Changes in buccal facial depth of female patients after extraction and nonextraction orthodontic treatments: A preliminary study

Abstract

Objective: This study was performed to investigate buccal facial depth (BFD) changes after extraction and nonextraction orthodontic treatments in post-adolescent and adult female patients, and to explore possible influencing factors.

Methods: Twelve and nine female patients were enrolled in the extraction and nonextraction groups, respectively. Changes in BFD in the defined buccal region and six transverse and two coronal measuring planes were measured after registering pretreatment and posttreatment three-dimensional facial scans. Changes in posterior dentoalveolar arch widths were also measured. Treatment duration, changes in body mass index (BMI), and cephalometric variables were compared between the groups.

Results: BFD in the buccal region decreased by approximately 1.45 mm in the extraction group, but no significant change was observed in the nonextraction group. In the extraction group, the decrease in BFD was identical between the two coronal measuring planes, whereas this differed among the six transverse measuring planes. Posterior dentoalveolar arch widths decreased in the extraction group, whereas these increased at the second premolar level in the nonextraction group. The treatment duration of the extraction group was twice that of the nonextraction group. No differences were found in BMI and Frankfort horizontal-mandibular plane angle changes between the groups. BFD changes in the buccal region moderately correlated with treatment duration and dental arch width change.

Conclusions: BFD decreased in adult female patients undergoing extraction, and this may be influenced by the long treatment duration and constriction of dentoalveolar arch width. However, nonextraction treatment did not significantly alter BFD.

Keywords: Adult treatment; Extraction vs. nonextraction; Soft tissue; Three-dimensional scanner.

Figure 1. A, The three-dimensional structured light scanning system; B, initial registration of facial scans before (blue) and after (red) treatment based on five landmarks; C, markings of the frontal-nasal-zygomatic region, the registered images, and shell-to-shell deviation maps showing good registration in the frontal-nasal-zygomatic region, with the error mostly within ± 0.5 mm (black).

Figure 2. A, Sagittal, transverse, and coronal reference planes; B, two coronal measuring planes; C, four landmarks (Sn, Ls, Li, and B′) located on the midsagittal profile and two landmarks (Sn-Ls and Ls-Li) defined as midpoints of vectors; D, six transverse measuring planes; E, anterior border of the buccal region: the planes parallel and 10 mm posterior to plane_AO and plane_O; F and G, frontal and lateral views of the buccal region; H, shell-to-shell deviation of the buccal region between the pretreatment and posttreatment scans; I, black dot showing the intersection of the two planes on the right side of the facial scan (plane_Co2 and plane_Ls, for example); J, distance between the bilateral intersection points defined as facial width; K, generated curves on the facial scan sliced by the measuring plane (plane_Sn-Ls shown as an example); L, generated transverse curves on pretreatment and posttreatment facial scans (right side); and M, curve-to-curve deviation of the generated curves.

Figure 3. A, Registration of maxillary dental casts based on the palatal stable region (black arrow); B, mutual transverse reference plane; C, measurement of dental and alveolar arch widths at two levels: the first molar (M1) and the second premolar (PM2) on the pretreatment cast.