Pilo R, Corcino G, Tamse A
Department of Oral Rehabilitation, Maurice and Gabriela Goldschleger School of Dental Medicine, Tel Aviv University, Israel.
J Endod. 1998 Jun;24(6):401-4. doi: 10.1016/S0099-2399(98)80020-4.
The residual dentin thickness in the coronal part of root canals of mandibular premolars after stepback preparation and flaring with Gates Glidden (GG) drills was assessed sequentially in a newly designed muffle device. Twelve extracted teeth were embedded in clear polyester resin, sectioned horizontally (1, 3, and 5 mm apically to the cementoenamel junction), and reassembled in the muffle device. The sequence of canal preparation was K-files to #40, then GG-2 and GG-4. After each procedure, the slices were separated and residual dentin thickness measured by a toolmaker microscope in four directions (buccal, lingual, distal, and mesial) and reassembled in the muffle device. Statistical analysis by three-way analysis of variance with repeated measures was undertaken. The difference in residual dentin thickness was highly significant with regard to instrument (control, K-40, GG-2, GG-4; p < 0.0001), slice (upper, middle, and lower; p < 0.0003), and direction (B, L, M, and D; p < 0.001). In each slice, the width of the mesial side was similar to the distal side, as was the buccal to the lingual sides. Reduction of residual dentin thickness in the mesiodistal direction, from the unprepared upper slice to the GG-4 prepared lower slice, was appreciably greater (35%) than in the buccolingual direction (5%).
在一种新设计的马弗炉装置中，对下颌前磨牙根管冠部在逐步后退预备并用盖茨·格利登（GG）钻扩孔后的剩余牙本质厚度进行了连续评估。将12颗拔除的牙齿嵌入透明聚酯树脂中，水平切片（在牙骨质牙釉质界根尖向1、3和5毫米处），并重新组装到马弗炉装置中。根管预备顺序为用K锉至#40，然后使用GG-2和GG-4。每次操作后，将切片分开，用工具显微镜在四个方向（颊侧、舌侧、远中侧和近中侧）测量剩余牙本质厚度，然后重新组装到马弗炉装置中。采用重复测量的三因素方差分析进行统计分析。剩余牙本质厚度在器械（对照、K-40、GG-2、GG-4；p < 0.0001）、切片（上部、中部和下部；p < 0.0003）和方向（B、L、M和D；p < 0.001）方面差异具有高度显著性。在每个切片中，近中侧的宽度与远中侧相似，颊侧与舌侧也相似。从未预备的上部切片到GG-4预备的下部切片，近远中方向剩余牙本质厚度的减少（35%）明显大于颊舌方向（5%）。
