The three-dimensional displacements of abutment teeth in fixed partial dentures (FPDs) during mastication were measured while changing the pontic occlusal design, for comparison against those of natural teeth. The purpose of this study was to clarify the influence of pontic occlusal form on the displacements of the abutment teeth, and to decide the optimum pontic occlusal design.
Three subjects, who each had a single missing tooth (upper first molar or second premolar), were chosen. After 3-unit FPDs were cemented, abutment tooth displacement during mastication was measured using a three-dimensional tooth displacement transducer Type M-3. The functional or non-functional cusp inclination of the pontic was changed gradually.
The flatter the inclination of the functional cusp of pontic became, the more the abutment teeth displaced in the buccal direction. The flatter the inclination of pontic non-functional cusp became, the less the abutment teeth displaced in the buccal direction, and the more the abutment teeth mostly displaced in the palatal direction.
If the inclination of the functional cusp of pontic becomes excessively flatter, or the inclination of pontic non-functional cusps becomes as steep as the natural teeth, non-physiological distortion may occur in periodontal tissues of the abutment teeth.