一种新型牙科二硅酸锂玻璃陶瓷的微观结构分析

目的:分析牙科二硅酸锂玻璃陶瓷的微观结构,探讨其可能的自增韧机制。方法:使用X射线衍射仪分析一种新型二硅酸锂玻璃陶瓷及IPS e.max Press LT和MO瓷块的物相组成,并使用扫描电镜观察其表面特征和裂纹扩展方式。结果:3种玻璃陶瓷的主晶相均为Li2Si2O5,次晶相均为Li2SiO3和Li3PO4。Li2Si2O5晶体均呈棒状,交错排列,形成互锁微结构。新型玻璃陶瓷的晶体尺寸大于LT和MO瓷块,其表面孔隙缺陷较后两者少而深。裂纹在这3种玻璃陶瓷中主要沿着晶体间较薄弱的玻璃相扩展。结论:新型玻璃陶瓷与IPS e.max Press LT和MO瓷块的微观结构相似,长棒状的Li2Si2O5晶体所形成的互锁微结构,以及内部的残余应力可对其起到增强增韧的作用。     

一种新型牙科二硅酸锂玻璃陶瓷的制备及性能分析

目的:介绍一种新型牙科二硅酸锂玻璃陶瓷的制备方法,并对其性能进行比较分析。方法:用烧结法二次着色工艺制备A2色新型玻璃陶瓷。对新型玻璃陶瓷和IPS e.max Press瓷块(LT A2、MO1和HO1)的弯曲强度、密度、弹性模量、硬度、断裂韧性、透明度及微观结构进行测量分析。结果:新型玻璃陶瓷除弯曲强度(315 MPa)低于MO瓷块(338 MPa)外(P<0.05),其余各项机械性能均与LT和MO瓷块相近(P>0.05)。新型玻璃陶瓷的透明度TP值(21.2)高于HO瓷块(16.5),但低于LT(27.8)和MO瓷块(27.5)(P<0.05)。新型玻璃陶瓷和IPS e.max Press瓷块的微观结构均表现为棒状的Li2Si2O5晶体交错排列,形成互锁微结构。结论:新型玻璃陶瓷的机械性能和微观结构与IPS e.max Press相近,透明度介于MO和HO瓷块之间,能满足临床要求。     

氧化磷含量对新型牙科玻璃陶瓷微观结构和强度的影响

目的：分析不同氧化磷含量对新型牙科二硅酸锂玻璃陶瓷微观结构和强度的影响。方法：通过调控Li2O、SiO2、K2O、Al2O3、ZrO2-P2O5玻璃系统中氧化磷（P2O5）的含量（0.5%,1.0%,1.5%和2.0%）,并进行相应的热处理,应用X射线衍射技术（XRD）,电子扫描显微术（SEM）分析制备的各组玻璃陶瓷的微观形貌,根据ISO6872标准测试玻璃陶瓷的弯曲强度,进行统计学分析。结果：各组玻璃陶瓷样本的主晶相均为二硅酸锂（Li2Si2O5）,随着P2O5含量的改变,析出晶体的形貌和分布有显著不同。1.0%组玻璃陶瓷具有最高的弯曲强度值。结论：通过调控P2O5含量,可制备具有高强度和适宜微观形貌的二硅酸锂玻璃陶瓷。     

IPS-Empress 2 玻璃陶瓷结构及性能的研究

目的 研究新型IPS-Empress 2牙科高强度陶瓷的显微结构和机械性能。方法采用原子力显微镜、扫描电子显微镜和X射线衍射仪，分析IPS-Empress 2的显微结构和晶相，用三点弯曲实验和压痕法测试其弯曲强度和断裂韧性。结果IPS-Empress 2玻璃陶瓷主要由二硅酸锂晶体和磷酸锂晶体组成，二者形成相互交错的三维网络式结构；这种玻璃陶瓷在热压铸前后晶体相保持不变，其三点弯曲强度和断裂韧性分别为300MPa和3．1MPam^1/2。结论IPS-Empress 2玻璃陶瓷的高强度和韧性与高含量的二硅酸锂晶体、相互锁结的网络结构和裂纹偏转有关。     

二硅酸锂玻璃陶瓷在前牙过小牙修复的临床应用

目的 评价二硅酸锂玻璃陶瓷在前牙过小牙修复中的临床应用。方法 对45例患者的87颗牙使用IPS e.max Press铸瓷贴面修复,于修复完成后1、6、12、24、36个月进行复查,参见改良加利福尼亚牙科协会（CDA）/Ryge标准进行评价,检查包括边缘适合性,瓷表面质地,颜色匹配,牙敏感症状和牙龈健康情况五个方面。结果 1个月复查时,11颗基牙出现牙敏感症状,予脱敏治疗处理后症状明显改善。6个月复查牙龈情况,9颗基牙出现牙龈炎症,经卫生宣教及系统牙周治疗后症状好转。1个月及6个月复查时,所有贴面边缘密合,完整性好,瓷表面质地良好。12个月复查时出现1颗贴面完整脱落,清洁处理后重新粘固未再次发生脱落。24个月复查时,一患者进食过程中前牙误咬硬物发生修复体崩折,牙本质暴露,予重新制作贴面进行修复。观察到36个月时7颗基牙出现不同程度龈退缩。结论 二硅酸锂玻璃陶瓷贴面适用于前牙区过小牙修复,可获得良好的临床效果和远期预后。     

铸造玻璃陶瓷的临床应用

铸造玻璃陶瓷简称铸造陶瓷(Castable),是当今口腔修复中最新的修复材料之一.由于这种材料在结构上与烤瓷相似,而且采用失蜡法来铸造修复体,制成修复体的各项机械性能如硬度、抗压强度等与牙釉质较接近,在形态准确性及边缘密合性上明显优于烤瓷.所以该材料一经出现,立刻引起口腔界的重视.我们在华东医院引进国外设备、材料的基础上,开展了铸造陶瓷的临床应用,现就将1992年10月至1993年12月间所进行的临床应用作一报告.     

铸造玻璃陶瓷在口腔修复中的应用现状

铸造玻璃陶瓷因有与牙釉质接近的透明度和折射率，使用其制做的嵌体，牙面，全冠，桥的外观颜色与自然牙相关无几，达到最佳这效果。各国学者都对其进行了研究，开发出各自的产品。随着临床应用，修复体碎裂则成了限制其发展的障碍。     

不同表面处理对国产口腔二硅酸锂玻璃陶瓷与树脂水门汀粘接强度的影响

目的探讨不同表面处理方式对国产口腔二硅酸锂玻璃陶瓷与树脂水门汀之间粘接强度的影响。方法选择尺寸为15 mm×13 mm×3 mm的二硅酸锂玻璃陶瓷试件,分别进行酸蚀实验和酸蚀后偶联处理实验。酸蚀实验选择128个玻璃陶瓷试件,按照随机数表法随机分为8个处理时间点(每个时间点样本量为16),使用4.5%氢氟酸分别进行0(对照)、10、20、30、40、60、120及180 s的表面酸蚀,再将酸蚀后试件分为偶联处理组(涂布硅烷偶联剂)和无偶联处理组(不涂布硅烷偶联剂)(每组样本量均为8),分别制作粘接试件;测试粘接强度并分析断裂模式。另选8个玻璃陶瓷试件分别行上述时间点酸蚀后进行扫描电镜观察。选择酸蚀实验中的最佳酸蚀时间,进行酸蚀后偶联处理实验。选择玻璃陶瓷试件24个,4.5%氢氟酸酸蚀后涂布偶联剂,分别进行室温放置、60及100℃热风处理60 s(每组样本量为8),之后制作粘接试件;测试粘接强度并分析断裂模式。另选3个试件分别进行酸蚀后偶联处理实验相应处理后再行红外光谱分析。结果无论是否使用偶联剂,试件在氢氟酸酸蚀30 s时均可获得最大粘接强度;酸蚀30 s条件下,偶联处理组粘接强度[(25.91±4.30)MPa]显著大于无偶联处理组[(20.27±4.92)MPa](P<0.05);若酸蚀时间过长(>30 s),则粘接强度下降明显,试件表面显示过酸蚀的微观形貌。酸蚀后偶联处理实验显示,60℃热风组粘接强度最大[(28.70±5.32)MPa],显著大于室温组[(20.08±3.64)MPa]和100℃热风组[(25.64±4.86)MPa](P<0.05),且试件断裂模式均为内聚破坏;红外光谱分析显示,60℃热风组试件表面Si—O—Si键生成量最多,100℃热风组次之,室温组最低。结论4.5%氢氟酸酸蚀二硅酸锂玻璃陶瓷的最佳酸蚀时间为30 s,涂布硅烷偶联剂可获得较理想的粘接效果;60℃热风处理可进一步提高二硅酸锂玻璃陶瓷与树脂水门汀之间的粘接强度。     

Effect of repeated firings and staining on the mechanical behavior and composition of lithium disilicate

ObjectiveTo evaluate the composition, flexural strength and fatigue behaviour of lithium disilicate ceramic (LD) after repeated firings and different staining techniques.MethodsLD discs were fabricated and divided according to number of firing cycles and staining technique: CO - control, discs were crystallized (850 °C/10 min); SC – single-step characterization – crystallization and staining (applied with a thin brush) were performed in a single step with one firing cycle (850 °C/10 min); and DC – double-step characterization – crystallization firing cycle was performed first (850 °C/10 min), followed by staining firing cycle (770 °C/90 s). Specimens were fired two, four or six times (one crystallization firing cycle and one, three or five staining firing cycles), resulting into 9 groups (n = 30): COII, COIV, COVI, SCII, SCIV, SCVI, DCII, DCIV and DCVI. The composition of the specimens was investigated (EDS, XRD, Raman spectroscopy), and the biaxial flexural strength (n = 10) and staircase tests (n = 20, 5 × 10⁴ cycles, 5 Hz) were performed. Data were subjected to one-way ANOVA and Tukey’s test (α = 0.05).ResultsEDS and XRD revealed amorphous content for stained groups. Biaxial flexural strength was not affected by repeated firings in any group, but stained groups presented lower flexural strength than control groups (p = 0.001). The fatigue limit results decreased in all groups compared to flexural strength. SC groups showed similar (SCII and SCIV) or even higher fatigue limits (SCVI) than the control groups, and DC showed the lowest fatigue limit values. SEM and Raman suggested that the interfaces between staining and the LD showed only an overlap for the DC groups, whereas for the SC it was suggested an interaction between the stain and the LD.SignificanceRepeated firings did not result in decreased lithium disilicate flexural strength.Staining affected flexural strength and also resulted in increased amorphous content in the characterized specimens. Single-step staining resulted in the highest fatigue limit.     

Biaxial flexural strength and translucent characteristics of dental lithium disilicate glass ceramics with different translucencies

PurposeThe aim of this study was to evaluate the biaxial flexural strength and translucent characteristics of dental lithium disilicate glass ceramics with different translucencies.MethodsTwo heat pressed lithium disilicate glass ceramics (IPS e.max Press and an experimental ceramic) and one computer aided design/ computer aided manufacture (CAD/CAM) lithium disilicate glass ceramic (IPS e.max CAD) with different translucencies were evaluated. Disk-shaped specimens of each group were subjected to a biaxial flexural strength (BFS) test. Translucent parameters (TP) were also tested at 0.5 mm and 1.0 mm thickness, respectively. X-ray diffraction (XRD) and SEM were used for crystalline and microstructural analysis.ResultsBFS values of two heat pressed lithium disilicate glass ceramics were significantly higher than the CAD/CAM counterpart. No difference in BFS between two heat pressed glass ceramic was found. There were significant differences in BFS and TP values among the tested subgroups with different translucencies for IPS e.max Press and IPS e.max CAD. No difference in crystalline composition was found among the tested glass ceramics, but microstructure with shorter and wider crystal was revealed for IPS e.max CAD ceramics.ConclusionsLithium disilicate glass ceramics with different translucencies demonstrated different BFS and TP values.     

Flexural resistance of heat-pressed and CAD-CAM lithium disilicate with different translucencies

Objective

To compare flexural strength of CAD-CAM and heat-pressed lithium disilicate.

Interfacial fracture toughness of different resin cements bonded to a lithium disilicate glass ceramic

Objectives

To evaluate the effect of HF acid etching and silane treatment on the interfacial fracture toughness of a self-adhesive and two conventional resin-based cements bonded to a lithium disilicate glass ceramic.

Methods

Lithium disilicate glass ceramic discs were prepared with two different surface preparations consisting of gritblasted with aluminium oxide, and gritblasted and etched with hydrofluoric acid. Ceramic surfaces with a chevron shaped circular hole were treated by an optimized silane treatment followed by an unfilled resin and then three different resin cements (Variolink II, Panavia F2, and Multilink Sprint). Specimens were kept in distilled water at 37 °C for 24 h and then subjected to thermocycling. The interfacial fracture toughness was measured and mode of failures was also examined. Data were analysed using analysis of variance followed by T-test analysis.

Results

No statistically significant difference in the mean fracture toughness values between the gritblasted and gritblasted and etched surfaces for Variolink II resin cement was found (P > 0.05). For the gritblasted ceramic surfaces, no significant difference in the mean fracture toughness values between Panavia F2 and Variolink II was observed (P > 0.05). For the gritblasted and etched ceramic surfaces, a significantly higher fracture toughness for Panavia F2 than the other cements was found (P < 0.05).

Conclusions

The interfacial fracture toughness for the lithium disilicate glass ceramic system was affected by the surface treatment and the type of luting agent. Dual-cured resin cements demonstrated a better bonding efficacy to the lithium disilicate glass ceramic compared to the self-adhesive resin cement.

Clinical significance

The lithium disilicate glass ceramic surfaces should be gritblasted and etched to get the best bond when used with Panavia F2 and Multilink Sprint resin cements, whereas for the Variolink II only gritblasting is required. The best bond overall is achieved with Panavia F2.     

Marginal adaptation of restorative resins in acid etched cavities

The purpose of the present work was to investigate the wall-to-wall polymerization contraction of restorative resins placed in acid etched cavities and to study the effect of water absorption and temperature changes on the formation of marginal gaps on such fillings. Fillings made in extracted human teeth were examined microscopically. Before filling the cavities including 1.5–2 mm peripheral enamel were etched with 35% H₃PO₄. When polished and examined immediately after setting, fillings of a number of brands showed no marginal gaps. Gaps due to continued polymerization were formed around some of these fillings after 1 day's storage in water at 37°C. These gaps did not close as a consequence of hygroscopic expansion of the fillings. Around fillings of the brands where no gaps were present immediately after setting, gaps were formed by cooling from 37 to 23°C. One day's storage in water at 37°C before polishing generally reduced the frequency of marginal gaps both directly and after cooling. Heating of the fillings increased the risk of gaps being formed by a subsequent cooling.     

GI—Ⅱ型牙用玻璃渗透氧化铝陶瓷的生物安全性评价

目的：研究评价GI－Ⅱ型牙用玻璃渗透氧化铝陶瓷材料的生物安全性。方法：利用仓鼠,NIH纯系小鼠,豚鼠等实验动物对材料进行急性毒性,细胞毒性,致敏性,口腔粘膜刺激性,溶血,微核等试验研究,结果：材料的溶血率低于5％,有良好的血液相容性,无明显的细胞毒性作用,未见任何急性毒性反应,对口腔粘膜无刺激性,无致敏性,微核试验未见潜在致突变性。结论：GI－II型牙用玻璃渗透氧化铝陶瓷材料的临床应用具有可靠的生物安全性。     

Microstructural development during heat treatment of a commercially available dental-grade lithium disilicate glass-ceramic

Objective

To elucidate the microstructural evolution of a commercial dental-grade lithium disilicate glass-ceramic using a wide battery of in-situ and ex-situ characterization techniques.

同色号树脂粘接剂与试色糊剂颜色和透光率一致性的对比研究

目的 分别测定单组分光固化树脂粘接剂与同色号试色糊剂的颜色与透光率,评价其一致性,以期为临床合理选择树脂粘接剂提供依据.方法 将树脂粘接剂A(Variolink Veneer)的7种色号(HV+3、HV+2、HV+1、MVO、LV-1、LV-2、LV-3)和树脂粘接剂B(Relyx Veneer)的5种色号(A1、A3、BO.5、WO、TR)与同色号试色糊剂注入直径10 mm、厚度2 mm的白色背景模具中,表面覆盖经筛检的盖玻片,对树脂进行光固化处理,分别测量色度值并计算同色号树脂粘接剂与试色糊剂的色度差(△L*、△a*、△b*)和总色差(△E),对总色差△E进行Tukey's多重t检验.将树脂粘接剂与试色糊剂制成厚0.15 mm的薄层,测量其在380～780 μm入射条件下的透光率,计算平均透光率,对同色号树脂粘接剂和试色糊剂的平均透光率进行配对t检验.结果 Tukey's多重t检验显示,TR色号树脂粘接剂与试色糊剂颜色总色差(1.11±0.18)的评价为a,LV-1(6.38±0.45)、LV-2(5.94±0.19)、Al(7.54±0.20)、WO(4.24±1.14)为b,HV+2(10.90±0.41)、HV+1(11.48±0.17)、LV-3(10.69±0.13)、BO.5(13.26±0.21)为c,HV+3(21.94±0.21)、MV0(29.78±0.14)、A3(32.67±0.19)为d(a、b、c、d代表树脂粘接剂与试色糊剂的颜色一致性依次降低).配对t检验显示,12种色号试件中7种色号(A1、TR、HV+3、HV+2、HV+1、LV-2、LV-3)树脂粘接剂和试色糊剂的平均透光率差异有统计学意义(P＜0.01).结论 本项研究中的大部分色号树脂粘接剂与同色号试色糊剂的颜色及透光率的一致性较低,在对颜色效果要求较高的病例中应谨慎使用.     

Immediate Placement of Dental Implants in the Esthetic Zone: A Systematic Review and Pooled Analysis

Background: Research interest on immediate placement of dental implants has shifted from implant survival toward optimal preservation of soft and hard tissues. The aim of this study is to systematically assess the condition of implant survival, peri‐implant hard and soft tissue changes, esthetic outcome, and patient satisfaction of immediately placed single‐tooth implants in the esthetic zone. Methods: MEDLINE, EMBASE, and CENTRAL databases were searched for publications up to June 2013. Studies reporting on implant survival, changes in hard and soft peri‐implant tissues, esthetic outcome, and patient satisfaction were considered. A pooled analysis was performed to identify factors associated with survival and peri‐implant tissue changes after immediate implant placement. Results: Thirty‐four studies were considered eligible. Immediate placement of single‐tooth implants in the esthetic zone was accompanied by excellent 1‐year implant survival (97.1%, 95% confidence interval [CI]: 0.958 to 0.980). Mean marginal peri‐implant bone loss was 0.81 ± 0.48 mm, mean loss of interproximal peri‐implant mucosa level was 0.38 ± 0.23 mm, and mean loss of peri‐implant midfacial mucosa level was 0.54 ± 0.39 mm. Regression analysis revealed that delayed provisionalization (odds ratio [OR] 58.03, 95% CI: 8.05 to 418.41, P <0.000), use of a flap (OR 19.87, 95% CI: 10.21 to 38.66, P <0.000), and use of a connective tissue graft (OR 4.56, 95% CI: 1.72 to 12.08, P <0.002) were associated with marginal peri‐implant bone‐level change >0.50 mm. Because of underreporting, esthetic results and patient outcome did not allow for reliable analysis. Conclusion: Immediate placement with immediate provisionalization of dental implants in the esthetic zone results in excellent short‐term treatment outcome in terms of implant survival and minimal change of peri‐implant soft and hard tissue dimensions.