Surface topography, optical properties, and biofilm adhesion of additive and subtractive-manufactured ceramic reinforced hybrid composite: an in-vitro study

This in vitro study aimed to assess the influence of manufacturing techniques (additive vs. subtractive) and surface finishing (glazing vs. polishing) on the average surface roughness (Ra), optical properties as mean color change (ΔE ab ), translucency parameter (TP) and opalescence parameter (OP), and microbial adhesion as colony-forming units per milliliter (CFU/mL) of ceramic-reinforced composite veneers subjected to toothbrush simulation and coffee immersion. Eighty veneers were fabricated ( n = 40 per manufacturing method) and assigned to four groups ( n = 20): printed-glazed, printed-polished, milled-glazed, and milled-polished groups. All specimens underwent a combined protocol of thermal cycling in coffee and simulated tooth brushing. Scanning electron microscopy was used to analyze the morphological characteristics of the groups. Ra was measured via contact profilometry. ΔE ab was assessed via spectrophotometry. The bacterial adhesion of Staphylococcus aureus and Streptococcus mutans was quantified as CFU/mL. Statistical analysis was performed using two-way ANOVA and repeated ANOVA with p ˃ 0.05 were considered as significant differences. Spearmen correlation analysis was performed to check the association between the groups. Additively manufactured glazed specimens demonstrated the greatest color change (ΔE ab = 2.45 ± 1.69) and average surface roughness increase (Ra = 0.371 ± 0.04 μm) following aging, while milled-polished specimens showed superior surface stability. Translucency decreased significantly in milled-polished groups (ΔTP = − 10.35 ± 4.80). Milled-polished surfaces exhibited the highest bacterial adhesion (980.80 ± 401.37 CFU/mL), whereas additively manufactured glazed surfaces demonstrated the lowest microbial colonization (679.78 ± 448.00 CFU/mL). The p-value was ˃ 0.05 for both manufacturing technology and surface condition treatments. Manufacturing technique and surface finishing significantly influenced optical stability and microbial adhesion of resin-ceramic hybrid veneers. Milled-polished specimens showed superior surface stability, whereas additively manufactured glazed surfaces demonstrated favorable microbial resistance. Clinicians should consider both fabrication method and finishing protocol when optimizing long-term esthetic and biological performance of veneer restorations.