Analysis of the Impact of Incisor Inclination Changes on Facial Aesthetics Post–Orthodontic Treatment for Class I Angle Malocclusion

Abstract Correcting dental malocclusion and attaining facial balance through hard and soft tissues are the outcomes of orthodontic treatment. This article aimed to analyze the impact of incisor inclination (U1-NA, L1-NB) change on facial aesthetics (aesthetic line) with extraction and non-extraction premolar teeth receiving fixed orthodontic treatment for class I angle malocclusion. The study design is cross-sectional, and the research methodology is analytical and observational. This study used 38 samples, which were divided into two groups: 19 extractions and 19 non-extractions. Evaluation of pre- and posttreatment cephalometric values for the upper and lower lips relative to the aesthetic line, U1-NA and L1-NB, is documented. The normality test for data uses the Shapiro–Wilk test to ascertain the analytical applicability of the standard data distribution. The paired sample t-test was used to assess different parameters before and after treatment. The threshold for significance was a p-value < 0.05. Data were analyzed via IBM SPSS for Windows. There were differences in values of the aesthetic line and U1-NA and L1-NB angles between extraction and non-extraction cases (p < 0.05). In the extraction group, there was a significant decrease in the value (p < 0.05), while in the non-extraction group there was a slight increase in the value, which was not significant (p > 0.05). In both groups, there was a relationship in the same direction between the U1-NA and L1-NB angle values and the aesthetic line values (p < 0.05). For Class I angle malocclusion orthodontic treatment, alterations to the aesthetic line's impact on the upper and lower lip profiles are directly proportional to shifts in the inclination angle of U1-NA and L1-NB. In comparison to the non-extraction group, the extraction group had substantially different aesthetic lines as well as U1-NA and L1-NB angle values.