Medical Research: Emerging Concepts and Applications Vol. 3

Adhesive restorations fail predominantly through fracture and caries at the restoration margin, and the resin-dentine interface has therefore become an attractive target for materials that kill or suppress bacteria. Since the incorporation of a polymerisable quaternary ammonium monomer into a dentine primer in the late 1990s, several hundred laboratory investigations have reported that antibacterial adhesives suppress biofilm viability, acidogenicity and biomass, frequently by several orders of magnitude, and often without measurable loss of immediate bond strength. Only one such system has reached widespread commercial availability, and the clinical evidence supporting a caries-preventive benefit remains thin. This critical narrative review examines whether the biological premise, the mechanistic evidence and the outcome data of antimicrobial dental adhesives cohere. Literature was identified through structured searching of open scholarly databases and indexes, supplemented by citation searching, with reference identity and digital object identifiers verified against registry records. The synthesis is organised around the causal model of secondary caries, the principal chemistries and their structure-activity relationships, the architecture of the laboratory models used to demonstrate efficacy, interactions with bonding performance and interfacial durability, biological safety and resistance, and clinical translation. Three findings dominate. First, wall lesion development in situ and in vitro is governed principally by interfacial gap dimension rather than by bacterial viability at an intact interface, which places much of the demonstrated antibacterial activity at a site where lesions do not readily form. Second, antibacterial activity of adhesive surfaces attenuates markedly with pellicle deposition, water ageing and thermal cycling, whereas most efficacy testing is performed on freshly cured specimens. Third, the largest clinical dataset available found no difference in restoration survival or in failure attributed to caries between an adhesive containing an antibacterial monomer and a conventional control. Confidence in the concept is currently limited by outcome measures that are only loosely connected to lesion progression, by short observation periods and by probable reporting bias. Priorities include ageing-inclusive testing protocols, gap-relevant model systems and adequately powered trials in demonstrably high-risk populations.