Comparative In Vitro Assessment of the Antimicrobial Properties of Irreversible Hydrocolloid Impression Material Modified with Two Different Nanoparticles

Background Dental impressions are frequently contaminated with oral microorganisms during clinical procedures, increasing the risk of cross-contamination between patients, clinicians, and dental laboratory personnel. Incorporating antimicrobial nanoparticles into impression materials may provide an alternative to conventional disinfection methods. This in vitro study evaluated and compared the antimicrobial efficacy of irreversible hydrocolloid impression material modified with titanium dioxide (TiO₂) and zirconium dioxide (ZrO₂) nanoparticles against Streptococcus mutans. Methodology A total of 120 disc-shaped specimens were prepared and allocated into five groups (n = 20): control, 2% TiO₂, 5% TiO₂, 2% ZrO₂, and 5% ZrO₂. Antimicrobial activity was assessed using the agar diffusion method by measuring the zone of inhibition after 24 hours of incubation. Data were analyzed using descriptive statistics, one-way analysis of variance (ANOVA), and Tukey's post hoc test (p ≤ 0.05). Results The control group exhibited no antimicrobial activity. Incorporation of both nanoparticles significantly increased the zone of inhibition (p < 0.001). The highest antimicrobial activity was observed in the 5% TiO₂ group (5.75 ± 0.43 mm), followed by 2% TiO₂ (4.98 ± 0.28 mm), 5% ZrO₂ (3.48 ± 0.28 mm), and 2% ZrO₂ (1.73 ± 0.17 mm). Antibacterial activity increased with nanoparticle concentration, and TiO₂ demonstrated significantly greater efficacy than ZrO₂. Conclusions Both TiO₂ and ZrO₂ nanoparticles enhanced the antimicrobial activity of irreversible hydrocolloid impression material, with TiO₂ showing superior efficacy. Nanoparticle incorporation represents a promising strategy for developing self-disinfecting impression materials; however, further investigations are needed before routine clinical application.