HIRAI Yoshito TOKYO DENTAL COLLEGE,DEPARTMENT OF DENTISTRY,PROFESSOR, 歯学部, 教授 (80119742)
ISHIKAWA Tatsuya TOKYO DENTAL COLLEGE,DEPARTMENT OF DENTISTRY,PROFESSOR, 歯学部, 教授 (30085708)
|Budget Amount *help
¥3,200,000 (Direct Cost : ¥3,200,000)
Fiscal Year 1999 : ¥1,100,000 (Direct Cost : ¥1,100,000)
Fiscal Year 1998 : ¥2,100,000 (Direct Cost : ¥2,100,000)
1.(1) The purpose of this study was to investigate histopathologically the effects on dental pulp intentionally exposed by Er : YAG laser. A total of 139 teeth of adult dogs which were received general anesthesia were divided into two groups ; laser and control groups. Immediately after the exposure, the pulp tissues which were not undergone any treatment were observed histopathologically in both groups. Seven and ninety days after the exposure, the pulp tissues of both groups which were directly capped with calcium hydroxide were examined. As a results, it is suggested that pulp tissues may undergo a healing process when the tissues were accidentally exposed by an Er : YAG laser as well as those by a rotary cutting instrument.
(2) To evaluate the adaptation of restorative materials to Er : YAG laser-prepared cavity,twoglass-inomer cements were filled and evaluated histopathologically.These results suggested its safety.
2.Adhesion of commercially resin bonding system to Er:YAG laser-irra
diated dentin has been reported lower than unlased dentin. The reason has been hypothesized that lased dentin had acid resistance, but not concluded. We immersed the lased dentin in lactic acid buffer (pH 4.0) for 24 hours and measured the dissolved Ca and P. Significantly difference was not found between lased and unlased dentin, and it suggested the lased dentin did not have acid resistance.
Several acid conditioner was applied to bovine dentin following irradiated by Er : YAG laser and bonded the PMMA rod with 4-META/MMA-TBB resin. The bonded teeth were tensile bond tested. Lased dentin had different characteristics to acid treatment on resin bonding from unlased dentin. Futhermore, the bond strength to untreated dentin was higher than any treated dentin in lased group. Hybrid layer has been reported 2-5μm-thickness, but in lased dentin, 30-80μm-thick of resin-penetrated layer was observed in cross-sectioned bonded specimen by scanning electron microscope. Our study has been continued to clarify the lower resin bonding to lased dentin.