Farjood Ehsan, Vojdani Mahroo, Torabi Kiyanoosh, Khaledi Amir Ali Reza
Assistant Professor, Department of Prosthodontics, School of Dentistry, Hormozgan University of Medical Sciences, Bandarabbas, Iran.
Professor, Dental Biomaterial Research Center, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran.
J Prosthet Dent. 2017 Jan;117(1):164-170. doi: 10.1016/j.prosdent.2016.04.010. Epub 2016 Jul 25.
Given the limitations of conventional waxing, computer-aided design and computer-aided manufacturing (CAD-CAM) technologies have been developed as alternative methods of making patterns.
The purpose of this in vitro study was to compare the marginal and internal fit of metal copings derived from wax patterns fabricated by rapid prototyping (RP) to those created by the conventional handmade technique.
Twenty-four standardized brass dies were milled and divided into 2 groups (n=12) according to the wax pattern fabrication method. The CAD-RP group was assigned to the experimental group, and the conventional group to the control group. The cross-sectional technique was used to assess the marginal and internal discrepancies at 15 points on the master die by using a digital microscope. An independent t test was used for statistical analysis (α=.01).
The CAD-RP group had a total mean (±SD) for absolute marginal discrepancy of 117.1 (±11.5) μm and a mean marginal discrepancy of 89.8 (±8.3) μm. The conventional group had an absolute marginal discrepancy 88.1 (±10.7) μm and a mean marginal discrepancy of 69.5 (±15.6) μm. The overall mean (±SD) of the total internal discrepancy, separately calculated as the axial internal discrepancy and occlusal internal discrepancy, was 95.9 (±8.0) μm for the CAD-RP group and 76.9 (±10.2) μm for the conventional group. The independent t test results showed significant differences between the 2 groups. The CAD-RP group had larger discrepancies at all measured areas than the conventional group, which was statistically significant (P<.01).
Within the limitations of this in vitro study, the conventional method of wax pattern fabrication produced copings with better marginal and internal fit than the CAD-RP method. However, the marginal and internal fit for both groups were within clinically acceptable ranges.
鉴于传统蜡型制作存在局限性，计算机辅助设计与计算机辅助制造（CAD-CAM）技术已作为制作熔模的替代方法得以发展。
本体外研究的目的是比较通过快速成型（RP）制作的蜡型所获得的金属基底冠与传统手工技术制作的金属基底冠的边缘适合性和内部适合性。
制作24个标准化黄铜代型，并根据蜡型制作方法分为2组（n = 12）。CAD-RP组被指定为实验组，传统组为对照组。采用横断面技术，使用数字显微镜在主代型上的15个点评估边缘和内部差异。采用独立t检验进行统计学分析（α = 0.01）。
CAD-RP组绝对边缘差异的总均值（±标准差）为117.1（±11.5）μm，平均边缘差异为89.8（±8.3）μm。传统组绝对边缘差异为88.1（±10.7）μm，平均边缘差异为69.5（±15.6）μm。分别计算为轴向内部差异和咬合面内部差异的总内部差异的总体均值（±标准差），CAD-RP组为95.9（±8.0）μm，传统组为76.9（±10.2）μm。独立t检验结果显示两组之间存在显著差异。CAD-RP组在所有测量区域的差异均大于传统组，具有统计学意义（P < 0.01）。
在本体外研究的局限性范围内，传统蜡型制作方法制作的基底冠比CAD-RP方法具有更好的边缘和内部适合性。然而，两组的边缘和内部适合性均在临床可接受范围内。
