Reorganization of muscle activity in patients with chronic temporomandibular disorders.
OBJECTIVE
To investigate whether reorganization of muscle activity occurs in patients with chronic temporomandibular disorders (TMD) and, if so, how it is affected by symptomatology severity.


METHODS
Surface electromyography (sEMG) of masticatory muscles was made in 30 chronic TMD patients, diagnosed with disc displacement with reduction (DDR) and pain. Two 15-patient subgroups, with moderate (TMDmo) and severe (TMDse) signs and symptoms, were compared with a control group of 15 healthy subjects matched by age. The experimental tasks were: a 5s inter-arch maximum voluntary clench (MVC); right and left 15s unilateral gum chewing tests. Standardized sEMG indices characterizing masseter and temporalis muscles activity were calculated, and a comprehensive functional index (FI) was introduced to quantitatively summarize subjects' overall performance. Mastication was also clinically evaluated.


RESULTS
During MVC, TMDse patients had a significantly larger asymmetry of temporalis muscles contraction. Both TMD groups showed reduced coordination between masseter and temporalis muscles' maximal contraction, and their muscular activity distribution shifted significantly from masseter to temporalis muscles. During chewing, TMDse patients recruited the balancing side muscles proportionally more than controls, specifically the masseter muscle. When comparing right and left side chewing, the muscles' recruitment pattern resulted less symmetric in TMD patients, especially in TMDse. Overall, the functional index of both TMDmo and TMDse patients was significantly lower than that obtained by controls.


CONCLUSIONS
Chronic TMD patients, specifically those with severe symptomatology, showed a reorganized activity, mainly resulting in worse functional performances.
Department of Otorhinolaryngology, Ophthalmology, and Head and Neck Surgery, School of Medicine, Ribeirão Preto, University of São Paulo, Brazil; Craniofacial Research Support Centre, University of São Paulo, Brazil.
Andrea
A
Mapelli
Department of Otorhinolaryngology, Ophthalmology, and Head and Neck Surgery, School of Medicine, Ribeirão Preto, University of São Paulo, Brazil; Craniofacial Research Support Centre, University of São Paulo, Brazil.
Bárbara Cristina
BC
Zanandréa Machado
Department of Otorhinolaryngology, Ophthalmology, and Head and Neck Surgery, School of Medicine, Ribeirão Preto, University of São Paulo, Brazil; Craniofacial Research Support Centre, University of São Paulo, Brazil.
Lucia Dantas
LD
Giglio
Functional Anatomy Research Center (FARC), Laboratory of Functional Anatomy of the Stomatognathic Apparatus, Dipartimento di Scienze Biomediche per la Salute, Faculty of Medicine, Università degli Studi di Milano, Italy.
Chiarella
C
Sforza
Department of Otorhinolaryngology, Ophthalmology, and Head and Neck Surgery, School of Medicine, Ribeirão Preto, University of São Paulo, Brazil; Craniofacial Research Support Centre, University of São Paulo, Brazil. Electronic address: cfelicio@fmrp.usp.br.
Cláudia Maria
CM
De Felício
D000328:Adult; D016022:Case-Control Studies; D002908:Chronic Disease; D004576:Electromyography; D005260:Female; D006801:Humans; D008297:Male; D008409:Mastication / Q000502:physiology; D008410:Masticatory Muscles / Q000503:physiopathology*; D009119:Muscle Contraction / Q000502:physiology; D013705:Temporomandibular Joint Disorders / Q000503:physiopathology*
Electromyography; Jaw muscles; Mastication; Motor control; Pain; Temporomandibular disorders