Related Experiment Video
Updated: Aug 5, 2026
Impact of Fabrication Techniques and Polishing Procedures on Surface Roughness of Denture Base Resins
Published on: January 17, 2025
Effect of candy coating and post-processing protocols on the cytotoxicity, surface roughness, and hardness of
Michael DeFee1, Joseph Duran2, Daniel L Alge3
1The MOD Institute, 320 Broad St. #210 Charleston, SC, 29401, USA.
Objectives:
Additive manufacturing has transformed restorative dentistry by enabling precise, cost-efficient, and customized prosthetics. However, the influence of post-processing on the mechanical and biological properties of 3D-printed composite resins remains uncertain.
Methods:
This study evaluated two commercially available resins - OnX Tough 2 (ONXT) and Apex Base (DB) - to assess the effects of six post-processing protocols on cytotoxicity, surface roughness, and hardness. Specimens were printed using a Sprintray Pro 55S printer and treated via: (1) manufacturer's instructions for use (IFU), (2) IFU plus polishing, (3) candy coating with extra glycerin curing, (4) candy coating with extra glycerin curing plus polishing, (5) candy coating with extra glycerin curing plus boiling water bath, and (6) varnish coating. Candy coating refers to the application of a thin layer of unpolymerized printing resin to the printed restoration prior to final curing. Cytotoxicity was assessed using an XTT assay in human gingival fibroblasts, surface roughness was measured by profilometry, and mechanical hardness was measured using Shore D testing.
Results:
All groups, except the varnish treatment, demonstrated cell viability comparable to the control (no resin) group, indicating low acute cytotoxic potential. The varnish coating significantly reduced viability (DB: 72.3%; ONXT: 61.4%). Surface roughness was highest for ONXT IFU control (Ra = 9.21 µm) and lowest for polished groups (DB: 1.16 µm; ONXT: 2.62 µm). Hardness values (83.8-90.5 Shore D) were stable across treatments, with minor reductions following glycerin curing in DB.
Conclusions:
Within the limitations of this in vitro study, post-processing protocols-particularly polishing and oxygen-free curing-improved surface roughness without adversely affecting cytotoxicity or hardness, while varnish coating reduced cell viability.
Clinical Significance:
Optimized post-processing protocols, including polishing and oxygen-free curing, may improve the surface quality and biological performance of 3D-printed dental resins. However, long-term studies and clinical validation are required before definitive clinical recommendations can be made.
