Funkenbusch Paul D, Rotella Mario, Chochlidakis Konstantinos, Ercoli Carlo
Professor, Department of Mechanical Engineering, Hajim School of Engineering and Applied Sciences, University of Rochester, Rochester, NY.
Former Resident and Implant Fellow, Division of Prosthodontics, Eastman Institute for Oral Health, University of Rochester, and Instructor, University of Toronto, Toronto, Ont., Canada.
J Prosthet Dent. 2016 Oct;116(4):558-563. doi: 10.1016/j.prosdent.2016.03.002. Epub 2016 May 5.
Laboratory studies of tooth preparation often involve single values for all variables other than the one being tested. In contrast, in clinical settings, not all variables can be adequately controlled. For example, a new dental rotary cutting instrument may be tested in the laboratory by making a specific cut with a fixed force, but, in clinical practice, the instrument must make different cuts with individual dentists applying different forces. Therefore, the broad applicability of laboratory results to diverse clinical conditions is uncertain and the comparison of effects across studies difficult.
The purpose of this in vitro study was to examine the effects of 9 process variables on the dental cutting of rotary cutting instruments used with an electric handpiece and compare them with those of a previous study that used an air-turbine handpiece.
The effects of 9 key process variables on the efficiency of a simulated dental cutting operation were measured. A fractional factorial experiment was conducted by using an electric handpiece in a computer-controlled, dedicated testing apparatus to simulate dental cutting procedures with Macor blocks as the cutting substrate. Analysis of variance (ANOVA) was used to assess the statistical significance (α=.05).
Four variables (targeted applied load, cut length, diamond grit size, and cut type) consistently produced large, statistically significant effects, whereas 5 variables (rotation per minute, number of cooling ports, rotary cutting instrument diameter, disposability, and water flow rate) produced relatively small, statistically insignificant effects. These results are generally similar to those previously found for an air-turbine handpiece.
Regardless of whether an electric or air-turbine handpiece was used, the control exerted by the dentist, simulated in this study by targeting a specific level of applied force, was the single most important factor affecting cutting efficiency. Cutting efficiency was also significantly affected by factors simulating patient/clinical circumstances and hardware choices. These results highlight the greater importance of local clinical conditions (procedure, dentist) in understanding dental cutting as opposed to other hardware-related factors.
牙齿预备的实验室研究通常针对除测试变量之外的所有变量采用单一值。相比之下，在临床环境中，并非所有变量都能得到充分控制。例如，一种新型牙科旋转切割器械在实验室中可能通过以固定力进行特定切割来测试，但在临床实践中，该器械必须由不同的牙医以不同的力进行不同的切割。因此，实验室结果在不同临床条件下的广泛适用性尚不确定，且各研究间的效果比较也很困难。
本体外研究的目的是检验9个过程变量对使用电动手机的旋转切割器械进行牙齿切割的影响，并将其与先前一项使用涡轮手机的研究结果进行比较。
测量了9个关键过程变量对模拟牙齿切割操作效率的影响。通过在计算机控制的专用测试设备中使用电动手机，以Macor块作为切割基质来模拟牙齿切割过程，进行了部分因子实验。采用方差分析（ANOVA）来评估统计学显著性（α = 0.05）。
四个变量（目标施加负荷、切割长度、金刚石粒度和切割类型）始终产生较大的、具有统计学显著性的影响，而五个变量（每分钟转数、冷却孔数量、旋转切割器械直径、一次性使用与否和水流速率）产生的影响相对较小，无统计学显著性。这些结果总体上与先前涡轮手机的研究结果相似。
无论使用电动手机还是涡轮手机，本研究中通过设定特定施加力水平模拟的牙医控制，是影响切割效率的最重要单一因素。切割效率还受到模拟患者/临床情况和硬件选择等因素的显著影响。这些结果凸显了局部临床条件（操作、牙医）在理解牙齿切割方面比其他与硬件相关的因素更为重要。
