Mohaghegh Mina, Firouzmandi Maryam, Ansarifard Elham, Ramazani Laleh
Department of Prosthodontics, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran.
Department of Restorative Dentistry, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran.
J Int Soc Prev Community Dent. 2020 Sep 28;10(5):652-658. doi: 10.4103/jispcd.JISPCD_25_20. eCollection 2020 Sep-Oct.
Use of monolithic zirconia for fabrication of all-ceramic crowns eliminates several shortcomings of layered zirconia crowns. Long-term success of restorations highly depends on the marginal fit. The crown thickness is among the factors that affect the marginal integrity. Meanwhile, reduced thickness of crowns has several advantages such as preservation of tooth structure. The aim of this study was to evaluate the marginal fit of monolithic zirconia crowns in reduced thickness and to compare the marginal fit of full-contour monolithic zirconia in different thicknesses with layered zirconia crowns.
In this study, two standard brass dies (7 mm × 5 mm length diameter) were prepared with a heavy chamfer finish line with 0.5 and 1 mm depth. By using a CAD-CAM system, 30 crowns were made in three groups ( = 10) of 1-mm thick layered zirconia, 1-mm thick monolithic zirconia, and 0.5-mm thick monolithic zirconia. Crowns were placed on master dies and randomly numbered. The marginal gap was measured on 18 points by using a digital microscope (×230). The mean ± standard deviation (SD) values were calculated and analyzed by Statistical Package for the Social Sciences (SPSS) software program through Kruskal-Wallis and Mann-Whitney tests (α = 0.05).
The marginal gap of 1-mm layered zirconia was significantly different from that of 1-mm monolithic zirconia ( = 0.001) and 0.5-mm monolithic zirconia ( = 0.004). Analysis of variance (ANOVA) revealed no significant difference between 0.5 and 1 mm thicknesses of monolithic zirconia ( = 0.141).
Marginal gap in all the three groups was clinically acceptable. The two different thicknesses of monolithic zirconia crowns had no significant effect on the restoration marginal fit; however, layered zirconia crowns showed a significantly higher marginal gap than monolithic zirconia crowns.
使用整体式氧化锆制作全瓷冠消除了分层氧化锆冠的几个缺点。修复体的长期成功高度依赖于边缘适合性。冠厚度是影响边缘完整性的因素之一。同时，减小冠的厚度有几个优点，如保存牙体组织。本研究的目的是评估厚度减小的整体式氧化锆冠的边缘适合性，并比较不同厚度的全轮廓整体式氧化锆与分层氧化锆冠的边缘适合性。
在本研究中，制备了两个标准黄铜代型（长径7mm×5mm），带有深度为0.5mm和1mm的粗面肩台精修线。通过计算机辅助设计与制造（CAD-CAM）系统，制作了三组（每组n = 10）冠，分别为1mm厚的分层氧化锆冠、1mm厚的整体式氧化锆冠和0.5mm厚的整体式氧化锆冠。将冠放置在主代型上并随机编号。使用数字显微镜（×230）在18个点测量边缘间隙。计算平均值±标准差（SD）值，并通过社会科学统计软件包（SPSS）软件程序，经Kruskal-Wallis检验和Mann-Whitney检验（α = 0.05）进行分析。
1mm厚的分层氧化锆冠的边缘间隙与1mm厚的整体式氧化锆冠（P = 0.001）和0.5mm厚的整体式氧化锆冠（P = 0.004）有显著差异。方差分析（ANOVA）显示，0.5mm和1mm厚度的整体式氧化锆之间无显著差异（P = 0.141）。
所有三组的边缘间隙在临床上均可接受。两种不同厚度的整体式氧化锆冠对修复体边缘适合性无显著影响；然而，分层氧化锆冠的边缘间隙显著高于整体式氧化锆冠。
