Effect of different washing and post-curing protocols on the fracture resistance of 3D-printed pediatric crowns after thermal cycling

Three-dimensional (3D) printing is increasingly used for pediatric crown restorations; however, post-processing procedures may critically influence their mechanical performance. This in vitro study evaluated the effects of washing and post-curing durations on the fracture resistance and fracture pattern distribution of 3D-printed pediatric crowns after thermal cycling. Ninety crowns fabricated using a digital light processing (DLP) printer were assigned to nine groups according to washing (0, 3, and 10 min of ultrasonic cleaning) and post-curing (0, 10, and 20 min) durations. After cementation onto standardized dies and 10,000 thermal cycles, fracture resistance was tested and fracture patterns were classified. Two-way analysis of variance revealed significant effects of washing and post-curing (p < 0.001), with post-curing demonstrating the strongest individual influence and a significant interaction between factors. The highest fracture resistance was observed with 10 min of ultrasonic washing followed by 10 min of post-curing, whereas prolonged post-curing reduced strength. Fracture patterns also differed significantly among groups. These findings indicate that mechanical performance depends on the coordinated interaction of post-processing steps. For the tested resin system, 10 min of ultrasonic washing followed by 10 min of post-curing appears to represent a clinically applicable protocol to maximize fracture resistance.