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. 2020 Dec;15(4):419-425.
doi: 10.1016/j.jds.2020.01.006. Epub 2020 Apr 7.

Effects of functional training after orthognathic surgery on masticatory function in patients with mandibular prognathism

Nobuhiko Kawai  1   2 , Manami Shibata  2 , Masahiko Watanabe  2 , Shinya Horiuchi  2 , Kenji Fushima  1 , Eiji Tanaka  2
Affiliations

Effects of functional training after orthognathic surgery on masticatory function in patients with mandibular prognathism

Nobuhiko Kawai et al. J Dent Sci. 2020 Dec.

Abstract

Background/purpose: Even after surgical orthodontic treatment, the level of masticatory function in patients with jaw deformities is still lower than that of healthy subjects. The purpose of this study was to evaluate the effects of functional training program using gum chewing exercise after orthognathic surgery on masticatory function in patients with mandibular prognathism.

Materials and methods: The study subjects were 16 patients with mandibular prognathism who underwent orthognathic surgery and 8 individuals with normal occlusion. Patients were divided into two groups (training group and non-training group; n = 8 per group). Functional training included gum chewing exercise and patient-education about masticatory function. The training; gum chewing exercise of 5 min twice a day for 90 days, started at 3 months after surgery. For each subject, electromyographic activities of masseter and temporalis muscles during maximum voluntary clenching (MVC) and jaw movement during gum chewing were recorded before and after surgical orthodontic treatment. Two parameters; activity index (AI: ratio of activity of masseter and temporalis muscles) and error index (EI: ratio of the number of abnormal chewing patterns), were used.

Results: In the training group, the AI value during MVC increased significantly and the EI value during gam chewing decreased significantly after surgical orthodontic treatment (AI: p < 0.01; EI: p < 0.01), indicating the improvement of activity balance of masseter and temporalis muscles and conversion of the jaw movement from abnormal to normal pattern (p < 0.01).

Conclusion: Our findings suggested that functional training using the gum chewing and patient-education exercise improved masticatory function in patients with mandibular prognathism.

Keywords: Gum chewing exercise; Mandibular prognathism; Masticatory function; Orthognathic surgery; Surgical orthodontic treatment.

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Conflict of interest statement

The authors declare no conflicts of interest with respect to the research and publication of this article.

Figures

Figure 1
Figure 1
Muscle activities of (A) masseter and (B) temporalis muscles during maximum voluntary clenching (MVC). T1: before preoperative orthodontic treatment, T2: after postoperative orthodontic treatment. Values are mean ± SD. Horizontal bars: mean value and SD of the control group. ns: no significant difference. ∗p < 0.05, ∗∗p < 0.01; compared with T1 and T2 in each group (by the paired t-test). †p < 0.05, ††p < 0.01; compared with the control group (by the unpaired t-test).
Figure 2
Figure 2
Activity index (AI) calculated during maximum voluntary clenching (MVC). T1: before preoperative orthodontic treatment, T2: after postoperative orthodontic treatment. Values are mean ± SD. Horizontal bars: mean value and SD of the control group. ns: no significant difference. ∗p < 0.05; compared with T1 and T2 in each group (by the paired t-test). †p < 0.05, ††p < 0.01; compared with control group (by the unpaired t-test).
Figure 3
Figure 3
Error index (EI) during chewing. T1: before preoperative orthodontic treatment, T2: after postoperative orthodontic treatment. Values are mean ± SD. Horizontal bars: mean value and SD of the control group. ns: no significant difference. ∗∗p < 0.01; compared with T1 and T2 in each group (by the paired t-test). ††p < 0.01; compared with control group (by the unpaired t-test).
Figure 4
Figure 4
Representative paths of the mandibular incisal point on the frontal plane, during normal gum chewing for 30 s in each group (green lines: opening path, red lines: closing path). T1: before preoperative orthodontic treatment, T2: after postoperative orthodontic treatment, CO: centric occlusion.
See this image and copyright information in PMC

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