Articulo De Fisiopatologia

Orthodontics

Pediatric Dentistry

Characteristics of masticatory muscles in children with unilateral posterior crossbite
Annicele da Silva Andrade(a) Maria Beatriz Duarte Gavião(b) Gustavo Hauber Gameiro(c) Moara De Rossi(a)

(a)

Graduate Student; (b) Professor – Department of Pediatric Dentistry, Piracicaba Dental School, University of Campinas, Piracicaba, São Paulo, Brazil.Professor, Department of Physiology, Universidade Federal do Rio Grande do Sul – UFRGS, Porto Alegre, Rio Grande do Sul, Brazil.

(c)

Abstract: The aim of this study was to detect possible differences in the EMG (electromiography) activity, chewing rate (CR), cycle duration (CD) and preferred chewing side (PCS) between children with and without unilateral posterior crossbite. Thirty-seven childrenaged from 7 to 10 years were selected from the clinic of the Department of Pediatric Dentistry, Piracicaba Dental School, Brazil, and divided into two groups: unilateral posterior crossbite (UPCB group, n = 17), and normal occlusion (NOccl group, n = 20). The PCS was determined using a visual spot-checking method. The EMG activity was recorded during mastication, and two chewing sequences of 20 swere evaluated to establish each subject’s CR (cycles/sec) and CD. UPCB and NOccl groups did not have a PCS. The EMG activity and the cycle characteristics did not differ between the groups. The correlations between CD, CR and EMG activity were statistically significant for the masseter and anterior temporalis muscles only in the NOccl group, in which there was also a significant correlation betweenthe EMG activity of masseter and anterior temporalis. In conclusion, these findings suggest that although children with and without UPCB presented a bilateral masticatory pattern with similar CR and CD, balanced EMG activity of masseter and anterior temporalis muscles was observed only in the NOccl group. These results indicate that in children, UPCB can alter the coordination of masticatorymuscles during mastication. Descriptors: Malocclusion; Electromyography; Mastication.

Introduction
Posterior crossbite is defined as a malocclusion in the canine, molar and/or premolar regions, characterized by the buccal cusps of the maxillary teeth occluding lingually against the buccal cusps of the corresponding mandibular teeth.1 It may develop during eruption of the primary dentition and caninvolve the permanent dentition at a later stage of development. It may originate from a skeletal or dental malrelationship, or both, and may lead to a mandibular displacement. 2 Some studies in children and adolescents have shown that posterior crossbite has been associated with asymmetrical function of the masticatory muscles, 3-5 signs and symptoms of temporomandibular disorders (TMD), such aspain, headache, and muscle tenderness,6,7 which may relate to the masticatory muscle performance.4,8 Various techniques have

Corresponding author: Maria Beatriz Duarte Gavião Av. Limeira, 901 Piracicaba - SP - Brazil CEP: 13414-903 E-mail: mbgaviao@fop.unicamp.br

Received for publication on Mar 25, 2010 Accepted for publication on Apr 29, 2010

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Braz Oral Res. 2010Apr-Jun;24(2):204-10

Andrade AS, Gavião MBD, Gameiro GH, De Rossi M

been used to monitor mastication.9 Among these techniques, electromyography (EMG), the measurement of the electrical activity of muscles, has found wide application.10 EMG has been used to identify differences in chewing patterns between individuals, and to classify them into groups according to their chewing efficiency.11 According toPlanas12 (1997), the crossbite side presents a greater number of occlusal contacts in function, being the preferred chewing side. However, these characteristics were not confirmed by other studies.9,13 Chewing side preference was defined by Christensen and Radue14 (1985) as: “when mastication is performed consistently or predominantly on the right or left side of the dentition”. Considering that...