抛光及上釉对氧化锆全冠与釉质间磨耗性能的影响

目的 研究抛光、上釉和抛光后上釉对氧化锆全冠与釉质间表面粗糙度和磨耗性能的影响.方法 将氧化锆全冠试件分为抛光组、上釉组和抛光后上釉组,每组各8个试件.釉质组为对照组.将新鲜拔除的上颌第三磨牙近中颊尖作为对颌牙.用表面粗糙度分析这三种处理方法对氧化锆全冠表面粗糙度的影响.通过磨耗试验观察这三种方法处理后的氧化锆全冠表面对釉质的磨耗.结果 表面粗糙度从小到大为抛光氧化锆全冠、抛光后上釉氧化锆全冠、上釉氧化锆全冠和釉质.对于瓷面而言,抛光氧化锆全冠磨耗最少;对于对颌釉质而言,抛光组釉质磨耗最少.结论 抛光组氧化锆全冠对釉质磨耗最小,氧化锆全冠表面粗糙度可帮助诊断其对对颌釉质的磨耗量.     

低温等离子处理对氧化锆粘接强度的影响

目的:研究低温等离子处理对氧化锆与树脂水门汀粘接强度的影响.方法:将80个氧化锆试件随机分为8组,每组10个:对照组(C),无处理.前处理剂组(PR),在氧化锆试件表面涂布前处理剂.喷砂组(SB),用Al2O3颗粒对氧化锆试件表面均匀喷砂.喷砂+前处理剂组(SBPR).低温等离子处理组(PL),将氧化锆试件中心置于常压喷出式低温等离子体发生器喷嘴下5mm处理10sec.低温等离子处理+前处理剂组(PLPR).喷砂+低温等离子处理组(SBPL).喷砂+低温等离子处理+前处理剂组(SBPLPR).分组处理后观察氧化锆试件表面形态,测量表面接触角及剪切粘接强度.结果:等离子处理组氧化锆试件表面形态未见明显改变,接触角明显减小.低温等离子处理组剪切粘接强度(16.81 MPa)明显高于对照组(9.41 MPa)和前处理剂组(10.28 MPa)(P＜0.05),与喷砂组(14.82 MPa)和喷砂+前处理剂组(18.34 MPa)相比差异无统计学意义(P＞0.05).喷砂+低温等离子处理+前处理剂组剪切粘接强度最高(23.95 MPa).XPS结果显示低温等离子处理使氧化锆试件表面氧元素(O)含量增加,碳元素(C)含量减少,碳/氧比值(C/O)减小.结论:低温等离子处理能显著的增加氧化锆表面的亲水性,显著提高氧化锆与树脂水门汀的粘接强度.     

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。     

The effects of cyclic loading and preparation on the fracture strength of zirconium-dioxide implants: an in vitro investigation

Objectives: Zirconia is a potential material for the fabrication of oral implants. The aim of this study was to evaluate the effects of cyclic loading and preparation on the fracture strength of a zirconia implant system. Materials and methods: Forty‐eight one‐piece implants were divided into two groups of 24 implants: group A (without modification) and group B (1 mm chamfer preparation). Groups A and B were divided into three subgroups of eight implants each (1=no artificial load, 2=artificial load [98 N; 1.2 million loading cycles], and 3=artificial load [98 N; 5 million loading cycles]). After completion of the loading, the fracture strength of each implant was determined in a universal testing machine. A two‐way analysis of variance was used, the continuous response variable (fracture strength in Newtons) is modeled as a function of preparation, cycles, and the corresponding interaction as explanatory variables. Results: The mean fracture strength values obtained for the groups were: A1 (no preparation, no load)=1928.73 N, A2 (no preparation, 1.2 million cycles)=2044.84 N, A3 (no preparation, 5 million cycles)=1364.50 N, B1 (preparation, no load)=1221.66 N, B2 (preparation, 1.2 million cycles)=967.11 N, and B3 (preparation, 5 million cycles)=884.89 N. Fracture values were significantly different between subgroups A1 vs. A3 and B1 vs. B3. There was no significant difference between subgroups A1 vs. A2 and B1 vs. B2. Conclusions: Preparation as well as cyclic loading can decrease the fracture strength resistance of zirconia implants. Nevertheless, even the lowest values of mean fracture strength of the implants used in our study seem to withstand average occlusal forces even after an extended interval of artificial loading. To cite this article:
Kohal RJ, Wolkewitz M, Tsakona A. The effects of cyclic loading and preparation on the fracture strength of zirconium‐dioxide implants: an in vitro investigation.
Clin. Oral Impl. Res. 22 , 2011; 808–814.
doi: 10.1111/j.1600‐0501.2010.02067.x     

Zirconia-implant-supported all-ceramic crowns withstand long-term load: a pilot investigation

OBJECTIVES: The purpose of this pilot investigation was to test whether zirconia implants restored with different all-ceramic crowns would fulfill the biomechanical requirements for clinical use. Therefore, all-ceramic Empress-1 and Procera crowns were cemented on zirconia implants and exposed to the artificial mouth. Afterwards, the fracture strength of the all-ceramic implant-crown systems was evaluated. Conventional titanium implants restored with porcelain-fused-to-metal (PFM) crowns served as controls. MATERIAL AND METHODS: Sixteen titanium implants with 16 PFM crowns and 32 zirconia implants with 16 Empress-1 crowns and 16 Procera crowns each--i.e., three implant-crown groups--were used in this investigation. The titanium implants were fabricated using the ReImplant system and the zirconia implants using the Celay system. The upper left central incisor served as a model for the fabrication of the implants and the crowns. Eight samples of each group were submitted to a long-term load test in the artificial mouth (1.2 million chewing cycles). Subsequently, a fracture strength test was performed with seven of the eight crowns. The remaining eight samples of each group were not submitted to the long-term load in the artificial mouth but were fracture-tested immediately. One loaded and one unloaded sample of each group were evaluated regarding the marginal fit of the crowns. RESULTS: All test samples survived the exposure to the artificial mouth. Three Empress-1 crowns showed cracks in the area of the loading steatite ball. The values for the fracture load in the titanium implant-PFM crown group without artificial loading ranged between 420 and 610 N (mean: 531.4 N), between 460 and 570 N (mean: 512.9 N) in the Empress-1 crown group, and in the Procera crown group the values were between 475 and 700 N (mean: 575.7 N) when not loaded artificially. The results when the specimens were loaded artificially with 1.2 million cycles were as follows: the titanium implant-PFM crowns fractured between 440 and 950 N (mean: 668.6 N), the Empress-1 crowns between 290 and 550 N (mean: 410.7 N), and the Procera crowns between 450 and 725 N (mean: 555.5 N). No statistically significant differences could be found among the groups without artificial load. The fracture values for the PFM and the Procera crowns after artificial loading were statistically significantly higher than that for the loaded Empress-1 crowns. There was no significant difference between the PFM crown group and the Procera group. CONCLUSIONS: Within the limits of this pilot investigation, it seems that zirconia implants restored with the Procera crowns possibly fulfill the biomechanical requirements for anterior teeth. However, further investigations with larger sample sizes have to confirm these preliminary results. As three Empress-1 crowns showed crack development in the loading area of the steatite balls in the artificial mouth, their clinical use on zirconia implants has to be questioned.     

Yield strength of zirconia and glass fibre-reinforced posts

The aim of this in vitro study was to evaluate the yield strengths of glass fibre-reinforced composite (FRC) posts and zirconia dioxide ceramic (ZDC) posts. Tapered glass FRC posts (DentinPost) and ZDC posts (Cerapost) of three sizes in diameter (ISO 50, 90, 110) were used for bending tests. Conventional prefabricated titanium posts of the same sizes served as control groups. The 0.2% yield strengths (R(0.2)) were tested on a universal testing machine. As zirconia posts fractured before they were yielded 0.2%, the fracture strength instead of the yield strength was recorded for these posts. One-way and two-way anova and Bonferroni-Dunn's multiple comparison tests were performed for the statistical analysis. The mean 0.2% yield strengths of the posts were 27 +/- 1 N for glass fibre-reinforced posts and 58 +/- 4 N for zirconia posts of ISO 50 (control group: 54 +/- 3 N). For ISO 90 yield strengths of 52 +/- 4 N for glass fibre-reinforced posts, 117 +/- 20 N for zirconia posts and 117 +/- 11 N for the control group were obtained. For ISO 110 mean yield strengths amounted to 73 +/- 5 N for glass fibre-reinforced posts, 166 +/- 23 N for zirconia posts and 141 +/- 12 N for the control group. Significantly higher yield strength was recorded for the zirconia and the titanium posts compared with the glass fibre-reinforced posts for the tested ISO sizes.     

基底瓷厚度变化对氧化锆双层瓷结构抗折强度的影响

目的 分析基底瓷厚度对氧化锆双层瓷结构抗折强度和断裂模式的影响.方法 将规格为15 mm×5mm完全烧结的氧化锆瓷块切割成5组,瓷片共25片,厚度分别为A组(0.3 mm),B组(0.4 mm),C组(0.6 mm),D组(0.8 mm),E组(1.0 mm).经过喷砂和超声清洗后,在所有瓷片上堆塑1.0 mm的饰面瓷并烧结,使各组的样本总厚度分别为1.3 mm,1.4 mm,1.6 mm,1.8 mm,2.0 mm.用电液伺服疲劳试验机对每个样本进行三点弯曲测试,对实验数据进行单因素方差分析及SNK组间比较,观察样本破坏模式.结果 各组抗折强度(MPa)均值分别为A组(352.31±10.80),B组(370.93±12.05),C组(480.19±19.14),D组(681.73±6.05),E组(699.06±29.22).除A组和B组、D组和E组组间外,其他各组组间差异明显(P＜0.05).断裂模式观察显示:A组出现分层,断裂碎片在4片以上;其它各组均无分层,断裂碎片多为2～3片.结论 在饰面瓷厚度不变的前提下,氧化锆双层瓷的抗折强度随基底瓷厚度增加而增强.     

Thermal Shock Resistance and Thermal Insulation Capability of Laser-Glazed Functionally Graded Lanthanum Magnesium Hexaluminate/Yttria-Stabilised Zirconia Thermal Barrier Coating

In this work, functionally graded lanthanum magnesium hexaluminate (LaMgAl₁₁O₁₉)/yttria-stabilised zirconia (YSZ) thermal barrier coating (FG-TBC), in as-sprayed and laser-glazed conditions, were investigated for their thermal shock resistance and thermal insulation properties. Results were compared with those of a dual-layered coating of LaMgAl₁₁O₁₉ and YSZ (DC-TBC). Thermal shock tests at 1100 °C revealed that the as-sprayed FG-TBC had improved thermal stability, i.e., higher cycle lifetime than the as-sprayed DC-TBC due to its gradient architecture, which minimised stress concentration across its thickness. In contrast, DC-TBC spalled at the interface due to the difference in the coefficient of thermal expansion between the LaMgAl₁₁O₁₉ and YSZ layers. Laser glazing improved cycle lifetimes of both the types of coatings. Microstructural changes, mainly the formation of segmentation cracks in the laser-glazed surfaces, provided strain tolerance during thermal cycles. Infrared rapid heating of the coatings up to 1000 °C showed that the laser-glazed FG-TBC had better thermal insulation capability, as interlamellar pores entrapped gas and constrained heat transfer across its thickness. From the investigation, it is inferred that (i) FG-TBC has better thermal shock resistance and thermal insulation capability than DC-TBC and (ii) laser glazing can significantly enhance the overall thermal performance of the coatings. Laser-glazed FG-TBC provides the best heat management, and has good potential for applications that require effective heat management, such as in gas turbines.