She devotes her professional time to work in oral rehabilitation in several private health institutions and in private practice.

Rodolfo Miralles

Dr. Rodolfo Miralles received his D.D.S. degree in 1975 from the University of Chile. He is a full professor and chief of the Oral Physiology Laboratory, Biomedical Sciences Institute, Faculty of Medicine, University of Chile. Dr. Miralles is a member of the International Association for Dental Research. He is also an associate editor of the Chilean Odontology Journal.

Mario Felipe Gutiérrez

Dr. Mario F. Gutiérrez received his D.D.S. degree in 2007 from the University of Chile. He is ad-honorem academic of the Restorative Department and of the Oral Physiology Course of the Faculty of Odontology, University of Chile. Dr. Gutiérrez is currently a staff member of the Oral Physiology Laboratory, Biomedical Sciences Institute, Faculty of Medicine, University of Chile. He devotes his professional time to work in oral rehabilitation in several private health institutions and in private practice.

Hugo Santander

Dr. Hugo Santander received his D.D.S. degree in 1981 from the University of Chile. He is currently a staff member of the Oral Physiology Laboratory, Biomedical Sciences Institute, Faculty of Medicine, University of Chile. Since 1982, Dr. Santander has dedicated his time and energies to diagnosis and treatment of cranio-cervicalmandibular (CCD) disorders in several private health institutions.

Aler Fuentes

Dr. Aler Fuentes received his D.D.S. degree in 2006 from the University of Talca, Chile. He is an academic of the Faculty of Odontology, University of Chile. Dr. Fuentes is currently a staff member of the Oral Physiology Laboratory, Biomedical Sciences Institute, Faculty of Medicine, University of Chile. He is in training to obtain his Master of Dental Sciences at the University of Chile.

María Javiera Fresno

Dr. Maria Javiera Fresno received her D.D.S. degree in 1988 from the University of Chile and a Master of Oral Rehabilitation in 2006 from the Andrés Bello University, Chile. She is a member of Oral Rehabilitation Department of Andrés Bello University, Chile. She is an assistant professor of the Prosthetics Department, Faculty of Odontology, University of Chile. She is currently a staff member of the Oral Physiology Laboratory, Biomedical Sciences Institute, Faculty of Medicine, University of Chile. She devotes her professional time to work in oral rehabilitation in private practice.

Saúl Valenzuela

Dr. Saúl Valenzuela received his D.D.S. degree in 1990 from the University of Chile. He is an assistant professor of Prosthetics Department, Faculty of Odontology, University of Chile. Dr. Valenzuela is currently a staff member of the Oral Physiology Laboratory, Biomedical Sciences Institute, Faculty of Medicine, University of Chile. He devotes his professional time to work in oral rehabilitation in several private health institutions and in private practice.