An MMP-inhibitor modified adhesive primer enhances bond durability to carious dentin

Objectives To evaluate the effect of adding a matrix metalloproteinase (MMP) inhibitor (BB94, Batimastat) to the primer of a three-step etch and rinse adhesive system on caries-affected dentin (CaD) MMP activity, and to assess the effect of such an inclusion on the chemical content of the CaD-adhesive interface. Methods Caries-infected dentin (CiD) was excavated selectively from freshly extracted human carious teeth using a chemo-mechanical agent. Each tooth was sectioned into three slabs through the CaD retained cavity. These were treated with either Optibond FL "OB" (Kerr, Orange, USA) without MMP inhibitor, or with 500 μM BB94 prior to the application of OB primer and bond, or with OB primer that contained 5 μM BB94. In situ zymography and Raman micro-spectroscopy were used to investigate MMP activity and the changes in the chemical content at the CaD/adhesive interface, respectively. Results Data showed the use of OB adhesive with BB94 resulted in immediate interfacial MMP inhibition, by direct application (93.3%) and by means of a drug delivery system (80%), as demonstrated by in situ zymography. Raman imaging revealed 33% higher resin infiltration into MMP-inhibited adhesive interfaces (SE 3.88). Significance Through competitive inhibition by batimastat (BB94), a proportion of the MMPs found in CaD were inhibited immediately and irreversibly. Such a competitive mechanism brings the adhesive primer close to the collagen matrix and enhances the dental adhesive wettability, which is a proposed mechanism to explain the presence of more resin within the hybrid layer.