Assessment of electromyographic activity in patients with temporomandibular disorders and natural mediotrusive occlusal contact during chewing and tooth grinding.
OBJECTIVE
The aim of this study was to investigate whether the presence of a natural mediotrusive contact influences electromyographic (EMG) pattern activity in patients with temporomandibular disorders (TMDs).


METHODS
Bilateral surface EMG activity of the anterior temporalis (AT), masseter (MM), and sternocleidomastoid (SCM) muscles was recorded in 43 subjects during unilateral chewing and tooth grinding. Thirteen patients had TMD and a natural mediotrusive contact (Group 1), 15 had TMD without a natural mediotrusive contact (Group 2), and 15 were healthy subjects without mediotrusive contacts (Group 3). All subjects were examined according to the Research Diagnostic Criteria for TMD (RDC/TMD). All EMG values were standardized as the percentage of EMG activity recorded during maximum isometric contraction on cotton rolls.


RESULTS
EMG activity from all muscles measured showed no significant differences between groups during chewing and grinding. Overall, in all groups, the EMG activity during chewing was higher in the working side than the non-working side in AT and MM muscles. During grinding, these differences were only found in masseter muscles (mainly in eccentric grinding). SCM EMG activity did not show significant differences during chewing and grinding tasks. Symmetry, muscular balance, and absence of lateral jaw displacement were common findings in all groups.


CONCLUSIONS
EMG results suggest that the contribution of a natural mediotrusive occlusal contact to EMG patterns in TMD patients is minor. Therefore, the elimination of this occlusal feature for therapeutic purposes could be not indicated.
a Faculty of Dentistry, Institute for Research in Dental Sciences , University of Chile , Santiago , Chile.|b Faculty of Medicine, Oral Physiology Laboratory, Biomedical Sciences Institute , University of Chile , Santiago , Chile.
Aler D
AD
Fuentes
c Functional Anatomy Research Center, Department of Biomedical Sciences for Health , Università degli Studi di Milano , Milan , Italy.
Chiarella
C
Sforza
b Faculty of Medicine, Oral Physiology Laboratory, Biomedical Sciences Institute , University of Chile , Santiago , Chile.
Rodolfo
R
Miralles
c Functional Anatomy Research Center, Department of Biomedical Sciences for Health , Università degli Studi di Milano , Milan , Italy.
Cláudia L
CL
Ferreira
c Functional Anatomy Research Center, Department of Biomedical Sciences for Health , Università degli Studi di Milano , Milan , Italy.|d Department of Otorhinolaryngology, Ophthalmology, and Head and Neck Surgery , School of Medicine of Ribeirão Preto, University of São Paulo , São Paulo , Brazil.
Andrea
A
Mapelli
c Functional Anatomy Research Center, Department of Biomedical Sciences for Health , Università degli Studi di Milano , Milan , Italy.|e Department of Medical and Surgical Specialties, Radiologic Sciences, and Public Health, Dental Clinic , Università degli Studi di Brescia , Brescia , Italy.
Gianluigi
G
Lodetti
f Department of Stomatology IV, School of Dentistry , Complutense University of Madrid , Madrid , Spain.
Conchita
C
Martin
D002012:Bruxism / Q000503:physiopathology*; D003766:Dental Occlusion; D004576:Electromyography; D006801:Humans; D008406:Masseter Muscle / Q000503:physiopathology; D008409:Mastication / Q000502:physiology*; D009334:Neck Muscles / Q000503:physiopathology; D013703:Temporal Muscle / Q000503:physiopathology; D013704:Temporomandibular Joint / Q000503:physiopathology; D013705:Temporomandibular Joint Disorders / Q000503:physiopathology* / Q000628:therapy*
Dental occlusion; Electromyography; Mastication; Masticatory muscles; Natural mediotrusive occlusal contact; Neck muscles; Temporomandibular disorders; Tooth grinding