脉冲Nd:YAG激光不同条件下照射牙根管壁的形态学观察

Morphological Changes of the Root Canal Wall Irradiation with Pulsed Nd:YAG Laser at Different Conditions.

目的 :观察不同条件下脉冲Nd :YAG激光照射牙根管壁后的清洁程度及管壁牙本质的超微结构改变。方法 :14颗离体人上前牙 ,常规根管预备后 ,分为对照组和激光照射组 ,后者按不同的功率、频率及管壁加墨汁与否 6种设定各 2颗牙分别进行照射 ,然后各组标本扫描电镜下观察并照像记录。结果 :①激光照射各组均较对照组根管壁玷污层减少 ;且随激光功率增大 ,管壁清洁度提高 ,管壁牙本质的超微结构变化增大。其中 2W 2 0 pps组管壁上无玷污层 ,根尖 1/ 3区尚有牙本质熔融、沉积。 3W 2 0pps、4W 2 0 pps组除上述变化外 ,根管壁牙本质熔融更为显著 ,并有程度不同的炭化和裂缝 ;② 2W 15 pps管壁清洁度较 2W 2 0pps组低 ;③ 1W 2 0 pps加墨汁后 ,根管清洁效果显著改善 ,并出现牙本质熔融、小管口封闭。结论 :激光剂量在 2W 2 0pps或在此以上时能有效去除根管壁玷污层 ,达到较理想的清洁效果 ,但只有较大剂量时才能熔融、封闭牙本质小管口 ;加墨汁能在低能量条件下显著增强激光作用效果。

The effects of pulsed Nd:YAG laser irradiation at different conditions on the cleanliness of root canal wall and the ultrastructure of its dentin were evaluated in vitro.Methods:Fourteen extracted human upper anterior teeth were randomly assigned to seven groups.Group 1 teeth were not lased as a control.Group 2～6 were received four power ,two frequencies levels and with initiator laser exposures, respectively.Then all specimens were examined by scanning electron microscopy.Results:① Compared with control group, smear layer on the root canal wall was reduced or removed completely in lased group; Such changes also occurred at different laser power levels .It showed no smear layer at 2W 20pps,and even melted dentin and occluded dentinal tubules on apical portion of the root canal wall.Carbonization and cracks were partly present in 3W 20pps and 4W 20pps group except for above changes. ②The cleanliness of root canal wall of 2W 15pps was less effective than that of 2W 20pps group. ③After being added black ink,1W 20pps group also showed free of smear layer and laser-melted appearance.Conclusions:Smear layer of the root canal wall can be removed by laser at or beyond 2W 20pps setting, but only higher energy levels may melt dentin and occlude the dentinal tubules orifices; Black ink can greatly enhance the effect of the laser on the root canal wall even at lower energy level.