Influence of the nano-hardness and elastic modulus of carious primary tooth dentin to resin adhesion

<Objective>目的：比较正常牙本质与龋坏牙本质的硬度和弹性对树脂粘接的影响。<Results>2.龋坏和完好牙本质的硬度、弹性和微拉伸强度：离体乳牙本质的物理性能低于恒牙本质，尤其是病变下和近髓牙本质。3.龋坏和完好牙本质粘接后的硬度和弹性：Clearfil Mega Bond（MB group，Kuraray Co.）和Single Bond（3M ESPE Co.Ltd.）用了与树脂/牙本质界面下的牙本质相比，界面牙本质的硬度更高，并且显示出与先前报道的恒牙相反的结果。界面牙本质的弹性模量低于界面下牙本质，与恒牙相同。4.健康牙本质与龋坏牙本质的微拉伸粘结强度（MTBS）：将MB或SB分别施加于离体乳牙本质上。制备哑铃形和棒状试样。哑铃形和棒状试样的平均MTBS值均较低，均在10 MPa以下。MB组与SB组、健全组与龋坏组之间无显著性差异。<Conclusion>与龋坏牙本质粘结时，龋坏组和健康组的HL较厚，MTBS较低。乳牙牙本质的性质可能与恒牙本质不同，因此基于恒牙牙本质设计的治疗可能不适合乳牙牙本质。因此，需要基于乳牙牙本质物理特性的新系统。

<Objective> :To compare the influence of the hardness and elasticity to resin adhesion between carious and sound dentin.<Results> :1.Development of originally designed jig system for micro-tensile strength Testing :New system for primary teeth has been developed.2.Hardness, elasticity and micro-tensile strengths of the carious and sound primary dentin :Physical properties of extracted primary tooth dentin were lower than permanent tooth dentin, especially for the dentin under the lesion and near me pulp.3.Hardness and elasticity of bonded carious and sound dentin :Clearfil Mega Bond (MB group, Kuraray Co.) and Single Bond (3M ESPE Co.Ltd.) were used. Compared to the dentin beneath the resin/dentin interface, the hardness of the interface dentin were higher and showed contrary results to previously reported permanent teeth. But, Young's modulus of the interface dentin were lower than dentin beneath the interface, same as for permanent teeth. No significant difference was found between the carious and sound groups.4.Micro-tensile bond strength(MTBS) for sound and carious dentin :MB or SB was applied on the extracted primary tooth dentin. Dumbbell-shaped and stick-shaped specimens were prepared. The mean MTBS of both dumbbell-shaped and stick-shaped specimens were low, and under 10MPa. No significant difference was found between the MB and SB, and sound and carious groups.<Conclusion> :When bonded to carious dentin, the HL was thicker, but the MTBS was low in both the carious and sound groups. The properties of primary tooth dentin might differ from permanent dentin, thus treatments designed based on permanent tooth dentin may not be optimized for primary tooth dentin. New system based on the physical properties of primary tooth dentin should be required.