| Budget Amount *help |
¥3,200,000 (Direct Cost: ¥3,200,000)
Fiscal Year 2006: ¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 2005: ¥1,700,000 (Direct Cost: ¥1,700,000)
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| Research Abstract |
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.
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