Influence of liners on bond strength between composite-resin and dentin

Objectives: This study evaluated the use of glass ionomer and calcium hydroxide resin liners on bond strength between composite resin and dentin. Methods: Bovine incisors were embedded in acrylic-resin and a flat dentin surface was created. Silicone matrices with 1 and 2mm diameter holes were fixed to the area of exposed dentin to limit the area of application of the resin-based liner. The specimens were divided in 7 groups (n=12): Group 1 (control) no liner. For groups 2, 4 and 6, Vitrebond-Plus (3M-ESPE), Ultrablend-Plus (Ultradent) and Vidrion F (SSWhite) were respectively applied to the exposed dentin using matrices with 1mm diameter holes. For groups 3, 5 and 7, the same liners were applied using matrices with 2mm diameter holes. The dentin was etched for 15s and Adper Single Bond 2 (3M-ESPE) used in dentin and liners. Filtek-Z350 (3M-ESPE) was inserted through a silicone matrix with a 5mm diameter hole placed over the liner-capped exposed dentin and with the liner centered within that hole. The specimens were subjected to thermo-mechanical cycling: 100,000 mechanical-cycles of 30 N at 4 Hz and 1000 thermal cycles (5°C, 37°C and 55°C). They were subjected to shear bond testing until failure. Data were analyzed by one-way ANOVA and Tukey multiple comparison test at a = 0.05. Results: Bond strengths (mean±SD in MPa) were in descending order: Vidrion F 2mm 4.87±1.79^a, control 3.47±2.06^ab, Vidrion F 1mm 2.94±1.01^b, Vitrebond 2-mm 2.82±1.62^b, Ultrablend 1-mm 2.82±1.61^b, Vitrebond 1mm 2.52±0.75^b, Ultrablend 2mm 2.26±0.88^b. Vidrion F had a significantly higher bond strength compared with other groups regardless of the application area. Bond strength of Vidrion F applied to 2mm holes was not significantly different from the control group. Conclusion: Within the limits of the present study, the use of liners cannot result in significant lowering of composite bond strength. Supported-FAPESP (process 2009/53182-3)