Regional bond strengths of resins to human root dentine

Objectives: The demand for restoration of root dentine defects such as cervical erosion and root caries has significantly increased recently, but there is limited information on the performance of the adhesive resins to radicular dentine. The purpose of this study was to measure the regional tensile bond strength (TBS) of composite bonded to human root and coronal dentine, and to observe the interface between resin and root dentine by SEM. Methods: Human extracted cuspid teeth were used to measure TBS with a new microtensile bond test. Enamel and cementum were removed from the labial tooth surfaces to form a long cavity preparation into dentine from the mid-crown to the apex of the root within the same tooth. All Bond 2 (all etch technique) or Imperva Bond (no etch) was bonded to dentine surfaces and covered with Protect Liner resin composite. The resin-bonded teeth were serially sliced into 16 sections at right angles to the long axis of the tooth, and the bonded surfaces were trimmed to give a bonded surface area of 1 mm² for TBS testing. Results: All Bond 2 bond strengths to coronal and apical dentine showed high values (23.5 MPa) but the bond strength was significantly lower on cervical root dentine. Imperva Bond produced a relatively high tensile bond strength to all regional areas. SEM showed that the thickness of the resin-infiltrated layer formed by All Bond 2 in root dentine was less than coronal areas. Resin infiltration with Imperva Bond was always less than 0.5 μm. The results suggest that high TBS values can be obtained with minimal resin infiltration in root dentine.