H. MENZEL*, M. KERN and J.R. STRUB (Dept. of Prosthodontics, Albert-Ludwigs University, Freiburg, FRG).
In the dental literature numerous methods are discussed concerning the selection of tooth shape, particularly the upper central incisor. The purpose of this study was to evaluate whether there is a correlation between the facial shape and the shape of the upper central incisor as proposed by J.L. WILLIAMS 1914 ("law of harmony").
Standardized portrait and anterior tooth photographs were made of 204 white dental students (102 females and 102 males) ranging in age from 18 to 30 years. Standardized enlargements of the facial and dental outlines of the upper right incisor were traced. Defined widths were measured and comparisons drawn between these outlines. By taking the ratio of two widths, width B being the widest stretch across the face and tooth, respectively, and width A being a defined parallel stretch to width B, the outlines were classified into tapered, ovoid and square-shaped, respectively.
Ovoid faces and tooth shapes were found most frequently (40.7 % and 39.2%, respectively). The face shape was related to the gender. Ovoid faces were equally distributed among females (40.2%) and males (41.2%). Tapered faces were more common in females (34.3%) than in males (20.6%) while square-shaped faces were less common in females (25.5%) than in males (38.2%). However, the shape of the upper central incisor was not distinguishable between females and males. The SPEARMAN correlation analysis showed no statistically significant correlation between facial shape and the shape of the upper central incisor, regardless of gender.
This study could neither confirm the theory that the upper central incisor tooth form is similar to the inverted facial shape nor the theory stating that female tooth form is more often ovoid and male tooth form is more often square-shaped. Therefore the guidelines concerning the selection of anterior teeth should be questioned.