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

本研究的目的是通过分析DBSs的结合强度与不同功率输出下声音牙本质的超形态学变化的一致性，来促进牙本质结合系统（DBSs）对激光牙本质的粘附性能。低功率（Er: YAG: 60 mJ/1 pps, CO2: 1 w/0.3 sec）激光消融完好牙本质降低了DBSs的粘附性能。然而，高、中能量激光烧蚀牙本质（Er: YAG: 250 mJ/1 pps, 150 mJ/1 pps, CO2: 3 w/0.3 sec）几乎没有降低牙本质的结合强度。在低功率激光牙本质的亚表层，脱钙试样的透射电镜观察发现，形成了含有变性胶原纤维的无定形基质物质（Er:YAG: 3-4μm, CO2: 1-2μm）。另一方面，在中、高能激光牙本质（Er:YAG: 250 mJ/1 pps, 150 mJ/1 pps, CO2: 3 w/0.3 sec）中，其形态结构与正常牙本质（Er:YAG）或牙本质亚表层既有少量无定形基质，又有胶原纤维撕裂，并有交叉条纹（CO2）。中、高功率激光烧蚀对胶粘剂的影响可能局限于胶粘剂的浅层，而不会导致胶粘剂性能的降低。根据本研究成果，明年将研究激光照射牙本质受影响浅层的去除方法以及激光照射牙本质专用DBS的开发。

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.