Felippe W T, Felippe M C S, Rocha M J C
School of Dentistry, Federal University of Santa Catarina, Florianópolis, SC, Brazil.
Int Endod J. 2006 Jan;39(1):2-9. doi: 10.1111/j.1365-2591.2005.01037.x.
To evaluate the influence of mineral trioxide aggregate (MTA) on apexification and periapical healing of teeth in dogs with incomplete root formation and previously contaminated canals and to verify the necessity of employing calcium hydroxide paste before using MTA.
Twenty premolars from two 6-month old dogs were used. After access to the root canals and complete removal of the pulp, the canal systems remained exposed to the oral environment for 2 weeks. Canal preparation was then carried out using Hedström files, under irrigation with 1% sodium hypochlorite, 1 mm short of the radiographic apex. After drying, the canals of two premolars in each dog were left empty (control group). The other eight teeth in each animal were divided into two experimental groups. The apical thirds of the canals of group 1 were filled with MTA. In the teeth of group 2, the canals were dressed with a calcium hydroxide-propylene glycol paste. After 1 week, the paste was removed and the apical third was filled with MTA. All teeth were restored with reinforced zinc oxide cement (IRM) and amalgam. The animals were killed 5 months later, and blocks of the teeth and surrounding tissues were submitted to histological processing. The sections were studied to evaluate seven parameters: formation of an apical calcified tissue barrier, level of barrier formation, inflammatory reaction, bone and root resorption, MTA extrusion, and microorganisms. Results of experimental groups were analysed by Wilcoxon's nonparametric tests and by the test of proportions. The critical value of statistical significance was 5%.
Significant differences (P < 0.05) were found in relation to the position of barrier formation and MTA extrusion. The barrier was formed in the interior of the canal in 69.2% of roots from MTA group only. In group 2, it was formed beyond the limits of the canal walls in 75% of the roots. MTA extrusion occurred mainly in roots from group 2. There was similarity between the groups for the other parameters.
Mineral trioxide aggregate used after root canal preparation favoured the occurrence of the apexification and periapical healing. The initial use of calcium hydroxide paste was not necessary for apexification to occur, and has shown to be strongly related to the extrusion of MTA and formation of barriers beyond the limits of the root canal walls.
评估三氧化矿物凝聚体（MTA）对牙根未完全形成且根管先前已被污染的犬牙根尖诱导成形及根尖周愈合的影响，并验证在使用MTA之前使用氢氧化钙糊剂的必要性。
使用来自两只6个月大犬的20颗前磨牙。开髓并完全去除牙髓后，根管系统暴露于口腔环境2周。然后使用Hedström锉进行根管预备，用1%次氯酸钠冲洗，距X线根尖1mm处停止。干燥后，每只犬的两颗前磨牙根管留空（对照组）。每只动物的另外八颗牙齿分为两个实验组。第1组根管的根尖三分之一用MTA充填。第2组牙齿的根管先用氢氧化钙 - 丙二醇糊剂封药。1周后，去除糊剂，根尖三分之一用MTA充填。所有牙齿均用增强型氧化锌粘固粉（IRM）和汞合金修复。5个月后处死动物，将牙齿及周围组织块进行组织学处理。研究切片以评估七个参数：根尖钙化组织屏障的形成、屏障形成水平、炎症反应、骨和牙根吸收、MTA挤出及微生物。实验组结果采用Wilcoxon非参数检验和比例检验进行分析。统计学显著性临界值为5%。
在屏障形成位置和MTA挤出方面发现显著差异（P < 0.05）。仅在MTA组69.2%的牙根中，屏障在根管内部形成。在第2组中，75%的牙根屏障形成超出根管壁范围。MTA挤出主要发生在第2组的牙根中。其他参数在各组之间相似。
根管预备后使用三氧化矿物凝聚体有利于根尖诱导成形和根尖周愈合的发生。氢氧化钙糊剂的初始使用对于根尖诱导成形的发生并非必要，且已表明与MTA挤出及根管壁范围之外的屏障形成密切相关。
