Subclinical failures of direct pulp capping of human teeth by using a dentin bonding system

The goal of this study was to examine the adhesive interface of pulp tissue to investigate subclinical failures after direct pulp capping (DPC) of human teeth by using a dentin adhesive system.

The pulps of 12 caries-free first premolars scheduled for extraction for orthodontic reasons were exposed and capped with the Single Bond adhesive system. The adhesive technique was carefully performed to ensure complete coverage of the exposed area and a satisfactory clinical aspect. After 1 (n = 6) and 30 days (n = 6), the teeth were extracted for evaluation of the adhesive interface under light microscopy and scanning electron microscopy. Brown-Brenn staining was used to detect bacteria.

The clinical aspect of direct pulp capping during the operation was satisfactory, and all patients were asymptomatic in the postoperative phase. Brown-Brenn staining revealed no bacterial microleakage at both time points. A hybrid layer was seen on all walls but decreased gradually toward the area of pulp exposure. In contrast to clinical data, light microscopy and scanning electron microscopy revealed important subclinical bond failures near the area of exposed pulp. Some frequent findings were gaps between the restoration and the dentin substrate; unpolymerized monomers under the adhesive layer; interface breaks with blood extravasation between the layers of the adhesive system; rupture of the odontoblast layer; and multinucleated giant cells close to the bonding agent.

The Single Bond adhesive system should not be used for direct pulp capping of human teeth because subclinical adhesive failures invariably occur at its interface with the pulp tissue.