Preservation of Dental Restoration Bond Strength through Interfacial Delivery of Antidegradative Agents

Stewart, Cameron 1 ; Hong, Jenny 2 ; Hatton, Benjamin 1, 3 ; Finer, Yoav 2, 3

1 Institute of Biomaterials and Biomedical Engineering ; 2 University of Toronto Faculty of Dentistry, University of Toronto ; 3 Department of Materials Science and Engineering

Human salivary and bacterial enzymes increase biodegradation of the restoration-tooth interface, and interfacial microbial proliferation and virulence, contributing to restoration failure. Antimicrobial restorative materials may reduce recurrent caries and prolong service life by limiting bacterial proliferation. Some antimicrobials affect hydrolysing enzymes, and therefore could affect the degradation of the restoration-tooth bond.

Objectives: to assess long-term effects of antimicrobial release from resin adhesive on restoration-tooth bond strength, and to explore the role of inhibition of relevant degradative enzymes on this effect.

Mini short-rod specimens of resin composite (Z250, 3M) bonded to human dentin (University of Toronto ethics approval #25793) with total-etch adhesive (Scotchbond MP, 3M) as provided or with 10%w/w antimicrobial drug-templated silica particles (with octenidine dihydrochloride, OCT)(N=10/group) were made. Specimen bond fracture toughness was measured via Microtensile Tester (Bisco) at 1 mm/minute loading, as-manufactured or post-incubation in simulated human salivary esterase (SHSE) for up to 6-months (37C, pH 7.2). Activity of model and salivary, enzymes, and adsorption of model and salivary enzymes to resin adhesive, were measured with and without OCT at 0.2, 2, and 20 µg/mL. 

Fracture toughness of antimicrobial restorations were preserved at the initial level and outperformed control at 6-months in SHSE (1.31±0.17 vs 0.86±0.30 MPa*m0.5). OCT inhibited model enzyme activity (-60% to -100%) and adsorption to resin adhesive (-30%). Adsorption of salivary enzymes was unaffected, but their activities were also inhibited (-46%).

The effect of the surfactant-drug OCT on enzyme activity depends on enzyme and substrate. This antimicrobial adhesive system has potential to preserve restoration bond through inhibition of enzymatic degradation and reduce adsorption of some enzymes over the adhesive, as well as prevent recurrent caries through its antimicrobial activity. This work presents a novel method for protecting dental restorations and extending service life and highlights the importance of studying materials in a realistic environment that models the challenges faced in vivo as these effects may significantly impact material performance.