Long-term evaluation of bond strength of CAD/CAM ceramics to resin cement

Abstract

OBJECTIVES: To evaluate the microtensile bond strength of three different CAD/CAM ceramics to six resin luting cements after long-term water storage. METHODS: Three CAD/CAM ceramics(IPS e.max CAD, VITA ENAMIC and VITA SUPRINITY) were prepared into blocks(14 mm×12 mm×4 mm). Final crystallization for IPS e.max CAD and VITA SUPRINITY was obtained. Surface treatments on the ceramics were initially hydrofluoric acid(HF)(IPS Ceramic Etching gel) for 60s and then a silane coupling agent(Monobond-S) for 60s. Two blocks of each ceramic were bonded with six resin cements respectively: Clearfil SA Cement, Variolink II®, 3M RelyX Ultimate, VITA Duo cement, seT and NX3. Bonded blocks were cut into beams of 1.0mm2 cross-sectional area and randomly distributed to two subgroups according to two water storage times: 6 and 12 months. They were tested in a universal testing machine. Fracture surfaces were examined with polarized microscopy and SEM to determine failure modes. These results were compared with the data previously reported for 24-hour, 1-month and 3-month. Three-way ANOVA and Bonferroni tests were used for statistical analysis(p<0.05). RESULTS: Three-way ANOVA showed that all three independent factors(ceramic, resin luting cement) had significant effects on the bond strengths(p<0.001). Bond strengths in all groups decreased as a function of storage time. The 24 hour data was significantly higher than the other groups. The bond strength tested at 3, 6 and 12 months showed no statistical difference. Overall, the bond strength in Vita Suprinity® groups was the highest while IPS e.max® CAD groups had the lowest value in three ceramics(p<0.05). Variolink® II had the highest bond strength overall, followed by VITA Duo cement, 3M RelyX™ Ultimate, NX3 and Clearfil SA Cement. seT presented the lowest bond strength. CONCLUSIONS: VITA Suprinity® and VITA Enamic® exhibited better long-term adhesion compared to IPS e.max® CAD. Different resin cements have different bonding behaviour according to prolonged water storage time.