Treatment decision of camouflage or surgical orthodontic treatment for skeletal Class III patients based on analysis of masticatory function

Abstract

Background/purpose: Surgical orthodontic treatment is recommended for patients with severe dentoskeletal discrepancies, while camouflage orthodontic treatment is recommended for patients with mild to moderate discrepancies. However, the decision as to which treatment should be chosen is complicated. The purpose of this study was to determine differences in masticatory function in patients who underwent camouflage and surgical orthodontic treatment for skeletal Class III malocclusion, as well as the usefulness of Wits appraisal in treatment decision based on masticatory functional analysis.

Materials and methods: The study subjects were 45 patients with skeletal Class III malocclusion (15 cases with camouflage orthodontics and 30 cases with orthognatic surgery) and 12 individuals with normal occlusion. We analyzed the pre-treatment records of electromyographic activities of masseter and temporalis muscles and jaw movements.

Results: There were no significant differences in various functional measurements between the camouflage and surgery groups. However, there were significant but not strong correlations between ANB and both masseter muscle activity (r = 0.36, p < 0.01) and expression ratio of abnormal chewing (r = -0.54, p < 0.01). Division of patients into two groups using a cutoff value of -6.0 mm for Wits appraisal showed a significant difference in masseter muscle activity between -6.0 mm or less group and the control (p < 0.01) but none between more than -6.0 mm group and the control.

Conclusion: Camouflage orthodontic treatment is inappropriate for patients with relatively severe dentoskeletal discrepancies. Wits appraisal of -6.0 mm is a potentially useful parameter for treatment decision.

Keywords: Camouflage orthodontic treatment; Masticatory function; Skeletal class III; Surgical orthodontic treatment; Wits appraisal.

Figure 1

Comparison of (A) muscle activities of the masseter and temporalis muscles, (B) activity index, and (C) error index among the control group, camouflage group, and surgery group. Values are mean ± SD. ∗p < 0.05, ∗∗p < 0.01 (ANOVA).

Figure 2

Relationship between ANB and masticatory function: (A) masseter muscle activity, (B) activity index, and (C) error index.

Figure 3

(A) Frequency distribution histogram of ANB in the camouflage and surgery groups. (B) Frequency distribution histogram of Wits appraisal in the camouflage and surgery groups. (C) Number of cases of the surgery group based on Wits appraisal of both −6.0 and −8.0 mm.

Figure 4

Relationship between Wits appraisal and masticatory function: (A) masseter muscle activity, (B) activity index, and (C) error index.

Figure 5

(A) Muscle activities of masseter and temporalis muscles, (B) activity index, and (C) error index based on Wits appraisal −6.0 mm. Values are mean ± SD. ∗∗p < 0.01 (ANOVA).

Figure 6

(A) Muscle activities of masseter and temporalis muscles, (B) activity index, and (C) error index based on Wits appraisal −8.0 mm. Values are mean ± SD. ∗p < 0.05, ∗∗p < 0.01 (ANOVA).