Orthodontic treatment improves gingival morphological symmetry parameters: a retrospective study

Abstract

Background: The pursuit of an aesthetically pleasing smile is closely tied to the symmetry of teeth and gingival morphology, yet the impact of orthodontic treatment on gingival contour symmetry remains underexplored. This study aims to investigate the effects of orthodontic treatment on gingival morphology symmetry.

Methods: This retrospective study includes 50 eligible patients as the experimental group and 50 healthy individuals as the control group. Digital intraoral scans were performed for malocclusion patients both before and after clear aligner treatment, as well as for individuals in the control group. Geomagic Control X software was used to assess quantitative indices affecting gingival morphology and contour symmetry. Specifically, mean deviation distance (MDD) was used to measure the average deviation of gingival points relative to the contralateral gingival contour, root mean square (RMS) to reflect the overall level of deviation across all gingival points, and the percentage within tolerance to indicate the proportion of points falling within the tolerance range. Statistical analysis was conducted using SPSS 24 software, with significance set at P < 0.05. The reproducibility of measurements was assessed by the intraclass correlation coefficient (ICC).

Results: Significant statistical differences in gingival contour symmetry measurements were observed within the study group before and after orthodontic treatment. (P < 0.001). Comparisons between the postorthodontic group and the control group revealed no significant differences in most gingival contour symmetry parameters. Additionally, there were no statistically significant differences in the mean changes of MDD and RMS across different tooth positions before and after orthodontic treatment. However, a statistically significant difference was observed in the changes of percentage within tolerance (p = 0.019) across tooth positions before and after orthodontic treatment.

Conclusion: Orthodontic treatment significantly enhances gingival contour symmetry in patients with mild anterior crowding and skeletal Class I malocclusion. A comparison of the gingival morphology symmetry in the anterior teeth between postorthodontic patients and healthy individuals revealed no statistically significant differences.

Trial registration: This study was approved by the Biomedical Research Ethics Committee of Stomatology Hospital of Fujian Medical University (approval no. 2024-14).

Supplementary Information: The online version contains supplementary material available at 10.1186/s12903-025-06452-x.

Keywords: Dental aesthetics; Digital intraoral scans; Gingival; Orthodontic treatment; Symmetry; Three-dimensional analysis.

Fig. 1

(A) Digital maxillary intraoral scan model of an orthodontic patient before treatment; (B) Digital maxillary intraoral scan model of an orthodontic patient after treatment; (C) Digital maxillary intraoral scan model of a healthy individual in the control group

Fig. 2

(A) Segmented digital model of the maxillary anterior region; (B) Extracted bilateral gingival curves from the model, with the yellow curve representing the gingival contour of teeth 11–13 and the red curve that of teeth 21–23.; (C) Extracted gingival contours of homologous teeth on both sides of the model, with the yellow curve representing the gingival contour of the canines, the green that of the lateral incisors, and the red that of the central incisors; (D, E and F) Software-generated mirror plane views at left 45°, frontal, and right 45° angles, respectively

Fig. 3

(A, B, C and D) The red curves represent the gingival contours of the right central incisor, lateral incisor, and canine, as well as the mirrored gingival curve of the anterior region, projected onto the opposite side to generate the mirror model; (E, F, G and H) Fitting of the gingival contours and curves between homologous teeth on both sides at specific positions; (I, J, K and L) Results of the deviation analysis for the gingival contours of the bilateral central incisors, lateral incisors, canines, and the gingival curve of the anterior region

Fig. 4

(A) Deviation analysis of the bilateral gingival curves in orthodontic patients before treatment; (B) Deviation analysis of the bilateral gingival curves in orthodontic patients after treatment; (C) Deviation analysis of the bilateral gingival curves in the control group of healthy individuals