Faculty of Dentistry, The University of British Columbia, Vancouver, BC, Canada.
Faculty of Dentistry, King Abdulaziz University, Jeddah, Saudi Arabia.
J Prosthodont. 2019 Mar;28(3):288-298. doi: 10.1111/jopr.13021. Epub 2019 Jan 27.
The marginal fit is an essential component for the clinical success of prosthodontic restorations. The aim of this study was to investigate the influence of different abutment finish line widths and crown thicknesses on the marginal fit of zirconia crowns fabricated using either standard or fast sintering protocols.
Six titanium abutments were fabricated for receiving zirconia molar crowns. Crowns were designed virtually and milled from partially sintered zirconia blanks and divided into 12 groups (n = 10/group). Crowns in groups 1 to 6 were sintered by standard sintering, while those in groups 7 to 12 were sintered by fast sintering. Groups were further categorized according to abutment finish line and crown thickness: G1/G7 (0.5 mm chamfer, 0.8 mm thick); G2/G8 (0.5 mm chamfer, 1.5 mm thick); G3/G9 (1.0 mm chamfer, 0.8 mm thick); G4/10 (1.0 mm chamfer, 1.5 mm thick); G5/G11 (1.2 mm chamfer, 0.8 mm thick); G6/G12 (1.2 mm chamfer, 1.5 mm thick). The marginal gaps were assessed at 8 locations using digital microscopy. The linear mixed effect model analysis was performed at a significance level of 0.05.
All vertical marginal gaps were within the clinically acceptable range (∼11-52 μm). G8 (FS, 0.5 mm chamfer, 1.5 mm thick) demonstrated the largest gaps (47.95 μm, 95% CI: 44.57-51.23), whereas G3 (SS, 1.0 mm chamfer, 0.8 thick) had the smallest marginal gap (14.43 μm, 95% CI: 11.15-17.71). A linear mixed effect models showed significant differences for the interaction between finish line × crown thickness × sintering (F = 18.96, p < 0.001). The lingual surfaces showed the largest gaps in both sintering protocols, while the mesial and mesiobuccal surfaces demonstrated the smallest gaps.
There was a significant interaction between finish line widths, crown thickness, and sintering protocol on the marginal gaps in both sintering protocols; 1.0 mm finish line preparations with either 0.8 mm or 1.5 mm occlusal reduction had better marginal fit in both sintering protocols compared to 0.5 mm or 1.2 mm finish lines. Smaller marginal discrepancies were observed for standard sintering crowns with a 0.5 mm finish line and 1.5 mm occlusal reduction. Conservative occlusal reduction should be accompanied with a 1.2 mm finish line to obtain better marginal fit for full-contoured zirconia crowns.
边缘适合性是修复体临床成功的一个重要组成部分。本研究的目的是研究不同基台肩台宽度和冠厚度对使用标准或快速烧结方案制作的氧化锆冠边缘适合性的影响。
为接收氧化锆磨牙冠制作了 6 个钛基台。冠在虚拟环境中设计，从部分烧结的氧化锆坯料中铣削而成，并分为 12 组（每组 10 个）。第 1 至 6 组通过标准烧结进行烧结，第 7 至 12 组通过快速烧结进行烧结。根据基台肩台和冠厚度进一步分类：G1/G7（0.5mm 倒角，0.8mm 厚）；G2/G8（0.5mm 倒角，1.5mm 厚）；G3/G9（1.0mm 倒角，0.8mm 厚）；G4/10（1.0mm 倒角，1.5mm 厚）；G5/G11（1.2mm 倒角，0.8mm 厚）；G6/G12（1.2mm 倒角，1.5mm 厚）。使用数字显微镜在 8 个位置评估边缘间隙。在 0.05 的显著性水平上进行线性混合效应模型分析。
所有垂直边缘间隙均在临床可接受范围内（~11-52μm）。G8（FS，0.5mm 倒角，1.5mm 厚）显示出最大的间隙（47.95μm，95%CI：44.57-51.23），而 G3（SS，1.0mm 倒角，0.8 厚）的边缘间隙最小（14.43μm，95%CI：11.15-17.71）。线性混合效应模型显示，肩台宽度、冠厚度和烧结之间的交互作用有显著差异（F=18.96，p<0.001）。在两种烧结方案中，舌侧表面的间隙最大，而近中面和近颊面的间隙最小。
在两种烧结方案中，肩台宽度、冠厚度和烧结方案之间存在显著的相互作用；与 0.5mm 或 1.2mm 肩台相比，1.0mm 肩台制备并进行 0.8mm 或 1.5mm 牙合面减径具有更好的边缘适合性。标准烧结冠的边缘差异较小，其肩台为 0.5mm，牙合面减径为 1.5mm。为了获得全瓷氧化锆冠更好的边缘适合性，应进行保守的牙合面减径，并采用 1.2mm 肩台。
