Dentin thickness, hardness, and Ca-concentration vs bond strength of dentin adhesives

The relationship between the tensile bond strength (TBS) and three dentin characteristics: remaining dentin thickness (RDT), Ca-concentration, and hardness, were investigated. Sixty-two extracted bovine incisors, divided into four groups, were prepared using 600-grit SiC paper to create flat dentinal surfaces. The materials tested in this study consisted of three commercially available and one experimental dentin bonding systems. The TBS and modes of failure were determined after storage for 24 h in 37 degrees C water. Then RDT, Ca-concentration, and hardness were measured. Data were statistically compared with TBS of each group. The mean bond strength of the commercial materials ranged from 2.5 +/- 0.9 MPa to 7.7 +/- 2.8 MPa. Correlations with Ca-concentration and RDT varied, depending on the product. The bond strength of the experimental material was 9.2 +/- 4.4 MPa and significantly correlated with RDT and hardness. With two of the dentin bonding agents, specimens showed a high number of cohesive fractures in dentin, 40% to 82%. It was concluded that the variability of TBS was influenced by dentinal characteristics in three of the four materials tested.