Dynamic smile evaluation in different skeletal patterns

Abstract

To evaluate dynamic smile in different skeletal patterns and to correlate vertical smile parameters with the underlying causative factors. A total of 150 participants ranging in age from 16-25 years were selected and divided into one of three groups-horizontal, average, and vertical skeletal pattern-using the following three cephalometric parameters: SN-MP, FMA, and Jarabak ratio. Videographic records of smile were obtained, and measurements were recorded and analyzed at rest, including upper lip length, and during smile, including maxillary incisal display, interlabial gap, intercommisural width, change in upper lip length, and smile arc. Differences among the three groups were subjected to two-way analysis of variance and post hoc and chi-square tests for smile arc. Correlations between vertical smile variables and vertical skeletal (N-ANS, N-Me) and dental cephalometric measurements (U1 to palatal plane) were also investigated. Vertical parameters were significantly increased in the vertical pattern when compared with the horizontal pattern, ie, upper lip length (P < .01), maxillary incisal display (P < .001), interlabial gap (P < .001), and change in upper lip length (P < .001), whereas intercommisural width was significantly decreased in vertical pattern when compared with the horizontal pattern (P < .001). Flat smile arc was seen more frequently in the horizontal pattern. Positive correlations were found between the N-Me, U1-PP, and change in upper lip length with vertical smile parameters. Different skeletal patterns exhibit their characteristic smile features. Upper lip length is not responsible for increased incisal display during smile. Increased incisal display during smile is more closely associated with upper lip elevation than vertical skeletal and dental factors.