Peters C I, Peters O A, Barbakow F
Endodontic Division, Department of Preventive Dentistry, Cariology and Periodontology, University of Zurich, Plattenstr. 11, CH-8028 Zurich, Switzerland.
Int Endod J. 2001 Mar;34(2):142-8. doi: 10.1046/j.1365-2591.2001.00367.x.
This study compared the appearance of root-end cavity preparations and the time required to prepare them using prototype ultrasonic diamond-coated (DC) and stainless-steel (SS) retrotips.
In 12 maxillary and 12 mandibular molar teeth 48 root-end cavities were prepared ultrasonically in the palatal, mesio-buccal, distal and mesial root-ends using DC and SS retrotips, alternately. Replicas of the resected root tips and the root-end cavities were examined under a scanning electron microscope (SEM), recording (i) incidence and extent of dentine cracks (ii) minimum remaining thickness of the dentine walls and (iii) surface quality of the resected root-ends. The time taken to complete the preparation was also recorded. Means of these parameters were compared for both types of retrotips using nonparametric tests.
No resected root-ends had cracks before preparation. However, after preparation one root-end cavity shaped by an SS retrotip had a microcrack visible at 23x magnification. Four and seven other root-ends had crazed surfaces in the DC and SS groups, respectively (P > 0.05). Remaining minimum dentine thickness was 0.56 +/- 0.28 mm and 0.71 +/- 0.24 for the DC and SS groups, respectively, and this difference was significant (P < 0.05). A root-end cavity in one specimen in the DC group was perforated. Preparation times ranged from 25 s to 361 s and were significantly lower for DC tips (P < 0.01) than the SS tips. The time required to prepare root-end cavities also differed between roots; root-end preparation in mandibular molars was more time consuming.
A better quality surface was produced by the prototype diamond-coated retrotips, in less time than the SS retrotips, which in turn caused fewer cracks than previously reported. DC retrotips removed more dentine than SS retrotips and should therefore be used with care to avoid overpreparation or perforation.
本研究比较了使用原型超声金刚石涂层（DC）和不锈钢（SS）倒锥钻制备根尖腔的外观以及制备所需时间。
在12颗上颌磨牙和12颗下颌磨牙中，使用DC和SS倒锥钻交替在上腭、近中颊侧、远中及近中根尖处超声制备48个根尖腔。切除的根尖和根尖腔的复制品在扫描电子显微镜（SEM）下检查，记录（i）牙本质裂纹的发生率和范围（ii）牙本质壁的最小剩余厚度（iii）切除根尖的表面质量。还记录了完成制备所需的时间。使用非参数检验比较两种倒锥钻的这些参数的均值。
制备前切除的根尖均无裂纹。然而，制备后，一个由SS倒锥钻制备的根尖腔在23倍放大倍数下可见微裂纹。DC组和SS组分别有4个和7个其他根尖表面出现裂纹（P>0.05）。DC组和SS组的剩余最小牙本质厚度分别为0.56±0.28mm和0.71±0.24mm，差异有统计学意义（P<0.05）。DC组一个标本中的根尖腔穿孔。制备时间从25秒到361秒不等，DC钻的制备时间显著低于SS钻（P<0.01）。不同牙根制备根尖腔所需时间也不同；下颌磨牙的根尖制备更耗时。
原型金刚石涂层倒锥钻产生的表面质量更好，所需时间比SS倒锥钻少，产生的裂纹也比先前报道的少。DC倒锥钻比SS倒锥钻去除的牙本质更多，因此使用时应小心避免过度制备或穿孔。
