Pecora J D, Capelli A, Guerisoli D M Z, Spanó J C E, Estrela C
Ribeirão Preto Dental School, University of São Paulo, Ribeirão Preto, SP, Brazil.
Int Endod J. 2005 Jul;38(7):430-5. doi: 10.1111/j.1365-2591.2005.00946.x.
To investigate the influence of cervical preflaring with different instruments (Gates-Glidden drills, Quantec Flare series instruments and LA Axxess burs) on the first file that binds at working length (WL) in maxillary central incisors.
Forty human maxillary central incisors with complete root formation were used. After standard access cavities, a size 06 K-file was inserted into each canal until the apical foramen was reached. The WL was set 1 mm short of the apical foramen. Group 1 received the initial apical instrument without previous preflaring of the cervical and middle thirds of the root canal. Group 2 had the cervical and middle portion of the root canals enlarged with Gates-Glidden drills sizes 90, 110 and 130. Group 3 had the cervical and middle thirds of the root canals enlarged with nickel-titanium Quantec Flare series instruments. Titanium-nitrite treated, stainless steel LA Axxess burs were used for preflaring the cervical and middle portions of root canals from group 4. Each canal was sized using manual K-files, starting with size 08 files with passive movements until the WL was reached. File sizes were increased until a binding sensation was felt at the WL, and the instrument size was recorded for each tooth. The apical region was then observed under a stereoscopic magnifier, images were recorded digitally and the differences between root canal and maximum file diameters were evaluated for each sample.
Significant differences were found between experimental groups regarding anatomical diameter at the WL and the first file to bind in the canal (P < 0.01, 95% confidence interval). The major discrepancy was found when no preflaring was performed (0.151 mm average). The LA Axxess burs produced the smallest differences between anatomical diameter and first file to bind (0.016 mm average). Gates-Glidden drills and Flare instruments were ranked in an intermediary position, with no statistically significant differences between them (0.093 mm average).
The instrument binding technique for determining anatomical diameter at WL is not precise. Preflaring of the cervical and middle thirds of the root canal improved anatomical diameter determination; the instrument used for preflaring played a major role in determining the anatomical diameter at the WL. Canals preflared with LA Axxess burs created a more accurate relationship between file size and anatomical diameter.
研究使用不同器械（盖茨 - 格利登钻、Quantec Flare系列器械和LA Axxess车针）对上颌中切牙工作长度（WL）处首根发生卡滞的锉的影响。
使用40颗牙根完全形成的人上颌中切牙。制备标准开髓洞形后，将06号K锉插入每个根管直至到达根尖孔。工作长度设定为距根尖孔短1mm。第1组在未预先扩大根管颈段和中段的情况下使用初始根尖器械。第2组使用90、110和130号盖茨 - 格利登钻扩大根管颈段和中段。第3组使用镍钛Quantec Flare系列器械扩大根管颈段和中三分之一段。第4组使用经亚硝酸钛处理的不锈钢LA Axxess车针预扩根管颈段和中段。每个根管使用手动K锉进行扩锉，从08号锉开始被动操作直至达到工作长度。逐渐增加锉的型号，直到在工作长度处感到卡滞，记录每颗牙的器械型号。然后在立体放大镜下观察根尖区，进行数码图像记录，并评估每个样本根管直径与最大锉直径之间的差异。
各实验组在工作长度处的解剖直径以及根管内首根发生卡滞的锉之间存在显著差异（P < 0.01，95%置信区间）。未进行预扩时差异最大（平均0.151mm）。LA Axxess车针在解剖直径与首根发生卡滞的锉之间产生的差异最小（平均0.016mm）。盖茨 - 格利登钻和Flare器械处于中间位置，两者之间无统计学显著差异（平均0.093mm）。
用于确定工作长度处解剖直径的器械卡滞技术并不精确。根管颈段和中三分之一段的预扩改善了解剖直径的确定；用于预扩的器械在确定工作长度处的解剖直径方面起主要作用。用LA Axxess车针预扩的根管在锉型号与解剖直径之间建立了更准确的关系。
