Effect of different surface treatments on the biaxial flexural strength of zirconia ceramics

Statement of problemDifferent surface treatments have been applied to zirconia restorations in clinical practice to increase the bond strength between zirconia and cement, but their effect on flexural strength is unknown.PurposeThe purpose of this in vitro study was to evaluate the effect of different surface treatments before and after sintering on the flexural strength of zirconia.Material and methodsSixty disk-shaped specimens with an initial diameter of 18.6 ±0.1 mm and thickness of 2 ±0.1 mm were prepared from preshaded presintered 3Y-TZP blocks. The specimens were randomly divided into 3 groups (n=20) according to surface treatments (Group Laser, Group APA, Group Rocatec), and the groups were then divided into 2 subgroups (n=10) according to surface treatment before and after sintering. The phase compositions of the groups were examined by using an X-ray diffractometer (XRD) with 3 randomly selected specimens from each group. Biaxial flexural strength testing was conducted using a universal testing machine to examine the flexural strength of the zirconia specimens. Two-way ANOVA and post hoc least significant difference tests were performed (α=.05).ResultsAccording to the XRD analysis, no monoclinic phases were determined on the surface of the presintered laser-treated specimens, but tetragonal phases were observed on the surface of the postsintered specimens. Surface treatment type and application stage (presintering to postsintering) have a significant effect on the biaxial flexural strength of the specimens (P<.05). The lowest biaxial flexural values were observed in the Laser group, and postsintered specimens showed higher biaxial flexural strength than presintered specimens (P<.05).ConclusionsPostsintered specimens showed higher monoclinic content than presintered specimens. Laser-treated specimens showed the lowest biaxial flexural strength for both presintered and postsintered specimens.     

Effects of core characters and veneering technique on biaxial flexural strength in porcelain fused to metal and porcelain veneered zirconia

PURPOSE

The purpose of this study was to assess the impact of the core materials, thickness and fabrication methods of veneering porcelain on prosthesis fracture in the porcelain fused to metal and the porcelain veneered zirconia.

MATERIALS AND METHODS

Forty nickel-chrome alloy cores and 40 zirconia cores were made. Half of each core group was 0.5 mm-in thickness and the other half was 1.0 mm-in thickness. Thus, there were four groups with 20 cores/group. Each group was divided into two subgroups with two different veneering methods (conventional powder/liquid layering technique and the heat-pressing technique). Tensile strength was measured using the biaxial flexural strength test based on the ISO standard 6872:2008 and Weibull analysis was conducted. Factors influencing fracture strength were analyzed through three-way ANOVA (α≤.05) and the influence of core thickness and veneering method in each core materials was assessed using two-way ANOVA (α≤.05).

RESULTS

The biaxial flexural strength test showed that the fabrication method of veneering porcelain has the largest impact on the fracture strength followed by the core thickness and the core material. In the metal groups, both the core thickness and the fabrication method of the veneering porcelain significantly influenced on the fracture strength, while only the fabrication method affected the fracture strength in the zirconia groups.

CONCLUSION

The fabrication method is more influential to the strength of a prosthesis compared to the core character determined by material and thickness of the core.     

The biaxial flexural strength of two pressable ceramic systems

The biaxial flexural strength of Optimal pressable ceramics and IPS Empress pressable ceramics were tested, compared and the micro-structures and compositions explored. The materials evaluated were Optimal shaded (Opcs) and unshaded (Opcus) ceramics and IPS Empress shaded (Ems) and unshaded (Emus) ceramics. Twenty-one disc specimens per material were prepared, heat-treated and tested. The piston on three-ball test ASTM F394-78 (1991) was used to test the specimens in a universal testing machine at a crosshead speed of 0.15 mm/min. Specimens were viewed in a scanning electron microscope and X-ray diffraction used to determine the phases present. Mean strengths (MPa +/- SD) were: Ems 120.1 +/- 20.5, Emus 135.8 +/- 16.0, Opcs 139.1 +/- 14.3 and Opcus 138.0 +/- 11.5. There was no statistically significant difference between Optimal shaded, Optimal unshaded and Empress unshaded strength values (p > 0.05). Empress shaded strength values were significantly lower than the other materials tested (p < 0.05). Weibull analysis provided m values: Ems 6.1, Emus 10.2, Opcs 12.8 and Opcus 13.9 and 1% and 5% probabilities of failure. Secondary electron imaging revealed a dense dispersal of leucite crystals in the glassy matrix of the Optimal ceramics of an average size 5.5 +/- 9.7 micron 2 for the Optimal shaded ceramic and 6.6 +/- 13.3 micron 2 for the Optimal unshaded ceramic. Leucite crystal agglomerates were evident for the Empress shaded material and a uniform distribution of fine leucite crystals (1.9 +/- 1.8 micron 2) for the Empress unshaded ceramic. Crystal and matrix microcracking were present in most of the material microstructures, together with porosity and tabular alumina platelets in the Optimal ceramics. X-ray diffraction revealed the presence of tetragonal leucite and small amounts of cubic leucite. Optimal ceramics and Empress unshaded ceramic provided higher strength and Weibull m values compared with Empress shaded ceramic. Inherent material defects were characterised and cubic leucite was identified.     

不同处理方式对热压铸造增强陶瓷的双轴弯曲强度影响的研究

目的研究不同处理方式对白榴石增强陶瓷的双轴弯曲强度的影响。方法试件的蜡型制作采用将融化的铸造蜡灌注于机械加工模具内,制成厚度和直径一致的蜡型。厚度为2.0 mm、直径为18 mm圆片,共40个。实验分组按照不同处理方式即:打磨和抛光、上釉和离子交换组。以不做打磨、上釉和离子交换的为对照组。根据ASTM标准F394-78.1991(美国材料实验协会)测试试件的双轴弯曲强度。经one-way ANOVA统计分析各实验组。同时辅以扫描电镜、X线衍射仪和能谱分析观察其结构的变化。结果不同处理方法与对照组比较双轴弯曲强度,差异有显著性(P<0.01)。不同处理方法组内的比较双轴弯曲强度,差异有显著(P<0.01)。结论热压铸陶瓷的不同处理均可以增加陶瓷的双轴弯曲强度,而以离子交换处理的影响最大。     

The effect of core material, veneering porcelain, and fabrication technique on the biaxial flexural strength and weibull analysis of selected dental ceramics

Purpose: The objective of this study was to compare the effect of veneering porcelain (monolithic or bilayer specimens) and core fabrication technique (heat‐pressed or CAD/CAM) on the biaxial flexural strength and Weibull modulus of leucite‐reinforced and lithium‐disilicate glass ceramics. In addition, the effect of veneering technique (heat‐pressed or powder/liquid layering) for zirconia ceramics on the biaxial flexural strength and Weibull modulus was studied. Materials and Methods: Five ceramic core materials (IPS Empress Esthetic, IPS Empress CAD, IPS e.max Press, IPS e.max CAD, IPS e.max ZirCAD) and three corresponding veneering porcelains (IPS Empress Esthetic Veneer, IPS e.max Ceram, IPS e.max ZirPress) were selected for this study. Each core material group contained three subgroups based on the core material thickness and the presence of corresponding veneering porcelain as follows: 1.5 mm core material only (subgroup 1.5C), 0.8 mm core material only (subgroup 0.8C), and 1.5 mm core/veneer group: 0.8 mm core with 0.7 mm corresponding veneering porcelain with a powder/liquid layering technique (subgroup 0.8C‐0.7VL). The ZirCAD group had one additional 1.5 mm core/veneer subgroup with 0.7 mm heat‐pressed veneering porcelain (subgroup 0.8C‐0.7VP). The biaxial flexural strengths were compared for each subgroup (n = 10) according to ISO standard 6872:2008 with ANOVA and Tukey's post hoc multiple comparison test (p≤ 0.05). The reliability of strength was analyzed with the Weibull distribution. Results: For all core materials, the 1.5 mm core/veneer subgroups (0.8C‐0.7VL, 0.8C‐0.7VP) had significantly lower mean biaxial flexural strengths (p < 0.0001) than the other two subgroups (subgroups 1.5C and 0.8C). For the ZirCAD group, the 0.8C‐0.7VL subgroup had significantly lower flexural strength (p= 0.004) than subgroup 0.8C‐0.7VP. Nonetheless, both veneered ZirCAD groups showed greater flexural strength than the monolithic Empress and e.max groups, regardless of core thickness and fabrication techniques. Comparing fabrication techniques, Empress Esthetic/CAD, e.max Press/CAD had similar biaxial flexural strength (p= 0.28 for Empress pair; p= 0.87 for e.max pair); however, e.max CAD/Press groups had significantly higher flexural strength (p < 0.0001) than Empress Esthetic/CAD groups. Monolithic core specimens presented with higher Weibull modulus with all selected core materials. For the ZirCAD group, although the bilayer 0.8C‐0.7VL subgroup exhibited significantly lower flexural strength, it had highest Weibull modulus than the 0.8C‐0.7VP subgroup. Conclusions: The present study suggests that veneering porcelain onto a ceramic core material diminishes the flexural strength and the reliability of the bilayer specimens. Leucite‐reinforced glass‐ceramic cores have lower flexural strength than lithium‐disilicate ones, while fabrication techniques (heat‐pressed or CAD/CAM) and specimen thicknesses do not affect the flexural strength of all glass ceramics. Compared with the heat‐pressed veneering technique, the powder/liquid veneering technique exhibited lower flexural strength but increased reliability with a higher Weibull modulus for zirconia bilayer specimens. Zirconia‐veneered ceramics exhibited greater flexural strength than monolithic leucite‐reinforced and lithium‐disilicate ceramics regardless of zirconia veneering techniques (heat‐pressed or powder/liquid technique).     

不同瓷粘结系统及表面处理方式对瓷与釉质间粘结强度的影响

目的 :探讨瓷与牙釉质粘结时不同瓷粘结系统与瓷表面处理方式的优化组合。方法 :以不同的瓷粘结系统和表面处理方式为影响因素 ,将瓷片分成 8组 ,分别与釉质粘结 ,测其剪切强度 ,统计分析所得数据 ,观察其断裂方式。结果 :处理组中以不喷砂磷酸酸蚀组的粘结强度最低 ,其余各组间无统计学差异。PanaviaF组剪切强度均值最高为 2 9.3 8MP ,邦多为 2 6.19MP。结论 :PanaviaF和邦多陶瓷粘结系统结合喷砂后磷酸酸蚀和HF酸蚀使用都可获得理想的粘结效果     

Effect of zirconia surface treatments on the shear strength of zirconia/veneering ceramic composites

Aim of the investigation was to assess the effect of different surface treatments on the bond strength of veneering ceramics to zirconia. In a shear test, the influences of polishing, sandblasting, and silica-coating of the zirconia surface on bonding were assessed with five different veneering ceramics. In addition the effect of liner application was examined. With one veneering ceramic, the impact of regeneration firing of zirconia was also evaluated. Statistical analysis was performed with one-way ANOVA and post hoc Scheffé's test. Failure in every case occurred in the veneering ceramic adjacent to the interface with a thin layer of ceramic remaining on the zirconia surface, indicating that bond strength was higher than the cohesive strength of the veneering ceramic. Shear strength ranged from 23.5 +/- 3.4 MPa to 33.0 +/- 6.8 MPa without explicit correlation to the respective surface treatment. Regeneration firing significantly decreased the shear strength of both polished and sandblasted surfaces. Findings of this study revealed that bonding between veneering ceramics and zirconia might be based on chemical bonds. On this note, sandblasting was not a necessary surface pretreatment to enhance bond strength and that regeneration firing was not recommended.     

高半透性氧化锆基底的不同处理对锆-瓷结合强度的影响

目的 探讨高半透性氧化锆的不同表面处理对其与饰瓷界面结合强度的影响,为临床提高氧化锆全瓷修复体的锆-瓷结合强度提供研究基础.方法 制作30个高10 mm、直径为10 mm的圆柱形KATA-NA氧化锆试件,分为四组,每组7个:①C组(对照组)打磨后直接堆塑饰瓷粉;②S组(喷砂组)打磨后喷砂,堆塑饰瓷粉;③B组(结合层组)...     

Effect of surface treatment on roughness and bond strength of a heat-pressed ceramic

STATEMENT OF PROBLEM: Bonding ceramic restorations to tooth structure relies on treatment of the ceramic intaglio surface, selection of a suitable resin luting agent, and appropriate treatment of prepared tooth structure. Various ceramic surface treatments have been advocated which produce different topographies and bond strengths, but little information is available to identify the interaction between the resulting surface topography and bond strength. PURPOSE: The purpose of this in vitro study was to evaluate the effect of surface treatments on surface roughness and bond strength to dentin and enamel of a commercially available heat-pressed dental ceramic (IPS Empress). MATERIAL AND METHODS: One hundred heat-pressed ceramic disks were fabricated according to the manufacturer's recommendations. Specimens were divided into 5 groups (n=20) and treated with 1 of the following: (1) etching with 9.5% hydrofluoric acid, (2) 50%, or (3) 60% orthophosphoric acid and airborne-particle abrasion with (4) 50-microm, or (5) 250-microm alumina for 10 seconds. Morphological changes obtained with the surface treatments were investigated with a surface texture analyzer on half of the treated specimens. Two additional specimens from each group were treated and prepared for scanning electron microscopy. The specimens were then used for a bond strength test. The treated specimens were silanated and luted with a composite resin luting agent (Nexus 2) to enamel (n=50) and dentin (n=50) surfaces with 10 specimens for each treatment group. The luted specimens were loaded to failure in a universal testing machine in the shear mode with a crosshead speed of 0.05 mm/min. The data were analyzed with 1-way ANOVA followed by the Ryan-Einot-Gabriel-Welsch Multiple Range Test (alpha=.05). RESULTS: Surface treatments resulted in significant differences for surface topography and shear bond strength (P<.001). Mean surface roughness (Ra) (SD) was (2.54 (0.21) microm) for ceramic surfaces treated with 50-microm aluminum powder. Treatment of ceramic specimens with 50% orthophosphoric acid appeared to result in a smoother surface (1.02 (0.38) microm). The highest mean bond strength (SD) to enamel (14.7 (0.6) MPa) and dentin (8.2 (1.5) MPa) was associated with hydrofluoric acid etching. The lowest mean bond strength (SD) to enamel (2.7 (0.8) MPa) and dentin (1.5 (0.1) MPa) was recorded for 50% phosphoric acid. CONCLUSIONS: Hydrofluoric acid treatment resulted in the generation of pores and grooves that produced the greatest bond strength between the ceramic and tooth dentin and enamel. Orthophosphoric acid treatment was the least effective surface treatment method evaluated. The results are applicable to only the all-ceramic/luting system evaluated.     

The influence of cement lute, thermocycling and surface preparation on the strength of a porcelain laminate veneering material.

OBJECTIVES: The purpose of the current study was to examine the impact of thermocycling on the development of surface flaws on the cemented surfaces of PLV restorations prepared by acid-etching or alumina (Al2O3) abrasion. METHODS: Sets of 30 Vitadur-alpha dentin porcelain discs (15 mm diameter, 0.9 mm thickness) were prepared by either abrading with 50 microm Al2O3 or hydrofluoric (HF) acid-etching. Further specimen series were coated with a resin luting cement prior to thermocycling to simulate the conditions encountered 'in service'. Mean fracture strengths, standard deviations and associated Weibull moduli (m) were determined using bi-axial fracture (ball-on-ring). RESULTS: The two-way ANOVA revealed significant differences between the mean strength values of the porcelain specimens abraded with 50 microm Al2O3 compared with the higher strength HF acid-etched specimens. Significant differences were also identified in the mean fracture strength data for the abraded cemented and acid-etched cemented groups with the abraded groups recording the highest strength levels. SIGNIFICANCE: Composite resin polymerisation shrinkage may help to strengthen porcelain surfaces by imposing a compressive stress on the porcelain surface. However, the strength of the HF etched cemented groups when bonded to composite resin were weaker than abraded specimens. Etching the porcelain does not only provide the necessary surface roughness conducive to mechanical interlocking but would appear to have a weakening effect on the porcelain surfaces.     

不同表面处理方式对Kavo氧化锆基底与饰瓷结合强度的影响

目的:研究不同表面处理方法对Kavo氧化锆底层材料与Noritake Cerabien饰面瓷结合强度的影响。方法:选择Kavo氧化锆陶瓷作为底层材料,随机分为4组,每组8个试件。A组为染色液浸泡着色+表面不喷砂;B组为染色液浸泡着色+表面喷砂;C组为不浸泡染色液+表面不喷砂;D组为不浸泡染色液+表面喷砂。4组底层材料采用粉浆涂塑法烧结饰面瓷后,使用材料试验机测试其剪切强度,采用SPSS10.0软件包对数据进行统计学分析。结果:采用喷砂处理的2组(B组和D组)材料,其剪切强度均高于未喷砂的2组(A组和C组),差异具有显著性(P<0.01);浸泡染色处理对剪切强度的无显著影响,A组与C组、B组与D组之间的差异无显著性(P>0.05)。结论:对Kavo氧化锆基底表面进行喷砂处理,可以提高基底冠与饰面瓷的结合强度;而浸泡染色则对两者结合力的强度无显著影响。     

3类修复体经3种瓷表面处理后与陶瓷托槽的粘结强度及去托槽后的瓷表面情况

目的研究3种瓷表面处理方法对3类修复体与陶瓷托槽粘结强度的影响以及去除托槽后瓷表面的情况。方法钴铬烤瓷、e-max铸瓷、二氧化锆全瓷3类修复体试件各36个,每类试件随机分为4组。除对照组为6个试件,其余各组每组10个试件。对照组不作任何处理。喷砂组,氧化铝喷砂4 s,冲洗、吹干后表面涂布硅烷偶联剂。磷酸组,质量分数37%磷酸酸蚀1 min,冲洗、吹干后表面涂布硅烷偶联剂。氢氟酸组,氢氟酸酸蚀2 min,冲洗、吹干后表面涂布硅烷偶联剂。使用光固化托槽粘结剂粘结陶瓷托槽。经37℃恒温水浴24 h后检测抗剪强度。观察托槽去除后瓷表面粘结剂残留情况和瓷面破损情况。结果 3种表面处理方法均能达到或超过有效粘结强度。采用喷砂并涂布硅烷偶联剂方法和氢氟酸酸蚀并涂布硅烷偶联剂方法,钴铬烤瓷试件的抗剪强度与e-max铸瓷和二氧化锆全瓷试件比较差异有统计学意义(P<0.05);磷酸酸蚀并涂布硅烷偶联剂方法中,3类修复体的抗剪强度差异无统计学意义(P>0.05)。3类修复体在使用氢氟酸并硅烷偶联剂处理后,抗剪强度较其他2种方法高,差异有统计学意义(P<0.05)。磷酸组的3类修复体瓷表面粘结剂残留指数得分最低,粘接剂残留最少,且瓷表面破坏最小。结论喷砂、磷酸酸蚀、氢氟酸酸蚀合并使用硅烷偶联剂处理钴铬烤瓷、e-max铸瓷、二氧化锆全瓷修复体,均能得到满意的粘结强度,而磷酸结合硅烷偶联剂方法去除托槽后对修复体表面的影响最小。     

不同表面处理方法对氧化锆基底材料与饰面瓷结合强度的影响

目的 比较不同表面处理方法对氧化锆基底与饰面瓷之间的结合强度及结合界面微观结构的影响。方法 将WIELAND氧化锆瓷块胚体烧结制成10 mm×5 mm×5 mm大小试件33个。将试件随机分为3组,每组11个。喷砂组在烧结前进行喷砂处理;处理剂组先喷砂处理,再烧结结合衬底瓷;对照组不做处理。3组基底瓷材料采用粉浆涂塑法烧结5 mm×5 mm×5 mm大小的饰面瓷。每组随机抽取1个基底瓷及双层瓷试件,采用扫描电镜、能谱分析方法,研究氧化锆底瓷与饰面瓷之间的结合情况。其余试件则通过电子拉伸机测试结合界面的剪切强度,并用SPSS 17.0软件对实验数据进行统计学分析。结果 喷砂组、处理剂组、对照组试件的剪切强度分别为（18.06±0.59）、（21.04±1.23）、（13.80±1.54） MPa,各组间差异均有统计学意义（P<0.01）。结论 氧化锆胚体烧结前喷砂处理能提高氧化锆基底冠与饰面瓷的结合强度,结合衬底瓷的应用能提高氧化锆基底冠与饰面瓷的结合强度。     

硅酸盐陶瓷表面不同粗化处理对其粘接强度影响的研究

目的:本实验的目的是研究瓷表面进行不同的表面粗化处理对其与树脂粘接剂粘接强度的影响.方法:VITA金属烤瓷四块(15mm×7mm×5mm)根据表面粗化方式的不同随机分为五组:无表面处理组(对照组)、喷砂-Porcelain Primer+FL-BONDⅡ组(S-PF组)、喷砂-HF+Porcelain Primer+FL-BONDⅡ组(S-H-PF组)、车针打磨-Porcelain Primer+FL-BONDⅡ组(B-PF组)、车针打磨-HF+Porcelain Primer+FL-BONDⅡ组(B-H-PF组).每组9个样本,采用微拉伸测力仪测力,所得数据采用方差分析进行统计学分析.采用扫描电子显微镜SEM观察瓷-树脂粘接界面的微观形貌.结果:结果显示对照组的粘接强度(17.0±1.7)MPa,S-PF组的粘接强度(24.1±3.5)MPa,S-H-PF组的粘接强度(24.5±4.2)MPa;B-PF组的粘接强度(24.2±4.4)MPa,B-H-PF组的粘接强度(29.9±7.5) MPa,粘接强度最大(P＜0.05).扫描电子显微镜(Scanning Electron Microscope,SEM)显示B-H-PF组获得最佳的粘接界面质量,其界面均匀、致密,未出现明显的裂隙,其他各组界面现不同程度的微小裂隙.结论:瓷表面经不同表面粗化处理对其粘接强度存在一定的影响,车针打磨结合HF可获得较好的粘接效果.