Evaluation of the bond strength of a low-fusing porcelain to cast Ti–24Nb–4Zr–7.9Sn alloy

The purpose of this study was to compare the bonding characteristics of titanium porcelain Duceratin bonded to Ti–24Nb–4Zr–7.9Sn (TNZS) alloy and commercial pure titanium (cp Ti). The bond strengths between porcelain and TNZS were tested by a three-point flexural device. The same tests for the cp Ti were used as for the control. Coefficient of thermal expansion (CTE) of TNZS was evaluated with a push-rod dilatometer. Interfacial characterization was carried out by X-ray energy-dispersive spectrometry (EDS) analysis operating in line scan mode. Additionally, microstructure characterizations of TNZS and cp Ti after debonding fracture were analyzed by scanning electron microscope (SEM) and EDS. The porcelain bond strength of TNZS alloy was 31.51 MPa, showing a significant increase relatively to that of cp Ti (23.89 MPa) (P < 0.05). Mean CTE values of TNZS alloy was 9.51 × 10− 6/°C exceeding the porcelain by 0.81 × 10− 6/°C, attesting to a better mechanical performance. Interfacial characterization showed the mutual diffusion of Ti, Si, O and Sn along the TNZS–ceramic interface. Both SEM and EDS results revealed that fracture modes of TNZS specimens exhibited a mixed mode of cohesive and adhesive failures. The results demonstrated that TNZS could be a good alternative for the metal–ceramic restoration in the future.