Three-Dimensional Digital Image Analysis of Skeletal and Soft Tissue Points A and B after Orthodontic Treatment with Premolar Extraction in Bimaxillary Protrusive Patients

Simple Summary Malocclusion is a misalignment or inappropriate relationship between the upper and lower dental arches when the jaws close. Orthodontics, such as tooth extraction, clear aligners, or dental braces, are frequently used to address malocclusion, followed by growth modification in children or orthognathic surgery in adults. The treatment goals are to improve facial and dental esthetics, functional occlusion, periodontal health, and stability. It is also feasible to achieve an esthetic improvement of the soft tissue. This study shows how soft tissues change after extraction of premolars in patients with Angle Class I bimaxillary alveolar protrusion through three-dimensional analysis. The results show that changes in soft tissue point A and skeletal point A are three-dimensionally related. Aim. To investigate the effect of changes in incisor tip, apex movement, and inclination on skeletal points A and B and characterize changes in skeletal points A and B to the soft tissue points A and B after incisor retraction in Angle Class I bimaxillary dentoalveolar protrusion. Methods. Twenty-two patients with Angle Class I bimaxillary dentoalveolar protrusion treated with four first premolar extractions were included in this study. The displacement of skeletal and soft tissue points A and B was measured using cone-beam computed tomography (CBCT) using a three-dimensional coordinate system. The movement of the upper and lower incisors was also measured using CBCT-synthesized lateral cephalograms. Results. Changes in the incisal tip, apex, and inclination after retraction did not significantly affect the position of points A and B in any direction (x, y, z). Linear regression analysis showed a statistically significant relationship between skeletal point A and soft tissue point A on the anteroposterior axis (z). Skeletal point A moved forward by 0.07 mm, and soft tissue point A moved forward by 0.38 mm, establishing a ratio of 0.18: 1 (r = 0.554, p < 0.01). Conclusion. The positional complexion of the skeletal points A and B was not directly influenced by changes in the incisor tip, apex, and inclination. Although the results suggest that soft tissue point A follows the anteroposterior position of skeletal point A, its clinical significance is suspected. Thus, hard and soft tissue analysis should be considered in treatment planning.