干湿环境下循环载荷对氧化锆-饰面瓷叠层瓷结构抗弯强度的影响

目的:比较干燥和唾液浸泡环境下动态循环加载对氧化锆/饰面瓷叠层瓷结构抗弯强度的影响。方法:制作氧化锆/饰面瓷叠层瓷结构圆片试件30个,随机分为干燥和唾液浸泡两组,循环加载10000次后进行双轴弯曲测试,光学显微镜观察其表面损伤及断裂面形貌。结果:在干燥环境下,经过10000次循环疲劳实验后,表面裂纹主要为赫兹锥状裂纹,破碎模式主要为完全断裂。而在唾液环境下,经过疲劳实验后,表面裂纹除了赫兹锥状裂纹外还有环状裂纹,破碎模式主要为饰瓷脱瓷,而且在干燥环境下的样品抗弯强度比在湿润环境下平均要高70%。结论:口腔内氧化锆全瓷修复材料长期使用后出现性能下降的疲劳现象,与牙科陶瓷修复体处于充满唾液的水环境有关。     

Effect of Different Cements on the Biomechanical Behavior of Teeth Restored with Cast Dowel‐and‐Cores—In Vitro and FEA Analysis

Purpose: To test the hypothesis that the type of cement used for fixation of cast dowel‐and‐cores might influence fracture resistance, fracture mode, and stress distribution of single‐rooted teeth restored with this class of metallic dowels. Materials and Methods: The coronal portion was removed from 40 bovine incisors, leaving a 15 mm root. After endodontic treatment and standardized root canal relief at 10 mm, specimens were embedded in polystyrene resin, and the periodontal ligament was simulated with polyether impression material. The specimens were randomly divided into four groups (n = 10), and restored with Cu–Al cast dowel‐and‐cores cemented with one of four options: conventional glass ionomer cement (GI); resin‐modified glass ionomer cement (GR); dual‐cure resin cement (RC); or zinc‐phosphate cement (ZP). Sequentially, fracture resistance of the specimens was tested with a tangential load at a 135° angle with a 0.5 mm/min crosshead speed. Data were analyzed using one‐way analysis of variance (ANOVA) and the Fisher test. Two‐dimensional finite element analysis (2D‐FEA) was then performed with representative models of each group simulating a 100 μm cement layer. Results were analyzed based on von Mises stress distribution criteria. Results: The mean fracture resistance values were (in N): RC, 838.2 ± 135.9; GI, 772.4 ± 169.8; GR, 613.4 ± 157.5; ZP, 643.6 ± 106.7. FEA revealed that RC and GR presented lower stress values than ZP and GI. The higher stress concentration was coincident with more catastrophic failures, and consequently, with lower fracture resistance values. Conclusions: The type of cement influenced fracture resistance, failure mode, and stress distribution on teeth restored with cast dowel‐and‐cores.     

Effect of Obturating Systems,Dowel Materials,and Adhesive Luting Techniques on the Resistance to Fracture of Endodontically Treated Teeth

Purpose: The aim of this study was to assess the role of obturating systems, dowel materials, and adhesive techniques on the resistance to fracture of endodontically treated teeth. Material and Methods: Eighty maxillary central incisors were selected and randomly divided into two groups according to the obturating system (n = 40); group I: gutta‐percha and Roeko sealer; group II: RealSeal. Both groups were further subdivided into two subgroups; subgroup A: using ceramic dowels (Cosmopost); subgroup B using fiber dowels (Easy Post). Each subgroup was assigned to two divisions according to the adhesive luting technique; division V (total‐etch) Variolink II resin cement; division U (self‐adhesive) RelyX Unicem. Composite core build‐up was made using a core former. Each specimen was loaded 2 mm from its incisal edge on the palatal side at a 135° angle with the long axis of the tooth using a universal testing machine with a load cell of 5 KN at a crosshead speed of 0.5 mm/min until fracture. Failure loads were recorded in N. Scanning electron microscopic examination at the dentin/resin interface (1000x) was performed. Three‐way ANOVA was used to test the effect of obturating system, dowel material, adhesive technique, and their interactions (obturating system * dowel material, obturating system * adhesive, dowel material * adhesive, obturating system * dowel material * adhesive). Duncan's test was used for pairwise comparison. The significance level was set at p≤ 0.05. Statistical analysis was performed with SPSS 16.0. Results : The mean resistance to fracture (617.4 N) was statistically significantly higher in the ceramic dowel with gutta‐percha and Variolink (GP/C/V) group than in the other groups. The RealSeal and RelyX fiber dowel group's mean resistance was the lowest and was significantly lower than the other groups. Conclusions : In this study, three factors played a part in enhancing the resistance to fracture of endodontically treated teeth. High resistance to fracture was achieved when ceramic dowels were luted with total‐etch technique in gutta‐percha‐obturated teeth.     

分根术联合铸造桩核冠技术保存修复重度缺损下颌磨牙

目的：评价分根术联合铸造桩核冠技术保存修复重度缺损下颌磨牙临床效果。方法：对23颗符合入选标准的重度缺损下颌磨牙进行根管和牙周基础治疗后予以分根,必要时进行牙半切除术或牙冠延长术。6周后,再进行铸造桩核联冠修复。结果：1颗患牙失败,另1颗失访。其余患牙都经过2年以上的临床观察,均能进行正常的咀嚼功能,无明显不适。结论：分根术联合铸造桩核冠技术保存修复重度缺损下颌磨牙疗效确切,可行。     

钾铝硅系统牙科玻璃陶瓷嵌体边缘适合性的实验研究

目的：研究双固化粘结剂粘结钾铝硅（K2O-Al2O3-SiO2）系统牙科玻璃陶瓷的微渗漏情况。方法：制备钾铝硅系统牙科玻璃陶瓷瓷锭;选择清理24颗离体牙,即刻完成根管充填;在每颗离体牙的颊舌面颈部各预备一个V类洞型;将离体牙随机分成两组,第1组离体牙不预备粘结间隙、第2组离体牙预备约100μm的粘结间隙;用＂热压铸入＂法制作牙科陶瓷嵌体,用VariolinkⅡ双固化粘结剂粘结;从每组样本中随机抽取6颗离体牙,浸入25℃的品红溶液中24h,测量染色剂在洞壁的染色深度;另外12颗离体牙浸入25℃的复方生理盐水中2个月,在SEM下观察样本粘结剂的丧失情况。结果：染色渗透实验和SEM分析显示,两组样本均在陶瓷/粘结剂界面产生较高的边缘封闭质量（组1样本中陶瓷/粘结剂界面裂隙量的平均值为（12.4±4.5）%,明显低于组1样本中粘结剂/牙体界面裂隙量的平均值（38.9±8.8）%;组2样本中陶瓷/粘结剂界面裂隙量的平均值为（32.6±15.8）%,明显低于组2样本中粘结剂/牙体界面裂隙量平均值（67.9±23.1）%;没有粘结间隙的样本比有粘结间隙的样本具有更好的边缘适合性能（组1样本粘结剂裂隙量的平均值（15.7±7.3）%,明显低于组2样本中者（57.4±19.5）%。结论：较大的粘结间隙不能完全补偿双固化粘结系统树脂的聚合收缩,在使用双固化粘结系统粘结K2O-Al2O3-SiO2系统牙科玻璃陶瓷嵌体时应该避免制备较大的粘结间隙。     

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提要：全瓷修复因其优良的美观效果及生物相容性等诸多优点,成为口腔修复的发展趋势之一。各类全瓷修复体通过黏结性树脂黏结于牙体表面,合理有效的瓷表面处理技术是影响瓷与树脂黏结的首要因素。本文就牙科陶瓷几种表面处理方法的研究及其在口腔修复中的应用做一综述。     

肩台瓷金瓷冠的临床应用效果和边缘密合度研究

【目的】评价肩台瓷金瓷冠的临床修复效果和边缘密合度。【方法】对临床上38个肩台瓷金瓷冠和40个普通金瓷冠修复后用硅胶获得间隙模型,然后用金属显微镜在放大100倍下进行测量,且1年后对修复效果进行复查随访。【结果】两组间的冠边缘密合度差异无统计学意义;两组间在边缘变色和牙龈灰线方面有显著统计学差异。【结论】应用肩台瓷可以提高金瓷冠的美观效果并可达到良好的边缘密合性。     

光源对天然牙与两种不同金属基底烤瓷冠颜色的影响

目的:研究光源改变后,天然牙与两种金属烤瓷全冠的颜色变化及它们之间是否存在同色异谱现象.方法:采用PR-650分光光度仪对A2色天然牙和A2色金合金、金沉积烤瓷全冠在参照体D65光源与A光源、CWF光源下的颜色参数L、a、b(国际发光照明委员会1976 L*a*b*系统)进行测量,比较其光谱反射曲线,同时通过计算特殊同色异谱指数来分析它们的同色异谱效应.结果:A2色天然牙和两种金属烤瓷全冠的L、a、b值随着光源的改变而改变,二者的变化趋势不完全一致,其差异有统计学意义;天然牙和金合金、金沉积烤瓷全冠之间的光谱反射曲线形状有较大区别,不同金属烤瓷全冠之间的光谱反射曲线形状也有一些区别,但是每条曲线都有五个以上的交叉点,在特定光源下可以达到同色,具有同色异谱效应;A2色天然牙与金合金、金沉积金属烤瓷全冠之间间色异谱指数在A光源下为2.03和2.46.在CWF光源下2.84和2.89.结论:光源对天然牙和金合金、金沉积烤瓷全冠的颜色有较大影响,A2色天然牙与两种金属烤瓷全冠之间存在较明显的同色异谱效应.