玷污层对新型三氧化矿物凝聚体根尖封闭性的影响

目的：评价根尖倒预备窝洞壁的玷污层对根尖倒充填材料新型三氧化矿物凝聚体（mineral trioxide aggregate，MTA）Plus封闭性的影响。方法：选取50颗单根管离体上颌前牙或前磨牙，以步退法根管预备至60#，冷牙胶侧方加压法充填根管，行根尖切除及超声倒预备处理后，随机均分成两组：实验组（Smear-组）用0.17 g/L乙二胺四乙酸溶液（ethylenediaminetetraacetic acid，EDTA）冲洗倒预备窝洞，对照组（Smear+组）用生理盐水冲洗。各抽取5颗离体牙，采用体视显微镜排除微裂。采用扫描电镜观察窝洞壁的玷污层去除情况及牙本质小管管口开放情况；其余40颗牙使用材料MTA Plus行根尖倒充填后，采用蔗糖定量流体渗漏法，在第1、7、14、21、28、35、42、49、56 d检测从冠方向根方渗漏出的蔗糖量。实验模型置于恒温箱（37 ℃，100%湿度）中保存。采用重复测量资料的方差分析比较两组同一时间点和同组不同时间点的渗漏量差异，显著性水平α=0.05。结果：在56 d的观察期内，Smear-组和Smear+组渗漏量差异无统计学意义（P>0.05），不同检测时间点的渗漏量差异有统计学意义（P<0.05）。结论：玷污层对根尖倒充填材料MTA Plus的封闭性无明显影响。

Effect of smear layer on apical sealing ability of mineral trioxide aggregate (MTA) Plus through the sucrose penetration mode

Objective： To investigate the effect of smear layer on apical sealing ability in teeth obturated with mineral trioxide aggregate (MTA) Plus as retrofilling materials. Methods: Fifty freshly extracted maxillary anterior teeth or premolars with single root canal were used in this study. All teeth were instrumented to master apical point 60# by using the step-back technique, obturated with lateral condensation technique, and then apical resected. A root-end cavity was then instrumented with an ultrasonic diamond coated tip. Then the selected teeth were randomly and equally divided into two groups (n=25). In the experimental group (smear-), the teeth were irrigated with 0.17 g/L ethylenediaminetetraacetic acid (EDTA) to remove smear layer on the root-end cavity wall; in the control group (smear+), the teeth were irrigated with physiological saline. Five teeth were extracted to evaluate the cleanliness of root end cavity walls under a videomicroscope, respectively. The scanning electron microscope (SEM) evaluation was also performed for the presence of smear layer and open tubule. For the additional 40 teeth, the root-end cavities were filled with MTA Plus. The quantitative apical leakage of each teeth was evaluated by measuring the concentration of leaked sucrose in apical reservoir on 1, 7, 14, 21, 28, 35, 42, 49 and 56 days, respectively. The samples were stored at 37 ℃ and 100% humidity for 56 days. Statistical analysis was done with ANOVA for repeated measurement design data. Results: Removal of the smear layer did not cause significantly less apical leaked sucrose than that when the smear layer was left intact for 56 days (P>0.05). There were statistically significant differences at the concentration of leaked sucrose among different observation time points (P<0.05) . Conclusion: It may be concluded that removing the smear layer may not be necessary in root end cavities filled with MTA Plus.