自酸蚀和全酸蚀树脂粘结剂对石英纤维桩固位力影响的比较研究

目的：比较自酸蚀和全酸蚀树脂粘结剂对石英纤维粘结后粘结强度的差异,为临床合理选择粘结剂提供实验依据。方法：选用正常人离体上颌中切牙16颗,经体外完善根管预备并完成根管充填后,于邻面釉牙骨质界水平截断并预备桩道,然后分别包埋在自凝塑料柱内固定。16颗离体牙被随机分成两组,每组各8例,分别用自酸蚀和全酸蚀树脂粘结剂粘结石英纤维桩于牙根桩道内,用力学试验机以1mm／min速度牵拉纤维桩,记录纤维桩与牙根脱离时的最大载荷并进行t检验统计分析。结果：自酸蚀树脂粘结剂石英纤维桩组的粘结强度（246．48N±103．58N）高于全酸蚀粘结剂石英纤维桩组（30．46N±5．41N）,完全随机设计资料的t检验显示P〈0．01,两者差异有显著性。结论：自酸蚀树脂粘结剂石英纤维桩的粘结强度明显优于全酸蚀石英纤维桩粘结剂。     

根管壁表面处理和不同粘结系统对纤维桩粘结强度的影响

目的研究不同根管牙本质壁表面处理方法及使用不同粘结系统对石英纤维桩粘结时根管不同部位剪切粘结强度的影响。方法36颗完整离体上中切牙唇侧釉牙骨质界冠方2.0mm处截冠后行根管治疗。专用钻根管预备,酸蚀后,分别采用生理盐水60s(对照组)、10%次氯酸钠(NaOCl)溶液60s、17%乙二胺四乙酸(EDTA)溶液60s与5.25%NaOCl溶液60s联用的根管壁处理方法,结合DUOLINK树脂粘结剂或LUXACORE核材料按析因设计配对行石英纤维桩粘结修复。包埋并切片后,置于MTSSynergie综合测试仪上采用1mm微推出法对不同根管段行剪切粘结实验,记录数值并行统计学分析。结果剪切粘结强度依次为(MPa):6.29±3.77,9.67±3.94,8.07±3.59,2.59±2.04,5.46±3.09,5.80±3.56。10%NaOCl处理组、17%EDTA溶液与5.25%NaOCl溶液联用组剪切粘结强度均明显增强(P<0.0001);DUOLINK树脂粘结剂组剪切粘结强度优于LUXACORE核材料组(P<0.0001);所有实验组中,剪切粘结强度自根管冠方向根方逐渐减弱。结论单独使用10%NaOCl溶液、17%EDTA溶液与5.25%NaOCl溶液联用处理根管壁增强了石英纤维桩修复根管不同部位尤其是根尖的剪切粘结强度。     

全酸蚀粘结系统与自粘结系统玻璃纤维桩核修复抗剪切强度的对比研究

目的 研究全酸蚀粘结系统与自粘结系统玻璃纤维桩的剪切粘结强度,为临床合理选择纤维桩及修复材料提供依据.方法 选取因牙周病或因正畸减数拔除的无龋、无裂纹前磨牙30颗,随机分为A、B两组,每组15颗.A组用全酸蚀粘结系统,用LuxaBond-Total Etch粘结剂和LuxaCore Z-Dual树脂粘结直径1.25 mm的LuxaPost玻璃纤维桩于离体牙根管内.B组用自粘结系统,用RelyX Unicem树脂水门汀粘结直径1.30 mm RelyX Fiber Post玻璃纤维桩于离体牙根管内.冠部保留5 mm纤维桩,堆厚6 mm的树脂核制备成样本.用万能力学试验机进行剪切粘结强度测试.独立样本t检验比较两组的抗剪切强度.结果 两组断裂方式不同,A组为纤维桩沿树脂与牙体交接处断裂,纤维桩未有松动或脱落;B组为桩核树脂沿树脂与牙体交接处脱落,纤维桩未有断裂.A组抗剪切强度为(393.06±168.38)N,B组抗剪切强度为(222.23±108.76)N,差异有统计学意义(P=0.004).结论 采用全酸蚀粘结系统与自粘结系统,玻璃纤维桩在根管内剪切粘结强度的差异显著,全酸蚀粘结系统优于自粘结系统.使用全酸蚀粘结系统,纤维桩与树脂结合优于自粘结系统.     

离体牙经不同根管封闭剂充填后纤维桩剪切粘结强度的对比研究

目的:研究不同根管封闭剂对两种纤维桩固位力的影响。方法:24颗离体上颌中切牙,截冠、预备根管,按根管封闭材料及纤维桩不同均分为4组。C-RP组:Cortisomol丁香酚类封闭剂,Rebilda Post纤维桩;C-ML组:Cortisomol封闭剂,Mac-rolockTM Post纤维桩;G-RP组:Guttaflow非丁香酚类封闭剂,Rebilda Post纤维桩;G-ML组:Guttaflow封闭剂,MacrolockTM Post纤维桩。自酸蚀粘结剂将纤维桩粘固,牙根切成1.5 mm薄片,行薄片推出实验,并观察断裂模式。扫描电镜观察粘结界面的显微结构。结果:C-RP、C-ML、G-RP、G-ML 4组剪切粘结强度(MPa)分别为5.89±2.89、7.46±2.71、7.66±3.00、9.24±3.03,C-RP粘结强度最低(P<0.05)。牙根颈、中、根尖部的剪切粘结强度依次降低(P<0.01)。扫描电镜观察:相比根尖部,颈部有明显树脂突;使用Guttaflow封闭剂组混合层厚度以及树脂突数目、长度优于使用Cortisomol组。结论:使用丁香酚类根管封闭会降低纤维桩剪切粘结强度;纤维桩修复后根尖部的粘结强度有待增强。     

纤维桩与根管不同处理后剪切粘结强度实验研究及电镜观察

目的比较四种不同粘结系统处理后纤维桩与根管各部剪切粘结强度,探讨其内在机理。方法 25颗完整离体尖牙于釉牙骨质界冠方2mm处截冠。根管治疗后分五组修复：DTlight纤维桩＋3M Unicem组,DTlight纤维桩＋可乐丽DCcore组,DTlight纤维桩＋Dual-link（Bisco）组,DTlight纤维桩＋Lux-acoreZ组（纤维桩表面涂布粘结剂）,DTlight纤维桩＋Luxacore组（纤维桩表面未涂布粘结剂）。包埋后切片对不同根管段行剪切粘结实验,体视显微镜下观察断裂模式,记录数据并统计分析;每组选取2个样本进行扫描电镜观察粘结界面形态。结果剪切粘结强度（MPa）依次为：6.61±1.82,7.72±2.03,5.35±1.42,10.15±0.67,7.25±0.71。体视显微镜观察显示绝大部分样本的断裂方式都是树脂/纤维桩界面断裂。扫描电镜观察显示不同处理后其显微结构各不相同。结论纤维桩修复的剪切粘结强度与粘结部位、粘结材料密切相关。     

不同材料的桩修复对上颌中切牙牙根应力分布影响的三维有限元分析

目的:应用三维有限元法研究不同材料的桩修复上颌中切牙后牙根应力分布的影响。方法:建立上颌中切牙桩冠修复三维有限元模型,应用ANSYS8.0有限元分析软件分析6种不同材料的桩对上颌中切牙牙根应力分布的影响,静态加载100牛顿(N),与牙长轴成45°角。结果:6种不同材料桩修复后牙根应力大小:石英纤维桩>聚乙烯纤维树脂桩>玻璃纤维树脂桩>铸造金合金桩>铸造钛合金桩>铸造Ni-Cr合金桩,但应力值相差很小。6种不同桩修复后桩-牙本质界面的应力大小:铸造Ni-Cr合金桩>铸造钛合金桩>铸造金合金桩>玻璃纤维树脂桩>聚乙烯纤维树脂桩>石英纤维桩,应力值相差较大。结论:高弹性模量的材料修复后改变牙本质应力分布的情况,易产生桩-牙本质界面的应力集中,从而使牙根易于折裂。弹性模量较低的纤维桩有利于应力更均匀的分布,不会产生桩-牙本质应力集中,有利于保护牙根。     

不同纤维桩与根管不同粘结处理修复后剪切粘结强度对比研究

目的比较四种不同粘结系统处理后不同纤维桩与根管各部的剪切粘结强度。方法45颗完整离体尖牙于釉牙骨质界冠方2 mm处截冠、根管治疗后随机分9组,使用两种纤维桩和四种粘结树脂及配套粘结剂修复:DTlight纤维桩,玻璃纤维桩,3MUnicem Rely XTM,DCcore Automix,Dual-link,Luxacore Z Automix。包埋后切不同根管段行剪切粘结实验并观察界面断裂类型,记录数据并统计分析。结果剪切粘结强度(MPa)为:D.T.light组:Luxacore Z Automix1(10.15±0.67)Mpa,DC coreAutomix(7.72±2.03)Mpa,Luxacore Z Automix2(7.25±0.71)Mpa,3MUnicem Rely XTM(6.61±1.82)Mpa,Dual-link(5.35±1.42)Mpa;玻璃纤维桩组:Luxacore Z Automix1(14.60±1.79)Mpa,3MUnicem Rely XTM(11.12±1.95)Mpa,DC core Automix(10.15±1.29)Mpa,Dual-link(8.55±1.40)Mpa。体视显微镜观察显示绝大部分样本的断裂方式都是粘结面型断裂。结论纤维桩修复的剪切粘结强度与纤维桩材料、粘结部位及粘结材料密切相关。     

离体牙经不同根管封闭剂充填后纤维桩剪切粘结强度的对比研究

目的：研究不同根管封闭剂对两种纤维桩固位力的影响。方法：24颗离体上颌中切牙,截冠、预备根管,按根管封闭材料及纤维桩不同均分为4组。C-RP组：Cortisomol丁香酚类封闭剂,Rebilda Post纤维桩;C-ML组：Cortisomol封闭剂,Mac-rolockTM Post纤维桩;G-RP组：Guttaflow非丁香酚类封闭剂,Rebilda Post纤维桩;G-ML组：Guttaflow封闭剂,MacrolockTM Post纤维桩。自酸蚀粘结剂将纤维桩粘固,牙根切成1.5 mm薄片,行薄片推出实验,并观察断裂模式。扫描电镜观察粘结界面的显微结构。结果：C-RP、C-ML、G-RP、G-ML 4组剪切粘结强度（MPa）分别为5.89±2.89、7.46±2.71、7.66±3.00、9.24±3.03,C-RP粘结强度最低（P〈0.05）。牙根颈、中、根尖部的剪切粘结强度依次降低（P〈0.01）。扫描电镜观察：相比根尖部,颈部有明显树脂突;使用Guttaflow封闭剂组混合层厚度以及树脂突数目、长度优于使用Cortisomol组。结论：使用丁香酚类根管封闭会降低纤维桩剪切粘结强度;纤维桩修复后根尖部的粘结强度有待增强。     

固化光源强度对双固化树脂粘结纤维桩强度的影响

目的研究不同光源强度对双固化树脂粘结纤维桩固位力的影响。方法 30颗离体前磨牙,截冠,预备根管,根管充填,BISCO Duo-link双固化粘结剂将BISCO DT light post纤维桩粘固。按纤维桩粘结时使用的固化光源强度不同分成3组:空白组不使用固化光源;低强度组使用600 MW/cm2LED强度固化光源;高强度组使用1 200 MW/cm2LED强度固化光源。沿垂直纤维桩长轴方向将牙根切成1 mm薄片,行薄片推出实验,记录推出力量,计算粘结强度。结果粘结强度:空白组<低强度组<高强度组。空白组、高强度组各自不同深度粘结强度无差别;低强度组粘结强度:根尖<根中<根颈。结论使用双固化树脂粘结剂粘结纤维桩时,固化光源强度增加,有利于增强不同深度粘结剂与桩的粘结强度,增加树脂粘结纤维桩的固位力。     

不同纤维桩的粘结强度及断裂界面研究

目的比较纤维带自制纤维桩、玻璃纤维桩和石英纤维桩与根管牙本质的粘结强度和界面破坏形式,为自制纤维桩在临床应用提供理论基础。方法选取30颗下颌前磨牙,截冠,取根部牙体组织,常规根管治疗后,随机分为纤维带自制纤维桩、玻璃纤维桩和石英纤维桩3组。三组纤维桩分别用同一种双固化树脂粘结剂粘结,包埋后分别切片制备1.3 mm的样本,置万能试验机上对不同根管段行剪切粘结实验,记录数值并行两因素方差分析。在高倍显微镜下观察所有试件破坏形式。结果剪切黏结强度值由大到小依次为纤维带自制纤维桩、石英纤维桩、玻璃纤维桩。纤维桩的剪切黏结强度由根管冠方向根方逐渐减弱,且纤维桩和根管深度之间无交互作用。结论桩的种类及不同的根管深度对纤维桩的粘结强度有影响。     

桩核修复方法对梭形根管牙断裂强度的影响

目的：比较3种不同桩核修复方法对梭形根管牙断裂强度的影响。方法：30颗近期拔除的上颌中切牙根管治疗后预备成梭形,随机分为3组,每组10颗。Ⅰ组行玻璃纤维桩、Luxacore树脂核和铸造全冠修复;Ⅱ组根管扩大预备后行铸造镍铬桩核和铸造全冠修复;Ⅲ组玻璃离子水门汀重塑根管后行铸造镍铬桩核和铸造全冠修复。Zwick z010型电子万能试验机测试断裂强度。结果：Ⅰ组与Ⅱ组、Ⅲ组试件牙的断裂强度差异有显著性,Ⅱ组与Ⅲ组差异无显著性。结论：梭形根管牙的断裂强度与其修复设计有关,采用玻璃纤维桩及树脂核修复有较高的断裂强度,且断裂方式利于再修复。     

Effect of Core Diameter and Surface Treatment on the Retention of Resin Composite Cores to Prefabricated Endodontic Posts

PURPOSE: With advances in adhesive dentistry and current emphasis on esthetic restorations, dowel systems have been developed to take advantage of these new techniques. Of interest when using these systems is the interaction between core materials and post materials. This investigation compared the tensile retentive force of two resin composite core materials to two metallic and one non-metallic prefabricated endodontic posts. Two dimensions of core build-up and two post-surface treatments were tested. MATERIALS AND METHODS: One hundred twenty posts (stainless steel, titanium alloy, and glass fiber-impregnated resin) were secured in a jig with 4 mm of the post extending into a cylindrical matrix. The matrix formed cylinders with diameters of 3 and 5 mm into which resin composite was inserted. The posts were treated or not treated with a bonding agent. After storage for 24 hours at 100% humidity, five specimens per condition were tested in an Instron testing machine at a crosshead speed of 0.5 mm/min. Failure loads were recorded in kilograms and failure modes were observed under light microscopy (40 x). Four-way analysis of variance and multiple comparison testing were used to compare means at the 0.05 level of significance. RESULTS: The means and standard deviations of tensile loads were calculated. All variables were significant in either main effects or interactions ( p<0.05). Fisher's PLSD intervals for post, core, treatment, and diameter were 2.0, 1.6, 1.6, and 1.6 kg, respectively. In most cases, the retentive force recorded for metallic posts was higher than that of glass fiber posts. Titanium posts had higher retentive forces than did the stainless steel posts. For metallic posts, 5-mm cores provided higher forces than 3-mm cores. In the glass fiber group, core diameter was not significant. For core materials, Build-It gave higher results with stainless steel posts, and FluoroCore gave higher results with the titanium ones. The surface treatment results were mixed. In the metallic post groups the adhesive failure data ranged between 80% and 100%, whereas in the glass fiber post groups, adhesive failures ranged between 60% and 70%. CONCLUSIONS: Within the limitations of this study, the metallic post groups always provided higher tensile retentive forces, with the titanium post groups showing higher retentive forces than the stainless steel ones. In the glass fiber post groups, different core diameters did not affect retention values.     

两种预成桩拉伸固位强度的体外研究

目的:比较用树脂粘接剂粘接的纤维增强复合树脂预成桩与用磷酸锌粘固的不锈钢预成桩的拉伸固位强度。方法:选择40颗因正畸拔除的下颌前磨牙,用金刚砂片在距釉牙骨质界冠方1 mm处去除牙冠,随机均分为4组,用预成桩配套用车针预备9 mm深的桩腔。对于不锈钢桩组,桩腔预备的直径为1.25 mm,用磷酸锌粘固粉粘固。对于纤维增强复合树脂桩组,桩腔预备的直径分别为1.00 mm、1.25 mm、1.50 mm,用树脂粘接剂粘接。储存24 h后,置于拉伸强度检测机上测量各组样本预成桩的拉伸固位强度,加载速度为5.0mm/m in,对各组的测量结果进行统计学分析。结果:各组预成桩的平均固位强度在(43.9±10.4)kg至(19.9±5.7)kg之间,磷酸锌粘固的不锈钢桩组的拉伸固位强度显著高于所有纤维桩组,1.00 mm纤维增强复合树脂桩组的固位强度明显低于其它组。结论:在本实验的研究条件下,磷酸锌粘固的不锈钢桩组固位强度最高。     

Fracture strength of teeth with flared root canals restored with glass fibre posts

OBJECTIVE: To investigate the fracture strength and pattern of failure of teeth with weakened roots reconstructed by different procedures. METHODS: In an in vitro study root posts were placed in 50 endodontically treated canines, divided into 5 groups (n=10) as follows: cast metallic post; glass fibre post with smaller diameter than the root canal; glass fibre post with smaller diameter than the root canal + glass fibre strips; glass fibre post with smaller diameter than the root canal + accessory glass fibre posts; anatomical post (glass fibre post with smaller diameter than the root canal, relined with low viscosity composite resin). Posts were luted with resin cement and the coronal portion of posts was constructed with composite resin. Metallic crowns were cemented on the posts. Specimens were submitted to compressive load in a universal testing machine. Fracture strength values of each group were compared. RESULTS: Fracture strength values were for Groups 1-5 respectively: 1087.06; 745.69; 775.41; 920.64; 876.12kgf, with significant differences between Groups 1 and 2 and between Groups 1 and 3 (p<0.05). Observed patterns of fracture were: Group 1 - 100% of roots fractured; Groups 2 and 4 - variable fracture modes; Group 3 - 60% of fractures occurred in the cervical root third; Group 5 - 50% of failures occurred in the coronal portion of the post. CONCLUSIONS: The fracture strength of teeth with cast metallic posts, teeth with anatomical posts or teeth with glass fibre posts combined with accessory posts was similar. All teeth restored with cast metallic posts presented fractures and were unfavourable to maintenance of the remaining tooth structure. Teeth with fibre posts (Groups 2 to 5) presented variable fracture modes; however, the maximum percentage of unfavourable fractures was 30%.     

Effects of mechanical cycling on the bonding of zirconia and fiber posts to human root dentin

PURPOSE: To evaluate the effect of cyclical mechanical loading on the bond strength of a fiber and a zirconia post bonded to root dentin. MATERIALS AND METHODS: Forty single-rooted human teeth (maxillary incisors and canines) were sectioned, and the root canals were prepared at 12 mm. Twenty randomly seleced specimens received a quartz fiber post (FRC) (D.T. Light-Post) and 20 others received a zirconia post (ZR) (Cosmopost). The posts were resin luted (All Bond 2 + resin cement Duo-link) and each specimen was embedded in epoxy resin inside a PVC cylinder. Ten specimens with FRC post and 10 specimens with ZR post were submitted to fatigue testing (2,000,000 cycles; load: 50 N; angle of 45 degrees; frequency: 8 Hz), while the other 20 specimens were not fatigued. Thus, 4 groups were formed: G1: FRC+O cycles; G2: FRC+2,000,000 cycles; G3: ZR+O cycles; G4: ZR+2,000,000 cycles. Later, the specimens were cut perpendicular to their long axis to form 2-mm-thick disk-shaped samples (4 sections/specimen), which were submitted to the push-out test (1 mm/min). The mean bond strength values (MPa) were calculated for each tooth (n = 10) and data were submitted to statistical analysis (alpha = 0.05). RESULTS: Two-way ANOVA revealed that the bond strength was significantly affected by mechanical cycling (p = 0.0014) and root post (p = 0.0325). The interaction was also statistically significant (p = 0.0010). Tukey's test showed that the mechanical cycling did not affect the bonding of FRC to root dentin, while fatigue impaired the bonding of zirconium to root dentin. CONCLUSION: (1) The bond strength of the FRC postto root dentin was not reduced after fatigue testing, whereas the bonding of the zirconia post was significantly affected by the fatigue. (2) Cyclical mechanical loading appears to damage the bond strength of the rigid post only.     

An in vitro study of the fracture resistance and the incidence ofvertical root fracture of pulpless teeth restored with six post-and-coresystems

STATEMENT OF PROBLEM: Posts and cores are often required with pulpless teeth to provide retention and resistance form for complete crowns. Nevertheless, conventional posts may increase the potential for root fracture. PURPOSE: This study compared the resistance to vertical root fracture of extracted teeth treated with post-core systems that were modified with polyethylene woven fibers (Ribbond) with those treated with conventional post-and-core systems. MATERIAL AND METHODS: Canal instrumentation was performed for 60 maxillary central incisors, and complete crown preparations were made. The coronal portion of each tooth was amputated, and 6 post-and-core systems were studied. Specimens were mounted in acrylic resin blocks with a layer of polyvinyl siloxane covering the roots. Loads were applied at an angle of 130 degrees and measured with a universal testing machine. Results were analyzed statistically with 1-way analysis of variance with Student-Newman-Keuls grouping and chi-square analysis. RESULTS. Cast posts and cores resulted in significantly higher failure thresholds than all others, except for prefabricated, comparably sized, parallel-sided posts with composite cores. All failures in the group with cast posts involved fracture of the teeth, whereas 70% of the teeth with comparably sized parallel-sided posts and composite cores failed as a result of tooth fractures and 30% experienced core fractures. The woven fiber post-core system was significantly lower in strength than all others, and exhibited significantly fewer vertical root fractures. CONCLUSIONS: Polyethylene woven fiber and composite resin without a prefabricated post resulted in significantly fewer vertical root fractures, but mean failure load was the lowest. Smaller diameter prefabricated posts combined with the polyethylene woven fiber and composite cores improved resistance to failure. Traditional cast posts and cores were the strongest of the 6 post-core systems.     

Effects of chemical surface treatments of quartz and glass fiber posts on the retention of a composite resin

STATEMENT OF PROBLEM: Failure of a fiber post and composite resin core often occurs at the junction between the 2 materials. This failure process requires better characterization. PURPOSE: The purpose of this study was to evaluate the effect of 2 chemical solvents, hydrogen peroxide and methylene chloride, on the shear bond strength of quartz and glass fiber posts to a composite resin. MATERIAL AND METHODS: Twenty-four posts (3 +/-0.1 mm in length) were prepared for each quartz (LIGHT-POST (LP)) and glass fiber (Cytec blanco (CB)) post. Posts were horizontally embedded in acrylic resin with half of the post diameter exposed. The exposed surfaces were successively ground with 400-, 800-, and 1200-grit silicon carbide papers, to ensure uniform smoothness. The specimens were divided into 3 subgroups (n=8) representing different surface treatment techniques, including application of silane for 60 seconds (S), etching with hydrogen peroxide for 20 minutes (H), and etching with methylene chloride for 5 seconds (M). Silane-treated specimens served as controls. A dual-polymerized composite resin (Tetric EvoCeram) was placed in a polytetrafluoroethylene mold (30 x 2 mm) positioned upon the post specimens and polymerized for 20 seconds with a light-emitting diode (LED) polymerization unit. The specimens were stored in water at 37 degrees C for 24 hours. Shear bond strength values (MPa) of posts and composite resin cores were measured using a universal testing machine with a crosshead speed of 0.5 mm/min. Data were analyzed by 2-way analysis of variance (ANOVA). Post hoc Tukey intervals for comparison among the 2 post materials and 3 surface treatment techniques were calculated (alpha =.05). The effect of the chemical surface treatments on glass and quartz fiber post surfaces were examined with a scanning electron microscope (SEM). RESULTS: There were significant differences between the shear bond strength for LP and CB (P<.001). For all groups, the application of H showed the highest bond strength values. There was no significant difference between the S and M groups (P>.05). The SEM observations demonstrated that the fiber post surfaces were modified after chemical surface treatment techniques. CONCLUSIONS: The surface treatment of quartz and glass fiber posts with hydrogen peroxide significantly enhanced the shear bond strength of the composite resin tested due to its ability to dissolve the epoxy resin matrix used in each post. The lowest bond strength was obtained with M and S groups. Application of methylene chloride to the fiber post surfaces for 5 seconds was not effective in increasing the shear bond strength of the fiber post to composite resin.     

三种复合树脂与玻璃纤维桩的微拉伸强度研究

目的：3种复合树脂材料与玻璃纤维桩微拉伸粘结强度的对比研究。方法：45个Parapost玻璃纤维桩随机分为3组，分别用3种不同的复合树脂：可乐丽菲露AP-X^TM、Ceram—X、ParaCore双重固化复合树脂桩核材料粘固制成桩核样本，制备好的样本切割成截面为1．0mm×1．0mm的条状试件用于微拉伸强度测试。结果：ParaCore与Ceram—X的微拉伸粘结强度显著高于AP-X^TM（P〈0．05），ParaCore和Ceram—X与纤维桩的微拉伸粘结强度没有显著性差异（P〉0．05）。结论：ParaCore与Ceram-X与玻璃纤维桩的粘结性能较好，适于临床塑核使用。     

In vitro evaluation of the retention of composite fiber and stainless steel posts

PURPOSE: This study compared the tensile retentive strength of composite fiber-reinforced dowels luted with a resin cement to stainless steel dowels luted with zinc phosphate cement. MATERIALS AND METHODS: The crowns of 40 extracted human mandibular premolars were removed with a separating disc 1-mm coronal to the cementoenamel junction. The teeth were randomly divided into 4 groups (n = 10). A post space was prepared in each specimen to a depth of 9 mm, using the drill supplied by the respective manufacturer. For the stainless steel post group, 1.25-mm-diameter posts were cemented with zinc phosphate cement. For the composite fiber reinforced groups, posts with diameters of 1.00, 1.25, and 1.50 mm were luted with a Bisphenol A-Glycidyl Methacrylate (BIS-GMA) resin bonding system (Jeneric/Pentron, Wallingford, CT) according to manufacturer specifications. The specimens were stored in a sealed container with a moist environment for 24 hours, placed in a fixture in an 801 Materials Test Systems (MTS) machine (MTS Systems Corp, Minneapolis, MN), and loaded in tension at a rate of 5.0 mm/min until failure. Differences among the 4 groups were determined using a one-way analysis of variance and Tukey-B post-hoc tests (alpha = 0.05). RESULTS: The mean loads to failure ranged from 43.9 +/- 10.4 kg for the stainless steel dowel group to 19.9 +/- 5.7 kg for the composite fiber-reinforced 1.00-mm-diameter group. The stainless steel post luted with zinc phosphate cement provided significantly greater tensile resistance than all composite fiber dowel groups. The retention of the 1.00-mm composite fiber-reinforced post was significantly less than the remaining groups. CONCLUSIONS: Under the conditions of this study, the stainless steel dowel luted with zinc phosphate cement provided significantly greater retention.     

Stress analysis of endodontically treated anterior teeth restored with different types of post material

Finite element analysis was performed to evaluate stress distribution in maxillary central incisors treated endodontically and restored with a post and an all-ceramic crown. Tensile stress at tooth root was analyzed using two-dimensional finite element models with different post diameters and lengths. One post length was 1/3 of the root (short), while the other was 2/3 of the root (long); one post diameter was 1/3 of the root (narrow), while the other was 2/3 of the root (wide). The following combinations were used for posts and cores: gold alloy cast post and core, commercial stainless steel post and resin core, and fiber post and resin core. Results showed that the fiber post produced less stress on the root dentin around the post tip than did the metal posts. This finding thus suggested that to reduce the stresses that cause root fracture, a long, thin fiber post should be used.