Analysis of surface characteristics of lased dentin and development of new adhesive system

为了提高牙本质粘接系统(DBSS)对激光牙本质的粘接性能，分析了不同功率输出下，DBSS粘结强度与声牙本质超微结构变化的一致性。低功率(Er：YAG：60mJ/1PPS，CO2：1w/0.3秒)激光烧蚀声牙本质降低了DBSS的粘接性能。然而，高能量和中能量激光(Er：YAG：250mJ/1pps，150mJ/1pps，CO2：3w/0.3s)几乎不会降低粘结强度。在低功率激光处理的牙本质亚表层中，脱钙标本的透射电子显微镜观察发现，脱钙后形成了含有变性胶原纤维的无定形基质物质(Er：Yg：3~4μm，CO_2：1~2μm)。而在中、高功率激光(Er：YAG：250mJ/1PPS，150MJ/1PPS，CO2：3w/0.3s)中，可观察到与完好的牙本质(Er：YAG)很难区分的形态结构，或亚表层有少量无定形基质和撕裂的横纹胶原纤维(CO2)。激光消融对中、高功率牙本质的影响可能仅限于表层，不会导致粘接性能的降低。根据本研究的成果，受影响的牙本质激光表层的去除方法和针对激光照射牙本质的DBS的开发将在下一年进行。

The aim of this study was to promote the adhesive properties of dentin bonding systems (DBSs) to lased dentin by analyzing the consistency of bond strengths of DBSs with ultra-morphological changes of sound dentin lased at various power output.Laser ablation of sound dentin at low power (Er : YAG: 60 mJ/1 pps, CO2: 1 w/0.3 sec) reduced adhesive properties of DBSs. However, high-and middle-energy laser ablation of dentin (Er : YAG: 250 mJ/1 pps, 150 mJ/1 pps, CO2: 3 w/0.3 sec) hardly reduced the bond strength. In the subsurface layer of low-power lased dentin, TEM observations of decalcified specimens revealed that the amorphous matrix substances containing denatured collagen fibers were generated (Er:YAG: 3-4μm, CO2: 1-2μm). On the other hand, in the middle or high power lased dentin (Er : YAG: 250 mJ/1 pps, 150 mJ/1 pps, CO2: 3 w/0.3 sec), such morphological structure as hardly distinguished from sound dentin (Er:YAG) or the subsurface dentin layer having both little amorphous matrix and torn collagen fibers with cross-striation (CO2) was observed. The effects of laser ablation on middle or high power might be limited to superficial layer, which did not cause the reduction in adhesive properties.From the achievements of this study, the removal method of the affected superficial layer of lased dentin and the development of the DBS specifically for laser-irradiated dentin will be investigated in the next year.