Department of Prosthetic Dentistry, College of Dentistry, King Khalid University, Abha, Saudi Arabia.
Oral and Maxillofacial Prosthodontics Department, College of Dentistry, King Abdulaziz University, Saudi Arabia.
Technol Health Care. 2021;29(6):1161-1171. doi: 10.3233/THC-202782.
The aesthetics and strength of anterior porcelain layered zirconia (PLZ) crowns are mainly affected by the zirconia (Zr) coping design. There is a need for a modified design to enhance aesthetics with strength.
The purpose of this study was to compare the fracture resistance of anterior PLZ crowns having modified CAD-CAM Zr coping designs (in terms of thickness and marginal collar designs) with standard Zr copings.
Fifty PLZ crowns were fabricated and divided into two groups: Gr 1: Standard Zr Coping (SZC) (control gr) with 0.5 mm thickness (Facial-F, Mesial-M, Distal-D, incisal-I, and Palatal-P) without a collar; Gr 2: Collar Zr Coping (CZC) (test gr) with 2.5 mm collar height on M, D, P and 0.2 mm F and variable facial wall thickness. Subgroups: Gr 2a: (CZC-0.5 mm) facial wall thickness 0.5 mm; Gr 2b: (CZC-0.4 mm) facial wall thickness 0.4 mm; Gr 2c: (CZC-0.3 mm) facial wall thickness 0.3 mm; Gr 2d: (CZC-0.2 mm) facial wall thickness 0.2 mm. The fracture load was determined and analysed using One-way ANOVA and Dunnet test.
The minimum fracture load was 927.36 ± 127.80 N observed for Gr 2c (CZC at 0.3 mm) while the maximum fracture load was 1373.61 ± 146.54 N observed for Gr 2a (CZC at 0.5 mm). A highly significant difference in mean fracture load among various Zr coping groups (p< 0.001) was determined.
Novel Zr coping design for anterior PLZ crowns can provide better aesthetics with strength. Reducing the thickness of Zr coping in the aesthetic zone to 0.2 mm and providing a modified collar design (2.5 mm collar height on M, D, P, and 0.2 mm F) would provide strength without jeopardizing aesthetics.
前牙烤瓷分层氧化锆（PLZ）冠的美观和强度主要受氧化锆（Zr）修复体设计的影响。需要一种改良设计来增强美观度并保持强度。
本研究旨在比较具有改良 CAD-CAM Zr 修复体设计（在厚度和边缘颈圈设计方面）的前牙 PLZ 冠的抗折强度与标准 Zr 修复体的差异。
制作 50 个 PLZ 冠并分为两组：Gr 1：标准 Zr 修复体（SZC）（对照组），厚度为 0.5mm（颊面-F、近中-M、远中-D、切缘-I 和腭面-P），无颈圈；Gr 2：颈圈 Zr 修复体（CZC）（实验组），在 M、D、P 上有 2.5mm 高的颈圈，在 F 上有 0.2mm 高，颊面壁厚有变化。亚组：Gr 2a：（CZC-0.5mm）颊面壁厚 0.5mm；Gr 2b：（CZC-0.4mm）颊面壁厚 0.4mm；Gr 2c：（CZC-0.3mm）颊面壁厚 0.3mm；Gr 2d：（CZC-0.2mm）颊面壁厚 0.2mm。采用 One-way ANOVA 和 Dunnet 检验确定并分析断裂载荷。
Gr 2c（CZC 为 0.3mm）的最小断裂载荷为 927.36±127.80N，Gr 2a（CZC 为 0.5mm）的最大断裂载荷为 1373.61±146.54N。确定了不同 Zr 修复体组之间平均断裂载荷存在显著差异（p<0.001）。
新型 Zr 修复体设计可增强前牙 PLZ 冠的美观度并保持强度。将 Zr 修复体的厚度在美学区域减少至 0.2mm，并采用改良颈圈设计（M、D、P 上有 2.5mm 高的颈圈，F 上有 0.2mm 高），可在不影响美观的情况下提供强度。
