Optimizing diphenyl(2,4,6‐trimethylbenzoyl)phosphine oxide concentration and post‐curing time to balance mechanical properties and color stability in a three‐dimensional‐printed restorative resin

Abstract

Three‐dimensional (3D) printing is widely used in dental restorations; however, optimization of photoinitiator concentration and post‐curing protocols remains critical to achieve a balance between mechanical and esthetic performance. This study evaluated the combined effect of diphenyl(2,4,6‐trimethylbenzoyl)phosphine oxide (TPO) concentration and post‐curing time on mechanical properties and color stability of a 3D‐printed restorative resin. A commercial photoinitiator‐free resin (BioPrint Prov, Horus 3D) was supplemented with TPO at 0.5, 1.0, and 1.5 wt% and fabricated using a digital light processing printer. Specimens were post‐cured for 30, 45, or 60 min under UV light, while non‐post‐cured (NoPC) samples served as controls. Flexural strength and elastic modulus were evaluated using a three‐point bending test. Color stability and translucency were assessed using spectrophotometry (CIELab/Δ E ₀₀ ) under storage conditions, including dry storage, water immersion, and coffee aging. Data were analyzed using two‐way

and Tukey's test. The 1.0% TPO and 30 min post‐curing combination provided best performance, with highest flexural strength and lowest color change after staining. Higher TPO concentration and prolonged post‐curing increased color alteration and yellowness. NoPC specimens showed inferior mechanical properties and greater discoloration. Translucency remained more stable in post‐curing groups. These findings indicate optimized photoinitiator concentration and controlled post‐curing time improve mechanical and esthetic outcomes in 3D‐printed restorative resins.