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Title: [An experimental study of the effect of extraction and retention of canine primary intruded teeth to the permanent successors].
Author: Zhang YX, Wu YH, Yao DS, Yang JY, Gao L.
Journal: Zhonghua Kou Qiang Yi Xue Za Zhi; 2018 May 09; 53(5):344-350. PubMed ID: 29972994.
Abstract:
Objective: To compare the influence of extraction and retention of the intruded dogs' teeth on permanent successors. Methods: Nine healthy 45-days-old Chinese rural puppies were selected, and six were submitted to the intrusion of the bilateral canine. Intruded teeth on the left side were extracted 30 minutes later and the teeth on the right side were kept in their sockets. After 8 months, all dogs were sacrificed. General observation, periapical radiograph and cone beam CT were used to observe the preoperative and postoperative deciduous teeth, permanent germs and permanent teeth development. The structure and content of successors' enamel were observed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Results: In the extraction groups, the enamel hypoplasia was found in 19 permanent successors, ectopic eruption in 2 cases and abnormal teeth were in 19 cases in total (79%). In the retention groups, enamel hypoplasia of the permanent successors occurred in 2 cases, root dilaceration in 6 cases, and ectopic eruption in 5 cases, retained deciduous teeth in 3 cases, and there were 22 abnormal teeth in total (92%). In blank control group, there was no abnormal teeth. The major effect of intruded deciduous teeth on the permanent successors exhibited enamel hypoplasia [85% (41/48)], presented as enamel coloration and enamel defect (P=0.416). Conclusions: The intruded deciduous teeth should be removed early in order to reduce the effect on the permanent teeth. 目的： 采用拔除或保留犬挫入乳牙，观察其对继承恒牙的影响，为乳牙挫入性损伤的治疗提供参考。 方法： 选取9只45天龄健康中华田园犬，每只犬双侧上下颌乳尖牙和第三乳切牙为实验牙，其中空白对照组3只，不做任何处理；实验组6只，施加外力致双侧上下颌乳尖牙和第三乳切牙齐龈挫入，左侧为拔除组，术后30 min拔除挫入乳牙；右侧为保留组，保留挫入乳牙。3组共72颗实验牙，每组24颗。术后8个月将所有实验犬麻醉处死，采用大体观察、根尖X线片、锥形束CT观察术前和术中乳牙、恒牙胚及术后继承恒牙釉质和牙根情况，扫描电镜及能谱分析观察恒牙釉质结构及成分。 结果： 拔除组：继承恒牙出现釉质发育不全19颗，伴异位萌出2颗，异常牙共19颗；保留组：继承恒牙出现釉质发育不全22颗，伴牙根弯曲6颗，异位萌出5颗，乳牙滞留3颗，异常牙共22颗；空白对照组：异常牙0颗。乳牙挫入伤对继承恒牙的影响主要为继承恒牙釉质发育不全，发生率为85%（41/48），主要表现为釉质着色和缺损。拔除组与保留组继承恒牙釉质发育异常率分别为79%（19/24）和92%（22/24），二者差异无统计学意义（P=0.416 ），但上述两组与空白对照组相比差异均有统计学意义（P值均<0.001）；参照改良Dean氟斑牙指数分级标准，拔除组与保留组继承恒牙釉质发育异常程度差异有统计学意义（P=0.032），拔除组对继承恒牙釉质发育的影响轻于保留组。扫描电镜观察显示：正常、着色、缺损区釉柱从规则的球拍状到笋状或蜂巢状，最后到条索状逐渐紊乱不规则。能谱分析显示：正常、着色、缺损区釉质Ca、P含量依次降低，但Ca/P无显著变化。 结论： 乳牙齐龈挫入性损伤应及早拔除乳牙，以减少其对继承恒牙的影响。.

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