Western University of Health Sciences College of Dental Medicine, Pomona, CA.
Department of Restorative Dentistry, Oregon Health & Science University, Portland, OR.
J Prosthodont. 2018 Jan;27(1):63-66. doi: 10.1111/jopr.12638. Epub 2017 May 17.
To evaluate the marginal gaps of CAD/CAM (CEREC 3) produced crowns made from leucite-reinforced glass-ceramic (IPS Empress CAD) blocks (LG), and lithium-disilicate (IPS e.max CAD) blocks before (LD-B), and after (LD-A) crystallization firing.
A human molar tooth (#19) was mounted with adjacent teeth on a typodont and prepared for a full-coverage ceramic crown. The typodont was assembled in the mannequin head to simulate clinical conditions. After tooth preparation 15 individual optical impressions were taken by the same operator using titanium dioxide powder and a CEREC 3 camera per manufacturer's instructions. One operator designed and machined the crowns in leucite-reinforced glass-ceramic blocks (n = 5) and lithium-disilicate blocks (n = 10) using the CEREC 3 system. The crowns were rigidly seated on the prepared tooth, and marginal gaps (μm) were measured with an optical microscope (500×) at 12 points, 3 on each of the M, B, D, and L surfaces of the leucite-reinforced glass-ceramic crowns and the lithium-disilicate crowns before and after crystallization firing. Results were analyzed by two-way ANOVA followed by a Tukey's post hoc multiple comparison test (α = 0.05).
The overall mean marginal gaps (μm) for the crowns evaluated were: LG = 49.2 ± 5.5, LD-B = 42.9 ± 12.2, and LD-A = 57.2 ± 16.0. The marginal gaps for LG and LD-B were not significantly different, but both were significantly less than for LD-A.
The type of ceramic material did not affect the marginal gap of CAD/CAM crowns. The crystallization firing process required for lithium-disilicate crowns resulted in a significant increase in marginal gap size, likely due to shrinkage of the ceramic during the crystallization process.
The marginal gap of CAD/CAM-fabricated lithium disilicate crowns increases following crystallization firing. The marginal gap still remains within clinically acceptable parameters.
评估 CAD/CAM（CEREC 3）制作的白榴石增强玻璃陶瓷（IPS Empress CAD）块（LG）和锂硅玻璃陶瓷（IPS e.max CAD）块（LD-A）在预烧（LD-B）和结晶烧制（LD-A）后的冠边缘间隙。
将一颗人类磨牙（#19）与相邻牙齿一起安装在牙体模型上，制备全冠陶瓷。牙体模型被组装在模型头中以模拟临床情况。牙齿预备后，根据制造商的说明，同一操作员使用二氧化钛粉末和 CEREC 3 相机对 15 个个体光学印模进行了拍摄。一位操作员使用 CEREC 3 系统设计并加工了白榴石增强玻璃陶瓷块（n = 5）和锂硅玻璃陶瓷块（n = 10）中的冠。将冠刚性地放置在预备好的牙齿上，使用光学显微镜（500×）在白榴石增强玻璃陶瓷冠和锂硅玻璃陶瓷冠的 M、B、D 和 L 表面的 12 个点上测量边缘间隙（μm），每个表面测量 3 个点，在预烧和结晶烧制之前和之后。结果采用双向方差分析，然后进行 Tukey 事后多重比较检验（α = 0.05）。
评估的冠的总体平均边缘间隙（μm）为：LG = 49.2 ± 5.5、LD-B = 42.9 ± 12.2 和 LD-A = 57.2 ± 16.0。LG 和 LD-B 的边缘间隙没有显著差异，但两者均显著小于 LD-A。
陶瓷材料类型不影响 CAD/CAM 冠的边缘间隙。锂硅玻璃陶瓷冠所需的结晶烧制过程导致边缘间隙尺寸显著增加，可能是由于陶瓷在结晶过程中的收缩所致。
CAD/CAM 制作的锂硅玻璃陶瓷冠在结晶烧制后边缘间隙增加。边缘间隙仍在可接受的临床参数范围内。
