Upper incisor position in the sagittal plane when smiling. A photographic and CBCT study

Abstract

Background: The aim of this study was to analyze the anteroposterior position between the upper incisors (UI) and the soft tissues based on photographs in which the head has been oriented along the Frankfort Horizontal Plane. Material and Methods: Restrospective case-control study carried out by analizing photographic and CBCT images of 109 patientes. The sample was divided into 4 different groups: 21 normocclusive (N), 29 Class II/1st, 29 Class II/2nd y 30 Class III. All patients were positioned using the Frankfurt plane (FH). From this aligned position of the head, a vertical line was drawn perpendicular to the FH passing through the Soft-Tissue Nasion (LN), and the distance in centimeters from of the UI to this vertical line was measured on both the CBCT and the photo of the patient’s profile. Results: the UI was located in front of the LN in the groups N, Class II/1st y Class III (0,4, 0,2, 0,1cm respectively) and behind the LN in the group Class II/2nd (0,2cm). There were significant differences between the Class II/2nd and Normocclusive groups and Class II/2nd and Class II/1st (p<0.001 y p=0.004 respectively). Conclusions: Orthodontic and/or surgical correction of various malocclusions can be planned based on the position of the UI with respect to the LN established in Normocclusive patients.