Influence of surface pretreatments on the repair bond strength of 3D-printed resin used for permanent restorations: an in vitro study.

INTRODUCTION: 3D-printed permanent resin-based materials have recognized as practical options for permanent restorations because of their mechanical properties, aesthetic performance, and ability to work with digital workflows. There is a lack of studies on identifying the appropriate surface pretreatments to improve repairability of 3D-printed permanent resin. Accordingly, this study assessed how different surface pretreatment conditions impact the repairability of 3D printed permanent resin utilized for definitive restorations. METHODS: Sixty cylindrical specimens from 3D-printed permanent resin (10 mm × 3 mm) were categorized according to their surface pretreatments into five groups after being subjected to 5000 thermocycles. The groups were as follows: Control (C), with no surface pretreatment; Diamond Bur (DB), in which the surfaces were roughened using a diamond bur; Sandblasting (SB), in which the surfaces were treated with airborne particle abrasion; Diamond Bur + Scotchbond Universal Adhesive (DB + SBU), in which diamond bur surface roughening was followed by the application of adhesive; and Sandblasting + Scotchbond Universal Adhesive (SB + SBU), in which airborne particle abrasion was followed by the application of adhesive. Onto the prepared CAD/CAM surfaces, a nanohybrid repair resin composite was packed. Subsequently, SBS and the mode of failure were conducted. Data were statistically analyzed using one-way analysis of variance, followed by Tukey's post hoc multiple comparison test at a p < 0.05. RESULTS: The SB + SBU group had the highest mean repair SBS value (17.45 ± 2.78), whereas the C group demonstrated the lowest SBS value (10.32 ± 2.56). The DB + SBU group exhibited a significantly higher SBS (p < 0.001) in comparison to the control group. No statistically significant difference was observed between the DB and SB groups. Adhesive failure were predominantly observed in the control group. Cohesive failures were observed in the SB + SBU and DB + SBU groups, while mixed failures were observed in all groups except control groups. CONCLUSIONS: Within limitations of this study, roughening with diamond bur can effectively improve repair bond strength of 3D-printed permanent resin without a determinable effect of air particle abrasion. Additionally, applying a bonding agent after mechanical surface roughening improve the repairability of the 3D printed resin utilized for permanent restoration.