Meeting Abstract

P1.153  Monday, Jan. 4  The Cheek during Mastication: Activity of the Buccinator Muscle HERRING, S.W.*; DUTRA, E.; CARIA, P.H.F.; RAFFERTY, K.L.; Univ. of Washington; Univ. of Washington; UNICAMP, Brazil; Univ. of Washington herring@u.washington.edu

The buccinator muscle forms the lateral wall of the mammalian oral cavity. It is presumed to aid mastication by maintaining bolus position. Such a function would involve thickening the cheek, possibly compressing the alveolar bone. Our objective was to evaluate buccinator activity during feeding, its dimensional changes, and the pressure exerted on its alveolar attachment in miniature pigs, Sus scrofa (n=6). EMG of the buccinator and other oral muscles was recorded along with sonomicromety of anteroposterior length and mediolateral thickness. Pressure transducers were placed beneath the mandibular origin of the buccinator. During mastication, buccinator EMG showed regular peaks that preceded those of the jaw closers. The buccinator shortened and thickened when it contracted. Positive pressures were observed at the mandibular attachment of the buccinator, increasing when the muscle was active. Pressure and dimensional changes were usually larger for apple and apricot than for nuts. Working and balancing sides could be distinguished with EMG but not with dimensional or pressure measures. Histological evaluation showed a complex interweaving of fibers closely associated with salivary glands. In conclusion, during mastication the buccinator thickens the cheek just before the closing stroke begins. Despite the fact that the muscle pulls on its attachment, the local mechanical environment at the alveolar bone is one of positive pressure. In addition to controlling the bolus, there may be an effect on salivation. Supported by NIH DE8513.