Relationships between soft tissues in a posed smile and vertical cephalometric skeletal measurements

• Posed smiles were measured in 3 dimensions and compared with vertical skeletal measurements.
• As SN-GoGn and anterior facial height increased, interlabial gap increased.
• As SN-GoGn and anterior facial height increased, smile index decreased.
• Some hard tissue measurements were significantly related to smile width.
• Some hard tissue measurements were significantly related to movements of the lower lip.

IntroductionThe purposes of this study were to measure the 3-dimensional parameters of the posed smile and to see whether there are any correlations with vertical cephalometric skeletal measurements.MethodsPretreatment records from a sample of 110 white girls between the ages of 12 and 18 years were gathered. The measurements of SN-GoGn, anterior facial height, and lower and upper facial height percentages were obtained from tracing lateral cephalograms. Superimposing the repose and the posed smile facial scans allowed for measurements to be obtained showing the movements in the x, y, and z dimensions of the upper and lower lips, the commissures, and the Cupid's bows. Correlations and multiple linear regression analyses were run to check for associations and predictive relationships between the cephalometric skeletal measurements and soft tissue changes.ResultsWe found significant moderate correlations and weak correlations. Significant multiple regression models were found for intercommissural width, smile index, and lower lip in the y and z dimensions.ConclusionsThere were moderate correlations showing that as SN-GoGn and anterior facial height increased, the interlabial gap increased as the smile index decreased. Significant relationships were found between certain hard tissue cephalometric measurements and the width of the smile as well as the movements of the lower lip.