AbdElaziz Mohammed H, Aldamaty Mohamed F, Omar Elsayed Ali, Elbadawy Adel A, Borzangy Sary, Alqutaibi Ahmed Y, Zafar Muhammad S
Substitutive Dental Sciences Department, College of Dentistry, Taibah University, Almadinah Almunawwarah 41311, KSA.
Department of Fixed Prosthodontics, Faculty of Dental Medicine, Al-Azhar University, Cairo 11651, Egypt.
J Taibah Univ Med Sci. 2024 Nov 29;19(6):1108-1116. doi: 10.1016/j.jtumed.2024.11.008. eCollection 2024 Dec.
This study was aimed at assessing the effects of various finish line designs and cement gap thicknesses on the fracture resistance of gradient zirconia crowns.
Sixty crowns were fabricated on stainless-steel dies with yttria multi-layered (YML) zirconia and categorized into three primary groups according to finish line type (knife-edge, chamfer, and rounded shoulder). Each group was further classified into two subgroups (n = 10) according to cement space thickness (50 or 80 μm). Optical impressions of the dies were acquired with an indirect laboratory scanner, and cement spaces (50 or 80 μm) were established for each finish line type in Exocad software. Subsequently, the zirconia crowns were milled, sintered, cemented onto their respective dies, thermomechanically aged, and subjected to loading until fracture. The data were statistically analyzed with one-way ANOVA and post hoc tests for pairwise comparisons. Additionally, two-way ANOVA was used to investigate interactions between two study variables.
No significant differences between chamfer and knife-edge patterns were observed, whereas the rounded shoulder pattern exhibited significantly higher failure load values. Similarly, no significant difference was observed between 50 μm and 80 μm cement space.
Knife-edge margins with YML gradient zirconia crowns provide a reliable alternative to shoulder margins, particularly in minimally invasive preparations. A cement space of 80 μm rather than 50 μm is preferred for various finish line designs.
本研究旨在评估不同的边缘设计和粘结剂间隙厚度对渐变氧化锆全冠抗折性能的影响。
采用氧化钇多层（YML）氧化锆在不锈钢代型上制作60个全冠，根据边缘类型（刃状、肩台、圆钝肩台）分为三个主要组。每组再根据粘结剂间隙厚度（50或80μm）进一步分为两个亚组（n = 10）。使用间接实验室扫描仪获取代型的光学印模，并在Exocad软件中为每种边缘类型设置粘结剂间隙（50或80μm）。随后，铣削、烧结氧化锆全冠，将其粘结到各自的代型上，进行热机械老化处理，然后加载直至断裂。数据采用单因素方差分析和事后检验进行两两比较的统计学分析。此外，采用双因素方差分析研究两个研究变量之间的相互作用。
未观察到肩台和刃状边缘设计之间存在显著差异，而圆钝肩台边缘设计的破坏载荷值显著更高。同样，50μm和80μm粘结剂间隙之间未观察到显著差异。
YML渐变氧化锆全冠的刃状边缘是肩台边缘的可靠替代方案，尤其是在微创预备中。对于各种边缘设计，80μm的粘结剂间隙比50μm更可取。
