A comparative study of strength and surface properties of permanent 3D-printed resins with CAD-CAM milled fixed dental prostheses

Purpose: To compare the strength, surface roughness, and hardness of newly introduced permanent three-dimensional (3D)-printed resin in comparison with computer-aided design and computer-aided manufacturing (CAD-CAM) milled materials. Materials and Methods: Three 3D-printed resins (NextDent C&B, Formlabs Permanent Crown, and VarseoSmile Crown plus) and two CAD-CAM milled (IPS e.max ZirCAD LT and VITA Enamic) resins were used to fabricate discs specimens. A total of 200 disc specimens were fabricated according to manufacturer recommendations. Within each group, half of the specimens were subjected to thermal cycling (5°C–55°C, the 30 s, 5000 cycles). Aged and nonaged specimens were evaluated for biaxial flexural strength (BFS), surface roughness, and hardness. Results were statistically analyzed using analysis of variance (ANOVA) and t-tests (α = 0.05). Results: Significant differences (p < 0.05) were observed in the BFS, surface roughness, and hardness between the 3D-printed and milled groups, before and after thermal aging. Overall, the CAD-CAM milled ceramic group had superior strength, surface roughness, and hardness when compared to all other groups (p < 0.001), except for surface roughness after thermal aging, which was similar in all groups (p = 0.063). Within each group, there was no significant difference (p > 0.05) in surface roughness after thermal aging. BFS values of 3D-printed materials were statistically similar. In terms of surface roughness, Formlabs specimens displayed the highest value before and after thermal cycling, when compared to other 3D-printed materials. Regarding hardness, the VarseoSmile Crown plus group demonstrated the highest values compared to other 3D-printed materials, before and after thermal cycling. Conclusion: Permanent 3D-printed resins have lower strength than CAD-CAM milled materials. 3D-printed permanent resin materials exhibited high roughness and comparable hardness to CAD-CAM materials. Thermal aging negatively affected the properties of 3D-printed permanent crowns. Owing to the low strength of 3D-printed permanent resins, they may not be recommended for clinical practice until further improvements in flexural strength are made to meet clinical standards.