Multimodal electrochemical platform for real-time mapping of heterogeneous ion release from bioactive-glass dental composites and its correlation with interfacial oral biofilm activity.

Abstract

Objectives: The clinical longevity of dental restorations is compromised by pathogenic biofilm colonization at the material-tooth interface. This study aimed to determine whether bioactive glass (BAG)-containing dental composites function as dynamically responsive interfaces, in which localized metal ion release directly modulates multispecies oral biofilm behavior, rather than acting as passive ion reservoirs.

Methods: A multimodal analytical platform was used to monitor interfacial dynamics. Scanning electrochemical microscopy (SECM) equipped with custom Ca²⁺, Mg²⁺, and Zn²⁺ ion-selective microelectrodes mapped the chemical microenvironment 20 µm above composite surfaces. Continuous impedance tracking and solid-state pH microsensors simultaneously quantified biofilm volume and localized acidification on resin, Ca-BAG, Mg-BAG, and Zn-BAG substrates.

Results: Mapping revealed highly heterogeneous ion-release profiles, yielding localized concentrations of 101.1 ± 13.6 µM Ca²⁺, 40.8 ± 21.2 µM Mg²⁺, and 16.1 ± 4.1 µM Zn²⁺ at pH 6.2, a greater than tenfold increase relative to pH 7.2. Zinc-releasing composites extended biofilm maturation to 7.4 ± 0.4 days versus 3.3 ± 0.1 days on resin controls, sustaining an interfacial pH ≥ 6.7 ± 0.2 at a biofilm volume of 29 µm³ /µm². Resin substrates acidified to pH 6.3 ± 0.2 under equivalent biofilm loading.

Significance: These findings establish a quantitative correlation between localized ion-release profiles and biofilm metabolic activity, consistent with a localized interference mechanism and reframing ion-releasing bioactive composites as dynamically responsive interfaces. The analytical framework provides a quantitative basis for the rational design of next-generation interfacially active biomaterials.