Er：YAG 激光用于比格犬牙髓切断术

目的：通过比格犬动物试验，观察铒钇铝石榴石(erbium:yttrium aluminium garnet，Er:YAG)激光去除比格犬冠髓后剩余牙髓的变化及牙本质桥形成情况，探索Er:YAG激光照射与牙髓反应及牙本桥形成的关系。方法： 选取2只12月龄雄性比格犬前磨牙为试验牙，共24颗，分别应用200 mJ/20 Hz Er:YAG激光、100 mJ/20 Hz Er:YAG激光及传统机械方法去除冠髓，三氧化矿物凝聚体( mineral trioxide aggregate，MTA)盖髓后充填。通过临床检查试验牙的动度和牙龈情况评价临床效果，拍摄试验牙平行投照X线根尖片评价影像学效果。试验术后1 d、2周、4周、8周拔牙，苏木精 伊红染色（Hematoxylin Eosin staining，HE）下观察根髓情况及牙本质桥形成情况。结果： 牙髓切断术后1 d、2周、4周、8周后机械去髓组和激光去髓组试验牙均无松动，牙龈无红肿瘘管等异常；X线片发现机械去髓组和激光去髓组试验牙均未见牙周膜增宽、根尖周低密度影、牙根内外吸收等影像学异常表现；HE染色组织学切片检查发现术后1 d、2周、4周、8周机械去髓组和激光去髓组试验牙根髓均未见明显炎症反应，2周时可见激光去髓组牙本质桥完全覆盖牙髓断面，而机械切髓组未见完整牙本质桥。结论： 100 mJ/20 Hz和200 mJ/20 Hz Er:YAG激光去髓对剩余根髓未见影响。

Preliminary research of Er:YAG laser used for pulpotomy of Beagle dogs

Objective:To investigate the effects of erbium:yttrium aluminium garnet (Er:YAG)laser irradiation on pulp and formation of dentin bridge.The beagle dogs'coronal pulp is amputated by Er:YAG laser.Methods:In the study,24 premolar teeth of two one-year-old Beagle dogs were used.They were divided into 3 groups:bur group,200 mJ laser group,100 mJ laser group.The coronal pulp were removed by traditional bur or 200 mJ/20 Hz or 100 mJ/20 Hz Er:YAG laser.Then,they were dressed with mineral trioxide aggregate (MTA)and sealed with resin.Clinical,radiological and histological ana-lyses were performed 1 day,2 weeks,4 weeks and 8 weeks after treatment.The mobility and gingiva si-tuation were evaluated for clinical evaluation.Periapical films were used for radiological evaluation.The extracted teeth were preserved in 10% formalin.After decalcification,tissue processing,paraffin embed-ding,serial sectioning at 5 μm thickness,staining (Hematoxylin and Eosin,HE),the samples were as-sessed by an independent observer for calcified bridge formation and radicular pulp inflammation.The mean thickness of dental bridge was measured if there was complete dental bridge.Results:Clinical evaluation:there were no signs of fistula or mobility or any abnormal symptoms in Er:YAG laser groups and bur group during the observation period.Radiological evaluation:there were no signs of widened pe-riodontal ligament or root absorption or periapical radiolucency in Er:YAG laser groups and bur group. Histological evaluation:there was no severe inflammation reaction in 200 mJ/20 Hz,100 mJ/20 Hz Er:YAG laser groups and bur group 1 day,2 weeks,4 weeks,8 weeks post-operation in Hematoxylin and Eosin staining.A complete dentin bridge could be observed in 200 mJ/20 Hz,100 mJ/20 Hz Er:YAG laser groups,while no complete dentin bridge in bur group 2 weeks post-operation.Complete dental bridge could be observed in each group 4 and 8 weeks post-operation.The mean thickness of dental bridge 4 weeks post-operation in 200 mJ laser group was 77 μm,100 mJ laser group 87 μm,and bur group 101 μm,and 8 weeks post-operation in 200 mJ laser group was 222 μm,100 mJ laser group 160μm,and bur group 152 μm.Conclusion:The 200 mJ/20 Hz and 100 mJ/20 Hz Er:YAG laser pulpoto-mies show no harm to radicular pulp and can promote the formation of dentin bridge.