Korean J Orthod.  2019 Jul;49(4):254-264. 10.4041/kjod.2019.49.4.254.

Short-term changes in muscle activity and jaw movement patterns after orthognathic surgery in skeletal Class III patients with facial asymmetry

Affiliations
  • 1Department of Orthodontics, Kyung Hee University School of Dentistry, Seoul, Korea. hyowon@khu.ac.kr
  • 2Department of Dentistry, Graduate School, Kyung Hee University, Seoul, Korea.
  • 3Department of Orthodontics, School of Dentistry, Seoul National University, Seoul, Korea.
  • 4Dental Research Institute, Seoul National University, Seoul, Korea.

Abstract


OBJECTIVE
To evaluate the short-term changes in masticatory muscle activity and mandibular movement patterns after orthognathic surgery in skeletal Class III patients with facial asymmetry.
METHODS
Twenty-seven skeletal Class III adult patients were divided into two groups based on the degree of facial asymmetry: the experimental group (n = 17 [11 male and 6 female]; menton deviation ≥ 4 mm) and control group (n = 10 [4 male and 6 female]; menton deviation < 1.6 mm). Cephalography, electromyography (EMG) for the anterior temporalis (TA) and masseter muscles (MM), and mandibular movement (range of motion [ROM] and average chewing pattern [ACP]) were evaluated before (T0) and 7 to 8 months (T1) after the surgery.
RESULTS
There were no significant postoperative changes in the EMG potentials of the TA and MM in both groups, except in the anterior cotton roll biting test, in which the masticatory muscle activity had changed into an MM-dominant pattern postoperatively in both groups. In the experimental group, the amount of maximum opening, protrusion, and lateral excursion to the non-deviated side were significantly decreased. The turning point tended to be shorter and significantly moved medially during chewing in the non-deviated side in the experimental group.
CONCLUSIONS
In skeletal Class III patients with facial asymmetry, the EMG activity characteristics recovered to presurgical levels within 7 to 8 months after the surgery. Correction of the asymmetry caused limitation in jaw movement in terms of both ROM and ACP on the non-deviated side.

Keyword

Class III orthognathic surgery; Facial asymmetry; Electromyography; Jaw movement

MeSH Terms

Adult
Electromyography
Facial Asymmetry*
Humans
Jaw*
Male
Masseter Muscle
Mastication
Masticatory Muscles
Orthognathic Surgery*
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