Comparative Evaluation of Antibacterial Activity of Three Universal Bonding Agents Against Streptococcus mutans on...

Secondary caries remains a leading cause of restoration failure, often resulting from residual bacteria persisting in demineralized dentin after minimally invasive cavity preparation. The incorporation of inherent antibacterial properties into universal bonding agents might offer a promising strategy to reduce this risk without additional disinfection steps. The aim of this in vitro study was to comparatively evaluate the antibacterial activity of three universal bonding agents against Streptococcus mutans using demineralized human dentin blocks as a simulated carious dentin model.

A total of 150 dentin blocks (4 mm × 4 mm, ~200 µm thick) were prepared from extracted human permanent molars, sterilized, and demineralized in 0.2 M sodium acetate buffer (pH 3.0) for four weeks, followed by washing in 0.02 M phosphate-buffered saline for one week. Each block was inoculated with 0.2 µL of S. mutans suspension and allowed to adsorb for 10 min. The blocks were randomly divided into five groups (n = 30 each): One Coat 7.0 Universal (Coltène/Whaledent AG, Altstätten, Switzerland), Single Bond Universal (3M ESPE/Solventum, St. Paul, Minnesota, USA), Tetric N-Bond Universal (Ivoclar Vivadent AG, Schaan, Liechtenstein), 0.2% chlorhexidine (positive control), and normal saline (negative control). Bonding agents were applied for 20 s in self-etch mode without light curing. Treated blocks were fragmented, homogenized, serially diluted, and plated on Mueller-Hinton agar. Plates were incubated anaerobically at 37 °C for 48 h, and colony-forming units (CFUs) were counted. Log-transformed CFU data were analyzed using one-way analysis of variance, followed by Tukey's honestly significant difference post hoc test (α = 0.05).

A statistically significant difference was observed between groups (F = 425.5, p = 0.001). The positive control (0.2% chlorhexidine) demonstrated the greatest bacterial reduction, followed by the universal bonding agents, which were significantly superior to that of the negative control (p = 0.001). Among the adhesives, Tetric N-Bond Universal exhibited significantly stronger antibacterial activity than One Coat 7.0 Universal (p = 0.024), whereas Single Bond Universal showed intermediate efficacy. All bonding agents achieved substantial CFU reduction relative to saline but remained inferior to chlorhexidine.

Universal bonding agents possess inherent antibacterial properties against S. mutans on demineralized dentin, with efficacy varying according to formulation and pH profile. Although not as potent as chlorhexidine, these agents may contribute to residual bacterial control in minimally invasive restorations, potentially lowering the risk of secondary caries. Long-term in vivo studies are required to confirm their clinical relevance.