The Effect of MMPs Inhibitors on Different Adhesive Systems

Objectives:This study aimed to evaluate the effect of adding matrix metalloproteinase(MMP) inhibitors to three dental adhesives on both the substrate MMP activity and on the adhesives' physical properties. The null hypothesis investigated was the addition of MMP inhibitors to dental adhesives will not inhibit substrate MMP activity and will reduce their physical interfacial properties. Methods:Two anti-MMPs (BB94 and GM6001) were added to three adhesive primers, OptibondFL(Kerr,USA), Prime&Bond NT(Dentsply,USA) and G-Bond(GC,UK) to create nine experimental groups including controls.The potential inhibitory effect on synthetic MMPs was tested by evaluating fluorometric assays, carried out in clear 96-well microtiter plates (Nunc,Denmark). Zymographic analysis assessed the enzymatic effect of the formulated adhesives on powdered dentinal MMPs. Microtensile testing, using 10 human extracted teeth for each group, evaluated the immediate and 3-month post-storage bond strengths in-vitro. Fluorescence confocal microscopy (TSM; Noran Instruments,USA) was used to evaluate the micro-permeability of the hybrid layer of bonded teeth, 45 zones in each group, after flooding the pulp chambers with RhodamineB. Results:Adhesives including anti-MMPs resulted in a significant loss of synthetic MMP activity (95%, P<0.05),confirmed by the inhibition of enzymatic reactions of dentinal MMPs shown in the zymographs. The immediate microtensile strength for Optibond FL(48.0MPa±20.3SD for“BB94”and 42.0MPa±18.7SD for“GM6001”) and G-Bond (34.8MPa±19.2SD for“BB94”and 41.7MPa±17.6SD for“GM6001”) increased significantly (P<0.05), when compared to controls (34.7MPa±18.7SD and 25.3MPa±15.7SD respectively). Post-storage data showed significant decrease(P<0.05) in the bond strength for G-Bond controls (12.2MPa±10.0SD) when compared to anti-MMPs groups (18.4MPa±16.1SDfor“BB94”and17.0MPa±13.2SDfor“GM6001”). Prime&Bond and G-Bond showed less RhodamineB seepage, to “hybrid layer” and to “adhesive” respectively, when anti-MMPs were added. Conclusions:The inclusion of anti-MMPs within commercial dental adhesive primers resulted in the inhibition of dentinal MMPs as well as the increase in initial bond strength with an improved sealing ability. The resistance to degradation of the hybrid layer enhanced the bond strength of single-step system following 3-month storage.