AIM To evaluate the influence of the location and design of endodontic access cavities on root canal shaping and filling ability, pulp chamber cleaning and fracture resistance of extracted human mandibular incisors. METHODOLOGY After pre-selection using periapical radiographs, forty extracted intact human mandibular incisors were scanned in a micro-computed tomographic device. The teeth were matched based on similar anatomical features of the canals and assigned to four experimental groups (n = 10) according to the endodontic access cavity and root canal preparation protocol: traditional/TRUShape (T/TRU); traditional/MTwo (T/MT); minimally invasive/TRUShape (MI/TRU); and minimally invasive/MTwo (MI/MT). The samples were scanned after root canal instrumentation and filling procedures. The parameters evaluated were as follows: volume and area of the root canal, noninstrumented canal areas, canal transportation and centring ratio, accumulated hard tissue debris, voids in root canal fillings and remnants of root canal filling materials in the pulp chamber. After root canal filling and cavity restoration procedures, the samples were submitted to a fracture resistance test. Data were statistically analysed using Shapiro-Wilk, one-way anova and Bonferroni tests with a significance level of 5% (α = 0.05). RESULTS There was no difference regarding all parameters evaluated before and after root canal preparation (volume and area of the root canal, noninstrumented canal areas, canal transportation and centring ratio, and accumulated hard tissue debris) amongst the groups (P > 0.05). MI/TRU and MI/MT groups were associated with significantly more voids in root canal fillings when compared to the T/TRU and T/MT groups (P < 0.05). Percentage of root canal filling material remnants in the pulp chamber after cleaning procedures and mean fracture resistance values were not significantly different amongst the four experimental groups (P > 0.05). CONCLUSIONS The location and design of the endodontic access cavity did not impact on root canal preparation nor resistance to fracture of extracted mandibular incisors, regardless of the instrument used. Minimally invasive access cavities were associated with significantly more voids in root canal fillings.

中文翻译：

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微创牙髓进入腔对根管成形和充盈能力，牙髓腔清洁以及拔除的人下颌切牙的抗断裂性的影响。

目的评估牙髓进入腔的位置和设计对拔除的人下颌切牙的根管成形和充盈能力，牙髓腔清洁和抗断裂性的影响。方法学在使用根尖周射线照相术进行预选后，在微型计算机断层扫描设备中扫描了四十个完整的人类下颌切牙。根据根管的相似解剖特征对牙齿进行匹配，并根据牙髓进入腔和根管制备方案将其分为四个实验组（n = 10）：传统/ TRUShape（T / TRU）；传统/ MTwo（T / MT）；微创/ TRUShape（MI / TRU）；和微创/ MTwo（MI / MT）。在根管置入和充填程序后对样品进行扫描。评估的参数如下：根管的体积和面积，非器械根管的面积，根管的运输和对中比，积聚的硬组织碎片，根管充填物中的空隙以及牙髓腔中根管充填材料的残留物。经过根管充填和腔体修复程序后，将样品进行抗断裂测试。使用Shapiro-Wilk，单向方差分析和Bonferroni检验对数据进行统计学分析，显着性水平为5％（α= 0.05）。结果各组之间在根管准备前后评估的所有参数（根管的体积和面积，非器械根管的面积，根管的运输和对中率以及硬组织碎屑的累积量）均无差异（P> 0.05）。与T / TRU和T / MT组相比，MI / TRU和MI / MT组与根管充盈的空隙明显相关（P <0.05）。在四个实验组之间，清洁程序后牙髓腔中根管充填材料残余物的百分比和平均抗断裂性值均无显着差异（P> 0.05）。结论无论使用何种器械，牙髓进入腔的位置和设计均不会影响根管的准备，也不会影响拔除的下颌切牙的断裂阻力。微创进入腔与根管充填物中明显更多的空隙相关。在四个实验组之间，清洁程序后牙髓腔中根管充填材料残余物的百分比和平均抗断裂性值均无显着差异（P> 0.05）。结论无论使用何种器械，牙髓进入腔的位置和设计均不会影响根管的准备，也不会影响拔出的下颌切牙的断裂阻力。微创进入腔与根管充填物中明显更多的空隙相关。在四个实验组之间，清洁程序后牙髓腔中根管充填材料残余物的百分比和平均抗断裂性值均无显着差异（P> 0.05）。结论无论使用何种器械，牙髓进入腔的位置和设计均不会影响根管的准备，也不会影响拔出的下颌切牙的断裂阻力。微创进入腔与根管充填物中明显更多的空隙相关。