Prediction of the shape and size of the maxillary anterior arch in edentulous patients.

The aims of the study were to examine the morphometric and angular relationships between the interincisive papilla and the maxillary anterior teeth, and to describe a clinical method derived from this analysis useful in sitting the upper front teeth. Plaster casts of upper jaws of adult patients with complete dentition, were selected. Two measurements were taken: the distance from the centre of the papilla to the most vestibular part of the labial surface of the anterior teeth; and the angles between the perpendicular to the median line and the line from the centre of the papilla to the most vestibular part of each tooth. The equation of the resulting parabola, corresponding to the upper frontal arch, can be applied to every maxillary dimension. Parabolas were divided into small, medium, and large, using the mean and standard deviations. Each curve was traced on a transparent base-plate shaped for intra-oral placement. In individuals with complete dentition the closest parabola to the maxillary frontal arch was selected and the distance between the lateral frenula measured. Statistical study demonstrated a correspondence between the interfrenulum distance and the parabolas. In edentulous patients the interfrenulum distance thus provides a curve useful in sitting the maxillary anterior arch.