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Posterior scissors‐bite: masticatory jaw movement and muscle activity
Author(s) -
Tomonari H.,
Kubota T.,
Yagi T.,
Kuninori T.,
Kitashima F.,
Uehara S.,
Miyawaki S.
Publication year - 2014
Publication title -
journal of oral rehabilitation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.991
H-Index - 93
eISSN - 1365-2842
pISSN - 0305-182X
DOI - 10.1111/joor.12148
Subject(s) - masticatory force , malocclusion , medicine , posterior teeth , bite force quotient , dentistry , occlusion , electromyography , orthodontics , mastication , temporal muscle , masseter muscle , mandible (arthropod mouthpart) , dental occlusion , surgery , biology , physical medicine and rehabilitation , botany , genus
Summary Scissors‐bite is a malocclusion characterised by buccal inclination or buccoversion of the maxillary posterior tooth and/or linguoclination or linguoversion of the mandibular posterior tooth. This type of malocclusion causes reduced contact of the occlusal surfaces and can cause excessive vertical overlapping of the posterior teeth. This case–control study is the first to evaluate both masticatory jaw movement and masseter and temporalis muscle activity in patients with unilateral posterior scissors‐bite. Jaw movement variables and surface electromyography data were recorded in 30 adult patients with unilateral posterior scissors‐bite malocclusion and 18 subjects with normal occlusion in a case–control study. The chewing pattern on the scissors‐bite side significantly differed from that of the non‐scissors‐bite side in the patients and of the right side in the normal subjects. These differences included a narrower chewing pattern (closing angle, P < 0·01; cycle width, P < 0·01), a longer closing duration ( P < 0·05), a slower closing velocity ( P < 0·01) and lower activities of both the temporalis ( P < 0·05) and the masseter ( P < 0·05) muscles on the working side. In 96% of the patients with unilateral posterior scissors‐bite, the preferred chewing side was the non‐scissors‐bite side ( P = 0·005). These findings suggest that scissors‐bite malocclusion is associated with the masticatory chewing pattern and muscle activity, involving the choice of the preferred chewing side in patients with unilateral posterior scissors‐bite.