Inner canthal distance and geometric progression as a predictor of maxillary central incisor width

Estimating the mesiodistal width of maxillary central incisors may be difficult when artificial teeth are selected for edentulous subjects. PURPOSE This study examined the relationship between inner canthal distance and maxillary central incisor mesiodistal width in terms of the geometric progression popularly known as the golden proportion.

Two hundred twenty-nine dentate Saudi subjects (120 males, 109 females; mean age 21.46 years) free from facial and dental deformities were examined. The mesiodistal width of each maxillary central incisor was measured between its interproximal contact points. The inner canthal distance was measured from medial angle to medial angle of the palpebral fissures of the eyes. The common ratios of geometric progression are 0.618 and 1.618. The inner canthal distance of each subject was multiplied by a decreasing function value of the geometric progression term (0.618) to provide the combined width of 2 central incisors. The product was then divided by 2 to obtain the width of a single maxillary central incisor. A t test was used to identify any significant differences in mesiodistal tooth width and inner canthal distance by gender. Agreement between the measured and calculated central incisor widths was evaluated with Pearson's correlation coefficients, as was intraexaminer reliability. Significance was set at alpha=.05.

The mean inner canthal distance of male and female subjects was 28.7 +/- 1.7 mm and 27.9 +/- 2.1 mm, respectively. The mean maxillary central incisor width of male and female subjects was 8.87 +/- 0.5 mm and 8.68 mm +/- 0.4 mm, respectively. Differences between the mean values for both measurements were significant (P =.002). The actual and calculated widths of the natural maxillary central incisors were found to be highly correlated (r =.943).

Within the population tested, a significantly higher mean inner canthal distance and maxillary central incisor width were recorded for male subjects. Inner canthal distance, when multiplied by a decreasing function value of the geometric progression term and then divided by 2, was a reliable predictor of maxillary central incisor width.