Comparative Analysis of the Mechanical and Biofilm Surface Formation of 3D Printed Resins and Milled PMMA Blocks With and Without Inorganic Fillers.

OBJECTIVES: Despite the growing number of studies assessing the performance of temporary restorative materials fabricated through CAD/CAM technologies, comparative analyses among 3D printed resins and milled PMMA blocks with differing compositions remain limited. This study compared mechanical and biofilm surface formation of 3D printed resins PMMA blocks with different compositions, using composite resin as control. MATERIAL AND METHODS: Bar‑shaped (25 × 2 × 2 mm) and disc‑shaped (6 × 2 mm) specimens were fabricated. Flexural strength was evaluated by three‑point bending (ISO 4049), and Vickers microhardness was recorded. Multispecies biofilm formation was quantified using CFU/mL and examined morphologically via SEM. Statistical significance was set at α = 0.05. RESULTS: The 3D printed resins and milled hybrid PMMA showed the lowest flexural strength, with no significant differences between them, while the composite resin achieved the highest and statistically superior values (p < 0.001). 3D printed resin without inorganic fillers showed the lowest Vickers microhardness values (12.66 ± 0.83 HK) while 3D printed resin with inorganic fillers (15.20 ± 1.94 HK) and milled conventional PMMA (16.03 ± 1.35 HK) exhibited higher values. However, none of them differed statistically from the 3D printed resin without inorganic fillers (p = 0.064). Conversely, milled hybrid PMMA (16.67 ± 2.10 HK) demonstrated significantly higher Vickers microhardness than 3 d printed resin with inorganic fillers (p < 0.001). Biofilm formation ranged from 2.26 × 107 to 2.82 × 107 CFU/mL, with no significant differences among materials (p > 0.05). CONCLUSIONS: Milled and 3D printed materials demonstrated comparable mechanical behavior while composite resin remained the performance benchmark. Material selection for provisional restorations should account for mechanical behavior and biological interactions, as surface treatment and clinical conditions may influence microbial colonization.