Natural mediotrusive contact: does it affect the masticatory and neck EMG activity during tooth grinding?
OBJECTIVE
There is scarce knowledge regarding the influence of a natural mediotrusive contact on mandibular and cervical muscular activity. The purpose of this study was to analyze the EMG activity of the anterior temporalis (AT) and sternocleidomastoid (SCM) muscles during awake grinding in healthy subjects with or without a natural mediotrusive occlusal contact.


METHODS
Fifteen subjects with natural mediotrusive occlusal contact (Group 1) and 15 subjects without natural mediotrusive occlusal contact (Group 2) participated. Bilateral surface EMG activity of AT and SCM muscles was recorded during unilateral eccentric or concentric tooth grinding tasks. EMG activity was normalized against the activity recorded during maximal voluntary clenching in intercuspal position (IP) for AT muscles and during maximal intentional isometric head-neck rotation to each side, for SCM muscles.


RESULTS
EMG activity of AT and SCM muscles showed no statistical difference between groups. EMG activity of AT muscle was higher in the working side (WS) than in the non-WS (NWS) in Group 1 during concentric grinding (0.492 vs 0.331, p = 0.047), whereas no difference was observed in Group 2. EMG activity of SCM was similar between working and NWSs in both groups and tasks. Asymmetry indexes (AIs) were not significantly different between groups.


CONCLUSIONS
These findings in healthy subjects support the assumption that during awake tooth grinding, central nerve control predominates over peripheral inputs, and reinforce the idea of a functional link between the motor-neuron pools that control jaw and neck muscles.
a Institute for Research in Dental Sciences, Faculty of Dentistry , University of Chile , Santiago , Chile.|b Oral Physiology Laboratory, Biomedical Sciences Institute, Faculty of Medicine , University of Chile , Santiago , Chile.
Aler D
AD
Fuentes
c Department of Stomatology IV, School of Dentistry , Complutense University of Madrid , Spain.
Conchita
C
Martin
d Department of Physiology and Biophysics, Biomedical Sciences Institute, Faculty of Medicine , University of Chile , Santiago , Chile.
Ricardo
R
Bull
b Oral Physiology Laboratory, Biomedical Sciences Institute, Faculty of Medicine , University of Chile , Santiago , Chile.
Hugo
H
Santander
a Institute for Research in Dental Sciences, Faculty of Dentistry , University of Chile , Santiago , Chile.|b Oral Physiology Laboratory, Biomedical Sciences Institute, Faculty of Medicine , University of Chile , Santiago , Chile.
Mario F
MF
Gutiérrez
b Oral Physiology Laboratory, Biomedical Sciences Institute, Faculty of Medicine , University of Chile , Santiago , Chile.
Rodolfo
R
Miralles
D003766:Dental Occlusion; D003768:Dental Occlusion, Centric; D004576:Electromyography; D005260:Female; D006801:Humans; D008297:Male; D008410:Masticatory Muscles / Q000502:physiology*; D009334:Neck Muscles / Q000502:physiology*; D055815:Young Adult
Dental occlusion; Electromyography; Jaw movement; Masticatory muscles; Natural mediotrusive occlusal contact; Neck muscles; Tooth grinding