Marginal and Internal Fit of CAD/CAM Crowns Fabricated Over Reverse Tapered Preparations
Marginal and Internal Fit of CAD/CAM Crowns Fabricated Over Reverse Tapered Preparations
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DOI：
10.1111/jopr.12715
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发表时间：
2019-02-01
影响因子：
4
通讯作者：
Nakamura, Takashi
中科院分区：
文献类型：
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作者：
Mejia, Jeison B. Carbajal;Yatani, Hirofumi;Nakamura, Takashi
目的 口内数字扫描可以准确记录单个基台牙齿预备体，无论其几何形状如何，并且可以设置 CAD 软件的算法来管理不同的基台形式。这项体外研究的目的是评估 CAD/CAM 氧化锆牙冠相对于传统和倒锥形制备物的边缘和内部贴合度。材料和方法 具有已知总咬合会聚 (TOC) 角度（-8 度、-4 度、0 度、8 度、12 度、16 度和 22 度）的牙冠制备物是从上颌左中切牙数字化创建的，并用丙烯酸树脂打印。接下来，使用 TRIOS 口内扫描仪扫描铸件，并使用 KaVo multiCAD 软件在具有正 TOC 角度的基台上使用默认参数（50 μm 水泥间距）设计牙冠，而反向锥形基台（负 TOC 角度）则以 0 度进行数字遮挡，并将额外的近远中间隙设置为 50 μm。然后，制作氧化锆牙冠，并使用硅胶复制技术记录其边缘和内部差异。所有复制品均在立体显微镜下以 50 倍放大倍数进行检查。收集的数据采用单向方差分析和事后 Tukey 检验进行边际拟合分析。对于轴向和切端配合，测量值不服从正态分布；因此，应用了 Kruskal-Wallis 和 Dunn/Bonferroni 多重比较检验 (p = 0.05)。结果 -8 度牙冠的平均边缘配合度 (58.2 +/- 6.0 μm) 与所有其余牙冠（范围 42.1-47.3 μm）有统计学差异 (p < 0.0001)。此外，当比较在正负 TOC 角度的基台上制作的牙冠时，内部配合具有统计学显着性 (p < 0.0001)。最大的中轴差异出现在 -8 度（165.5 μm）和 -4 度（130.8 μm）组中；然而，在评估切面贴合度时，它们显示出最小的差异（分别为 67.3 和 81.8 μm）。结论 在本研究的条件下，在倒锥形预备体上制作的氧化锆牙冠的边缘和内部贴合度在临床可接受的值范围内。
Purpose Intraoral digital scanning can accurately record single abutment tooth preparations despite their geometry, and the algorithms of the CAD software can be set to manage different abutment forms. The purpose of this in vitro study was to evaluate the marginal and internal fit of CAD/CAM zirconia crowns fabricated over conventional and reverse-tapered preparations. Materials and Methods Crown preparations with known total occlusal convergence (TOC) angles (-8 degrees, -4 degrees, 0 degrees, 8 degrees, 12 degrees, 16 degrees, and 22 degrees) were digitally created from a maxillary left central incisor and printed in acrylic resin. Next, casts were scanned with a TRIOS intraoral scanner, and crowns were designed with KaVo multiCAD software using default parameters (50 mu m cement space) on abutments with positive TOC angles, whereas reverse-tapered abutments (negative TOC angles) were digitally blocked out at 0 degrees and had an extra mesiodistal gap set to 50 mu m. Then, zirconia crowns were fabricated, and their marginal and internal discrepancies were recorded with the silicone replica technique. All replicas were examined under a stereomicroscope at 50x magnification. Collected data were analyzed with one-way ANOVA and post hoc Tukey test for marginal fit. For the axial and incisal fit, measured values did not follow a normal distribution; therefore, the Kruskal-Wallis and the Dunn/Bonferroni multiple comparison tests were applied (p = 0.05). Results The mean marginal fit of -8 degrees crowns (58.2 +/- 6.0 mu m) was statistically different (p < 0.0001) from all the remaining crowns (range 42.1-47.3 mu m). Also, the internal fit was statistically significant when comparing crowns fabricated over abutments with positive and negative TOC angles (p < 0.0001). The largest median axial discrepancies were found in the -8 degrees (165.5 mu m) and -4 degrees (130.8 mu m) groups; however, when evaluating the incisal fit, they showed the smallest discrepancies (67.3 and 81.8 mu m, respectively). Conclusions Under the conditions of this study, the marginal and internal fit of zirconia crowns fabricated over inverse-tapered preparations is within clinically accepted values.