Prolonged post-washing in ethanol decreases bond strength of additively manufactured crown materials

Abstract

This study aimed to investigate the effect of post-washing duration and crown thickness on the bond strength between additively manufactured crown materials and dental cement in vitro. Rectangular-shaped specimens of two thicknesses (1.5 and 2.0 mm) were additively manufactured from permanent VarseoSmile Crown (VC) and long-term temporary NextDent (ND) materials. The specimens were post-washed (n = 160) in ethanol for 5 minutes, 10 minutes, 1 hour, and 8 hours then cemented with dual-cure resin cement. Twenty PMMA (TC) were milled as a control. A chevron-notch test was performed to measure the maximum load until failure (N). Interfacial bond strength (J/m2) was calculated and statistically analysed. The mode of failure was analysed by scanning electron microscopy (SEM). There was a significant difference in the bond strength between all groups (p < 0.01). VC at 1.5mm thickness post-washed for 10 minutes showed the highest mean bond strength (1.77 ±0.96 J/m2) while VC at 2.0mm thickness post-washed for 8 hours showed the lowest (0.22 ±0.10 J/m2). Exposure to ethanol for 8 hours resulted in lower bond strength. Within the type of material, there were no differences in bond strength between the thicknesses when post-washed for the same duration. Prolonged post-washing of AM crown materials can significantly decrease the bond strength to resin cement. There were no differences between the permanent and long-term temporary AM materials. When post-washed for 5 minutes, AM materials observed comparable or higher bond strength values compared to PMMA. The output of this research serves as a guide for dental practitioners, emphasising the importance of adhering to correct post-washing procedures for optimal bond strength of additively manufactured crown materials.

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