Dentin bond strength of an experimental adhesive system containing calcium chloride, synthetic peptides derived from dentin matrix protein 1 (pA and pB), and hydroxyapatite for direct pulp capping and as a bonding agent

The purpose of this study was to evaluate the microtensile bond strength (μTBS) of an experimental adhesive system containing calcium chloride (CaCl2), synthetic peptides derived from dentin matrix protein 1 (DMP1: pA and pB), and hydroxyapatite experimentally developed for direct pulp capping to human dentin. Clearfil SE Bond/Primer (SEP) and Bond (SEB) were used for each experimental group as the matrix agents. Experimental self-etching primers included: primer-I, SEP containing 10 wt% CaCl2, and primer-II, SEP containing a 10 wt% compound of pA and pB. The experimental bonding agent was a mixture of SEB and 10 wt% hydroxyapatite. Specimens were divided into five experimental groups, including the control, according to the mode of primer application. Primer-I was primarily applied, followed by primer-II for group 1, primer-I as the primary and SEP as the secondary for group 2, SEP as the primary and primer-II as the secondary for group 3, and SEP was applied twice for group 4, and SEP was applied once for the control. Clearfil SE Bond adhesive system was used as the control. Flat dentin surfaces of human molars were assigned to bonding tests. After each experimental primer was applied to the dentin surface, each experimental bonding agent was applied and photopolymerized, and then resin composite paste (Clearfil Flow FX and Clearfil AP-X) was placed and photopolymerized. The specimens were subjected to μTBS testing. The data were compared using analysis of variance (ANOVA) and post-hoc Bonferroni/Dunn tests. Results showed that the minimum mean value of μTBS was 15.4 MPa for group 1, while the maximum mean value of μTBS was 52.7 MPa for the control. There were significant differences among the experimental groups, except for group 4 and the control. The experimental primers containing CaCl2 or DMP1 negatively affected the μTBS value of the experimental adhesive system to dentin.