Thompson S A, Dummer P M
Department of Restorative Dentistry, Dental School, University of Wales College of Medicine, Cardiff, UK.
J Endod. 1997 Nov;23(11):698-702. doi: 10.1016/S0099-2399(97)80405-0.
The aim of this study was to determine the shaping ability of Lightspeed nickel-titanium rotary instruments in simulated canals. Forty canals consisting of four different shapes in terms of angle and position of curvature were prepared by Lightspeed instruments using the technique recommended by the manufacturer. This report describes the efficacy of the instruments in terms of preparation time, instrument failure, canal blockages, loss of canal length, and three-dimensional canal form. Overall, the mean preparation time for all canals was 8.12 min with canal shape having no significant effect on the speed of preparation. No instruments deformed or separated during the study, and none of the canals became blocked with debris. Seventeen canals retained their original working length, but 16 gained in length and 7 lost length. There was no significant difference between the canal shapes in terms of the mean loss of distance or category of distance change. Apical stops as judged from intracanal impressions were present in 23 of the canals but they were all judged to be of poor quality. The canals were found to be smooth in the apical half of the canal in 36 specimens and in the coronal half of 24 specimens. All the canals had poor taper characteristics, and only 16 specimens showed good flow characteristics. Under the conditions of this study, Lightspeed instruments prepared canals rapidly, with no fractures, canal blockages, and with minimal change in working length. The three dimensional form of the canals was compromised as flow and taper were less than ideal, presumably as a result of an ineffective stepback procedure. The results imply that either the stepback sequence should be modified or another instrument with increased taper should be used to refine the canal walls before obturation.
本研究的目的是确定Lightspeed镍钛旋转器械在模拟根管中的塑形能力。使用Lightspeed器械按照制造商推荐的技术，制备了40条根管，这些根管在弯曲角度和位置方面具有四种不同的形状。本报告从预备时间、器械折断、根管堵塞、根管长度丧失以及三维根管形态等方面描述了这些器械的效果。总体而言，所有根管的平均预备时间为8.12分钟，根管形状对预备速度没有显著影响。在研究过程中，没有器械发生变形或分离，也没有根管被碎屑堵塞。17条根管保持了其原来的工作长度，但16条根管长度增加，7条根管长度缩短。在平均长度丧失或长度变化类别方面，根管形状之间没有显著差异。根据根管内印模判断，23条根管存在根尖止点，但它们均被判定质量较差。在36个标本中，根管在根尖段的下半部分是光滑的，在24个标本中，根管在冠段的下半部分是光滑的。所有根管的锥度特征均较差，只有16个标本显示出良好的流畅性特征。在本研究条件下，Lightspeed器械能快速预备根管，没有折断、根管堵塞情况，工作长度变化最小。由于流畅性和锥度不理想，根管的三维形态受到影响，这可能是由于逐步后退法无效所致。结果表明，要么应修改逐步后退顺序，要么应使用另一种锥度更大的器械在充填前对根管壁进行修整。
