Which condition should prevent the use of an abutment tooth in RPD?

An abutment tooth in a removable partial denture (RPD) is critical for providing support and stability. The presence of carious lesions on a tooth is a significant concern because it compromises the structural integrity and health of that tooth. Caries can lead to further deterioration, potential tooth loss, and might affect the overall function and longevity of the RPD.

Using a carious tooth as an abutment can result in failure of the restoration and complications in the patient's oral health. It is important that any abutment tooth should be free from disease or decay to ensure it can adequately support the RPD and withstand functional forces over time. Therefore, a tooth with carious lesions should be treated or restored before it can be considered a viable abutment for an RPD.

On the other hand, existing restorations, minor tooth contours, and the age of the patient typically do not exclude a tooth from being used as an abutment, as long as the tooth itself is healthy and functional. Minor adjustments can often be made to accommodate restorations or tooth shapes, and a patient's age does not inherently affect the choice of abutment teeth.