Department of Endodontics, Faculty of Dentistry, Estácio de Sá University, Rio de Janeiro, RJ, Brazil.
Department of Pediatric Dentistry and Orthodontics, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
Int Endod J. 2018 Jun;51(6):684-690. doi: 10.1111/iej.12873. Epub 2017 Dec 6.
To evaluate the effects of progressive apical enlargement on the amount of unprepared root canal surface area and remaining dentine thickness.
The root canals of 30 extracted mandibular incisors with Vertucci's type I configuration were instrumented with rotary HyFlex CM instruments (Coltene-Whaledent, Altstätten, Switzerland) up to 4 instruments larger than the first one that bound at the working length (WL). Teeth were scanned in a micro-computed tomography (micro-CT) device before canal preparation and after instrumentation with the 2nd, 3rd and 4th larger instruments. The amount of unprepared surface area in the full canal or in the apical 4 mm as well as the remaining dentine thickness at 10 mm from the WL were calculated and compared. The general linear model for repeated measures adjusted by Bonferroni's post hoc test was used for statistic analysis.
There was a significant reduction in the amount of unprepared areas after each increase in preparation size (P < 0.01). This was observed for both the full canal length and the 4-mm apical segment. The amount of remaining dentine was also significantly reduced after each file size (P < 0.01). However, dentine thickness always remained greater than 1 mm, even after using the largest instrument.
Apical preparations up to 4 instruments larger than the first one to bind at the WL caused a significant progressive reduction in the unprepared canal area.
评估渐进式根尖扩大对未预备根管表面积和剩余牙本质厚度的影响。
对 30 颗下颌切牙进行研究，这些切牙具有 Vertucci Ⅰ型形态，使用 HyFlex CM 旋转器械（Coltene-Whaledent，Altstätten，瑞士）进行根管预备，比第一次到达工作长度（WL）的器械大 4 号。在根管预备前和使用第二、第三和第四大器械后，使用 micro-CT 设备对牙齿进行扫描。计算并比较全根管或根尖 4mm 内未预备表面积以及距 WL 10mm 处剩余牙本质厚度。采用重复测量的一般线性模型，并用 Bonferroni 事后检验进行统计分析。
每次增加预备尺寸后，未预备区域的数量都会显著减少（P<0.01）。这在全根管长度和 4mm 根尖段都有观察到。每次使用更大的器械后，剩余牙本质的数量也显著减少（P<0.01）。然而，即使使用最大的器械，牙本质厚度始终保持在 1mm 以上。
根尖预备至比第一次到达 WL 的器械大 4 号，会导致未预备根管区域的显著逐渐减少。
