The buccinator during mastication: A functional and anatomical evaluation in minipigs.
OBJECTIVE
The buccinator muscle forms the lateral wall of the 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 and contributing to malocclusions. However, neither buccinator deformation nor its effect on pressure has been demonstrated. Our objective was to evaluate buccinator EMG during feeding, its changes in length and thickness, and the pressure exerted on its alveolar attachment, using miniature pigs as an animal model.


METHODS
EMG of the buccinator and other oral muscles was recorded with fine-wire electrodes. Anteroposterior length and mediolateral thickness of the buccinator were evaluated with implanted sonomicrometry crystals, and pressure was measured by flat transducers placed beneath the mandibular origin of the buccinator. Recordings were made during feeding and muscle stimulation. Tissues were collected postmortem for histology.


RESULTS
During mastication, buccinator EMG showed regular peaks that preceded those of the jaw closers. Pattern differences clearly distinguished working and balancing sides. 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. Histological evaluation showed a complex interweaving of fibres closely associated with salivary tissue.


CONCLUSIONS
Buccinator contraction does thicken the cheek, and during mastication this activity takes place just as the closing stroke begins. In addition to controlling the bolus, there may be an effect on salivation. Despite the fact that the muscle pulls on its attachment, the local mechanical environment at the alveolar bone is one of positive pressure.
Dutra
Eliane H
EH
Department of Orthodontics, University of Washington, Seattle, WA 98195-7446, USA.
Caria
Paulo H F
PH
Rafferty
Katherine L
KL
Herring
Susan W
SW
D000539:Alveolar Process / Q000033:anatomy & histology; D000818:Animals; D002610:Cheek / Q000033:anatomy & histology; D004576:Electromyography; D005152:Facial Muscles / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000502:physiology*; D005260:Female; D008297:Male; D008409:Mastication / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology*; D012469:Salivary Glands / Q000033:anatomy & histology; D013552:Swine; D013556:Swine, Miniature; D014160:Transducers, Pressure; D014463:Ultrasonography