Effect of Polymerization Accelerator on Dentin Bonding

Presently, resin composites are indispensable for dental restorative treatment because of their favorable esthetic and mechanical properties. In particular, the adhesion of resin composites to dentin has been rapidly improved by progress resin adhesive systems. Of late, resin restorative procedures have been simplified with the development of adhesive systems with fewer processing steps. One of the latest developments in adhesive dentistry is the one-step adhesive system which combines the function of each dentin etching, priming and bonding agent in one step, and of which the adhesiveness to enamel and dentin has been widely reported . Because one-step bonding agents can provide an easy bonding treatment, they eliminate technique sensitivity during the restorative treatment and provide stable bond strength with less influence of operator’s skill. For example, for AQ Bond (Sun Medical, Moriyama, Japan), a one-step bonding agent which has been placed on the market, its special applicator (Eponge, Sun Medical, Moriyama, Japan) is impregnated with aromatic sulfinate (referred to as “sulfinate” hereafter) as a polymerization accelerator so that it can be mixed with AQ Bond agent immediately before application, which is characteristic of this bonding system, the so-called applicator system. Recently, this bonding system has been improved, and AQ Bond Plus (Sun Medical, Moriyama, Japan), which also comprises its characteristic applicator system, is now commercially available. In AQ Bond Plus, Catabrush (Sun Medical, Moriyama, Japan) is impregnated with Nphenylglycine (referred to as “NPG” hereafter) together with sulfinate . To date, it has been reported that the bond strength to dentin is higher with AQ Bond Plus using Catabrush than with AQ Bond . Therefore, the addition of NPG was thought to affect the magnitude in the bond strength by different components added to these applicators. However, there has been no report so far in which NPG alone was applied to the applicator system. In this study, therefore, the possible effects of adding NPG to the applicator were examined in order to enhance the bond strength of one-step bonding agents to dentin. By referring to the abovementioned knowledge on AQ Bond and AQ Bond Plus, sulfinate alone, sulfinate/NPG mixed and NPG alone samples were added to AQ Bond Plus agent to examine the influence of adding NPG on the dentin adhesiveness and the degree of conversion of these bonding agent and to elucidate possible factors which may help an increase in the adhesiveness of one-step bonding agent adding NPG to dentin. In addition, an optimal concentration of NPG to be added to the applicator system was also examined.