ABSTRACT
This study was conducted in order to determine the effect of vertical dimension variation on the electromyographic (EMG) activity of the sternocleidomastoid and trapezius muscles. The study was performed on 15 healthy subjects. Basal tonic electromyographic (BT-EMG) recordings were performed by placing surface electrodes on the left sternocleidomastoid and trapezius muscles. BT EMG activity was recorded upon varying the vertical dimension every five millimeters from vertical dimension of occlusion to 45 millimeters of jaw opening (series 1), following the habitual opening path. Afterward, BT-EMG activity was recorded every millimeter from vertical dimension of occlusion to 4 mm, and then every two millimeters from four to ten millimeters (series 2). In series 1, a significant increase of BT-EMG activity was observed in both muscles (simple logarithmic regression analysis). In series 2, a significant increase was observed in the sternocleidomastoid muscle whereas trapezius muscle did not present a significant change. BT-EMG behavior of the sternocleidomastoid muscle in series 2 could be relevant when dentists increase vertical dimension by means of intermaxillary appliances during a short-term period. Moreover, these results add further information to the concept of the interrelatedness between the different components of the cranio cervical-mandibular system.
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Notes on contributors
Rodolfo Miralles
Dr. Rodolfo Miralles received his D.D.S. degree in 1975 from the University of Chile. He is a full professor and member of the Oral Physiology Laboratory, Biomedical Sciences Institute, Faculty of Medicine, University of Chile. Dr. Miralles is a member of the Chilean Endodontics Society and the International Association for Dental Research. He is also an associate editor of the Chilean Odontology Journal.
Carolina Dodds
Dr. Carolina Dodds received her D.D.S. degree in 1999 from the University of Chile. During her work on the study presented here, she was a research fellow of the Oral Physiology Laboratory, Biomedical Sciences Institute, Faculty of Medicine, University of Chile.
Arturo Manns
Dr. Arturo Manns received his D.D.S. degree from the University of Chile in 1966 and his Odont. Dr. degree from the University of Tubingen. He is a full professor and chief of the Oral Physiology Laboratory, Biomedical Sciences Institute, Faculty of Medicine, University of Chile. Dr. Manns is a member of the Chilean Society of Oral Rehabilitation, Latin-American Society of Gnathology, and the International Association for Dental Research.
Carmen Palazzi
Dr. Carmen Palazzi received her D.D.S. degree in 1967 from the University of Chile. She is an assistant professor and a staff member of the Oral Physiology Laboratory, Biomedical Sciences Institute, Faculty of Medicine, University of Chile. Dr. Palazzi is a member of the International Association for Dental Research.
Clara Jaramillo
Dr. Clara Jaramillo received her D.D.S. degree in 1994 and obtained a postgraduate degree in oral rehabilitation in 1999 from the CES University, Medellin, Colombia. She is a research fellow of the Oral Physiology Laboratory, Biomedical Sciences Institute, Faculty of Medicine, University of Chile. Dr. Jaramillo is dedicated to oral rehabilitation in a private health institution and in private practice.
Verónica Quezada
Dr. Verónica Quezada received her D.D.S. degree in 1987 from the University of Chile. She is a research fellow of the Oral Physiology Laboratory, Biomedical Sciences Institute, Faculty of Medicine, University of Chile. Dr. Quezada is dedicated to oral rehabilitation in a private health institution and in private practice.
Gabriel Cavada
Mr. Gabriel Cavada received his statistical technician degree in 1996 from the University of Chile and a Master of Bioestadistics in 1998 from the same university. He is an assistant professor of the Public Health School, Faculty of Medicine, University of Chile. Mr. Cavada is a member of the Chilean Chapter of Biometrics Society and the Chilean Statistics Society.