Influence of Thermal Expansion on the Bond Strength of Nanozirconia and Veneering Ceramics

Abstract

This study was aimed to determine the coefficient thermal expansion (CTE) of colloidal-processed slip-casted novel nanozirconia (Zir) and to elucidate the effect of the differences in CTE values between zirconia cores and veneering porcelains on core–veneer shear bond strength (SBS). CTE measurement was performed on core materials (CMs; Zir and Cercon® [Cer]) and veneering ceramics (VCs; Ceram Kiss® [CK], VITA VM9® [VM9], and IPS e.max Ceram® [e.max]). The SBS test was conducted on six groups of core–veneer samples (Zir–CK, Zir–e.max, Zir–VM9, Cer–CK, Cer–e.max, and Cer–VM9). The mean CTE values (× 10− 6/°C ± standard deviation) of Zir and Cer were 7.86 ± 0.47 and 7.82 ± 0.49, respectively. CK, VM9, and e.max recorded mean CTE values of 7.20 ± 0.62, 7.20 ± 0.29, and 7.10 ± 0.46, respectively. No statistically significant differences were found among the CTE values of CMs and between those of VCs. Zir–VM9 recorded the highest mean SBS value (MPa) of 149.48 ± 67.64, whereas Cer–e.max produced the lowest SBS value of 44.07 ± 16.49. Combinations with high CTE disparities produced low SBS values. CTE discrepancies affected the SBS of veneered zirconia restorations. The novel zirconia showed similar performance and can be used as an alternative to commercial zirconia.