Vertical dimensional changes of the lips in the North American black patient after four first-premolar extractions

The purpose of this investigation was to evaluate the vertical dimensional changes of the lips in the North American black patient after four first-premolar extractions. A sample of 15 patients treated at the Orthodontic Clinic of Howard University College of Dentistry was selected. Pretreatment and posttreatment lateral cephalograms were traced on acetate tracing paper: landmarks of the skeletal and soft tissues were identified, and angular and linear measurements were made. Changes in the vertical dimensions of the lips used the Frankfort horizontal as a reference plane and changes in the horizontal dimensions of the lips used the pterygoid plane as a reference plane. Statistical significance was tested by means of two-tailed t tests and Pearson's r correlations. Findings indicated that retraction of the maxillary incisors correlated with an increase in upper lip depth, an increase in interlabial vertical dimension, and an increase in the inferomentolabial angle. The increase in interlabial vertical dimension correlated with an increase in the horizontal dimension of the upper lip relative to upper incisor retraction. This increase in interlabial vertical dimension relative to upper incisor retraction differed significantly from the results of the study by Jacobs1 on a sample of white patients treated with four first-premolar extractions. It is necessary to investigate this difference in future studies using larger sample sizes.