[An analysis of angles related to gingival cone and marginal gingiva in natural dentition]

There are no reports on numerical investigation of suitable shapes of restoration. This study examines the relationship between gingival cone and marginal gingiva in natural dentition, and discusses the standard angles for giving a suitable shape at the gingival cone of restoration.

Twenty dental casts of healthy subjects with normal dentition were examined. The angles between gingival cone and marginal gingiva (CG angle), and the angles between gingival cone and the long axis of the tooth crown (CA angle) were measured.

The mean CG angles of each site were measured between 96.7 degrees (palatal surface of the upper first molar) and 123.9 degrees (labial surface of the lower central incisor). Within the same kind of teeth, lower significant differences were observed among upper and lower, or buccal and lingual surfaces. The CG angles of anterior teeth were 9.5 to 19.2 degrees larger than those of posterior teeth. The CA angles of anterior teeth were negative, and the apex of gingival cone of anterior teeth was directed toward the incisal edge. Conversely, the CA angles of posterior teeth were positive, and the apex was directed toward the root apex. Significant negative correlation was found between CA angle and CG angle (p<0.001).

These results suggested that the relationship between gingival cone and marginal gingiva is fairly constant throughout their angles, and that the cervical shape could affect the shape of marginal gingiva.