IPS e.max Press LT易美铸瓷低度透明瓷块铸造全冠修复后牙缺损的临床观察

目的观察和评价IPS e.max Press LT易美铸瓷低度透明瓷块铸造全冠修复后牙缺损的效果。方法共选取63例98个IPS e.max Press LT易美铸瓷低度透明瓷块整体铸造全瓷冠修复体,修复3~12个月后按照美国公共健康协会的修正标准进行修复体评估。结果有93%的修复体颜色、形态、边缘着色、边缘密合度等各项检查达到A级,无崩瓷情况发生。结论IPS e.max Press LT易美铸瓷低度透明瓷块整体铸造全瓷冠具有较好的修复效果。     

前牙全瓷冠饰瓷崩裂断口形貌分析

目的 通过断口形貌观察分析临床失效的前牙全瓷冠,分析疲劳损伤的起源和发展,以期为优化全瓷冠桥修复体的临床设计及修复工艺提供依据.方法 收集临床失效前牙二硅酸锂基瓷冠( IPS EmpressⅡ)3例,玻璃渗透氧化铝瓷冠(In-Ceram)2例,采用体视显微镜和扫描电子显微镜观察断裂面,分析特征形貌.结果 5例全瓷冠主要失效模式均为唇侧饰瓷内聚破坏,裂纹起源于切端咬合接触区,并由切端向龈端扩展,裂纹源附近饰瓷内部见较多气孔缺陷.结论 饰瓷内聚破坏是全瓷修复失效的重要原因;饰瓷内部易出现制作缺陷,成为双层瓷修复体的薄弱环节;改良饰瓷制作及烧结工艺,设计多点咬合接触将有助于减少饰瓷崩瓷.     

IPS e.max Press 热压铸后牙全瓷冠的临床研究

［摘要］ 目的 评价后牙IPS e.max press 全瓷铸造冠的临床效果。方法 共选取1 217例1 533颗后牙IPS e.max Press 铸瓷全冠修复体,修复3~24个月后,按照美国公共健康协会的修正标准进行修复体评估。结果 96.6%的修复体保持完整,未出现破裂、崩瓷、脱落、基牙冠折等并发症,患者满意度较高。结论 IPS e.max Press 全瓷修复体的近期修复效果良好。     

CAD／CAM制作的整体硅酸锂全瓷冠与饰面瓷一氧化锆全瓷冠的比较研究：模拟疲劳试验下的破坏模式与可靠性

目的：本研究的目的在于评估CAD／cAM制作的整体硅酸锂全瓷冠与手工饰瓷的氧化锆全瓷冠的体外疲劳表现和可靠性。材料和方法：利用CAD设计并采用快速成型技术制作下颌磨牙进行全冠预备后的基牙模型,通过CAD／CAM系统分别完成全解剖式的19颗硅酸锂全瓷冠（IPS e.maxCAD）和21颗手工饰瓷的氧化锆全瓷冠（IPS e.max ZirCAD／Ceram）。用树脂粘结材料将上述全瓷冠粘结于前期储存在水中的拟牙本质复合树脂模型上。在模拟口腔运动的疲劳试验中,用半径318mm的碳钨压头从全瓷冠的远颊尖加力并缓慢向舌侧滑动07mm．用三种不同的步进应力方法测试,直到试件发生破坏。当试件出现大块崩瓷或冠折裂时视为失败。如果承受高负载（〉900N）时试件仍未出现失败．则测试方法改变为应力比r呈阶梯式变化的疲劳试验。计算应力水平概率曲线及可靠性。结果：手工饰瓷的氧化锆全冠加载200N负荷完成10万次循环时出现崩瓷,其可靠性〈0．01（0．03～000,双侧90％的可信区间）。在整个步进应力（18万循环,900N）模拟1：3腔运动疲劳试验中未发生CAD／CAM制作的整体硅酸锂全瓷冠的失败,在应力比r的疲劳试验（100万循环．100～1000N）中整体硅酸锂全瓷冠也未见失败。1100～1200N负载可能是阈值范围．硅酸锂全瓷冠出现破坏或折裂。结论：基于目前的疲劳试验结果．CAD／CAM制作的全解剖式硅酸锂全瓷冠具有较高的抗疲劳特性．而手工饰瓷的氧化锆全瓷冠在较低负载的循环试验过程中易出现崩瓷。     

IPS e.max CAD全瓷冠修复的短期临床评价

目的 对IPS e.max CAD全瓷冠近期修复效果进行观察和评价。 方法 共选取469例542颗前、后牙IPS e.max CAD全瓷冠修复体,修复3~12个月后,按照美国加州牙科协会(CDA)制定的全瓷修复临床评定标准进行修复体评估。 结果 97.2%的修复体保持完整,未出现破裂、崩瓷、脱落、基牙冠折等并发症,患者满意度较高。 结论 IPS e.max CAD全瓷修复体的近期修复效果良好。     

气孔缺陷对磨牙双层全瓷冠力学性能影响的有限元研究

目的研究饰瓷气孔缺陷对磨牙二硅酸锂（LDG）及氧化锆（Y-TZP）双层全瓷冠力学性能的影响。 方法制作上颌第一磨牙LDG双层全瓷冠,使用显微CT扫描并三维重建分析饰瓷内气孔缺陷的尺寸及分布。分别构建上颌第一磨牙LDG及Y-TZP双层全瓷冠三维有限元模型,根据CT数据于饰瓷内添加气孔缺陷并进行加载;A组为对颌牙以200 N加载于牙冠模拟牙尖交错位时的垂直向受力;B组为以200 N与牙长轴呈45°加载于牙冠近、远中舌尖颊斜面,模拟侧方受力;C组为压头垂直位移1 mm加载于牙冠中央窝,模拟体外实验中的加载;计算最大主应力并分析气孔缺陷对其数值的影响。 结果LDG与Y-TZP在各载荷条件下的应力分布近似;垂直向加载时牙尖接触区应力集中,最大应力分别为51.683、50.084 MPa,存在气孔时,应力集中于牙尖接触应力区的气孔缺陷,最大应力上升至290.72、285.92 MPa;45°斜向加载时拉应力集中于核瓷颈部,气孔缺陷无应力集中,最大应力不变;体外加载时中央窝、沟及加载点应力集中,最大应力为107.3、125.41 MPa,存在气孔时,应力集中于拉应力区的气孔缺陷,最大应力上升至359.93、322.39 MPa。 结论饰瓷气孔缺陷对双层全瓷冠应力分布的影响与受载方式有关,位于拉应力集中区的气孔缺陷是导致冠失效的因素。     

Ceramage聚合瓷和IPS e.max Press材料磨损实验

目的 分析Ceramage和IPS e.max Press材料的耐磨性差异,为临床选择合适的非金属修复体材料提供参考.方法 收集近3个月内拔除的完整上颌第一磨牙10颗、无磨损上颌第三磨牙20颗.使用特定车针修整上颌第三磨牙腭尖形态,使成为标准化釉质加载尖,随机分为Ceramage釉质对照组和IPS e.max Press釉质对照组.将离体第一磨牙标本沿牙体颊舌侧中点连线平行牙长轴方向纵切为近中、远中两部分,随机分为Ceramage嵌体组和IPS e.max Press嵌体组;将样本近远中邻面片切成平面后进行Ⅰ类洞嵌体预备,以相应材料制作嵌体,Varolink N粘结.用自制咀嚼磨损测试机于20 N加载力下循环20万次,采用Kavo PREPassistant扫描系统测量样本的磨损深度.分析两组嵌体材料的磨损量、釉质对照组磨损量差异.结果 嵌体与釉质的磨损量分别为:Ceramage嵌体组材料磨损量(298.30±40.02)μm、釉质对照组(206.60±49.17)μm;IPS e.max Press嵌体组材料磨损量(212.90±61.21)μm、釉质对照组(217.00±25.10)μm.两组嵌体材料的磨损量结果表明,IPS e.max Press全瓷材料的磨损量小于Ceramage瓷聚体(P<0.05).Ceramage嵌体磨损量大于Ceramage釉质对照组磨损量(P<0.05),而IPS e.max Press嵌体组与釉质对照组之间磨损量差异无统计学意义(P>0.05).结论 Ceramage瓷聚体材料耐磨性较IPS e.max Press全瓷材料差.Ceramage瓷聚体磨损量大于天然牙釉质,耐磨性较牙釉质差;IPS e.max Press耐磨性好.     

IPS e.max Press铸瓷全冠近期修复效果的临床观察

目的：对IPS e.max Press铸瓷全冠近期修复效果进行观察和评价。方法：共选取35例56个IPS e.max Press铸瓷全冠修复体,修复3-18个月后,按照美国公共健康协会（APHA）的修正标准进行修复体评估,并记录患者满意度。结果：修复体颜色、形态、功能、舒适度各项满意率为94%以上,有96%的修复体颜色、形态、边缘着色、边缘密合度、继发龋各项检查达到A级。结论：IPS e.max Press是一种修复效果较好的全瓷修复材料。     

不同基底瓷厚度对IPS e.max press全瓷冠应力影响的有限元分析

目的：基于有限元数值计算方法探讨不同基底瓷厚度对IPS e.max press全瓷冠应力的影响。方法：建立下颌第一磨牙形态试件,基底瓷厚度分别为0.30 mm、0.50 mm、0.75 mm、1.00 mm、1.20 mm五组全瓷冠轴对称的有限元模型,模拟最大咬合力600 N垂直加载于半球形加载头,得出全瓷冠应力分布状态。结果：五组模型应力分布区域相似,全瓷冠最大主应力峰值均位于基底瓷层内,主要集中在加载区下方邻接粘结剂的基底瓷处;饰面瓷的最大主应力峰值主要集中在饰面瓷咬合面与半球形加载头接触的外侧周围;基牙及粘结剂最大主应力峰值均集中在肩台处。全瓷冠压应力峰值主要集中在加载区下方与半球形加载头接触的饰面瓷区域;IPS e.max press全瓷冠的基底瓷厚度对全瓷冠、基底瓷、饰面瓷、基牙及粘结剂的最大主应力均有影响。结论：IPS e.max press全瓷冠在正常咬合力作用下,可以在满足美观的基础上,尽量增加基底瓷厚度,以期增加全瓷冠整体断裂强度,提高使用寿命。     

铸瓷髓腔固位冠修复个别上前牙错位的疗效观察

目的探讨IPS e.max Press铸瓷髓腔固位冠在个别上前牙错位修复中的临床疗效。 方法选择15例个别上前牙错位的患者,经完善根管治疗和（或）牙周治疗,1~2周后制作IPS e.max Press铸瓷髓腔固位冠,树脂粘接剂粘固。并于6个月、1年后复查修复体的颜色、形态、边缘密合性、牙龈健康情况、基牙及修复体的保存情况。 结果1年内所有修复体边缘密合、牙龈健康、颜色美观;除1例基牙移位外,其余髓腔固位冠无松动移位。保存率100%（15/15）,临床可接受率为93.3%（14/15）。 结论IPS e.max Press铸瓷髓腔固位冠用于个别上前牙错位的修复可取得良好的效果。     

不同直径压头对磨牙e.max全瓷冠失效模式的影响

目的比较不同直径压头对e．max全瓷冠抗折强度及失效模式的影响。方法20个e．max全瓷冠随机分为A、B两组，分别采用直径为4mm、10mm的压头进行抗折试验，记录试件的抗折载荷值．体视显微镜观察其失效模式。结果两组试件抗折载荷值差异有统计学意义（P=0.012）。A组试件破坏局限于修复体，可见加载区域的锥状裂纹及起于黏结界面的放射状裂纹；B组试件由近远中向裂为两瓣．伴有基牙的损伤。结论不同直径压头对全瓷冠抗折载荷及失效模式均有影响。大直径压头加载时，冠的抗折载荷值大于小压头加载；小直径压头加载时，其折裂模式与临床全瓷冠的失效模式相似。     

Effect of the shades of background substructures on the overall color of zirconia-based all-ceramic crowns

PURPOSE

The objective of this study was to determine the effect of the color of a background substructure on the overall color of a zirconia-based all-ceramic crown.

MATERIALS AND METHODS

Twenty one posterior zirconia crowns were made for twenty subjects. Seven premolar crowns and six molar crowns were cemented onto abutments with metal post and core in the first and second group. In the third group, eight molar crowns were cemented onto abutments with a prefabricated post and composite core build-up. The color measurements of all-ceramic crowns were made before try-in, before and after cementation. A repeated measure ANOVA was used for a statistical analysis of a color change of all-ceramic crowns at α=.05. Twenty four zirconia specimens, with different core thicknesses (0.4-1 mm) were also prepared to obtain the contrast ratio of zirconia materials after veneering.

RESULTS

L^*, a^*, and b^* values of all-ceramic crowns cemented either on a metal cast post and core or on a prefabricated post did not show significant changes (P>.05). However, the slight color changes of zirconia crowns were detected and represented by ΔE^*_ab values, ranging from 1.2 to 3.1. The contrast ratios of zirconia specimens were 0.92-0.95 after veneering.

CONCLUSION

No significant differences were observed between the L^*, a^*, and b^* values of zirconia crowns cemented either on a metal cast post and core or a prefabricated post and composite core. However, the color of a background substructure could affect the overall color of posterior zirconia restorations with clinically recommended core thickness according to ΔE^*_ab values.     

Fracture frequency of all-ceramic crowns during dynamic loading in a chewing simulator using different loading and luting protocols

OBJECTIVE: The purpose of this laboratory study was to compare the frequency of failures (complete fractures or partial cracks) of molar crowns made of two different all-ceramic materials during dynamic loading in a chewing simulator, as well as the fracture load when subjected to static loading, in relation to different dynamic loading and luting protocols. METHODS: One hundred and forty-four molar crowns fabricated with IPS Empress or an experimental e.max Press material with high translucency (e.max Press Exp) were luted on CAD/CAM milled PMMA abutments (first lower molar, circular chamfer) either with Variolink or glass-ionomer cement (GIC). All crowns were loaded according to three different loading protocols (n=12 per group) and two force profiles (sinusoidal, rectangular) in a pneumatically driven chewing simulator with a steel stylus (? 8mm) and they underwent simultaneous thermocycling (5 degrees C/55 degrees C). After each phase the crowns were evaluated with regard to fractures or cracks. After dynamic testing, the crowns that did not fail were subjected to compression loading until complete fracture in a universal testing machine (UTM). As control groups, unloaded crowns were also subjected to a UTM. Survival statistics with log-rank tests were applied for the results of the dynamic loading, while ANOVA with post hoc Tukey B was used for the fracture load results and two-way ANOVA was carried out for logarithmically transformed data. Weibull statistics were calculated for pooled fracture load data of the dynamically loaded and control groups. RESULTS: In the 144 IPS Empress crowns, complete fractures were observed in 9 crowns and partial cracks in another 3 crowns. When the data was pooled, a statistically significant increase in fractures occurred when the sinusoidal force profile was applied compared to a rectangular force profile (log-rank, p<0.05). No fractures occurred in the e.max Press Exp crowns. The two-way ANOVA showed that the type of luting protocol used had the most significant effect on the fracture load of both materials. In conjunction with Empress, however, the luting material influenced the variability twice as much as in e.max Press Exp. There was no statistically significant difference in the fracture load of GIC-luted e.max Press Exp crowns and that of the Variolink luted Empress crowns. The force profile had a significant effect on the fracture load only of the Empress crowns but not of the e.max Press Exp crowns. Weibull statistics revealed a higher scattering of the data of dynamically loaded crowns compared to that of the control groups. CONCLUSIONS: For testing all-ceramic materials, dynamic loading is indispensable to draw valid conclusions on clinical performance of all-ceramic molar crowns. A sinusoidal profile is advisable, while a gradual increase of the force amplitude does not significantly affect the results.     

Resistance to fracture of two all-ceramic crown materials following endodontic access

STATEMENT OF PROBLEM: There is currently no protocol for managing endodontic access openings for all-ceramic crowns. A direct restorative material is generally used to repair the access opening, rendering a repaired crown as the definitive restoration. This endodontic procedure, however, may weaken the restoration or initiate microcracks that may propagate, resulting in premature failure of the restoration. PURPOSE: The purpose of this in vitro study was to evaluate how an endodontic access opening prepared through an all-ceramic crown altered the structural integrity of the ceramic, and the effect of a repair of this access on the load to failure of an all-ceramic crown. MATERIAL AND METHODS: Twenty-four alumina (Procera) and 24 zirconia (Procera) crowns were fabricated and cemented (Rely X Luting Plus Cement) onto duplicate epoxy resin dies. Twelve crowns of each were accessed to simulate root canal treatment therapy. Surface defects of all accessed specimens were evaluated with an environmental scanning electron microscope. The specimens were repaired with a porcelain repair system (standard adhesive resin/composite resin protocol) and were loaded to failure in a universal testing machine. Observations made visually and microscopically noted veneer delamination from the core, core fracture, shear within the veneer porcelain, or a combination thereof. A Kruskal-Wallis test was used to determine if a significant difference (alpha=.05) in load to failure existed between the 4 groups, and a Mann-Whitney test with a Bonferroni correction (P<.0125) was used for multiple comparisons. A Weibull analysis was also used to estimate the Weibull modulus and characteristic failure for each group. RESULTS: All specimens exhibited edge chipping around the access openings. Some displayed larger chips within the veneering porcelain, and 4 zirconia crowns showed radial crack formation. There was a significant difference in load to failure among all groups with the exception of the alumina intact and repaired specimens (P=.695). The alumina crowns generally showed fracture of the coping with the veneering porcelain still bonded to the core, whereas the zirconia copings tended not to fracture but experienced veneering porcelain delamination. CONCLUSION: Endodontic access through all-ceramic crowns resulted in a significant loss of strength in the zirconia specimens but not in the alumina specimens.     

The in vitro failure of all-ceramic crowns and the connector area of fixed partial dentures using bilayered ceramic specimens: the influence of core to dentin thickness ratio.

AIMS: To assess the effect of core to dentine thickness ratio on the bi-axial flexure strength and fracture mode and failure origin using bilayered ceramic specimens as an in vitro assessment for all-ceramic crowns and the connector area of fixed partial dentures (FPDs). METHODS: Sets of 30 bilayered composite discs, with a core layer thickness of 1mm and with core to dentine thickness ratios of 2:1, 1:1 and 1:2, were tested in bi-axial flexure with both the reinforcing core and veneering dentine loaded in tension. Mean flexure strengths, standard deviations and associated Weibull moduli (m) were determined. Optical microscopy was employed for identification of the fracture mode and failure origin for the failure all-ceramic crowns and the connector area of FPDs. RESULTS: For a core thickness of 1mm the core to dentine thickness ratio failed to influence the bi-axial flexure strength data when both the reinforcing core and veneering dentine porcelain were tested in tension. The number of fracture fragments, frequency of occurrence of specimen delaminations, Hertzian cone formations and sub-critical radial cracking in the bilayered dental ceramic composite disc-shaped specimens were dependent on the core to dentine thickness ratio and the surface loaded in tension. SIGNIFICANCE: The fracture mode and failure origin in bilayered ceramics tested to represent the failure mode of all-ceramic crowns and FPDs was dependent upon the core to dentine thickness ratio employed. However, the conventional wisdom regarding bilayered ceramic specimens with core thicknesses greater than 1mm are not followed when the core thickness was reduced to 1mm since the fracture resistance was not dependent on the core to dentine thickness ratio.     

Effect of different veneering techniques on the fracture strength of metal and zirconia frameworks

PURPOSE

To determine whether the fracture strengths and failure types differed between metal and zirconia frameworks veneered with pressable or layering ceramics.

MATERIALS AND METHODS

A phantom molar tooth was prepared and duplicated in 40 cobalt-chromium abutments. Twenty metal (IPS d.SIGN 15, Ivoclar, Vivadent, Schaan, Liechtenstein) and 20 zirconia (IPS e.max ZirCAD, Ivoclar) frameworks were fabricated on the abutments. Each framework group was randomly divided into 2 subgroups according to the veneering material: pressable and layering ceramics (n=10). Forty molar crowns were fabricated, cemented onto the corresponding abutments and then thermocycled (5-55℃, 10,000 cycles). A load was applied in a universal testing machine until a fracture occurred on the crowns. In addition, failure types were examined using a stereomicroscope. Fracture load data were analyzed using one-way ANOVA and Tukey HSD post-hoc tests at a significance level of 0.05.

RESULTS

The highest strength value was seen in metal-pressable (MP) group, whereas zirconia-pressable (ZP) group exhibited the lowest one. Moreover, group MP showed significantly higher fracture loads than group ZP (P=.015) and zirconia-layering (ZL) (P=.038) group. No significant difference in fracture strength was detected between groups MP and ML, and groups ZP and ZL (P>.05). Predominant fracture types were cohesive for metal groups and adhesive for zirconia groups.

CONCLUSION

Fracture strength of a restoration with a metal or a zirconia framework was independent of the veneering techniques. However, the pressing technique over metal frameworks resisted significantly higher fracture loads than zirconia frameworks.     

The in-vitro clinical failure of all-ceramic crowns and the connector area of fixed partial dentures: the influence of interfacial surface roughness

OBJECTIVES: To assess the effect of interfacial surface roughness on the flexure strength and fracture mode and origin utilizing an in-vitro assessment of the clinical failure conditions expected for all-ceramic crowns and the connector area of fixed partial dentures (FPDs) using bilayered ceramic specimens tested in bi-axial flexure. METHODS: Sets of 20 bilayered composite discs, with core:dentine thickness ratio of 2:1 and interfacial surface roughnesses determined by alumina abrasion with different alumina particle sizes, were tested in bi-axial flexure with both the reinforcing core and veneering dentine loaded in tension. Mean flexure strengths, standard deviations and associated Weibull Moduli (m) were determined. Optical microscopy was employed for identification of the fracture mode and origin for the failure all-ceramic crowns and the connector area of FPDs. RESULTS: The interfacial surface roughness influenced the bi-axial flexure strength and reliability of the flexure strength data when both the reinforcing core and veneering dentine porcelain were tested in tension. The number of fracture fragments, frequency of occurrence of specimen delaminations, Hertzian cone formations and sub-critical radial cracking in the bilayered dental ceramic composite disc-shaped specimens was also dependent on the interfacial surface roughness and the surface loaded in tension. CONCLUSIONS: The fracture resistance, failure mode and failure origin in bilayered ceramics tested to represent the clinical failure mode of all-ceramic crowns and FPDs are dependent upon the interfacial surface roughness and the modulus of the material in tension.     

Effect of loading method on the fracture mechanics of two layered all-ceramic restorative systems.

OBJECTIVE: The aim of this research was to evaluate both the fracture and impact strength of two core veneered all-ceramic systems and to reveal whether the speed of loading affects fracture mechanism. METHODS: The absorbed energy by (IPS)Empress-Eris crowns and Cercon-Ceram S crowns in a fracture strength test was compared by the energy absorbed in an impact strength test. The principles of fractography were used to identify fracture origin and dimensions and to calculate the stress at failure. Finite element analysis (FEA) was used to rationalize the results. RESULTS: For the (IPS)Empress 2-Eris crowns, there was a significant difference in the energy absorbed for the fracture test and the impact test, where for the Cercon-Ceram S, there was no significant difference. Despite the high strength of the zirconia cores there was no significant difference in the energy absorbed between the two systems in the impact strength test. The dominant mode of failure of layered all-ceramic restorations under occlusal loading is cone cracking in the veneering ceramic. SIGNIFICANCE: It was concluded that to exploit the high strength of the zirconia cores the strength of the veneering ceramic has to improve as delamination and cone cracking of the veneer are the most expected failure modes.     

高度抛光无釉瓷氧化锆全瓷冠的临床效果研究

目的评估高度抛光无釉瓷氧化锆全瓷冠的临床效果。方法牙体缺损磨牙80颗,分为2组,40例40颗患牙进行高度抛光无釉瓷的氧化锆全瓷冠修复（试验组）,40例40颗患牙常规制作钯金烤瓷牙单冠修复（对照组）。戴固后即刻、3个月、6个月、12个月、24个月、36个月临床观察和评价修复体破损和对袷牙磨耗情况,比较2组修复体的存留率和成功率。结果试验组中有1件修复体出现小面积瓷裂,修复后12个月2件全瓷冠对冶天然牙牙出现I级磨耗。对照组中有3件修复体出现小面积瓷裂,但对殆天然牙均无明显磨耗。试验组和对照组修复体3年存留率分别为100％和97．5％,成功率分别为97．5％和90％,差异均无统计学意义（P〉0．05）。结论高度抛光无釉瓷氧化锆全瓷冠修复磨牙牙体缺损不易破损,对猞天然牙磨耗轻微,成功率高.