脉冲Nd:YAG激光根管内照射对犬牙根尖周组织安全性的实验研究

Study on the security of periapical tissue during radiation of root canal of dog by pulsed Nd:YAG laser in vivo

目的 :探讨脉冲Nd :YAG激光根管内照射对犬牙根尖周组织的安全性 ,确定适宜的激光照射剂量。方法 :选用 5只健康成年犬 ,每只犬利用 18个牙 2 6个根管。实验牙无菌条件下常规根管预备、暂封 ,确定根尖周组织恢复正常后 ,依次分对照组、2 0 /s 1.5W加增强剂、2 0 /s 2 .0W加增效剂、2 0 /s 2 .0W和 2 0 /s2 .5W共 5组分别进行激光根管内照射。分期处死动物 ,制作牙颌组织石蜡和超薄切片 ,观察照射后 1、15、30、6 0d牙根尖周的组织学及超微结构变化。结果 :健康牙齿根管预备后经 15d根尖周组织已恢复正常 ;激光照射后 1dⅡ、Ⅳ组无明显改变 ,Ⅲ、Ⅴ组有明显的急性损伤和炎症表现 ,Ⅴ组损伤更为显著 ;照射后 15dⅡ、Ⅳ组已完全恢复正常 ,而Ⅲ、Ⅴ组呈慢性炎症表现 ,并累及牙骨质及牙槽骨 ;照射后 30d ,Ⅲ、Ⅴ组损伤的根尖周组织出现不同程度修复 ,到 6 0d时已基本正常 ,并有骨组织沉积。结论 :该激光 2 0 /s 2 .0W或 2 0 /s 1.5W加增效剂对牙周组织是安全的 。

AIM:To study the security of periapical tissue when the dog root canal walls were lased by pulsed Nd:YAG laser in vivo , and to determine the reliable parameters.METHODS:Five healthy adult dogs were used in the experiment.Twenty-six roots of eighteen teeth in each dog were prepared routinely under sterile conditions and then well sealed. After the periapical tissue to be healed normally, the prepared root canals were divided into control group and four different lased groups:The dogs were killed at 1 d, 15 d, 30 d, 60 d respectively.The histopathological changes and ultrastructure of periapical tissue were examined.RESULTS:The periapical tissue recovered at 15 d after the root canals were prepared with routine method.There was no obvious damage in group Ⅱ and group Ⅳ at 1 d after irradiation, but there were significant damage and inflammation in group Ⅲ and especially in group Ⅴ. The periapical tissue showed chronic inflammation in group Ⅲ and group Ⅴ at 15 d after lased and the damage to cementum and alveolar bone were also seen.The periapical tissue of group Ⅱ and group Ⅳ recovered at 15 d. The repair reactions appeared in group Ⅲ and group Ⅴ at 30 d and the periapical tissue was completely healed at 60 d with apparent deposition of cementum alveolar bone.CONCLUSION:The parameters of 20/s 2.0 W and 20/s 1.5 W(ink added) seem to be efficient and safe when pulsed Nd:YAG laser is applied in root canal therapy.But when the root canals were lased with higher outputs, the generated heat can damage the periapical tissue. [