Bruxing patterns in children compared to intercuspal clenching and chewing as assessed with dental models, electromyography, and incisor jaw tracing: preliminary study.

The purpose of the present study was to compare bruxing patterns in children with chewing and maximum intercuspal clenching as defined in a clinical and laboratory environment. Six non-bruxing controls and six children who actively bruxed according to parent reports were evaluated. Both control and experimental subjects were assessed by an initial questionnaire, intraoral examination, extraoral examination, dental study models, incisor mandibular tracking, and bilateral surface electromyographic recordings (e.g., EMG). Bruxing was defined as grinding, clenching, or both in combination. The clinical examination consisted of an intraoral examination of the dentition, number of occlusal contacts, and wear facets. Dental study models were used to substantiate the intraoral findings for occlusal contact and wear facets. The mandibular incisors position was tracked during opening, closing, laterotrusion, protrusion, and chewing and compared to the bruxing movements in the experimental subjects. Bilateral surface EMG signals from the temporalis and masseter muscles were recorded in three maximum intercuspal clenches, ten chewing cycles on sugarless gum, and during simulated bruxing. The dental contacts were equal in number bilaterally in both control and bruxing subjects. Both groups demonstrated wear facets, but the bruxing subjects had more facets. The wear facets indicated lateral excursions but not clenching. Only the incisor jaw tracking and bilateral EMG differentiated the bruxing patterns. In those subjects (n = 4) who clenched during bruxing, the EMG pattern was not similar to that of intercuspal clenching and demonstrated its own unique muscle recruitment for the temporalis and masseter muscles. In the subjects who exhibited lateral excursions for bruxing (n = 2), the pattern of muscle recruitment of the two-closing muscles in terms of amplitude was similar for both the bruxing and chewing gum. Our findings support a concept that bruxing may depend upon factors that modify coactivation of muscle recruitment and do not depend upon occlusal contacts.