Waplington M, Lumley P J, Walmsley A D
Department of Restorative Dentistry, School of Dentistry, University of Birmingham, U.K.
Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 1997 Mar;83(3):387-92. doi: 10.1016/s1079-2104(97)90247-x.
Ultrasonic root end preparation is now a recognized clinical procedure. Advantages claimed include improved access to the surgical site (because of reduced root end bevel), and faster more conservative preparation of the root end cavity. However, cracking of the root face has been reported after preparation.
The aim of this study was to determine the incidence of root end cracking at varying ultrasonic power levels with a replica technique and scanning electron microscopy.
The root canals of 55 single-rooted teeth were prepared to size 40 apically and obturated with laterally condensed gutta perch and sealer. Root ends were resected at 90 degrees 3 mm from the apex. Class 1 cavities (n = 5) were prepared with retro tips in a Neosonic handpiece with different power settings. Time of preparation and load applied were constant. Another experimental group (n = 5) was prepared with a no. 1 rotary bur. A replica technique with addition-cured silicone impression material and epoxy resin was used to prevent drying artefacts. Specimens were viewed under scanning electron microscope for alterations of the root face.
Results showed no root face cracking across the full range of instrument power settings, although chipping of the retrograde cavity margins was observed. No cracking was noted in bur-prepared teeth.
超声根尖预备如今是一种公认的临床操作。其宣称的优点包括改善对手术部位的操作（由于根尖斜面减小），以及更快速、更保守地预备根尖腔。然而，有报道称预备后根面出现了裂纹。
本研究的目的是采用复制技术和扫描电子显微镜确定不同超声功率水平下根尖裂纹的发生率。
将55颗单根牙的根管根尖预备至40号，并用侧向加压牙胶和封闭剂进行充填。根尖在距根尖3mm处90度切除。使用Neosonic手机中的倒充填钻针在不同功率设置下制备1类洞（n = 5）。预备时间和施加的负荷保持恒定。另一个实验组（n = 5）用1号旋转车针进行预备。采用加成型硅橡胶印模材料和环氧树脂的复制技术以防止干燥假象。在扫描电子显微镜下观察标本根面的改变。
结果显示，在整个器械功率设置范围内均未出现根面裂纹，尽管观察到倒充填洞边缘有崩裂。用旋转车针预备的牙齿未发现裂纹。
