Correlation between microhardness and wear resistance of dental alloys against monolithic zirconia

PURPOSEThe aim of this study is to compare the hardness according to the conditions of metal alloys. Moreover, the correlation between the cast crown hardness before and after wear testing and the degree of wear for each dental alloy was assessed.MATERIALS AND METHODSCast crowns of three metal alloys (Co-Cr, gold, and Ni-Cr alloys) opposing smooth-surface monolithic zirconia were used. The Vickers microhardness of the ingot (which did not undergo wear testing) and the cast crown before and after wear testing were measured for each alloy. Two-way ANOVA and Scheffé tests were used to compare the measured hardness values. Moreover, the Pearson correlation coefficient was used to evaluate the relationship between the surface hardness and the wear of the cast crown (α=.05).RESULTSThere was no significant difference in the hardness before and after wear testing for the gold alloy (P>.05); however, the hardness of the worn surface of the cast crown increased compared to that of the cast crown before the wear tests of Ni-Cr and Co-Cr alloys (P<.05). Furthermore, there was no correlation between the wear and hardness of the cast crown before and after wear testing for all three metal alloys (P>.05).CONCLUSIONThere was a significant difference in hardness between dental alloys under the same conditions. No correlation existed between the surface hardness of the cast crown before and after wear testing and the wear of the cast crown.     

In-vitro wear of natural tooth surface opposed with zirconia reinforced lithium silicate glass ceramic after accelerated ageing

Objective

To evaluate the effect of different pH media on zirconia-reinforced lithium silicate glass ceramic and how they interact with opposing dentition after being aged in different pH cycling and high temperature conditions.

Excessive wear of natural tooth structure by opposing composite restorations

Extreme care must be taken to evaluate the probable effect of using certain restorative materials to oppose existing tooth structure, particularly when dentin is exposed. In addition, frequent recall examination, every one or two months, is necessary to catch any problems in their beginning stages and to solve them before greater damage can be caused. It is also suggested that evaluation of any occlusal habits be made before deciding on a plan to alter vertical dimension and to carefully consider the effects of the materials used in a restoration on the opposing arch.     

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.     

Relative wear of enamel opposing low-fusing dental porcelain

PURPOSE: This study evaluated the wear of human enamel opposing 5 low-fusing dental porcelains and a traditional feldspathic control. In a second experiment, the repeatability of the test method and the effect of ceramic overfiring on enamel wear were also evaluated. MATERIALS AND METHODS: Five low-fusing dental porcelains--Finesse (FI), Rhapsody (RP), IPS d.Sign (DS), Omega 900 (OM), and Duceram LFC (LFC)--and 1 traditional feldspathic porcelain--VMK 68 (VMK)--were formed into disks (n = 10) and used as substrate for the wear test. Enamel was harvested from extracted human molars and machined into cusps with a 5-mm spherical radius (n = 60). The Oregon Health Sciences University oral wear simulator was used to simulate chewing and the size of the resulting enamel wear facets (in mm(2)) were evaluated after a specified number of chewing cycles. A portion of the experiment was duplicated to assess the repeatability of the data and determine the effects of overfiring on enamel wear. Data were subjected to analysis of variance and post hoc tests to determine significant differences. After wear testing, scanning electron micrographs were made using representative ceramic samples from each group. RESULTS: The results indicate that none of the low-fusing ceramics resulted in significantly less wear than the VMK control. In fact, 3 of the low-fusing porcelains (OM, RP, LFC) resulted in significantly greater enamel wear than VMK. Enamel wear was not significantly affected (p = 0.29) by the increased ceramic firing temperature. Wear data were repeatable, with no significant difference (p = 0.56) between the enamel wear from 2 separate experiments. The results from both experiments indicated that ceramic material significantly affected enamel wear (p <0.001). There was significantly less enamel wear opposite DS than LFC. CONCLUSIONS: This work suggests that variations in ceramic composition and microstructure may affect the opposing enamel wear, but that low-fusing temperatures do not necessarily guarantee low enamel wear. Although the clinical relevance of this testing apparatus may be questioned, the testing method was repeatable.     

浸泡着色氧化锆陶瓷及其比色板的色度学研究

目的:测定浸泡着色的Vita In-Ceram YZ氧化锆陶瓷试样和染色液比色板的色度值。方法:制备5组陶瓷试样,分别用LL1至LL5染色液浸泡着色2min,1530℃烧结2h,磨床单面磨至1.5mm厚度,黑色背景下用分光光度计对陶瓷试样和染色液比色板进行颜色测定。计算试样和比色板之间的色差以及计量心理量的明度差、色相角差、彩度差。结果:染色后试样的色度值范围为L:59.81-78.93;a:0.36-9.36;b:19.62-26.91。试样与染色液比色板的色空间相近,色差值4.02-6.96个NBS单位。两者之间差异最大的是色相角差,均值7.38;其次是彩度差,均值2.31;最小为明度差,均值2.29。结论:染色液比色板与浸泡着色氧化锆陶瓷之间具有良好的颜色适合性。对氧化锆基底瓷的颜色调控应同时包括明度、彩度和色相角。     

氟磷灰石玻璃陶瓷、长石质饰瓷与天然牙摩擦磨损性能的研究

目的：研究牙科氟磷灰石玻璃陶瓷、长石质饰瓷与天然牙在干摩擦和唾液润滑条件下的摩擦磨损学性能。方法：制备涂覆IPS-emaxcream和Vita vm9 2种饰面瓷的氧化锆-饰面瓷双层材料试样,尺寸为20 mm×20 mm×4.5 mm,各20个。利用MMV-1摩擦磨损试验机,通过设置不同大小的垂直载荷和转速,分别在干摩擦和唾液润滑条件下,对2种氧化锆-饰面瓷试样进行摩擦磨损试验。采用SPSS 17.0软件包进行单因素方差分析和t检验,确定各组间摩擦系数和磨损量是否存在差异。结果：氟磷灰石玻璃陶瓷在唾液润滑条件下的动态摩擦系数和磨损量显著大于干摩擦条件下的数值;与氟磷灰石玻璃陶瓷相反,长石质饰瓷在干摩擦时的动态摩擦系数和磨损量显著大于在唾液润滑条件下的数值。在干摩擦和唾液润滑条件下,氟磷灰石玻璃陶瓷的磨损量均小于长石质饰瓷。扫描电镜显示,在唾液润滑条件下,氟磷灰石玻璃陶瓷及对应天然牙表现出比干摩擦更为严重的磨损表面。在干摩擦条件下,长石质饰瓷及对应天然牙较氟磷灰石玻璃陶瓷磨损更为严重,在唾液润滑条件下差异较小。结论：与长石质饰瓷相比,氟磷灰石玻璃陶瓷与天然牙在干摩擦条件下表现出更优越的耐磨损性能。加入唾液后,能减少2种饰瓷摩擦磨损性能之间的差异。     

二氧化锆与钴铬合金修复体精细抛光后对天然牙磨耗的影响

［摘要］ 目的 研究临床上精细抛光对二氧化锆及钴铬合金修复体材料与天然牙间磨耗的影响。方法 使用表面粗糙度仪测量修复体材料抛光前后的粗糙度值（Ra）。在摩擦磨损测试机上,模拟口腔内的力学和化学环境,进行天然牙与不同处理的修复体材料间的摩擦磨损实验,测量两者间摩擦系数（μ）。测量实验前后各磨擦对象的自身质量损失（Δm）,扫描电镜观察实验后天然牙表面。结果 各实验组中表面Ra,不烧结饰瓷抛光组（0.933±0.186）μm小于不抛光组（2.350±0.327）μm（P=0.000）;烧结饰瓷组抛光组（2.300±0.189）μm小于不抛光组（4.200±0.871）μm（P=0.000）;钴铬合金抛光组（0.250±0.083）μm小于不抛光组（1.200±0.894）μm（P=0.000）,有统计学意义。对磨天然牙自身质量损失量（Δm）,不烧结饰瓷抛光组（6.067±0.921）mg小于不抛光组（16.690±2.113）mg（P=0.001）;烧结饰瓷抛光组（5.893±0.838）mg小于不抛光组（14.016±0.063）mg（P=0.000）;钴铬合金抛光组（4.573±1.954）mg小于不抛光组（11.433±1.087）mg（P=0.008）有统计学意义。各组修复材料自身质量损失量（Δm）不烧结饰瓷抛光组（0.300±0.010）mg小于不抛光组（0.800±0.010）mg（P=0.001）;烧结饰瓷抛光组（0.456±0.055）mg小于不抛光组（0.650±0.086）mg（P=0.031）;钴铬合金抛光组（10.236±0.357）mg小于不抛光组（14.300±0.526）mg（P=0.000）有统计学意义。抛光组的摩擦系数：不烧结饰瓷氧化锆0.068,烧结饰瓷热氧化锆0.095,钴铬合金0.063明显小于不抛光组不烧结饰瓷二氧化锆0.096,烧结饰瓷二氧化锆0.119,钴铬合金0.103,差异有统计学意义。结论 修复体表面精细抛光,可以有效降低其表面粗糙度,减小其与牙釉质间的摩擦系数,避免天然牙的过度磨耗。     

牙科氧化锆瓷摩擦磨损性能的研究

目的研究牙科氧化锆瓷的摩擦磨损性能以及与天然牙釉质摩擦磨损性能匹配情况。方法微摩擦磨损试验机上,以滑石瓷为对磨物,人工唾液润滑下对Upcera ST和Zenostar Zr Translucent氧化锆瓷、牙釉质和饰面瓷进行摩擦磨损实验。实验前,用激光共聚焦显微镜测试件表面粗糙度Ra;实验结束后,光学显微镜下观察滑石瓷磨斑形貌、测量滑石瓷磨斑面积;激光共聚焦显微镜测量试件磨斑宽度;扫描电镜下观察试件磨斑的微观形貌。采用单因素方差分析进行统计学分析。结果饰面瓷的磨斑宽度大于其它3种材料（P〈0.01）,饰面瓷对磨物滑石瓷磨斑面积大于氧化锆瓷和牙釉质（P〈0.05）。结论与饰面瓷对比,氧化锆瓷具有更佳耐磨性及较低对磨物磨损,并且与天然牙釉质的磨擦学性能相似。     

Influence of porcelain veneering on the marginal fit of Digident and Lava CAD/CAM zirconia ceramic crowns

PURPOSE

Marginal fit is a very important factor considering the restoration''s long-term success. However, adding porcelain to copings can cause distortion and lead to an inadequate fit which exposes more luting material to the oral environment and causes secondary caries. The purpose of this study was to compare the marginal fit of 2 different all-ceramic crown systems before and after porcelain veneering. This study was also intended to verify the marginal fit of crowns originated from green machining of partially sintered blocks of zirconia (Lava CAD/CAM system) and that of crowns obtained through machining of fully sintered blocks of zirconia (Digident CAD/CAM system).

MATERIALS AND METHODS

20 crowns were made per each system and the marginal fit was evaluated through a light microscope with image processing (Accura 2000) at 50 points that were randomly selected. Each crown was measured twice: the first measurement was done after obtaining a 0.5 mm coping and the second measurement was done after porcelain veneering. The means and standard deviations were calculated and statistical inferences among the 2 groups were made using independent t-test and within the same group through paired t-test.

RESULTS

The means and standard deviations of the marginal fit were 61.52 ± 2.88 µm for the Digident CAD/CAM zirconia ceramic crowns before porcelain veneering and 83.15 ± 3.51 µm after porcelain veneering. Lava CAD/CAM zirconia ceramic crowns showed means and standard deviations of 62.22 ± 1.78 µm before porcelain veneering and 82.03 ± 1.85 µm after porcelain veneering. Both groups showed significant differences when analyzing the marginal gaps before and after porcelain veneering within each group. However, no significant differences were found when comparing the marginal gaps of each group before porcelain veneering and after porcelain veneering as well.

CONCLUSION

The 2 all-ceramic crown systems showed marginal gaps that were within a reported clinically acceptable range of marginal discrepancy.     

6种不同修复材料与天然牙牙釉质摩擦、磨耗性能的比较

目的：通过体外摩擦、磨耗实验,比较临床常用的陶瓷材料、多种合金及天然牙釉质的摩擦、磨耗性能,为临床上选择与对颌牙磨耗性能相近的修复材料,更好地保护对颌牙提供一定的实验依据。方法：将陶瓷、纯钛、钛合金、镍铬合金、金钯合金、银汞合金和近期拔除的成人下颌第三磨牙的釉质平面,与滑石瓷磨头磨耗机上对磨。耐磨性能的评定采用称重法。用针一盘磨损试验仪测定各种材料的滑动摩擦系数。应用SPSS11．5软件包进行统计学处理．对各试件、天然牙的质量损失量进行统计学分析,对比分析摩擦系数。结果：单位面积的磨损量以天然牙釉质最小,但与瓷块、银汞合金、金钯合金无显著性差异（P〉0．05）,与其余各组均有显著性差异（P〈0．01）;纯钛最大,与其余各组均有显著性差异（P〈0．01）,镍铬合金、金钯合金与其余各组均有显著性差异（P〈0．01）。瓷块的摩擦系数稳定在0．68,银汞合金的摩擦系数为0．12,金钯合金的摩擦系数为0．11,镍铬合金为0.41,纯钛为0.38,钛合金为0．48,天然牙釉质为0．65。结论：6种修复材料的耐磨性均比天然牙釉质差．纯钛的耐磨性最小,钛合金及镍铬合金、金钯合金次之,陶瓷的耐磨性最大。     

低温时效性对牙科用氧化锆耐磨性能的影响

目的探讨低温时效对牙科用氧化锆耐磨性能的影响。 方法本实验对偶球为对照氧化锆球和经低温时效处理的氧化锆球（134℃,100 h）,对磨材料为牙釉质（n= 8）,每个氧化锆对偶球（n= 8）对应1个牙釉质样本。将样本和对偶球固定在磨耗试验仪上,磨耗实验条件：10 000、20 000和50 000个磨耗循环,频率1.2 Hz,载荷49 N。随后用三维轮廓扫描仪确定每组牙釉质样本磨痕的体积损失和深度损失,并测定磨耗前后氧化锆球表面的粗糙度。用微压痕实验方法检测氧化锆球的维氏硬度。应用SPSS 20.0软件包对实验数据进行统计学分析,采用双因素方差分别分析牙釉质样本的深度损失（μm）和体积损失（mm³ × 10^-3）以及氧化锆对偶球的粗糙度（μm）,采用单因素方差分析氧化锆对偶球硬度结果,选择Tukey HSD检验进行组间两两比较。 结果实验结果显示,10 000次磨耗循环后低温时效处理组和对照组牙釉质样本的深度损失（1.43 ± 0.07,1.46 ± 0.12）和体积损失（2.36 ± 0.45,2.31 ± 0.34）差异无统计学意义（F_深度损失= 0.721,P_深度损失= 0.610;F_体积损失= 0.0552,P_体积损失=0.801）;而经过20 000和50 000次磨耗循环后老化处理组对磨的牙釉质样本深度损失（F_{20 000}= 4.573,P_{20 000}= 0.0364;F_{50 000}= 49.385,P_{50 000}<0.001）和体积损失（F_{20 000}= 5.769,P_{20 000}= 0.0210;F_{50 000}= 61.792,P_{50 000}<0.001）显著低于对偶球为对照组氧化锆球组。10 000和20 000次磨耗后低温时效组的氧化锆球的表面粗糙度（0.0402 ± 0.0055,0.0366 ± 0.0061）与对照组（0.0406 ± 0.0035,0.0391 ± 0.0059）差异均无统计学意义（F_{10 000}= 0.0314,P_{10 000}= 0.873;F_{20 000}= 0.693,P_{20 000}= 0.416）,而磨耗50 000次后老化处理组氧化锆球的粗糙度（0.0596 ± 0.0045）显著高于于对照组氧化锆球（0.0386 ± 0.0027）,差异有统计学意义（F_{50 000}= 128.793,P<0.001）。低温时效处理组氧化锆的维氏硬度为1257.0 ± 54.5（HV1）显著低于对照组氧化锆球1385.8 ± 28.7（HV1,F= 124.789,P<0.001）。 结论低温时效处理导致牙科用氧化锆材料硬度降低,耐磨性能下降（20 000和50 000次磨耗循环后）。     

Fracture resistance of porcelain veneered zirconia crowns with exposed lingual zirconia for anterior teeth after thermal cycling: An in vitro study

Statement of problem

In some clinical conditions minimally invasive complete crown tooth preparations are indicated. This is especially true when gross removal of tooth structure would weaken the remaining tooth or violate the vitality of the dental pulp.

Objective

The purpose of this study was to investigate the influence of (1) exposed lingual zirconia with veneered zirconia crowns, and (2) reduced lingual thickness of monolithic lithium disilicate crowns on the fracture resistance of the crowns after cyclic loading. Metal-ceramic crowns with exposed lingual metal served as controls.

Materials and methods

Twenty-four maxillary central incisor crowns were fabricated in identical shape on metal testing dies in 3 groups: metal-ceramic crowns (MC, n = 8), veneered zirconia crowns (VZ, n = 8), and monolithic lithium disilicate crowns (MO, n = 8). A conservative preparation design with 0.75 mm lingual clearance was used for each crown system. All crowns were cemented to their corresponding crown preparations with self-adhesive resin cement (Multilink Automix). The crowns were subjected to 1000 cycles of thermal cycling, then cyclic loading of 111 N by means of a stainless steel ball, and 50,000 cycles of loading were applied for the fatigue test. Fatigue loading was followed by a continuously increasing compressive load, at a crosshead speed of 1 mm/min until failure. The compressive load (N) required to cause failure was recorded. Means were calculated and analyzed with one-way ANOVA and the Tukey HSD test (α = .05).

Results

There was a significant difference between MO vs. MC (P = .0001), MO vs. VZ (P = .0001), and VZ vs. MC (P = .012).

Conclusions

There was a significant difference in the mean fracture resistance of MC, VZ, and MO crowns in this in vitro study. The MC group recorded the highest mean fracture strength.     

Suitability of 3D printed pieces of nanocrystalline zirconia for dental applications

ObjectivesThe main goal of this work is to evaluate the suitability of nanostructured zirconia pieces obtained by robocasting additive manufacturing (AM), for dental applications.MethodsThe density, crystalline structure, morphology/porosity, surface roughness, hardness, toughness, wettability and biocompatibility of the produced samples were compared with those of samples obtained by conventional subtractive manufacturing (SM) of a similar commercial zirconia material. Chewing simulation studies were carried out against dental human cusps in artificial saliva. The wear of the material was quantified and the wear mechanisms investigated, as well as the influence of glaze coating.ResultsAM samples, that revealed to be biocompatible, are slightly less dense and more porous than SM samples, showing lower hardness, toughness and wettability than SM samples. After chewing tests, no wear was found both on AM and SM samples. However, the dental wear was significantly lower when AM samples were used as counterbody. Concerning the glazed samples, both coated surfaces and dental cusps suffered wear, being the cusps’ wear higher than that found for unglazed samples. More, cusps tested against AM coated samples suffered less wear comparatively to those opposed to SM coated samples.SignificanceOverall, the results presented in this paper show that AM processed nanostructured zirconia can be used in dental restorations, with important advantages from the point of view of processing and tribological performance. Moreover, the option for glaze finishing should be carefully considered both in SM and AM processed specimens.     

二氧化锆全瓷冠在前牙美容修复中的应用

目的:探讨二氧化锆全瓷冠在前牙美容修复的应用。方法:选择58例患者的86颗前牙,二氧化锆全瓷冠修复,观察1年。结果:86颗二氧化锆全瓷冠在修复完成第1天及6个月五项评价指标均达到A级(100%),12个月边缘完整性(97.6%)和牙龈状况(97.6%)达到B、C级各1例。结论:二氧化锆全瓷冠在前牙美学修复中的临床效果较理想。     

自然牙牙裂综合征患者牙磨耗的自身对照研究

目的:调查自然牙裂综合征病例中患牙磨耗模式,评价牙磨耗在自然牙裂综合征(cracked tooth syndrome,CTS)组和自身对照(OC)组间有无差别。方法:49例CTS组患牙,以对侧同名牙为对照组,取研究模观察。结果:(1)磨耗指数:CTS组得1分者8个(16.33%),得2、3分者33个(67.35%),得4分者8个(16.33%);对照组得1分者14个(28.57%),得2、3分者29个(59.18%),得4分者6个(12.24%)。2组相比差异无显著性(P>0.05);(2)相对磨耗:上颌前磨牙舌尖和下颌第一磨牙近颊尖CTS组与对照组具有统计学差异(P<0.05);(3)牙折方向:上颌前磨牙和上颌第二磨牙以近远中向裂为主,依次占各自折裂牙样本的91.67%和88.89%,而上、下颌第一磨牙及下颌第二磨牙的牙折裂方向没有表现出明显趋向性。结论:上颌前磨牙舌尖及下颌第一磨牙近颊尖磨耗相对不足与牙折裂密切相关。     

Effect of fatigue on biaxial flexural strength of bilayered porcelain/zirconia (Y-TZP) dental ceramics

Objectives

The aim of this study was to evaluate the effect of fatigue on biaxial flexural strength of bilayered disks of two Y-TZP cores.

Methods

Twenty bilayered veneer/zirconia disks were fabricated from each material (Lava veneer + core, 3 M/ESPE, and Cercon veneer + core, Densply). Ten specimens from each material were tested for biaxial flexural strength either with or without being subjected to fatigue (20,000 cycles, 2 Hz, 200 N load) in a universal testing machine (1 mm/min). Stresses generated at the core and the veneer, at the top and the bottom surfaces, and the interface of bilayered disk were calculated using Huesh's solutions. Data were statistically analyzed using Weibull statistics. The fractured core was also examined via Raman spectroscopy and the monoclinic fraction was calculated at the top, the middle of thickness, and the bottom of the cross-section of fractured core. The results of monoclinic fraction were statistically analyzed by Three-Factor ANOVA with Repeated Measures on One Factor.

Results

Weibull modulus (m) of Cercon control (CC), Cercon fatigue (CF), Lava control (LC) and Lava fatigue (LF) were between 11.8 and 14.3, 7.1 and 13.1, 9.4 and 13, and 7.1 and 8.2, respectively. There were no significant differences between characteristic strength (σ₀) of CC (970.9 MPa) and CF (947.7 MPa) (p > 0.05). For Lava, σ₀ of LF (1444.8 MPa) was significantly higher than LC (1240.5 MPa) (p < 0.05). At the interfaces, σ₀ values of CC and CF groups were not significantly different while LF showed significantly higher σ₀ than LC. The monoclinic zirconia was significantly lower for CF than CC and significantly higher for LF than LC.

Significance

Fatigue showed different effects on the strength of Cercon and Lava ceramic systems. Decreases in m values were observed at the interfaces of two materials after fatigue.     

饰面瓷厚度对氧化锆全瓷冠抗压缩破坏力的影响

目的：研究饰面瓷厚度对氧化锆全瓷冠抗压缩破坏力的影响。方法：常规 CAD-CAM制作氧化锆筒状基底冠25个,厚度均为0．5 mm,随机分为 A、B、C、D、E 5组,饰面瓷厚度依次为0．5、1．0、1．5、2．0、2．5 mm。万能材料试验机测试各组试件抗压缩破坏力值。采用 SPSS13．0统计软件对测试结果进行统计分析。用扫描电镜（SEM）观察试件断裂面微观结构。结果：A ～E 组试件抗压缩破坏力值依次为：（1279．96±42．85）N、（2235．44±50．14）N、（2216．38±48．97）N、（2169．22±60．40）N、（2028．70±47．37）N。A 组、E 组氧化锆全瓷修复体的抗压缩破坏力值均低于其他3组（P ＜0．01）;其余组间抗压缩破坏力值无统计学差异（P ＞0．05）。扫描电子显微镜观察发现,A 组、E 组氧化锆全瓷修复体基底瓷－饰面瓷结合界面处不平坦,较为疏松;饰瓷层出现气孔及微裂纹增多、增大。结论：饰面瓷厚度低于1．0 mm 及高于2．0 mm 时,修复体的微观结构可能会受到影响,从而氧化锆全瓷冠整体抗压缩破坏力的性能受影响,建议临床应用时严格控制饰面瓷厚度。     

5种着色剂对牙科氧化锆陶瓷色度的影响

目的:研究5种着色剂对牙科氧化锆陶瓷色度影响的规律,为量化着色剂的添加比例提供依据。方法:在纳米氧化锆粉体中掺入不同比例的5种着色剂,200MPa冷等静压成型,于高温烧结炉中烧结到1400℃并保温2h,将烧结体研磨至(1.0±0.1)mm厚。观察烧结体的色泽并用色度仪测试其色度值。结果:氧化铒(Er_2O_3)能够使氧化锆陶瓷呈红色,对烧结体的b*值和L*值无影响。氧化铈(CeO_2)和氧化镨(Pr_6O_(11))均能使氧化锆陶瓷呈黄色,而对烧结体的a*值和L*值无明显影响。氧化铁(Fe_2O_3)能使氧化锆陶瓷呈黄褐色,随着剂量的增加,a*和b*值均增大,L*值略有下降。氧化锰(MnO_2)能够有效降低氧化锆陶瓷烧结体的明度,对a*和b*值无明显影响。结论:5种梯度着色氧化锆陶瓷能够覆盖牙科陶瓷所需的色度范围,值得进一步的研究与开发。