上顎中切歯の支台歯形成における基準軸の検討

抄録

In many reports and publications, the axis of the tooth crown is used as the standard axis for tooth preparation of vital teeth. However, in 1968, Oohashi reported reduction of survival tooth substance in the mesial horn of the pulp chamber when the axis of the tooth crown was chosen as the axis of tooth preparation for treatment of the upper central incisor. Furhermore, in such cases, unexpected pulp exposure and extended tooth reduction are frequently observed clinically. Considering the position of the coronal portion of the preparation relative to the pulp cavity, we examined whether the axis of the tooth crown is the most appropriate choice as the standard axis of the tooth preparation.
The following results were obtained with extracted upper central incisors as specimens.
1. More survival tooth substance was found on the distal side of the axial surface than on the mesial side when tooth preparation was done according to the axis of the tooth crown.
2. The distance from the incisal surface to the distal horn of the pulp chamber was longer than that to the mesial horn of the pulp chamber.
3. In order to maintain an even thickness of the distal and mesial survival tooth substance, it was found that the standard axis should be tilted to the mesial side at about 2.9 degrees relative to the axis of the tooth crown.