Abstract
The aim of this study was to detect possible differences in the EMG (electromyography) activity, chewing rate (CR), cycle duration (CD) and preferred chewing side (PCS) between children with and without unilateral posterior crossbite. Thirty-seven children aged 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 s were 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 between the 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 masticatory muscles during mastication.
Highlights
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]
Some studies in children and adolescents have shown that posterior crossbite has been associated with asymmetrical function of the masticatory muscles,[3,4,5] signs and symptoms of temporomandibular disorders (TMD), such as pain, headache, and muscle tenderness,[6,7] which may relate to the masticatory muscle performance.[4,8]
Graph 1 shows the comparison between sides in the UPCB and NOccl groups
Summary
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 can involve 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]. EMG has been used to identify differences in chewing patterns between individuals, and to classify them into groups according to their chewing efficiency.[11]
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