The influence of preparation design and resin type on the marginal adaptation of 3D printed resin onley restorations

Aim: This study compares the marginal adaptation of onley restorations fabricated from two different 3D printed resins with two different preparation designs in plastic teeth. Materials and Methods: This study used two different 3D printed crown resins (Crowntec, Saremco Dental AG, and VarseoSmile Crown Plus, Bego) to produce 80 restoration samples. Two different preparation designs were applied for the two resins, dividing the samples into four groups: Group 1: VarseoSmile Crown Plus + Shoulder preparation, Group 2: VarseoSmile Crown Plus + Flat preparation, Group 3: Saremco Crowntec + Shoulder preparation, Group 4: Saremco Crowntec + Flat preparation. The samples were prepared in accordance with the design rules for shoulder and flat preparation. Prepared models were scanned with a 3D intraoral scanner (Trios, 3Shape, Copenhagen, Denmark). Designs were created using CAD software (ExoCAD 2.4 Plovdiv; ExoCAD GmbH, Darmstadt, Germany). Chitubox V1.7.0 (Guangdong, China) 3D printing software was used to set a 50 µm layer thickness and a 0° print orientation, and the models were sliced. Then, restorations were fabricated with a 3D printer (Phrozen sonic mini 8K SLA device, Phrozen Technology, Hsinchu City, Taiwan). Each restoration was examined under a stereomicroscope (Leica S6 D; Leica Microsystems Inc) at x40 magnification. Measurements were recorded at 18 predetermined locations per tooth. Statistical analysis was performed using one-way ANOVA and Tukey's HSD posthoc tests. Results: Statistical analysis revealed that those produced with Saremco Crowntec (Group 3-4) showed better marginal adaptation than those produced with VarseoSmile Crown Plus (Group 1-2). There is a statistically significant difference (p<0.05). Although the flat preparation groups showed better marginal adaptation than the shoulder groups, no statistically significant difference was found (p>0.05). The lowest marginal gap was observed in the observed occlusal, while the highest adaptation was observed in the mesial. Conclusion: Resin type and location may influence the marginal adaptation of onley restorations, but further studies are necessary. Keywords: Marginal adaptation, Onley, Preparation design, 3D printer