Effect of TiO2–SiO2 sol–gel coating on the cpTi–porcelain bond strength

The effects of TiO2–SiO2 sol–gel coating with different firing temperatures (300 °C, 500 °C, and 750 °C) on the cpTi–porcelain bond strength were investigated in the present study. Prior to applying the low-fusing dental titanium porcelain, the phase, surface morphology, surface roughness and static water contact angle of the intermediate layer were evaluated. The cpTi–porcelain bond strength was measured using the three-point flexure test according to ISO 9693 standard. Statistical analyses were made using one-way ANOVA and Dunnett-t test. Significantly higher bond strength of TiO2–SiO2/750 °C (specimens coated with TiO2–SiO2 sol–gel coating and fired at 750 °C for 1 h) when compared to the control group was observed (p < 0.05). No rutile phase was found in all the tested specimens coated with TiO2–SiO2 sol–gel coating. The surface morphology of the intermediate layer was apparently different with different firing temperatures. It was found that the static water contact angle of TiO2–SiO2/750 °C significantly decreased (p < 0.05). However, no markedly different Ra of TiO2–SiO2/500 °C and TiO2–SiO2/750 °C in comparison to that of the control group was observed (p > 0.05). The results show that the TiO2–SiO2 sol–gel coating fired at 750 °C for 1 h can notably improve the cpTi–porcelain bond strength and may be suitable for clinical use.

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► The effects of TiO2–SiO2 sol–gel coating, under different firing temperatures (300 °C, 500 °C, and 750 °C), on the cpTi–porcelain bond strength were investigated for the first time.
► The cpTi–porcelain bond strength of specimens, coated with TiO2–SiO2 sol–gel coating and fired at 750 °C for 1 h, was significantly improved in comparison to that of the control group.
► The failure of the cpTi–porcelain system with TiO2–SiO2 sol–gel coating fired at 750 °C for 1 h occurred not only at the titanium–oxygen interface, but also at the TiO2–SiO2 sol–gel coating.
► The TiO2–SiO2 intermediate coating fired at 750 °C for 1 h may be suitable for clinical use to enhance the poor bond strength.