The effects of rinsing and curing conditions on the biocompatibility of 3-dimensional-printed resin orthodontic brackets.

INTRODUCTION

The incorporation of 3-dimensional (3D) printing into orthodontics offers new opportunities for in-office fabrication of resin brackets. However, concerns remain regarding the cytotoxic effects of residual monomers because of incomplete polymerization during postprocessing. This study evaluates the biocompatibility of two 3D-printed dental resins using varying postprocessing protocols.

METHODS

Two resins, SprintRay ceramic crown (SprintRay Inc, Los Angeles, Calif) and SprintRay crown (SprintRay Inc), were 3D printed into standardized discs and processed under 3 experimental conditions: (1) no postprint cure vs postprint cure; (2) postprint cured with prolonged rinsing; and (3) air cured vs glycerin cured. Human periodontal ligament fibroblasts were exposed to each disc for 24 hours. Cell viability was evaluated with Calcein AM (Invitrogen,Thermo Scientific, Carlsbad, Calif) staining and fluorescence quantification. Statistical analysis used Student t test with significance set at P <0.05.

RESULTS

Uncured discs displayed significantly higher cytotoxicity than cured discs (P <0.05). Prolonged rinsing for 1 week significantly reduced cytotoxicity in both resins, with no further reduction at 2 weeks. Glycerin immersion during curing further reduced cytotoxicity and eliminated significant differences between the 2 resins (P >0.05).

CONCLUSIONS

Postcuring reduces the cytotoxicity of 3D-printed resins, though not entirely. Prolonged rinsing and glycerin immersion significantly improved the biocompatibility. These postprocessing modifications can enhance the clinical biocompatibility of 3D-printed orthodontic brackets and support the need for optimized postprocessing protocols in clinical applications.