Effect of modified glaze application protocols on color stability of 3D-printed permanent dental resins

This study aimed to evaluate the effect of four different surface‑treatment protocols-including a novel Optiglaze before post‑curing approach on the surface morphology and color stability of two 3D‑printed permanent resin materials following thermocycling and staining procedures.

Two permanent crown materials were fabricated and then divided into four groups, each subjected to one of the following surface‑treatment protocols: mechanical polishing (MP), Optiglaze applied after post‑curing (OG‑Post), Optiglaze applied before post‑curing (OG‑Pre), or a combined pre‑/post‑curing Optiglaze protocol (OG‑Pre/Post). A total of 248 specimens (n = 10 per material × surface treatment × staining solution) were prepared. Color measurements were performed at baseline, after 10,000 thermocycles, and following 30‑day immersion in artificial saliva, coffee, or red wine using a spectrophotometer (VITA EasyShade V). Color changes were assessed using the CIEDE2000 (ΔE₀₀) formula in relation to perceptibility (PT₀₀ = 0.81) and acceptability (AT₀₀ = 1.81) thresholds. Data were analyzed using mixed‑design ANOVA and adjusted post‑hoc tests with statistical significance set at p < 0.05. Surface morphology and glaze layer characteristics were examined using field‑emission scanning electron microscopy (FE‑SEM) on representative specimens, including both surface and cross‑sectional analyses (n = 1).

Thermocycling significantly increased ΔE₀₀ values in all groups (p < 0.05), with the greatest change observed in the VarseoSmile MP specimens, which exceeded AT₀₀. Staining solutions significantly affected color change (p < 0.001), and coffee and red wine caused ΔE₀₀ values above AT₀₀ across all groups. OG‑Pre demonstrated significantly lower ΔE₀₀ values than OG‑Post (p < 0.05), particularly in Crowntec specimens. MP groups exhibited significantly higher ΔE₀₀ values than all Optiglaze‑treated groups (p < 0.05). FE‑SEM analysis revealed smoother, more homogeneous, and better‑integrated glaze layers in OG‑Pre specimens, with fewer surface defects.

Applying Optiglaze before post‑curing represents an effective surface treatment strategy that enhances glaze integration, improves surface morphology, and provides superior resistance to discoloration compared with conventional post‑cure glazing.