Chlorhexidine-loaded bioactive glass for incorporation into adhesive systems: Mechanical properties, antibacterial activity, cell viability, and hydroxyapatite precipitation

Aim To evaluate the effect of chlorhexidine-functionalized bioactive glass (45S5) addition on mechanical and bioactive properties of experimental self-etching adhesives. Material and methods The bond of two-step self-etching adhesives were used in the following groups: (1) Magic Bond (commercial control – hydrophobic adhesive); (2) Experimental bond without bioglass (experimental control); (3) Experimental bond + 5% 45S5 glass (wt%); (4) Experimental bond + 20% 45S5 glass (wt%); (5) Experimental bond + 5% chlorhexidine-functionalized 45S5; (6) Experimental bond + 20% chlorhexidine-functionalized 45S5. Hourglass-shaped specimens were made to obtain data on mechanical properties (cohesive strength and elastic modulus). Adhesive discs were made for bacterial activity evaluation using Streptococcus mutans UA159 biofilms. The materials’ cell viability (%) was tested using the MMT assay technique. For the evaluation of mineral precipitation, adhesive discs were made, kept in PBS for 28 days and used for SEM/EDS analyses. Results The 45S5 CHX group (20%) presented the lowest values of mechanical properties (p < 0.001). On the other hand, only groups containing 45S5 previously functionalized with chlorhexidine, in any of the concentrations tested, were able to prevent biofilm formation (p < 0.001). None of the tested adhesives presented cytotoxicity, being similar to the commercial negative control (p > 0.05). SEM and EDS analyses revealed the functionalization of 45S5 bioactive glass with chlorhexidine did not impair the bioactivity of the newly developed adhesive systems. Conclusion Despite reducing some mechanical properties of the experimental adhesive system, the functionalization of bioglass particles with chlorhexidine reduces biofilm formation, does not compromise its biocompatibility, and maintains the mineral precipitation.