ObjectiveThis study aimed to quantitatively assess the relationship of smile esthetic variables with various types of malocclusion, and identify the cephalometric factors affecting smile measurements.MethodsThis retrospective study included 106 patients who were treated with retention at the orthodontic department of Taipei Medical University Hospital. Hard-tissue variables were measured using lateral cephalographic tracings, and nine smile esthetic variables were measured using facial photographs. The patients were divided into three groups according to their overjet (< 0, 0–4, and > 4 mm). An analysis of variance was conducted to compare the pretreatment cephalometric variables and smile esthetic variables among the three groups. Multiple linear regression analysis was performed to identify the cephalometric factors affecting the smile measurements in each group.ResultsExcept the upper midline and buccal corridor ratio, all of the smile measurements differed significantly among the three groups before orthodontic treatment. Some of the smile characteristics were correlated with the cephalometric measurements in different types of malocclusion. The overjet was the major factor influencing the smile pattern in all three types of malocclusion.ConclusionsSmile characteristics differ between different types of malocclusion; the smile may be influenced by skeletal pattern, dental procumbency, or facial type. These findings indicate that establishment of an optimal horizontal anterior teeth relationship is the key to improving the smile characteristics in different types of malocclusion.

Objective To investigate whether overbite affects smile esthetics. Methods This study involved 106 patients with complete pretreatment records. Lateral cephalometric tracings were used to measure hard tissue variables. Frontal smile and upper occlusal photographs were used to measure nine smile esthetic variables: arc ratio, number of teeth, upper incisor exposure, upper midline, buccal corridor ratio, smile index, archform index, lower teeth exposure, and interlabial gap. The patients were classified into three groups according to their overbites (B1: 0–4 mm, B2: >4 mm, and B3: <0 mm). Analysis of variance was performed to compare 14 cephalometric measurements and the 9 smile esthetic variables. Multiple linear regression analysis was performed to determine the influencing cephalometric factors. Results Only upper incisor exposure was significantly different among the groups. In the multiple linear regression analysis, upper incisor exposure was positively associated with the distance from the upper incisor to the palatal plane in Group B2. No significant correlations were observed between cephalometric measurements and smile variables in Groups B1 and B3. Conclusions Smile variables were not significantly different among patients with various overbite malocclusions with the exception of upper incisor exposure. Overbite malocclusions do not appear to influence smile esthetics in adult patients.