Abstract
BackgroundTo evaluate the three-dimensional (3D) changes after mandibular setback surgery (MSS) in skeletal Class III malocclusion using cone-beam computed tomography (CBCT) and a structured light-based scanner.MethodsTwenty-eight adult Korean patients with skeletal Class III malocclusion treated by MSS were evaluated. CBCT and facial scan images were recorded one week before and six months after surgery. To use an identical 3D coordinate system, superimposition was performed, and nine skeletal and 18 soft tissue landmarks were identified. Changes in the landmarks and correlation coefficients and ratios between hard and soft tissue changes were evaluated. Paired t test and Pearson’s correlation test were performed.ResultsAfter MSS, the amount of transverse correction was 2.45 mm; mandibular setback, 5.80 mm; and vertical reduction, 1.64 mm at the menton, on average. In the transverse axis, there were significant changes and correlations in the lips and chin and an increasing gradient of ratios from the lower lip to the chin. In the anteroposterior axis, the lower lip and chin moved backward significantly and showed notable correlation with hard tissue movement. In the vertical axis, significant upward movement was observed in the landmarks related to the chin, but only lower facial height was significantly decreased.ConclusionsSoft tissue changes according to hard tissue movement after MSS exhibited a distinct pattern of an increasing gradient from the lips to the chin in a transverse aspect.
Highlights
To evaluate the three-dimensional (3D) changes after mandibular setback surgery (MSS) in skeletal Class III malocclusion using cone-beam computed tomography (CBCT) and a structured light-based scanner
There were significant changes in most landmarks related to the lips (Ls, Stomion superius (Stms), Ch ctl, Stomion inferius (Stmi), Labrale inferius (Li), p < 0.05; Ch dev, p < 0.01, Table 4) and all landmarks related to the chin (B’, Pog’, Me’, all p < 0.05)
The accuracy of superimposing the surface image of CBCT and the facial scan has been evaluated in previous studies, which reported that the image fusion was acceptable with a minimum error less than 1 mm [11–13]
Summary
To evaluate the three-dimensional (3D) changes after mandibular setback surgery (MSS) in skeletal Class III malocclusion using cone-beam computed tomography (CBCT) and a structured light-based scanner. There are only a few studies of 3D soft tissue changes using facial scan imaging after orthognathic surgery in mandibular prognathism [4,5,6]. In previous studies using 2D lateral cephalograms, skeletal changes after orthognathic surgery were evaluated only in an anteroposterior or vertical dimension, but. Cone-beam computed tomography (CBCT) provides 3D information about deep skeletal structures and superficial skin but has disadvantages in soft tissue evaluation due to a low resolution with large slice gaps, the absence of color values, and a long scanning time [7, 8]. CBCT and surface scanning data should be combined to evaluate the relationship between hard and soft tissue changes more accurately
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