种植基台背景色及粘接剂颜色对不同厚度高透氧化锆修复体颜色的影响研究

 目的　研究种植基台背景色及粘接剂颜色对3种不同厚度高透氧化锆修复体颜色的影响，为粘接剂的选择提供指导方案。方法　制备不同厚度（1.5、2.0、2.5 mm）的高透氧化锆修复体各20个。将3种厚度修复体分别使用3种颜色粘接剂粘接于喷砂后的种植基台上，记为1.5 mm透明、有色、白色研究组，2.0 mm透明、有色、白色研究组，2.5 mm透明、有色、白色研究组；将未粘接于种植基台上的3种厚度修复体记为1.5 、2.0 和2.5 mm对照组；每组修复体各5个。应用VITA Easyshade Ⅴ比色仪测量各组修复体的色彩参数（CIE L*a*b*），并计算粘接前后修复体的色差值（ΔE），对比肉眼可察觉阈值和临床可接受阈值，以评价种植基台背景色及粘接剂颜色对不同厚度修复体颜色的影响程度。结果　（1）种植基台背景色对不同厚度修复体颜色的影响分析：1.5 mm透明研究组ΔE（8.51）高于临床可接受阈值；2.0 mm透明研究组ΔE（2.03）低于临床可接受阈值，但高于肉眼可察觉阈值；2.5 mm透明研究组ΔE（1.26）低于肉眼可察觉阈值。（2）粘接剂颜色对不同厚度修复体颜色的影响分析：当修复体厚度为1.5 mm时，仅有色研究组ΔE低于临床可接受阈值，但仍高于肉眼可察觉阈值，且不同粘接剂组间ΔE比较，差异有统计学意义（F = 21.941，P < 0.05）；当修复体厚度为2.0 mm时，不同粘接剂组间ΔE比较，差异有统计学意义（F = 13.683，P < 0.05），且均低于临床可接受阈值，仅有色研究组ΔE低于肉眼可察觉阈值，但有色研究组ΔE与透明研究组ΔE比较，差异无统计学意义（P > 0.05）；当修复体厚度为2.5 mm时，不同粘接剂组间ΔE比较，差异无统计学意义（F = 0.683，P > 0.05），且均低于肉眼可察觉阈值。结论　种植基台背景色及粘接剂颜色均会对较薄高透氧化锆修复体的颜色造成影响。在种植义齿修复过程中，当设计的修复体厚度< 2.5 mm时，推荐使用与修复体颜色一致的有色粘接剂；当修复体厚度≥ 2.5 mm时，种植基台背景色和粘接剂颜色对修复体颜色的影响较小，3种粘接剂均可使用。     

Inlay‐retained cantilever fixed dental prostheses to substitute a single premolar: impact of zirconia framework design after dynamic loading

The purpose of this in‐vitro study was to evaluate the influence of the framework design on the durability of inlay‐retained cantilever fixed dental prostheses (IR‐FDPs), made from zirconia ceramic, after artificial ageing. Forty‐eight caries‐free human premolars were prepared as abutments for all‐ceramic cantilevered IR‐FDPs using six framework designs: occlusal–distal (OD) inlay, OD inlay with an oral retainer wing, OD inlay with two retainer wings, mesial–occlusal–distal (MOD) inlay, MOD inlay with an oral retainer ring, and veneer partial coping with a distal box (VB). Zirconia IR‐FDPs were fabricated via computer‐aided design/computer‐aided manufacturing (CAD/CAM) technology. The bonding surfaces were air‐abraded (50 μm alumina/0.1 MPa), and the frameworks were bonded with adhesive resin cement. Specimens were stored for 150 d in a 37°C water bath during which they were thermocycled between 5 and 55°C for 37,500 cycles; thereafter, they were exposed to 600,000 cycles of dynamic loading with a 5‐kg load in a chewing simulator. All surviving specimens were loaded onto the pontic and tested until failure using a universal testing machine. The mean failure load of the groups ranged from 260.8 to 746.7 N. Statistical analysis showed that both MOD groups exhibited significantly higher failure loads compared with the other groups (i.e. the three OD groups and the VB group) and that there was no significant difference in the failure load among the OD groups and the VB group. In conclusion, zirconia IR‐FDPs with a modified design exhibited promising failure modes.     

Effect of finishing/polishing techniques and low temperature degradation on the surface topography,phase transformation and flexural strength of ultra-translucent ZrO2 ceramic

ObjectiveTo investigate the effect of different surface finishing and polishing regimes and low temperature degradation on flexural strength, phase transformation and surface topography of ultra-translucent ZrO₂ ceramic.Methods300 (n = 15/group) of conventional zirconia (Z: Ice Zirkon Transluzent) and ultra-translucent zirconia (UT: Prettau Anterior) bar-specimens were made and divided according to the "Finishing/Polishing" - (C — Control, B — diamond rubber polishers, P — adjusting with burs, PB — adjusting with burs + diamond polishers, PG — adjusting with burs + glaze), "Low temperature Degradation (LTD)" (with or without a treatment at 127 °C, 1.7 bar/24 h). Then, a 3-point mini flexural test was performed in a universal testing machine (1 mm/min, 500 kgf load cell). SEM, EDS, XDR, AFM, optical profilometry and Weibull analysis were performed. Data were analyzed by 3-way ANOVA and Tukey’s post-test (5%).ResultsGroups ZPB_D (1670 ± 253 MPa), ZB_D (1664 ± 217 MPa), and ZB (1655 ± 3678 MPa) showed significantly higher flexural strength than the UTPG group (372 ± 56 MPa). The Weibull modulus was significantly higher for the ZP_D group compared to the UB, UC_D, UP_D and UPB_D, while UTB, UTC_D and UTP_D had the lowest value. Monoclinic phases were observed only in the conventional zirconia groups and were more evident after LTD. Diamond rubber polishers presented less roughness for both zirconias.SignificanceThe use of diamond rubber polishers is the most suitable finishing/polishing method for zirconia ceramic restorations and that final glazing reduces the fracture resistance of these materials.     

稀土氧化物着色钇稳定四方多晶氧化锆陶瓷与饰面瓷匹配性的研究

目的:探讨通过添加稀土氧化物着色剂而制备的钇稳定四方多晶氧化锆陶瓷与饰面瓷的匹配性。方法:以稀土氧化物(Pr6O11,CeO2,Er2O3)和过渡元素氧化物(MnO2)为着色剂,采用粉体掺杂方法,在四方多晶氧化锆陶瓷粉体中添加不同质量分数的着色剂,制备出6组钇稳定四方多晶氧化锆陶瓷,测定其与Vita VM9饰面瓷的抗热震性能及界面结合强度。采用SAS6.12软件包对数据进行单因素方差分析。结果:6组钇稳定四方多晶氧化锆陶瓷与Vita-VM9饰面瓷烧结后,各组在60℃～240℃测试过程未发现径向或层间开裂或裂纹现象,加热温度>240℃。6组钇稳定四方多晶氧化锆陶瓷与VitaVM9饰面瓷界面的抗剪切强度值为(36.03±3.82)～(37.98±4.89)MPa,均高于纯四方氧化锆陶瓷组的剪切强度值,但各组与纯四方氧化锆陶瓷的抗剪切强度值无显著差异(P>0.05)。结论:稀土氧化物着色钇稳定四方多晶氧化锆陶瓷与饰面瓷的匹配性达到临床应用水平。     

Clinical study of the internal gaps of zirconia and metal frameworks for fixed partial dentures

The aim of this clinical study was to compare the internal gaps between abutment teeth and posterior fixed partial dentures (FPDs) fabricated utilizing milled zirconia and cast gold-alloy frameworks. As part of an ongoing randomized controlled clinical trial, 32 three-unit FPDs (16 zirconia and 16 metal-ceramic) in 25 patients were randomly selected for adaptation measurements. During the bisque-stage ceramic try-in, an A-silicone impression material was placed between the abutment teeth and the framework. The internal gap, corresponding to the thickness of the replica, was measured under magnification at the following locations: cervical, axial, and occlusal (cusp-tips and central). The internal gaps of FPDs with zirconia frameworks were significantly larger in cervical, axial, and centro-occlusal regions (cervical: 189.6 ± 71.8  μ m vs. 118.6 ± 31.5  μ m; axial: 140.5 ± 38.3  μ m vs. 95.7 ± 18.1  μ m; and centro-occlusal: 192.0 ± 66.5  μ m vs. 153.1 ± 69.8  μ m). The cervical gaps next to the pontics were significantly larger compared with those of the outer walls in both types of FPDs (zirconia: mean difference 67.7 ± 114.7  μ m; metal-ceramic: mean difference 30.0 ± 71.2  μ m). Posterior three-unit FPDs incorporating milled zirconia frameworks exhibited larger internal gaps than those constructed using conventional metal-ceramic techniques.