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.     

着色氧化锆材料喷雾造粒浆料的制备

目的：研究氧化锆材料浆料流变特性,浆料中固含量、聚乙烯醇（PVA）含量和球磨时问对氧化锆喷雾造粒浆料的影响。方法：选取浆料固含量（30wt％、40wt％、50wt％）,PVA加入量（1wt％、2wt％、3wt％）,球磨时间（8h、16h、24h）作为氧化锆材料制备浆料的生产条件,以浆料的平均粘度和沉降度为评价指标。采用三因素三水平正交实验设计,优选出制备氧化锆浆料的最佳工艺组合。结果：优选出的最佳工艺组合结果为浆料固含量为50wt％,PVA加入量为3wt％,球磨时间为24h。结论：通过最佳工艺得到了高固含量、低粘度、稳定性好、着色剂分散均匀的氧化锆喷雾造粒浆料。     

高透、超透氧化锆陶瓷半透明度和弯曲强度的比较

目的 比较不同氧化锆(高透、超透)材料的光学与机械性能,为新型氧化锆材料的研发 及临床应用提供实验依据。方法 实验组为高透型氧化锆(高透 A、高透 B、高透 C)和超透型氧化锆组 (超透 A、超透 B、超透 C),对照组为玻璃陶瓷。切取边长 7 mm、厚度分为 3 个水平(0.5、1.0、1.5 mm, n=6)的正方形试件共 126 个用于检测试件的半透明度;切取长 25 mm、宽 4 mm、厚 1.2 mm,倒角 0.1 mm 的试件共 90 个(n=15)用于检测弯曲强度。比较各组内及组间差异,使用单因素方差分析统计数据 结果。结果 (1)3 种厚度的玻璃陶瓷半透明度显著高于其他组别(P<0.01)。品牌相同时 :3 种厚度下的 超透 A 半透明度均优于高透 A(P<0.01);0.5 mm 与 1.5 mm 的高透 B 与超透 B 无明显差异,1.0 mm 的超 透 B 优于高透 B(P<0.01);厚度为 0.5 mm 和 1.0 mm 时,高透 C 与超透 C 的差异无统计学意义;厚度 1.5 mm 时,超透 C 半透明度优于高透 C(P<0.01)。氧化锆类型相同时 :厚度为 0.5 mm 的高透 C、超透 A、超透 B 和超透 C 的半透明度为各组最优(P<0.01);厚度为 1.0 mm 时,高透 B、超透 B 为各组最优(P<0.01);厚度为 1.5 mm 时,高透 B、超透 B 的半透明度为各组最优(P<0.01)。(2)品牌相同时,高透型氧化锆的 弯曲强度均优于超透型(P<0.01);氧化锆类型相同时 :高透 B、超透 A 和超透 B 的弯曲强度为各组最优 (P<0.01)。结论 (1)超透氧化锆半透明度不低于同品牌高透氧化锆,差异与厚度有关。(2)3 种厚度的 玻璃陶瓷半透明度最优。(3)高透氧化锆弯曲强度显著优于超透氧化锆,两者均高于 300 MPa。     

全锆冠机械性能的研究现状及与临床应用的关系

临床中可供全锆冠修复选择的氧化锆材料种类较多。传统全锆冠以机械性能见长,而透明氧化锆冠的美学性能更佳、机械性能相对较弱。材料选定后,临床操作和修复后口内使用均会对全锆冠的机械性能产生影响。本文从临床角度出发,对修复设计、加工制作、试戴、粘接和口内使用的全流程中如何结合全锆冠机械性能进行临床决策,以及临床过程如何对其机械性能产生影响等问题进行总结及探讨,为全锆冠的临床应用和研究提供参考。     

Importance of tetragonal phase in high-translucent partially stabilized zirconia for dental restorations

ObjectivesFor the use of partially stabilized zirconia (PSZ) as high-translucent zirconia, the importance of cubic phase (c-ZrO₂) is commonly emphasized without much attention for the remaining tetragonal phase (t-ZrO₂). The aim is to understand whether the crystal structure and microstructure of t-ZrO₂ have paramount influences on the properties of PSZ.MethodsTwo grades of 5 mol% yttria-stabilized PSZ ceramics were prepared by different processing routes. A 5 mol % yttria co-precipitated zirconia (T5Y) was compared with a 3 and 8 mol% yttria-stabilized powder mixture grade with a bimodal grain size distribution (B5Y). The phase composition and lattice parameters were studied with x-ray diffraction (XRD) and Rietveld analysis. Mechanical properties were compared in terms of hardness, toughness and biaxial bending strength with Weibull analysis. Their translucency and aging stability were also characterized, and the microstructure before and after aging were followed by scanning electron microscopy (SEM).ResultsT5Y and B5Y having similar phase composition (about 40% t- and 60% c-ZrO₂) showed the same basic properties (density, hardness and toughness), but the lattice parameters of t-ZrO₂ and the concomitant microstructure were completely different. The t-ZrO₂ phase in T5Y had a higher yttria content and a lower tetragonality (c/a) of 1.0126 ± 0.0002, whereas the t-ZrO₂ phase in B5Y was comparable to that in conventional 3Y-TZPs with a tetragonality of 1.0153 ± 0.0002. Consequently, B5Y showed a lower strength with lower Weibull modulus, being less translucent and more aging susceptible as compared to T5Y. The translucency and aging susceptibility of B5Y were even comparable to those of conventional 3Y-TZP.SignificanceNot only the phase composition with high cubic phase content but also the lattice parameters and the yttria content in the remaining t-ZrO₂ played a determinant role for PSZs to be used as ‘high-translucent’ zirconia.     

Complete rehabilitation of patients with bruxism by veneered and non-veneered zirconia restorations with an increased vertical dimension of occlusion: an observational case-series study

PurposeTo assess the clinical performance of the complete rehabilitation of a series of patients with bruxism treated by teeth- and implant-supported veneered and non-veneered zirconia restorations with an increased vertical dimension of occlusion (VDO).MethodsTen patients with bruxism, aged 62–70 years, were treated with 108 veneered and 142 non-veneered zirconia restorations and attended the recall appointment. The mean observation period was 28.2 (±16.8) months. The patients were identified from records, and clinical details were retrieved from their files. In the recall appointment, the restorations were evaluated using modified California Dental Association (CDA) criteria. The periodontal probing depth, bleeding index, presence of caries and implant survival and success rate were recorded.ResultsNo biological complications were recorded for any restorations. The success and survival rate of all implants was 100%. The overall mean survival and success rate of all restorations was 99.6%. In the veneered group, the predominant complication was minor veneer chipping (13.9%) on the incisal edge, which required only polishing (grade 1); in the non-veneered group, the predominant failure was open proximal contacts between the implant restoration and adjacent teeth (9%); only one implant restoration needed repair. One restoration was replaced due to a horizontal tooth fracture.ConclusionsWithin the limitations of this study, we conclude that the survival and success rate of monolithic zirconia restorations installed in patients with bruxism was excellent, although the veneered zirconia restorations showed a high rate of minor veneer chipping, which required only polishing.     

Fracture resistance of all-ceramic crowns placed on a preparation with a slice-formed finishing line

Summary  The purpose of this study was to determine the fracture resistance of all-ceramic crowns with a core of a zirconia ceramic, using various stabilizing oxides and luted on a preparation with a slice-formed finishing line. Ten cores made of HIPed yttrium-oxide partially stabilized zirconia (HIPed Y-TZP) and five cores of densely-sintered magnesia partially stabilized zirconia (Mg-PSZ) were made. The Mg-PSZ cores and five of the HIPed Y-TZP cores were made with a thickness of 0·2 mm. A further five cores 0·1-mm thick were made of HIPed Y-TZP. All 15 cores were then veneered with a feldspar ceramic and luted onto a stylized steel master die model with a slice-formed finishing line. The specimens were then loaded until fracture occurred. The HIPed Y-TZP specimens with the 0·2 mm core exhibited significantly higher fracture resistance than the Mg-PSZ specimens ( P  = 0·004) and the HIPed Y-TZP specimens with the 0·1 mm core ( P  = 0·001). The fracture resistance of the Mg-PSZ specimens was significantly ( P  = 0·015) higher than that of the HIPed Y-TZP specimens with the 0·1 mm core. The fracture resistance determined was equal or superior to reported values for bite forces and all-ceramic crowns. Thus, it seems likely that the type of restorations evaluated have the potential for successful use on a slice-formed preparation. However, long-term studies are essential in order to assess the performance of this ceramic system in a clinical context.     

Mechanical properties,aging stability and translucency of speed-sintered zirconia for chairside restorations

ObjectiveTo evaluate the performance of zirconia ceramics sintered in a speed sintering induction furnace by comprehensive understanding of their optical and mechanical properties, microstructure, phase composition and aging stability, in comparison to ceramics sintered in a conventional furnace.MethodsSpeed sintered (SS) Katana STML_SS (Kuraray Noritake) (total thermal cycle/sintering time/dwell temperature: 30 min/16 min/1560 °C) and CEREC Zirconia (CEREC Zr_SS) (Dentsply Sirona) (15 min/2 min/1578 °C) were compared to conventionally sintered (CS) Katana STML_CS (6.8 h/2 h/1550 °C) and inCoris TZI_CS (4 h/2 h/1510 °C). The translucency parameter (TP) and contrast ratio (CR) were measured with a spectrophotometer. The chemical composition of the materials was determined by XRF and phase composition was characterized using XRD. Hydrothermal aging behavior was evaluated by measuring the tetragonal-to-monoclinic ZrO₂ phase transformation after accelerated hydrothermal aging in steam at 134 °C. The indentation fracture toughness, Vickers hardness and biaxial strength of the sintered ceramics were assessed.ResultsSpeed and conventionally sintered zirconia revealed similar density, microstructure, average strength and hydrothermal aging stability. Both Katana STML_SS/CS 5Y-PSZ ceramics were characterized with a higher content of cubic phase (≈53 wt%), which resulted in a higher amount of Y₂O₃ in the remaining tetragonal ZrO₂ phases compared to the 3Y-TZP CEREC Zr_SS and inCoris TZI_CS (8 and 20 wt%, respectively). The sintering program did not affect the hydrothermal aging behavior of Katana STML_SS and CEREC Zr_SS. TP of Katana STML_SS (TP ≈ 32) was not affected by speed sintering, while the translucency of CEREC Zr_SS (TP = 14) was significantly reduced. Hardness, fracture toughness and Weibull characteristic strength of Katana STML_SS and CEREC Zr_SS also reached the optimal level, but speed sintering substantially lowered their mechanical reliability.SignificanceSpeed sintering of 3Y-TZP and 5Y-PSZ in a speed sintering induction oven appeared suitable for clinical applications. However, further studies should focus on improving of translucency and mechanical reliability of the speed-sintered zirconia ceramics.     

Retention of zirconia copings on zirconia implant abutments cemented with provisional luting agents

Summary  The purpose of this study is to measure and compare the retentive force of zirconia-based all-ceramic crowns cemented on zirconia abutments using five provisional luting agents. In addition, the effect of sandblasting and thermocycling on the retentive force was evaluated. Two hundred zirconia abutments and copings were fabricated (Procera system; Nobel Biocare) and divided into five groups. Hy bond temporary cement hard (Hard), Hy bond temporary cement soft (Soft), experimental temporary cement (New), Tempbond NE (Temp) and Freegenool temporary pack (Pack) were used according to the manufacturers' instructions. Each group was divided into two groups, one with and one without sandblasting. Furthermore, thermocycling up to 2000 cycles was conducted on half of each group. After 24 h and thermocycling, the retentive force was measured using a universal testing machine. The data were subjected to analysis of variance, and comparisons of the means were performed with a Games–Howell test at a level of 95%. As a result, Hard showed the highest retentive force, sandblasting was effective for improving the durability, and no effect of sandblasting was detected in the others. New showed stability of the retentive force even after thermocycling. The retentive force of Temp and Pack decreased significantly after thermocycling even with sandblasting. The retentive forces were different from the provisional cement and sandblasting, and Temp and Pack may not be appropriate for the retention of single-tooth zirconia abutments and coping restorations.     

Full zirconia fixed detachable implant-retained restorations manufactured from monolithic zirconia: clinical report after two years in service

The most frequently encountered problem with fixed detachable dental prostheses is loosening or fracture of the prosthetic screws. Other problems include wear, separation or fracture of the resin teeth from the metal/acrylic prosthesis, chipping or fracture of porcelain from the metal/ceramic or zirconia/ceramic prosthesis, and fracture of the framework in some free-end prostheses. For this type of prosthesis it is necessary to place the implants in a position that enables occlusal or lingual access so as not to impair the esthetics. This clinical report describes the restoration of a patient with complete fixed detachable maxillary and mandibular prostheses made of monolithic zirconia with angled dental implants with buccal access. The prostheses were esthetically pleasing, and no clinical complications have been reported after 2 years.     

着色剂对口腔修复用钇稳定氧化锆 陶瓷粉体制备的影响

目的 探讨着色剂氧化铁（Fe2O3）、氧化铈（CeO2）对口腔修复用钇稳定氧化锆陶瓷（Y-TZP）制备粉体的影响。方法 按照一定比例将口腔修复用Y-TZP粉体和着色剂（Fe2O3 0.15%或CeO2 4%）分别混合,配置成具有一定固含量的Y-TZP喷雾干燥浆料。通过喷雾造粒的方法进行着色和未着色Y-TZP粉体造粒。粉体分成3组,分别为未着色Y-TZP组、0.15%Fe2O3着色Y-TZP组、4%CeO2着色Y-TZP组,分别利用激光粒度分析仪和光学显微镜进行3组粉体粒径和形貌的测量和分析。结果 3组口腔修复用Y-TZP造粒粉体的颗粒D50总体均数差异有统计学意义（P<0.05）。均数两两比较时,0.15%Fe2O3着色Y-TZP粉体D50与未着色Y-TZP粉体、4%CeO2着色Y-TZP粉体D50均数差异有统计学意义（P<0.05）;未着色Y-TZP粉体与4%CeO2着色Y-TZP粉体D50均数差异无统计学意义（P>0.05）。Fe2O3、CeO2作为Y-TZP的内着色剂,粉体大多成球形。结论 CeO2作为口腔修复用Y-TZP的着色剂,对造粒粉料的粒径分布以及成球性能影响不大;Fe2O3作为着色剂进行内着色对颗粒的粒径产生一定的影响。     

二氧化锆色度和透光性与临床全瓷冠修复

目的：比较2种二氧化锆的色度学指标和透光率,以指导临床修复。方法??制作Vita?In-Ceram?YZ二氧化锆试件共36块,分为6组。其中5组分别采用染色剂LL1~LL5号按照染色步骤进行染色,第6组为空白对照组,烧结后得到0.5?mm厚度试件。制作厚度为0.5?mm?Sirona?inCorisZI二氧化锆试件共30块,分为5组,每组6块。对11组试件进行测色,指标包括L*、a*、b*值和可见光积分透射比（τ值）。结果???不论是Vita或是Sirona瓷块,随着瓷块号增加,其瓷块的明度（L*）值亦随之下降。同时可见光积分透射比（τ值）亦随之下降。Vita?In-Ceram?YZ和Sirona?InCoris?ZI不同颜色的二氧化锆透光率存在差异,颜色相近的瓷块透光率相似,但色度差较大。结论??选择透明度高的二氧化锆材料可以更好地再现牙齿的颜色。     

Comparison of fracture-load values of cantilevered FDPs

Abstract

Objective. Evaluation of the effect of different framework designs and of fatigue on the fracture-load values of cantilevered fixed dental prostheses (FDPs). The load values were compared with those for lithium disilicate ceramic and metal–ceramic FDPs. Materials and methods. Fifty cantilevered FDPs were manufactured using a zirconia framework veneered with a feldspathic ceramic. Ten FDPs were made from a lithium disilicate ceramic and 10 were designed as metal–ceramic FDPs. All FDPs were anchored by two premolar crowns to replace a missing premolar. Twenty of the 50 zirconia FDPs were regarded as the control groups; these were divided into two groups—with and without fatigue. The other 30 zirconia FDPs were divided into three test groups with different framework designs. The load to fracture was measured and fracture sites were identified. The Kruskal–Wallis test and the Mann–Whitney U-test were used for statistical analysis. Results. Most of the all-ceramic FDPs fractured within the distal wall of the terminal crown abutment. The mean fracture-load ranged between 346–493 N for the FDPs with the 0.7 mm framework. Mean values for the three zirconia test groups ranged from 529–590 N. Reinforcement of the framework resulted in significantly higher fracture-loads than for the control group. Values for lithium disilicate restorations were significantly lower than those for the test groups and the values for the metal–ceramic group were significantly higher than those for the test groups. Conclusion. Although reinforcement of the distal crown core might enhance the fracture resistance of all-ceramic cantilever FPDs, they cannot yet be unreservedly recommended for clinical use.     

40单位inCoris ZI二氧化锆CAD/CAM种植修复体的临床观察

目的:探讨inCorisZI二氧化锆全瓷修复在种植修复的临床应用。方法:选取ITI种植术后病例,采用CEREC技工CAD/CAM系统修复,根据修改的USPHS标准,观察时间6～18月,对修复效果进行评价。结果:18例患者植入38个种植体,冠桥等共40单位修复体,仅1例饰瓷脱落,其余修复体均正常,修复体成功率为95%。结论:从近期效果看,初步认为种植体的CAD/CAM二氧化锆全瓷修复是可行的。