Chailertvanitkul P, Saunders W P, MacKenzie D
University of Glasgow Dental School, UK.
Int Endod J. 1996 Jul;29(4):242-8. doi: 10.1111/j.1365-2591.1996.tb01376.x.
The aim of this in vitro study was to determine the effect of removal of the smear layer on canal obturation as measured by penetration of bacteria from a coronal direction. One hundred and twenty extracted human teeth with straight, single root canals were decoronated. The canals were prepared using the modified double-flared technique with balanced force under copious irrigation. The apical matrix was prepared to size 40 and apical patency subsequently confirmed with a size 15 file. The teeth were divided randomly into experimental groups (80 teeth) and control groups (40 teeth). The root canals of 40 experimental and 20 control teeth were rinsed with 40% citric acid and 2% NaOCl to remove the smear layer before obturation. In experimental groups, 20 teeth with smear layer intact and 20 teeth with smear layer removed were obturated with lateral condensation of cold gutta-percha and Apexit sealer. A further 20 teeth with smear layer intact and 20 teeth with smear layer removed were obturated with the Trifecta technique with the same sealer. In control groups, 10 teeth with smear layer intact and 10 teeth with smear layer removed were obturated with lateral condensation of cold gutta-percha and Apexit sealer. These teeth were completely sealed both coronally and apically to serve as negative controls. The remaining 20 teeth with either smear layer intact or smear layer removed were not obturated and served as the positive controls. The root surface of each tooth was sealed with nail varnish. The cut end of a polypropylene tube was sealed around the coronal part of each root canal so that bacteria placed therein could move only through the obturated canal space. Each root was placed in a glass bottle containing sterile Todd-Hewitt Broth (THB) and aliquots of 0.5 ml of THB were injected into the polypropylene tube. The model system was centrifuged at 168 g. An innoculum of Streptococcus sanguis in THB was placed in each coronal chamber at 5-day intervals and daily observations were made for bacterial growth in the apical reservoir for 90 days. All positive control teeth showed bacterial penetration within 24 h, while the negative control teeth remained uncontaminated throughout the test period. Leakage through the experimental teeth was variable ranging from 7 to 86 days. There was no statistical significant difference (P > 0.05) in leakage between the obturated canal when the smear layer was either removed or intact.
本体外研究的目的是通过测量细菌从冠方方向的渗透情况，来确定去除玷污层对根管充填的影响。选取120颗拔除的具有直的单根管的人牙，去除牙冠。采用改良双喇叭口技术，在大量冲洗下以平衡力预备根管。将根尖部预备至40号，随后用15号锉确认根尖通畅。将牙齿随机分为实验组（80颗牙）和对照组（40颗牙）。40颗实验组牙齿和20颗对照组牙齿的根管在充填前用40%柠檬酸和2%次氯酸钠冲洗以去除玷污层。在实验组中，20颗玷污层完整的牙齿和20颗玷污层已去除的牙齿用冷牙胶侧方加压充填法和Apexit封闭剂进行充填。另外20颗玷污层完整的牙齿和20颗玷污层已去除的牙齿用Trifecta技术和相同的封闭剂进行充填。在对照组中，10颗玷污层完整的牙齿和10颗玷污层已去除的牙齿用冷牙胶侧方加压充填法和Apexit封闭剂进行充填。这些牙齿在冠方和根尖方均完全封闭，作为阴性对照。其余20颗玷污层完整或已去除的牙齿不进行充填，作为阳性对照。每颗牙齿的根面用指甲油密封。将聚丙烯管的切割端密封在每个根管的冠部周围，使得置于其中的细菌只能通过已充填的根管空间移动。将每颗牙根置于装有无菌托德-休伊特肉汤（THB）的玻璃瓶中，并将0.5 ml的THB等分试样注入聚丙烯管中。该模型系统以168 g进行离心。每隔5天将血链球菌接种于THB中置于每个冠部腔室，并在90天内每天观察根尖部储存器中的细菌生长情况。所有阳性对照牙齿在24小时内均显示细菌渗透，而阴性对照牙齿在整个试验期间均未被污染。实验组牙齿的渗漏时间从7天到86天不等。去除或保留玷污层时，充填根管的渗漏情况无统计学显著差异（P>0.05）。
