可切削渗透陶瓷复合体试件断面的显微结构分析

目的比较不同制备条件下形成的可切削渗透陶瓷（MIC）复合体断面显微结构,从显微结构层面提供与陶瓷强度相关的证据。方法制备氧化铝基体,将可切削渗透云母玻璃渗透其中并晶化,根据烧结时间和渗透时间制备条件的不同分为：充分烧结渗透组、烧结时间不足组和渗透时间不足组。制作试件,测定其三点弯曲强度及弹性模量,并在扫描电镜下观察复合体断面。结果渗透时间不足组及烧结时间不足组的三点弯曲强度及弹性模量均低于充分烧结渗透组,并可在断面显微结构上找到典型的结构缺陷。氧化铝中玻璃渗透锋面和玻璃与氧化铝复合体界面分析显示：未渗透玻璃的氧化铝基体断面较已渗透的复合体断面整齐;单一玻璃内部有大而长的裂纹,复合体内则没有。结论足够的烧结和渗透时间是保证MIC材料均一性和强度的关键。     

Effect of overglazed and polished surface finishes on the compressive fracture strength of machinable ceramic materials

Controversy prevails over the effect of overglazing on the fracture strength of ceramic materials. Therefore, the effects of different surface finishes on the compressive fracture strength of machinable ceramic materials were investigated in this study. Plates prepared from four commercial brands of ceramic materials were either surface-polished or overglazed (n=10 per ceramic material for each surface finish), and bonded to flat surfaces of human dentin using a resin cement. Loads at failure were determined and statistically analyzed using two-way ANOVA and Bonferroni test. Although no statistical differences in load value were detected between polished and overglazed groups (p>0.05), the fracture load of Vita Mark II was significantly lower than those of ProCAD and IPS Empress CAD, whereas that of IPS e.max CAD was significantly higher than the latter two ceramic materials (p<0.05). It was concluded that overglazed and polished surfaces produced similar compressive fracture strengths irrespective of the machinable ceramic material tested, and that fracture strength was material-dependent.     

A 3-year study of inlays milled from machinable ceramic blocks representing 2 different inlay systems.

OBJECTIVE: The aim of this study was to evaluate the clinical performance of ceramic inlays made from machinable ceramic blocks. METHOD AND MATERIALS: The 2 inlay systems involved computer-aided design and computer-aided machining (Cerec Cos 2.1) or copy-milling technique (Celay). The study comprised 15 Celay inlays and 15 Cerec inlays placed in 17 patients. The inlays were evaluated clinically at baseline (1 week) as well as 1 and 3 years later (modified California Dental Association quality evaluation system). RESULTS: One Celay inlay fractured after 1 year of service, and 2 Cerec inlays were replaced, 1 after 6 months and 1 after 1 year, because of pulpal pain and persisting hypersensitivity. One Celay inlay lost retention after 2 years. At the 3-year evaluation, chipping and hairline cracks were seen in 2 Celay inlays. Progressive disintegration of the marginal luting cement was seen for both Celay and Cerec inlays. The remaining 25 inlays performed satisfactorily throughout the 3-year period. CONCLUSION: Because of their relatively high failure rate, these inlays should be reserved for esthetic indications.     

可切削渗透陶瓷复合体试件断面的显微结构分析

目的 比较不同制备条件下形成的可切削渗透陶瓷(MIC)复合体断面显微结构,从显微结构层面提供与陶瓷强度相关的证据.方法 制备氧化铝基体,将可切削渗透云母玻璃渗透其中并晶化,根据烧结时间和渗透时间制备条件的不同分为:充分烧结渗透组、烧结时间不足组和渗透时间不足组.制作试件,测定其三点弯曲强度及弹性模量,并在扫描电镜下观察...     

不同垫底材料对髓腔固位冠抗折强度影响的相关力学分析

目的 研究经不同垫底材料行根管治疗后的上颌前磨牙，在全瓷髓腔固位冠修复后的抗折强度，为临床髓腔固位冠修复时垫底材料的选择提供理论参考。方法 收集30颗离体上颌第一前磨牙，进行根管治疗和牙体预备，根据垫底材料的不同随机分为复合树脂组、流体树脂组及玻璃离子组（n=10），采用CAD-CAM技术制作全瓷髓腔固位冠，对样本进行5000个周期冷热循环（5℃及55℃，各30 s）。随后用万能测试仪进行抗折强度的测试，记录折裂负荷值及折裂模式并对结果进行统计学分析。结果 复合树脂组、流体树脂组及玻璃离子组的折裂负荷值分别是(713.87±205.59) N、(777.70±229.48) N及（725.48±214.58） N,3组间的差异无统计学意义（P=0.784）；各组试件的折裂模式以可修复性为主。结论 髓腔固位冠修复后整体强度受垫底材料的影响较小，但临床可选用流动性及封闭性较好的材料（如流体树脂）。     

Effect of different luting procedures on the seating of ceramic inlays

This in vitro study evaluated the effect of different luting procedures on the proper seating of ceramic inlays and on the marginal seal through microleakage testing. Sixty mesial-, occlusal-, distal- (MOD) cavities were prepared in third molars, and distributed among four groups. In the control group 1, the cavity surface was treated with dentin and enamel bonding agents; ceramic inlays were placed into the cavity and light cured. In group 2, the dentin and enamel bonding agents were cured prior to the placing of the inlays, and following the insertion. In group 3, the inlays were luted without enamel bonding. In group 4, the inlays were cemented using a one-bottle bonding and two times light curing. The groups with only one time light curing at the end of the luting process exhibited the smallest luting space following cementation. The smallest dye penetration values were obtained for the two groups with separate light curing of the dentin bonding agent. Reducing the film thickness of polymerized dentin bonding agents, i.e. by changing the composition of the bonding agents, could facilitate proper seating of ceramic inlays together with a better marginal seal.     

Indentation fracture toughness and dynamic elastic moduli for commercial feldspathic dental porcelain materials.

OBJECTIVE: The purpose of this study was to evaluate and compare the indentation fracture toughness, true hardness and dynamic elastic moduli for 14 commercial dental porcelain materials. METHODS: The specimens were fired according to manufacturer instructions. The density of the specimens (n=3) was measured by means of the water displacement technique. Dynamic Young's shear and bulk moduli and Poisson's ratio (n=3) were measured using a non-destructive ultrasonic technique using 10 MHz lithium niobate crystals. The true hardness (n=3) was measured using a Knoop indenter and the fracture toughness (n=3) was determined using a Vickers indenter and a Tukon hardness tester. Statistical analysis of the data was conducted using ANOVA and a Student-Newman-Keuls (SNK) rank order multiple comparative test. RESULTS: The SNK rank test analysis for the mean dynamic Young's modulus and fracture toughness was able to separate 14 dental porcelain materials into seven and nine groups, respectively, at p=0.05. The elastic moduli, true hardness and indentation fracture toughness for opaque porcelains were significantly higher than incisal; and body materials at p=0.05. SIGNIFICANCE: The indentation fracture toughness and the ultrasonic test methods exhibit lower coefficient of variation compared to conventional methods and have considerable advantage for ceramic dental materials in that only small specimens are required to produce an acceptable number of data for statistical analysis.     

3种可切削树脂陶瓷复合材料机械性能比较

目的:采用体外研究方法,比较3种可切削树脂陶瓷复合材料的挠曲性能、断裂韧性及硬度。方法:选择Upcera Hyramic、3M Lava Ultimate、Vita Enamic和对照组玻璃陶瓷Vitablocs MarkⅡ,分别制作成长、宽、高为16 mm×4 mm×1.0 mm、2.0 mm的挠曲强度实验试件,17 mm×4 mm×3 mm的断裂韧性实验试件和厚度为4 mm的硬度实验试件。应用万能实验机以 0.5 mm/min 的加载速度,测量并计算试件挠曲强度值和断裂韧性值;应用显微硬度仪测量并计算硬度值;扫描电镜观察试件断面粗糙程度。采用SPSS17.0软件包对实验数据进行单因素方差分析。结果:厚度1 mm时,各组挠曲强度值为Hyramic（207.7515±13.12） MPa>Vita Enamic（182.0286 ±15.18）MPa>Lava Ultimate（145.8469±8.98）MPa>Vitablocs MarkⅡ（103.0542 ±18.19）MPa;挠曲模量为Vitablocs MarkⅡ（49.49±5.50）GPa>Vita Enamic（40.65±3.80）GPa>Hyramic（14.89±2.38）GPa>Lava Ultimate（7.09±1.24）GPa。厚度2 mm时,各组挠曲强度值为Hyramic（208.1986±25.07）MPa>Lava Ultimate（172.9297±12.73） MPa>Vitablocs MarkⅡ（158.6587±15.37）MPa>Vita Enamic（155.3670±13.77）MPa;挠曲模量为Vitablocs MarkⅡ（24.07±1.86）GPa>Vita Enamic（19.64±0.98）GPa>Hyramic（10.35±0.87）GPa>Lava Ultimate（8.68±0.86）GPa。断裂韧性为Vita Enamic（1.6357±0.16）MPa·m^1/2>Lava Ultimate（1.4286±0.11）MPa·m^1/2>Vitablocs MarkⅡ（1.3233±0.10）MPa·m^1/2>Hyramic（1.0614±0.09） MPa·m^1/2。各实验组硬度均显著低于对照组。结论:根据ISO 6872/2008,3种可切削树脂陶瓷复合材料均满足临床强度需要。其中,Hyramic在不同厚度条件下都表现出了较高的挠曲强度,是比较理想的后牙修复材料;而Vita Enamic在1 mm时具有更高的机械强度,且韧性好,适用于后牙咬合空间有限且咬合力较大的患者的修复,即贴面。     

3种树脂水门汀对可切削玻璃陶瓷粘接后断裂强度的影响

目的：研究3种树脂水门汀对可切削玻璃陶瓷粘接后断裂强度的影响。方法收集人离体磨牙60颗,垂直牙长轴磨除面釉质;将IPS e.max CAD瓷块加工成片状试件,用体积分数9.5%氢氟酸凝胶处理后,随机分成3组,每组20个,分别使用Multilink? N多功能粘接系统+Monobonds?S（A组）、RelyX?Ultimate树脂水门汀+Scotchbond?通用粘接剂（B组）、RelyX?Unicem 2树脂水门汀（C组）进行粘接;每组瓷片粘接后再分成1、2两个亚组,每组10个,A1、B1、C1组不进行冷热循环,A2、B2、C2组进行冷热循环。在万能试验机上测试所有瓷片的断裂载荷。结果 A1、A2、B1、B2、C1、C2组的试件断裂载荷值分别为：（1763±128）N、（1563±115）N、（1861±135）N、（1676±137）N、（1446±153）N、（1038±95）N。各组试件断裂载荷差异存在统计学意义（F=52.279,P＜0.001）,不同种树脂水门汀（F=94.104,P＜0.001）、冷热循环（F=63.818,P＜0.001）分别对瓷片断裂载荷有显著影响。LSD检验结果显示,A、B、C 3组试件断裂载荷值差异具有统计学意义（P＜0.05）,其中B组的断裂载荷最高,C组最低。结论不同种树脂水门汀对瓷片粘接后断裂强度的影响不同,同时处理瓷片和牙面的树脂水门汀可提高瓷片粘接后的断裂强度。冷热循环降低粘接后瓷片的断裂强度。     

氟金云母类切削陶瓷材料增强强度的研究

目的　研制一种新型的钙云母增强陶瓷 ,探讨提高氟金云母类切削陶瓷材料强度的方法。方法　以氟金云母类切削陶瓷DicorMGC的材料配方为基础 ,设计钙云母增强陶瓷的材料组成 ,通过基础玻璃制备、晶化热处理 ,得到玻璃陶瓷。用X射线衍射法分析陶瓷的晶相成分 ,用三点抗弯法测量材料的强度。结果　得到了钙云母增强的新型切削陶瓷 ,其三点抗弯强度达到 (2 10 2±14 7)MPa。结论　采用内部增强的方法可以提高氟金云母类切削陶瓷材料的强度     

陶瓷表面离子交换处理对不同基核的铸造陶瓷冠抗碎裂载荷影响

目的 研究陶瓷表面离子交换处理对不同基核的后牙铸造陶瓷冠抗碎裂载荷的影响.方法 16颗拔除的无龋坏磨牙进行标准基牙预备,以及自制金属代型、树脂代型、大小规格统一.制成厚度为1.5±0.1mm的Cerinate铸造陶瓷冠,上釉后对冠进行离子交换处理,以树脂粘固剂分别粘固于牙齿、金属代型、树脂代型上,垂直加压于全冠直至碎裂,经统计分析.结果 离子交换处理后,粘固于牙齿上的铸造陶瓷冠的抗碎裂载荷明显高于粘固于金属代型、树脂代型上的(P＜0.01).结论 离子交换处理可增加不同基核的铸造陶瓷冠的抗碎裂载荷.由于采用了树脂粘结剂材料,因此有利于提高铸造陶瓷冠与牙齿粘结后的整体强度.     

IPS-Empress 2玻璃陶瓷不同表面增韧处理的研究

目的:研究不同表面处理方法对IPS-Empress2玻璃陶瓷断裂韧性的影响.方法:模拟口腔潮湿的环境下,对IPS-Empress2玻璃陶瓷进行抛光、上釉、离子交换不同表面处理,采用压痕法(IM)求得不同表面处理后材料的断裂韧性,通过扫描电镜现察不同表面处理后陶瓷表面形态结构;采用X射线衍射仪对材料晶相改变进行定性分析;采用能谱分析仪对材料元素含量改变进行定量分析.结果:不同处理方法与对照组之间有高度统计学意义(P＜0.01);不同处理组间比较,上釉组与抛光组比较差异无显著性(P＞0.05);离子交换组与抛光组,上釉组比较差异有显著性(P＜0.05).结论:表面离子交换增强技术能显著增加IPS-Empress2玻璃陶瓷断裂韧性.其增强效果均优于表面抛光和上釉.表面离子交换组处理后陶瓷材料内部晶体含量增加,表面Na 被K 置换.     

Microshear bond strength of resin bonding systems to machinable ceramic with different surface treatments

PURPOSE: The bond strength and bond durability of two high-viscosity dual-curing resin luting agents with different surface treatments of ceramic were investigated. MATERIALS AND METHODS: GN-I machinable ceramic surfaces were treated with 37% phosphoric acid for 30 s (PA), 5% hydrofluoric acid for 5 s (HF-5), 10 s (HF-10), or 30 s (HF-30), or blasting with 50-microm Al2O3 for 10 s (AB). The roughness of the ceramic surface was measured. Treated ceramic surfaces were bonded with three resin bonding systems (RBS): Ceramic Primer/LinkmaxHV (CP/LMHV), Monobond S/VariolinkIIHV (MBS/VLIIHV), or MBS/Heliobond/VLIIHV (MBS/HB/VLIIHV). A microshear test was used to measure the bond strength after 24 h (TC 0) and subsequent thermocycling (TC 10,000 at 4 degrees C and 60 degrees C). ANOVA was performed for statistical analysis, with significance set at p < 0.05. RESULTS: For three RBSs, bond strength at TC O was not affected, regardless of ceramic surface treatment (p > 0.05). All combined groups of ceramic surface treatment and resin bonding system decreased after 10,000 thermal cycles, especially groups treated with alumina blasting and bonded with each of three RBSs (p < 0.05). MBS/HB/VLIIHV with each surface treatment did not improve the bond strength and durability compared with MBS/VLIIHV. CONCLUSION: CP/LMHV and MBS/VLIIHV obtained sufficient bond strength and bond durability to GN-I machinable ceramic by only cleaning with PA; the application of HB may not be necessary.     

Microleakage of different cementation techniques in Class V ceramic inlays

Microleakage between the restorative materials and the cavity walls of teeth remains a problem. The purpose of this study was to evaluate the microleakage around Class V ceramic inlay restoration using three different cementation techniques. Class V preparations were made on the buccal surfaces of 45 freshly extracted premolar teeth. The teeth were randomly divided into three groups of 15. In the first group, dentine bonding agent (DBA) (Clearfil Liner Bond 2V) was applied immediately after the tooth preparation (D-DBA). In the second group, DBA was applied to the prepared cavities while luting ceramic inlays (I-DBA). In the third group, DBA was not applied at either stage (No-DBA). Impressions were made and ceramic inlays (Ceramco II) fabricated and cemented in the Class V cavities. The restorations were stored in water at room temperature for 24 h. All restorations were thermocycled and then subjected to a dye penetration test. After sectioning, leakage at cavity/restoration interface was scored. Statistical analysis was performed using Kruskal-Wallis, Mann-Whitney U and Wilcoxon's signed tests. Results showed no significant difference among three different cementation techniques (P > 0.05). Microleakage at the dentine margins was greater than that at the enamel margins (P < 0.05).     

The effect of different reinforcements on the fracture toughness of materials for interim restorations

STATEMENT OF PROBLEM: Fracture of an interim fixed partial denture (FPD) may jeopardize the success of the interim prosthodontic treatment phase and cause patient discomfort. PURPOSE: The purpose of this study was to compare the fracture toughness of a polymethyl methacrylate (PMMA) resin and a bis-acryl composite (BAC) resin reinforced with stainless steel wire, glass fiber, and polyethylene fiber. MATERIAL AND METHODS: Four groups (n=13) of each of the 2 materials were prepared for the single-edge notch 3-point-bending test. Three groups had the different reinforcements, and the group without reinforcement served as the control. Using a universal testing machine, peak load to fracture was recorded and fracture toughness (K(IC)) was calculated in MNm(-1.5). Median K(IC) values were compared by means of nonparametric ANOVA (Kruskal-Wallis test, alpha=.05). RESULTS: For the controls, the fracture toughness for PMMA resin (K(IC)=27.9) was significantly lower (P<.01) than for BAC resin (K(IC)=31.2). Glass fibers and stainless steel wire reinforcements produced significantly higher fracture toughness for both PMMA (K(IC)=34.4, P<.01, and K(IC)=39.0, P<.001, respectively) and BAC resin (K(IC)=42.3, P<.001, and K(IC)=44.0, P<.001, respectively), but the polyethylene fibers did not (K(IC)=25.8, P>.10, for PMMA resin and K(IC)=33.1, P>.10, for BAC resin). There was no significant difference between the fracture toughness of the wire and glass fiber reinforcements for both interim materials (P>.10 in both instances). CONCLUSIONS: Of the 3 reinforcement methods evaluated, wire and glass fiber reinforced the PMMA and BAC resin materials best.     

Flexural strength and moduli of hypoallergenic denture base materials

STATEMENT OF PROBLEM: Hypoallergenic denture base materials show no residual methyl methacrylate (MMA) or significantly lower residual MMA monomer content compared to polymethyl methacrylate-based (PMMA) heat-polymerizing acrylic resin. There is insufficient knowledge of the mechanical properties of hypoallergenic denture base materials to warrant their use in place of PMMA-based acrylic resins for patients with allergic reaction to MMA. PURPOSE: This in vitro study compared flexural strength and flexural modulus of 4 hypoallergenic denture base materials with flexural strength/modulus of a PMMA heat-polymerizing acrylic resin. MATERIAL AND METHODS: The following denture base resins were examined: Sinomer (heat-polymerized, modified methacrylate), Polyan (thermoplastic, modified methacrylate), Promysan (thermoplastic, enterephthalate-based), Microbase (microwave-polymerized, polyurethane-based), and Paladon 65 (heat-polymerized, methacrylate, control group). Specimens of each material were tested for flexural strength and flexural modulus (MPa, n = 5) according to ISO 1567:1999. The data were analyzed with 1-way analysis of variance and the Bonferroni-Dunn multiple comparisons post hoc analysis for each test variable (alpha=.05). RESULTS: Flexural strength of Microbase (67.2 +/- 5.3 MPa) was significantly lower than Paladon 65 (78.6 +/- 5.5 MPa, P <.0001). Flexural strength of Polyan (79.7 +/- 4.2 MPa, P =.599), Promysan (83.5 +/- 3.8 MPa, P =.412), and Sinomer (72.3 +/- 2.1 MPa, P =.015) did not differ significantly from the control group. Significantly lower flexural modulus was obtained from Sinomer (1720 +/- 30 MPa, P =.0007) compared to the PMMA control group (2050 +/- 40 MPa), whereas the flexural modulus of Promysan (2350 +/- 170 MPa, P =.0005) was significantly higher than the PMMA material. Microbase (2100 +/- 210 MPa, P =.373) and Polyan (2070 +/- 60 MPa, P =.577) exhibited flexural modulus similar to the PMMA material. The tested denture base materials fulfilled the requirements regarding flexural strength (>65 MPa). With the exception of Sinomer, the tested denture base resins passed the requirements of ISO 1567 regarding flexural modulus (>2000 MPa). CONCLUSION: Flexural modulus of Promysan was significantly higher than the PMMA material. Microbase and Sinomer exhibited significantly lower flexural strength and flexural modulus, respectively, than PMMA. The other groups did not differ significantly from the control group.     

不同基底对Sirona CEREC Blocs可切削陶瓷断裂强度的影响

目的：研究不同材料及形状的基底代型对Sirona CEREC Blocs可切削陶瓷断裂强度的影响.方法：选择人第三磨牙12颗,随机分为2组.第1组垂直于牙长轴去除骀面釉质,第2组制成牙本质片.用FiltekZ250光固化复合树脂分别复制第一组和第二组试件各6颗.用Multilink9 Speed树脂粘接剂将瓷片粘接于所有基底代型试件上,粘接1h后储存于37℃蒸馏水中24h,然后测试瓷片断裂强度值,并在光学显微镜下观察粘接破坏情况.结果：树脂牙代型做基底时,瓷片的断裂载荷最高,与离体牙组差异有统计学意义（P＜0.05）,但与树脂片组间差异无统计学意义（P＞0.05）.离体牙组的瓷片断裂载荷高于牙本质片组,差异有统计学意义（P＜0.05）.结论：不同材料及形状的基底代型对全瓷材料的强度均有影响,光固化复合树脂做基底时无论是牙状还是片状,瓷片的断裂载荷都高于对应的离体牙组.