How does one determine the number of abutments to be used?
There is no rigid rule. Determining factors include:
1. The greater the number of pontics, the greater the increase in loading forces on the abutments
2. The position of the pontics affects the loading forces of the abutments: the more posterior the pontics, the greater the loading forces on the abutments.
3. The crown-to-root ratio of the abutments (bone support): a periodontally compromised mouth increases the abutment-to-pontic ratio.
4. Roots of the abutments that are parallel to each other distribute the loading forces down the long axis of the teeth. When the loading forces do not fall within the long axis of the tooth, the lateral forces on the abutments are increased. This situation necessitates the use of additional abutments.