Inhibition of matrix metalloproteinase activity in human dentin via novel antibacterial monomer

• A new monomer DMADDM was tested as an inhibitor against MMPs for its potential to combat degradation of dentin collagen and the dentin–resin bond.
• DMADDM exhibited a strong anti-MMP effect, reaching more than 90% inhibition on rhMMP-8 and rhMMP-9 with 5% or more of DMADDM.
• The use of DMADDM preserved the mechanical stiffness and hindered the dissolution of demineralized human dentin.
• DMADDM is promising for use in bonding agents to prevent dentin collagen degradation in the hybrid layer and prolong the dentin–restoration bond..

ObjectiveDentin–composite bond failure is caused by factors including hybrid layer degradation, which in turn can be caused by hydrolysis and enzymatic degradation of the exposed collagen in the dentin. The objectives of this study were to investigate a new antibacterial monomer (dimethylaminododecyl methacrylate, DMADDM) as an inhibitor for matrix metalloproteinases (MMPs), and to determine the effects of DMADDM on both soluble recombinant human MMPs (rhMMPs) and dentin matrix-bound endogenous MMPs.MethodsInhibitory effects of DMADDM at six mass% (0.1% to 10%) on soluble rhMMP-8 and rhMMP-9 were measured using a colorimetic assay. Matrix-bound endogenous MMP activity was evaluated in demineralized human dentin. Dentin beams were divided into four groups (n = 10) and incubated in calcium- and zinc-containing media (control medium); or control medium + 0.2% chlorhexidine (CHX); 5% 12-methacryloyloxydodecylpyridinium bromide (MDPB); or 5% DMADDM. Dissolution of dentin collagen peptides was evaluated by mechanical testing in three-point flexure, loss of dentin mass, and a hydroxyproline assay.ResultsUse of 0.1% to 10% DMADDM exhibited a strong concentration-dependent anti-MMP effect, reaching 90% of inhibition on rhMMP-8 and rhMMP-9 at 5% DMADDM concentration. Dentin beams in medium with 5% DMADDM showed 34% decrease in elastic modulus (vs. 73% decrease for control), 3% loss of dry dentin mass (vs. 28% loss for control), and significantly less solubilized hydroxyproline when compared with control (p < 0.05).SignificanceThe new antibacterial monomer DMADDM was effective in inhibiting both soluble rhMMPs and matrix-bound human dentin MMPs. These results, together with previous studies showing that adhesives containing DMADDM inhibited biofilms without compromising dentin bond strength, suggest that DMADDM is promising for use in adhesives to prevent collagen degradation in hybrid layer and protect the resin–dentin bond.