Changes in stomatognathic function induced by orthognathic surgery in patients with mandibular prognathism.
OBJECTIVE
This study was designed to investigate the changes in stomatognathic function through orthognathic treatment in patients with mandibular prognathism.


METHODS
Thirty-six patients with mandibular prognathism were tested and compared with 30 healthy controls with normal occlusion. For each subject, the occlusal contact area and occlusal force were measured during maximum voluntary clenching (MVC). Activities of the masseter and temporalis muscles were recorded during MVC and voluntary gum chewing. Jaw movement was analyzed during chewing on the left and right sides. For the analyses, 2 parameters, asymmetry index (AI) and error index (EI), were established to further investigate the nature of masticatory function. AI was used to evaluate the bilateral balance of masticatory muscle activity, and EI indicates the rate of abnormal jaw movement pattern.


RESULTS
In patients with mandibular prognathism, the occlusal contact area and maximum bite force decreased before surgery, and increased after surgery. The masseter and temporal muscle activities also decreased before surgery, but showed no substantial increase even after surgery. The occlusal and muscle efficiency exhibited significantly smaller values in the patient group than in the controls, irrespective of treatment stages. The AI decreased after surgery. The EI decreased significantly after surgery, but was still significantly greater in the patient group than in the controls.


CONCLUSIONS
It is suggested that masticatory muscles in the patients with mandibular prognathism may adapt to the new environment achieved with surgically corrected dentofacial structure, although the activities remain at lower levels as compared with the controls.
Nakata
Yoshiko
Y
Orthodontic Clinic, Hiroshima University Hospital, Hiroshima, Japan. yono@hiroshima-u.ac.jp
Ueda
Hiroshi M
HM
Kato
Masaaki
M
Tabe
Hideki
H
Shikata-Wakisaka
Noriko
N
Matsumoto
Eka
E
Koh
Myongsun
M
Tanaka
Eiji
E
Tanne
Kazuo
K
D000222:Adaptation, Physiological; D000328:Adult; D000704:Analysis of Variance; D001732:Bite Force; D016022:Case-Control Studies; D003768:Dental Occlusion, Centric; D003936:Diagnosis, Computer-Assisted; D005260:Female; D006801:Humans; D007574:Jaw Relation Record; D008297:Male; D008334:Mandible / Q000002:abnormalities / Q000502:physiology* / Q000503:physiopathology / Q000601:surgery; D008409:Mastication / Q000502:physiology*; D008410:Masticatory Muscles / Q000502:physiology / Q000503:physiopathology; D009068:Movement; D019647:Oral Surgical Procedures; D009971:Orthodontics, Corrective; D011378:Prognathism / Q000503:physiopathology* / Q000601:surgery*; D016896:Treatment Outcome