Hardness and elasticity of bonded carious and sound primary tooth dentin

Objective: Although biomechanical properties of bonded dentin are important for resin restorations, no information for primary teeth has been reported. This study evaluated the hardness and elastic modulus of bonded carious and sound primary tooth dentin using two adhesive systems. Methods: Twelve sound primary molars and 17 carious primary molars were bonded with Clearfil SE Bond (SE: Kuraray) or Single Bond (SB: 3M) and the resin-dentin interface was measured with a nano-indentator and observed with a SEM. Data was statistically analyzed using ANOVA subsequent application of Fisherʹs PLSD at p<0.01. Results: Compared to the dentin beneath the interface, the hardness of the interface dentin was not significantly different (carious-SE, sound-SE and sound-SB groups) or was significantly higher (carious-SB group). Youngʹs modulus of the interface dentin was not significantly different (carious-SE, carious-SB and sound-SB groups) or was significantly lower (sound-SE group) than that for the dentin beneath the interface. In the comparison of the measurement on the interface dentin, the hardness showed no significant differences among all the groups. The Youngʹs modulus of the sound-SE group was significantly lower than that of the carious-SE and sounds-SB groups, but no significant difference was observed between the carious-SB and other groups. Conclusions: Physical properties of bonded primary tooth dentin might differ from that of permanent tooth dentin.