In vivo fracture resistance of implant-supported all-ceramic restorations

STATEMENT OF PROBLEM: Because of their specific mechanical properties, all-ceramic restorations demonstrate a lower fracture resistance than ceramic restorations supported by metal substructures. However, advances have been made in the fabrication of high-strength all-ceramic abutments for anterior implants. No previous study has compared the fracture loads between 2 different all-ceramic abutments restored by glass-ceramic crowns. PURPOSE: The purpose of this in vitro investigation was to quantify the fracture load of implanted-supported Al(2)O(3) and ZrO(2) abutments restored with glass-ceramic crowns. MATERIALS AND METHODS: Two ceramic abutments were tested: an Al(2)O(3) abutment (CerAdapt) and a ZrO(2) abutment (Wohlwend Innovative). The abutments (n = 10) were placed on Br?nemark dental implants and prepared for restoration with glass-ceramic crowns (IPS Empress). After fabrication, in accordance with the manufacturer's guidelines, the crowns were bonded to the all-ceramic abutments with a dual-polymerizing resin luting agent. The fracture loads (N) were determined by force application at an angle of 30 degrees by use of a computer-controlled universal testing device. The data were analyzed with the unpaired t test (alpha=.05). RESULTS: Statistical analysis showed significant differences between both groups (P=.001) of all-ceramic abutments, with mean fracture load values of 280.1 N (+/- 103.1) for the Al(2)O(3) abutments and 737.6 N (+/- 245.0) for the ZrO(2) abutments. CONCLUSION: Within the limitations of this study, both all-ceramic abutments exceeded the established values for maximum incisal forces reported in the literature (90 to 370 N). The ZrO(2) abutments were more than twice as resistant to fracture as the Al(2)O(3)-abutments.     

Evaluation of the marginal fitness of tetragonal zirconia polycrystal all-ceramic restorations

Tetragonal zirconia polycrystals stabilized with 3 mol-% yttria (TZP) exhibit good mechanical properties, favorable esthetic appearance and translucency. Despite this, zirconia has not been widely used for all-ceramic restorations due to the difficulty of shaping it. A new process called the cercon smart ceramics system overcomes this limitation by milling ceramic blanks in a porous, presintered and yet easily machinable state which are afterwards sintered to full density. The sintering shrinkage is compensated for by enlarging the shape prior to machining. Not only the fracture resistance but also the marginal fitness are important for all-ceramic restorations to produce satisfactory results. In this comparative in vitro study, the marginal fitness of TZP all-ceramic crowns and fixed partial dentures (FPDs) were examined. The marginal discrepancies of the FDs (29.3 microns) were not significantly different from those of the crons (31.3 microns). The results of this work suggest that 1) The marginal fitness of all-ceramic restorations fabricated by the Cercon system was satisfactory for clinical use. 2) The dimensional stability of the Cercon substructure was maintained during firing of the porcelain and successive glazing.     

Effect of connector design on fracture resistance of zirconia all-ceramic fixed partial dentures

The purpose of the present study was to determine the relationship between cross-sectional design and fracture load using a static load bearing test in yttria-stabilized tetragonal zirconia polycrystal ceramic frameworks on a molar fixed partial denture. The test framework was designed as a 3-unit bridge with two abutment teeth at the second premolar and second molar of the mandible. The cross-sectional area of the connector was 9.0, 7.0, or 5.0mm(2). In terms of shape, the cross-section was either circular or oval, with a height/width ratio of 1:1, 3:4, or 2:3. For each of the 9 combinations of cross-sectional area and shape, 5 frameworks were prepared (45 in total). Frameworks were cemented to a metallic test model with adhesive resin cement. After fracture load was measured, the percentage of fracture sites was determined and the fracture surfaces observed. In terms of cross-sectional area, there was a statistically significant difference in fracture load between 9.0, 7.0, and 5.0mm(2). No significant difference in fracture load was observed between any two shapes of connector (p>0.05). The fracture load of all frameworks with a cross-sectional area of 9.0 or 7.0mm(2) was over 880 N, which was recognized as parafunctional occlusal force. Fracture occurred at the distal connector in 82.2% of all frameworks on average. Fracture load decreased as cross-sectional area of the connector became smaller. The cross-sectional shape used in the present study was less influential on fracture load. It appears to be clinical possible to apply a connector with a cross-sectional area of 7.0mm(2). Fracture often occurred at the distal connector between the pontic and the abutment, corresponding to the second molar.     

In vitro failure and fracture resistance of veneered and full-contour zirconia restorations

ObjectivesThis study evaluated the failure and fracture resistance of zirconia-based fixed partial dentures (FPDs) under the influence of different surface treatments and adjustment procedures.MethodsSeven groups (n = 8/group) of three-unit zirconia-based FPDs were fabricated in anatomic design (AD) or anatomically reduced design (ARD) and surfaces were prepared according to clinical relevance: #1: AD – sintered; #2: AD – sintered – glazed; #3: AD – sintered – sandblasted – glazed; #4: AD – sintered – polished – grinded (contact points adjusted); #5: AD – sintered – polished – grinded – repolished; #6: ARD – sintered – veneered; #7: control: analogous to #3 but without thermal cycling (TC) and mechanical loading (ML). FPDs were adhesively bonded to polymethylmethacrylate abutment teeth. TCML (TC: 6000 × 5°/55°; ML: 1.2 × 10⁶ × 50 N, 1.6 Hz) was conducted in a chewing simulator with steatite spheres as antagonists. Failures were monitored and fracture resistance was determined after ageing. Data were analysed statistically with Mann–Whitney U-test (Kolmogorov–Smirnov-test; α = 0.05). FPDs were subjected to scanning electron microscopy for fractographic failure analysis.ResultsNone of the FPDs failed during TCML, but showed wear at contact points. Median fracture force ranged between 1173.5 N (#4) and 1316.0 N (#3) without significant (p = 0.910) differences between the groups or in comparison to the control (p > 0.462).ConclusionsZirconia restorations showed high resistance to failures and fracture under different surface treatment variations. Full-contour polished or glazed zirconia FPDs might be an alternative to common veneered restorations.     

优化设计Upcera超透氧化锆全瓷修复体的临床应用

目的：总结运用CAD/CAM系统优化设计Upcera超透氧化锆材料针对修复空间有限的病例进行修复的效果,并探讨其临床应用价值。方法：选择21例(23件)修复空间有限且要求行氧化锆全瓷修复患者,通过Sirona inEOS采集诊断蜡型与代型的光学印模,并将两者叠加,运用系统软件设计出面与诊断蜡型面一致、而颊面和邻面虚拟回切约1~1.5 mm的氧化锆底核,经Sirona inLab MC XL加工Upcer超透氧化锆材料后,完成局部饰瓷。嘱患者定期随访,并参照改良美国加州牙科协会评价标准对修复体进行评价,同时对患者进行满意度问卷调查。结果：经过6~12个月随访,除1件修复体因基牙根折拔除外,其余修复体均保持形态完整、色泽协调、边缘密合、咀嚼功能良好、无食物嵌塞等现象,患者对修复体美观和功能均满意(满意度>95.5%)。结论：通过CAD/CAM系统优化设计,制作了类似“颊烤”的超透氧化锆全瓷冠,在针对某些特殊病例修复时,如修复空间有限、紧咬牙、夜磨牙等患者,短期效果较好。     

Effect of in vitro aging on the flexural strength and probability to fracture of Y-TZP zirconia ceramics for all-ceramic restorations

ObjectivesDental zirconia restorations should present long-term clinical survival and be in service within the oral environment for many years. However, low temperature degradation could affect their mechanical properties and survival. The aim of this study was to investigate the effect of in vitro aging on the flexural strength of yttrium-stabilized (Y-TZP) zirconia ceramics for ceramic restorations.MethodsOne hundred twenty bar-shaped specimens were prepared from two ceramics (ZENO Zr (WI) and IPS e.max^® ZirCAD (IV)), and loaded until fracture according to ISO 6872. The specimens from each ceramic (n_x = 60) were divided in three groups (control, aged for 5 h, aged for 10 h). One-way ANOVA was used to assess statistically significant differences among flexural strength values (P < 0.05). The variability of the flexural strength values was analyzed using the two-parameter Weibull distribution function, which was applied for the estimation of Weibull modulus (m) and characteristic strength (σ₀). The crystalline phase polymorphs of the materials (tetragonal, t, and monoclinic, m, zirconia) were investigated by X-ray diffraction (XRD) analysis, Raman spectroscopy and Fourier transform infrared (FTIR) spectroscopy.ResultsA slight increase of the flexural strength after 5 h, and a decrease after 10 h of aging, was recorded for both ceramics, however statistically significant was for the WI group (P < 0.05). Both ceramics presented a t → m phase transformation, with the m-phase increasing from 4 to 5% at 5 h to around 15% after 10 h.SignificanceThe significant reduction of the flexural strength after 10 h of in vitro aging, suggests high fracture probability for one of the zirconia ceramics tested.     

Eliminating coronal discoloration when cementing all-ceramic restorations over metal posts and cores.

Opaque procelain was fused over metal posts and cores. This procedure permitted the definitive all-ceramic restorations to possess a more uniform shade between teeth restored with metal posts and cores and adjacent vital teeth.     

Fracture resistance and reliability of new zirconia posts

STATEMENT OF PROBLEM: The radicular portion of zirconia endodontic posts often need to be reshaped to achieve a definitive form and may be airborne-particle abraded to improve adhesion during luting. Therefore, the surface of the tetragonal zirconia ceramics may be transformed and damaged, influencing the mechanical properties of the material. PURPOSE: This study compared the fracture resistance of prefabricated zirconia posts with a new retentive post-head after different surface treatments. MATERIAL AND METHODS: Experimental zirconia posts of 2 different diameters, 1.3 mm and 1.5 mm, were produced from commercially available zirconia powder. A cylindro-conical outline form was used for the root portion of the system and a post-head with 3 retentive rings was designed. Sixty posts of each diameter were divided into 3 groups (n=20). Group 1 was ground with a coarse grit diamond bur; Group 2 was airborne-particle abraded with 110-microm fused alumina particles, and Group 3 was left as-received (controls). Posts were luted into the root-shaped artificial canals with the Clearfil adhesive system and Panavia 21 adhesive resin luting agent. The posts were loaded in a universal testing machine at an inclination of 45 degrees with the constant cross-head speed of 1 mm/min. The fracture load (N) necessary to cause post fracture was recorded, and the statistical significance of differences among groups was analyzed with 1-way ANOVA followed by the Fischer LSD test (alpha=.05). The variability was analyzed using Weibull statistics. RESULTS: Load to fracture values of all zirconia posts depended primarily on post diameter. Mean fracture loads (SD) in Newtons were 518.4 (+/-101.3), 993.6 (+/-224.1), and 622.7 (+/-110.3) for Groups 1 through 3, respectively, for thicker posts, and 385.9 (+/-110.3), 627.0 (+/-115.1), and 451.2 (+/-81.4) for Groups 1 through 3, respectively, for thinner posts. Airborne-particle-abraded posts exhibited significantly higher resistance to fracture (P<.05) than those in the other 2 groups for diameters 1.3 mm and 1.5 mm. Grinding reduced Weibull modulus compared with controls, and the values were 4.1 and 6.5 for thicker and thinner posts, respectively. CONCLUSION: Within the limitations of this study, the results suggest that grinding leads to a significant drop in load to fracture of zirconia posts, whereas airborne-particle abrasion increased the fracture load.     

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目的比较3种纤维桩修复下颌第一前磨牙的抗折性,并分析影响因素。方法选择2006年12年至2007年2月南昌大学附属口腔医院外科门诊因正畸需要而拔除的下颌第一前磨牙36颗,保留2mm的牙本质肩领,随机分成A、B、C3组,牙体预备后分别用3种纤维桩(A组:石英纤维桩-复合树脂核;B组:碳纤维桩-复合树脂核;C组:玻璃纤维桩-复合树脂核)及后牙树脂完成桩核修复,固定于万能材料测试机上加载直至标本发生折裂,记录标本破坏时的瞬间力值及实验牙的折裂类型。采用SPSS13.0软件包对结果作单因素方差分析。结果破坏性力学试验的测试结果为A组(399.24±33.84)N,B组(358.11±22.82)N,C组(220.32±23.98)N,对各组样本的破坏性试验力值进行单因素方差分析表明:3组的抗折强度为A>B>C(P<0.01)。结论石英纤维桩、碳纤维桩、玻璃纤维桩抗折强度依次递减,折断模式都有利于重新修复,均适用于临床修复。     

CAD/CAM氧化锆全瓷冠联合玻璃纤维桩的临床应用研究

目的探讨CAD/CAM氧化锆全瓷冠修复体的临床应用及其美学性、稳定性和生物相容性。方法应用计算机辅助设计和计算机辅助制作技术,对25例患者的40颗牙齿采用氧化锆全瓷联合纤维桩修复,采用金铂烤瓷冠修复为对照组,随访患者12个月,对两组修复体色彩的口内适应性、冠体有无破损和脱落及修复前、后牙周指标、局部龈沟液水平和龈沟液中碱性磷酸酶水平进行监测。结果氧化锆全瓷修复体的色彩更接近口内自然环境,无破损及脱落,患者满意率达到100%,而对照组满意率仅为40%。两组修复体治疗后一年内牙周情况比较,差异具有统计学意义(P<0.05)。氧化锆全瓷组修复后同修复前龈沟液量及龈沟液中碱性磷酸酶水平相比差别均无统计学意义(P>0.05),而金铂烤瓷冠组同等情况比较差异具有统计学意义(P<0.01)。结论通过CAD/CAM技术完成的氧化锆全瓷冠联合纤维桩修复增加了冠修复的美学效果,其稳定性及生物相容性均佳,值得在临床上推广。     

Maximising the fracture resistance of dentine-bonded all-ceramic crowns

Results of previous studies have indicated that the use of different ceramic materials and differing bonding/luting systems may affect resistance to fracture of teeth restored with dentine-bonded crowns. It is the purpose of this investigation to examine in vitro fracture resistance of dentine-bonded ceramic crowns, using materials in combination which have demonstrated increased fracture resistance when they are used individually. Ten sound maxillary premolar teeth were selected. These teeth were prepared for full crowns in a similar manner to previous, related studies. Standardised crowns were constructed in a leucite reinforced ceramic (Empress: Ivoclar-Vivadent, Liechten-stein) and placed using a dentine-bonding system and resin-composite luting system (3M; St. Paul, MN, USA). Compressive force was applied through a 4 mm diameter steel bar applied to the occlusal surface of the restored specimens. A mean fracturing force of 1.67 kN was recorded, statistical analysis indicating that this was significantly greater than any previously used combination of ceramic material and bonding/luting system, and greater than a group of sound, unrestored teeth. The fracture resistance of teeth restored in vitro by dentine bonded crowns may be enhanced by the combination of the materials described.     

Bonding-cementation of all-ceramic restorations

The objective of this article is to synthesize the current scientific data relating to the bonding of ceramic restorations in order to present a reliable and reproductive clinical method for the general practitioner. The different ceramic treatments are explained with a distinction between those which can be etched and the others. A precise check list is suggested for the conditioning of dental tissues and ceramic surfaces.     

全瓷修复体前牙比色现况调查

目的：了解全瓷修复体前牙比色情况,增强医生对全瓷牙与天然牙颜色匹配度的认识,进一步提高修复体比色质量。方法：搜集全瓷修复体前牙加工单共474份,根据医生所在单位等级将加工单分为3组,对其比色信息进行调查。调查内容包括患者牙位、年龄、性别,包括医生是否分区比色或特殊配色、是否有数码摄影辅助比色、是否记录患者特征色,特殊解剖结构,包括染色、隐裂、发育沟等项目。结果：3组调查项目的差异主要集中在年龄、性别、分区比色或特殊配色、数码摄影辅助比色方面。结论：全瓷修复体前牙的比色表达情况受到普遍忽视,医生对于全瓷材料前牙的分区比色或数码摄影辅助比色等技术有待进一步加强。     

三种银汞合金黏结修复方法修复缺损后牙冠抗裂强度的比较

目的 评价三种不同的银汞黏接剂应用于黏接银汞修复时,修复后牙冠的抗裂强度的差异.方法 选40颗因正畸需要拔除的新鲜上颌第一前磨牙,在牙合面制备近远中三面洞形,分为4组(直接银汞充填组;树脂加强型玻璃离子水门汀组;玻璃离子水门汀组;树脂型银汞黏接剂组).样品在37℃水浴72h,5℃到55℃水浴循环2500次,然后用振动动态测试系统进行抗折实验,记录时间.结果 ANOVA和T检验显示直接银汞合金充填组与其余各组间均有显著差异,树脂加强型玻璃离子组与树脂型银汞黏接剂组较其他实验组有更高的牙冠抗折力.结论 黏接银汞修复是一项有效的技术,并且用树脂加强型玻璃离子作黏接剂能更有效地提高牙冠的抗折力,值得在临床推广应用.     

不同粘接系统联合银汞充填窝洞后牙体抗力的实验研究

目的 比较研究不同的粘接系统应用于银汞合金充填后,对牙体折裂强度的影响.方法 48颗完整上颌第一前磨牙,随机分为4组,A组为完整牙齿,B、C、D组经制备MOD标准洞型后,分别采用银求合金直接充填、全酸蚀粘接剂联合银汞合金充填和自酸蚀粘接剂联合银汞合金充填.所有试件充填完成后,在电子万能试验机上.以横梁位移速率1.0 mm/min垂直于(牙合)面加载,记录牙齿折裂的最大折裂强度并行统计学分析.结果 4组试件的折裂强度(N)依次为1064.9±202.8、549.1±70.2、928.7±135.2和858.9±133.2.与银汞合金直接充填相比,采用粘接剂的两组试件折裂强度显著增强(P＜0.01);但不同粘接剂组间比较未见明显差异(P＞0.05).结论 在使用银汞合金充填窝洞前,辅助使用全酸蚀或自酸蚀粘接剂,均可显著提高牙体的折裂强度.     

Fracture resistance of single-tooth implant-supported all-ceramic restorations: an in vitro study

STATEMENT OF PROBLEM: High-strength ceramic materials can be used to fabricate esthetic and stable implant-supported single-tooth restorations. No study was identified that compared the fracture resistance of individual components of single-tooth implant-supported all-ceramic restorative systems after artificial aging. PURPOSE: The purpose of this in vitro study was to evaluate the fracture resistance of single-tooth implant-supported all-ceramic restorations consisting of alumina all-ceramic restorations on different implant abutments and to identify the weakest component of the restorative system. MATERIAL AND METHODS: Forty-eight standardized maxillary central incisor alumina crowns (Procera) were fabricated for each of the 3 test groups (n = 16) (Control group Ti, titanium abutments; Group Al, alumina abutments; Group Zr, zirconia abutments) for the Replace implant system. The crowns were adhesively luted using a resin luting agent (Panavia 21) and artificially aged through dynamic loading and thermal cycling. Afterwards, all specimens were tested for fracture resistance using compressive load on the palatal surfaces of the crowns. Kruskal-Wallis analysis of variance and post hoc Wilcoxon rank sum tests were performed to test for differences in fracture resistance values (alpha = .05). RESULTS: All test specimens survived the artificial aging process using simulated oral conditions. No screw loosening was recorded. The median fracture resistance was 1454 N, 422.5 N, and 443.6 N for groups Ti, Al, and Zr, respectively. Significant differences were found for the fracture resistance comparisons of group Ti with groups Al and Zr (Kruskal-Wallis test, P < .001). The test results for the comparison of groups Al and Zr were not significant. CONCLUSION: All 3 implant-supported restorations have the potential to withstand physiologic occlusal forces applied in the anterior region.