Relationship Between the Changes in the Inclination of the Incisors and Soft Gingival Tissue Remodeling During the First Phase of Orthodontic Treatment Without Premolar Extraction

Background/Objectives: The present study aimed to investigate how the changes in the inclination of the upper and lower incisor regions during the alignment phase of orthodontic treatment (OT) without premolar extraction influence the height and thickness of the gingiva around these incisors. Methods: This prospective clinical study included 62 patients undergoing OT without premolar extraction. Cone beam computed tomography and intraoral 3D scans were taken before and after the alignment phase, and superimposed using specialized software. The changes in the inclination of each tooth, alveolar bone height (ABH), clinical crown height (CCH), and gingival thickness on the level of the cement–enamel junction (CEJ) and 1 mm below it were determined on both tooth sides. Results: The alignment phase of OT was accompanied by an increase in CCH on the buccal side of both upper and lower incisors. In contrast, on the palatal/lingual sides, either a decrease or an increase in CCH was observed, depending on the direction and amount of the changes in the inclination. Furthermore, in many cases, a decrease in the gingival thickness was observed, which was especially pronounced on the palatal side of the upper incisors after proclination. The changes in the CCH and gingival thickness on the palatal/lingual sides exhibited a weak to moderate correlation with the changes in the inclination. In addition, a very weak to weak correlation between the changes in gingival parameters and ABH was observed. Conclusions: Our data suggest that there is some soft tissue remodeling during the alignment phase of OT, and the changes in soft tissue parameters exhibit some dependency on the changes in inclination. Potential changes in the soft tissue should be considered in planning orthodontic treatment.