Comparative Assessment of Maxillary Central Incisor Position in Thai Females with Facial Harmony VS. Pre-Orthodontic Treatment

Abstract

The antero-posterior (AP) position of maxillary central incisors (MCI) to the forehead profiles was described by L.F. Andrews as a useful method to assess attractiveness relative to the MCI position. The purpose of this study was to assess the AP position of the MCI in relation to forehead profile among Thai females and compare this MCI position between facial harmony (FH) and pre-orthodontic (pre-OD) groups. Out of 123 lateral smile profile photographs with MCI clearly visible of adult female volunteers (ages 18-30 years), 33 photographs with harmonious facial profiles were selected as the FH group. Thirty-three matched age and gender pre-orthodontic patient photographs were randomly selected as the pre-OD group. All photographs were consistently recolored, resized and rotated to estimated natural head position (ENHP). Landmarks of MCI position and forehead profile were located and measured. The mean distance between Forehead Anterior Limited Line and Dentition Anterior Limited Line (FALL-DALL distance) representing AP position of MCI was significantly different between the FH and pre-OD groups (-0.18±4.42 mm VS 3.49±3.35 mm respectively, p<.001). No significant differences were observed in forehead inclination between the two groups (12.80±5.69 degrees VS 15.05±3.48 degrees respectively, p=.058). There was a significant positive correlation between FALL-DALL distance and forehead inclination in the FH group (r=0.497, p=.003). The linear regression equation for prediction of MCI position (FALL-DALL distance) from forehead inclination was: FALL-DALL distance (mm) = (Forehead inclination (degree)x0.39) -5.76. To achieve facial harmony in orthodontic treatment planning, forehead inclination could be one of the important landmarks to determine the appropriate AP position of MCI.