Surface Roughness and Microbial Adhesion on Four Provisional Prosthodontic Restorative Materials

Objective: The aim of this study was to evaluate surface roughness (R_a) and microbial adhesion on four provisional prosthodontic materials in comparison to zirconium oxide. Methods: Four provisional prosthodontic restorative materials were evaluated in this study: poly methyl methacrylate (PMMA) acrylic resin (ALIKE; GC America Inc., Alsip, IL, USA), dimethacrylate (Bis-acryl) resin (Integrity; Dentsply Sirona, Charlotte, NC, USA), 3D-printed temporary crown and bridge resin (Formlabs Inc., Somerville, MA, USA), prepolymerized poly methyl methacrylate (milled PMMA) (Harvest Dental Laboratory Products, Brea, CA, USA), and zirconium oxide (Ivoclar Vivadent AG, Liechtenstein, Germany). A total of 90 samples were prepared and divided into two groups per material (treated and untreated). Provisional material samples were prepared per manufacturer's instructions, polished with the same sequence using acrylic burs followed by Acrylipro silicone polishers (Brasseler, Savannah, GA, USA), and pumice with a goat brush. Zirconia was polished with a green grinding stone (ZR Grinders; Brassseler, Savannah, GA, USA), followed by a feather lite (Dialite ZR polisher; Brasseler, Savannah, GA, USA). The Ra of all samples was measured using a digital profilometer. Sterilized samples were incubated in Todd Hewitt yeast extract (THY) broth containing Candida albicans SC5314 and Streptococcus mutans BM71 at 37 °C under anaerobic conditions for 72 h. Subsequently, the number of colony-forming units (CFU) adhered to each sample was determined by serial dilution plating. Normality and homoscedasticity were assessed prior to statistical analysis. Welch's ANOVA was then performed to evaluate differences among all samples, followed by Games-Howell post hoc tests for pairwise comparisons. A p < 0.05 was considered significant in all experiments. Results: Zirconia demonstrated the lowest surface roughness and significantly reduced adhesion of S. mutans and C. albicans compared to all other materials (p < 0.001). Milled PMMA exhibited significantly lower roughness and microbial adhesion than conventional PMMA (p < 0.001), with no significant difference from Printed PMMA in microbial adhesion. Additional pairwise differences were observed between Bis-acryl and PMMA (p = 0.0425), Milled and Printed PMMA (p < 0.0001), and Bis-acryl and Printed PMMA (p < 0.0001). Conclusions: Zirconia and milled PMMA showed superior surface properties and reduced microbial adhesion, supporting their use in long-term provisional restorations. Materials with higher microbial retention, such as self-curing PMMA, bis-acryl, and 3D-printed resins, may be less suitable for extended use. These findings guide material selection to improve clinical outcomes and highlight the need for further in vivo research.