Abstract
3D-printed dental crowns are becoming increasingly common. For restorative success, they must be cemented securely in the mouth to withstand masticatory forces. Post-cleaning of the crowns is critical to remove any hazardous residue, however, anecdotal evidence suggests dental practitioners clean 3D-printed objects for longer than recommended. How the cleaning duration effects the bond between the crown material and cement is unknown. The study aimed to measure and compare the bond strength of 3D-printed crowns after different cleaning durations.
Total 160 rectangular-shaped specimens were 3D-printed in two clinically common crown thicknesses (1.5 and 2.0 mm) from permanent and long-term temporary crown materials, then cleaned in ethanol for 5 mins (manufacturer’s recommendation), 10 mins, 1 hour, and 8 hours (n = 10 per group). Twenty milled crown materials served as a control. Specimens were bonded to dental cement and the maximum load (N) until failure was measured to calculate bond strength (J/m2). Statistical analysis was performed using one-way ANOVA and Tukey’s post-hoc test. Scanning electron microscopy (SEM) was conducted.
The 2.0 mm permanent 3D-printed material cleaned for 8 hours showed the lowest mean (0.22 ±0.10 J/m2) while the 1.5 mm permanent 3D-printed material cleaned for 10 mins showed the highest (1.77 ±0.96 J/m2). Bonds of milled materials were weaker (P < 0.05) than 3D-printed. No significant difference was found between crown thicknesses within the same material (P > 0.05). Both 3D-printed crown materials cleaned for 5 mins showed significantly higher bond strength (P < 0.05) compared to 8 hours. SEM images suggests surface degradation from 5 mins to 8 hours impacting mechanical interlocking.
At 5 mins, both 3D-printed materials observed optimal bonding to dental cement. After 1 hour and 8 hours, bonding effectiveness may reduce significantly. Therefore, dental practitioners must exercise caution when cleaning to ensure the long-term success of 3D-printed crowns.