目的：对外伤引起的年轻恒前牙冠折露髓行活髓切断术，并于2年以上追踪观察其根管、根尖孔发育情况。
Objective:To treatment the young permanent incisors with exposed pulps in crown by pulpotomy and observe the growth of root canals and apexogenesis following up over 2 years.
从横切面上观察到，不定根原基起源于髓射线与维管形成层交叉的部位。
From cross sections of stems-cuttings, a primordium of adventitious roots originates from the cross region of pith rays and vascular cambium.
结果无痛治疗（27.3%）、冠髓切断术（21.6%）、橡皮障的应用（1.4%）、氟化物的使用、咬合诱导等工作开展情况还有待加强。而根管治疗、窝沟封闭的应用情况比较好。
Results It is necessary to improve the use of analgesia ( 27.3% ), pulpotomy ( 21.6% ), rubber dam ( 1.4% ) and fluoride, the related work of occlusion guidance should be reinforced.
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