The purpose of this study was to objectively define and quantify triangular, square, and square/tapered maxillary central incisors. In this study, the shape of maxillary central incisor crowns was investigated in 100 healthy individuals. The results showed that when the contact surface/crown length ratio is less than 43%, the tooth is triangular in shape; when the ratio is more than 57%, the tooth is square in shape; and when the ratio is between 43% and 57%, the tooth is defined as square/tapered. Since it has been shown that the morphologic characteristics of the gingiva and periodontium are partly related to the shape of the teeth, a means of truly defining the shapes of the incisors is now available. This is significant in predicting esthetics, bone volume, and susceptibility to recession, pocketing in the natural dentition, and ridge shrinkage for prosthetic tooth replacement.