Impregnation by dentine bonding agents into instrumented root-face dentine

Objectives: To examine the penetration of unfilled resin into instrumented root-face dentine, facilitated by five commercially available dentine bonding agents. Methods: Upper third molar teeth were decoronated, and a given dentine bonding agent and resin composite applied to the instrumented root face, according to the manufacturerʹs instructions. A control specimen was similarly prepared but no dentine primer was applied prior to resin composite. The teeth were sectioned longitudinally and the sectioned surface demineralized and deproteinated. Specimens were examined by scanning electron microscopy (SEM) for resin tag length and density in different areas of the root face. Results: Specimens treated with dentine bonding agent systems exhibited minimum resin penetration of peripheral root-face dentine and much longer penetration of resin tags in dentine above the pulp chamber. A possible ‘hybrid’ layer of resin-impregnated dentine was observed in all specimens where a dentine bonding agent system had been used but was not observed in control specimens. Resin tags were also more sparsely observed in control specimens. Conclusion: Resin tag penetration is superior in both density and length of penetration in dentine overlying and adjacent to the pulp chamber, with shorter and sparser penetration exhibited in peripheral root-face dentine. The possible clinical implications of these observations are discussed.