Mansour Fatema Khaled, Ibrahim Rabab Mohammed, Mansour Hoda, Hamdy Ahmed Mohamed
Faculty of Oral and Dental Medicine, October University of Modern Sciences and Arts, Cairo, Egypt.
Faculty of Dentistry, Cairo University, Cairo, Egypt.
BDJ Open. 2021 May 10;7(1):17. doi: 10.1038/s41405-021-00072-7.
Accuracy of internal fit and microleakage for CAD-CAM systems used in metal coping fabrication and veneered with layering or pressing porcelain in ceramometallic restoration is unclear.
A master metal die was milled to resemble the right mandibular first molar preparation for coverage with ceramometallic restoration. Master die was duplicated to twenty-four resin specimen dies.They were divided into two groups according to metal coping construction technique using either conventional (C) or CAD (D) wax. Each group was subdivided into two subgroups (n = 6) according to the technique of porcelain veneering (layered or pressed) to fabricate ceramometallic restorations, where subgroup (CL, DL) were conventionally layered by porcelain and (CP, DP) were press veneered. A standardized thickness of metal and porcelain was performed in all specimens as per manufacturer's instructions for techniques ceramometallic restoration construction. Evaluation of internal fit was done with silicone replica technique using stereomicroscope at ×24 magnification where the thickness of silicon layer was measured at 20 reference points on each specimen. Then specimens were subjected to thermocycling. Sectioned specimens were assessed for microleakage using a stereomicroscope at ×12 magnification along die-cement interface with a five scale score.
Mean internal gap values of veneering showed a statistically nonsignificant difference between specimens made with layering(L) and pressing(P). Different techniques of wax construction showed a non-significant difference in internal gap values between specimens made with conventional(C) and CAD(D) waxing. However, a significant difference was found in the internal gap at different sites. The highest internal gap was found at the occlusal surface, while the lowest gap was found at the finish line. The highest mean microleakage score was found with CAD wax and press veneering, while the lowest mean microleakage score was found with conventional wax and press veneering.
Both construction techniques of ceramometallic restoration were considered reliable in restoration production within a clinically acceptable range regarding internal fit and microleakage. There is a strong positive correlation between internal fit and microleakage of ceramometallic restoration constructed.
在金属烤瓷修复体中，用于制作金属基底冠并采用分层或压铸瓷进行饰面的CAD-CAM系统的内部适合性和微渗漏的准确性尚不清楚。
制作一个主金属代型，使其类似于右下颌第一磨牙预备体，用于金属烤瓷修复体覆盖。将主代型复制成24个树脂标本代型。根据制作金属基底冠的技术，使用传统（C）或CAD（D）蜡，将它们分为两组。每组再根据烤瓷饰面技术（分层或压铸）细分为两个亚组（n = 6），以制作金属烤瓷修复体，其中亚组（CL、DL）采用传统方法分层堆瓷，（CP、DP）采用压铸饰面。按照金属烤瓷修复体制作技术的制造商说明，在所有标本中进行标准化的金属和瓷层厚度设置。使用体视显微镜，在24倍放大倍数下，采用硅橡胶复制技术评估内部适合性，在每个标本的20个参考点处测量硅橡胶层的厚度。然后对标本进行热循环处理。使用体视显微镜，在12倍放大倍数下，沿着代型 - 粘结剂界面，以五级评分评估切片标本的微渗漏情况。
饰面的平均内部间隙值在分层（L）和压铸（P）制作的标本之间无统计学显著差异。不同的蜡制作技术在使用传统（C）和CAD（D）蜡制作的标本的内部间隙值上无显著差异。然而，在不同部位发现内部间隙存在显著差异。咬合面的内部间隙最大，而在边缘线处间隙最小。CAD蜡和压铸饰面的平均微渗漏评分最高，而传统蜡和压铸饰面的平均微渗漏评分最低。
就内部适合性和微渗漏而言，两种金属烤瓷修复体的制作技术在临床可接受范围内被认为在修复体制作中是可靠的。所制作的金属烤瓷修复体的内部适合性和微渗漏之间存在强正相关。
