Influence of prefabricated post dimensions on restored maxillary central incisors

The aim of this study was to test the following hypothesis: biomechanical performance (fracture strength and stress distribution) of restored teeth is less sensitive to post diameter and post length when using glass fibre posts than when using stainless steel posts. First, an experimental fracture strength test was performed on 80 extracted human maxillary central incisors. Teeth were decoronated, treated endodontically and restored (40 with glass fibre posts and 40 with stainless steel posts), and the length and diameter of the posts varied uniformly. Failure loads were recorded and results were compared using an ancova analysis. Secondly, the finite element technique was used to develop a model of the restored tooth. The post diameter had a significant effect on the biomechanical performance of teeth restored with stainless steel posts. Lower failure loads were found as post diameter increased. However, the post diameter of those teeth restored with glass fibre posts, and the post length for both post systems under consideration, did not affect the biomechanical performance of restored teeth to a significant degree. The stress distributions predicted by the developed model corroborated these findings, confirmed the assumed hypothesis, and permitted the proposal of the use of glass fibre posts to achieve a restorative technique that is less sensitive to post dimensions, and thus more robust.     

Ti2448分裂型根管桩对上颌中切牙应力分布影响的三维光弹应力分析

目的:研究分裂型设计的低弹性模量Ti2448根管桩对上颌中切牙及其牙周支持组织应力分布影响的三维光弹应力分析。方法:分别制作铸造钴铬合金、Ti2448根管桩各12个,再取两种金属桩各6个切割出裂隙(高度4.5 mm,宽度0.3 mm)。分别制作牙根和牙槽骨的环氧树脂模型,将各部件组合后根据桩钉材料、形态设计与加载方式将模型分为8组。采用三维光弹应力分析法比较两种设计形式的钴铬合金和Ti2448根管桩对上颌中切牙及其牙周支持组织应力分布影响的三维光弹应力的差别。结果:同一种材料不同设计形式桩之间相比,无论是钴铬合金,还是Ti2448,牙槽骨各部位的应力值都是分裂型桩低于不分裂桩,差异均有统计学意义(P<0.05)。4组间应力值相比,各部位均以钴铬合金不分裂型桩最高,钴铬合金分裂型次之,Ti2448不分裂型再次之,Ti2448分裂型最低,各组间相比差异均有统计学意义(P<0.05)。结论:不同弹性模量材料金属根管桩以及其形态设计都对牙根应力分布有明显的影响,弹性模量与牙体组织接近的Ti2448分裂型根管桩可以达到保护牙根防止折裂的效果。     

Stress analysis of an upper central incisor restored with different posts

The effect of different anatomic shapes and materials of posts in the stress distribution on an endodontically treated incisor was evaluated in this work. This study compared three post shapes (tapered, cylindrical and two-stage cylindrical) made of three different materials (stainless steel, titanium and carbon fibre on Bisphenol A-Glycidyl Methacrylate (Bis-GMA) matrix). Two-dimensional stress analysis was performed using the Finite Element Method. A static load of 100N was applied at 45 degrees inclination with respect to the incisor's edge. The stress concentrations did not significantly affect the region adjacent to the alveolar bone crest at the palatine portion of the tooth, regardless of the post shape or material. However, stress concentrations on the post/dentin interface on the palatine side of the tooth root presented significant variations for different post shapes and materials. Post shapes had relatively small impact on the stress concentrations while post materials introduced higher variations on them. Stainless steel posts presented the highest level of stress concentration, followed by titanium and carbon/Bis-GMA posts.     

下颌磨牙残冠纤维桩核冠修复的有限元应力分析

目的 分析下颌第一磨牙残冠不同缺损壁数的情况下,不同数目、不同部位的纤维桩核冠修复的应力分布情况和应力大小.方法 利用三维有限元法建立下颌第一磨牙残冠2壁和3壁缺损情况下,不同数目和不同部位的纤维桩核冠修复模型,施加225N垂直向的静态载荷及动态载荷.记录两种载荷下各部位牙本质von Mises应力最大值和最大主应力.结果 下颌磨牙2种缺损状态在动静态载荷下,未植入纤维桩组最大Von Mises应力最大,均高于植入纤维桩组,近中植入2根纤维桩组和植入3根纤维桩组的应力分布最均匀.下颌磨牙3壁缺损在静态载荷下,植入3根纤维桩组最大,Von Mises应力明显小于其他2组.结论 2壁缺损情况下,考虑选择植入1根纤维桩.3壁缺损情况下,可以考虑通过增加纤维桩数量来分散应力,减小牙体折裂风险.     

三种方式修复严重缺损的上颌中切牙抗折性能研究

目的：比较三种方式修复严重缺损的上颌中切牙的抗折性能,探讨保存残根残冠更合理的修复方式。方法：36颗上颌中切牙随机分为3组,根管治疗后平齐唇侧釉牙本质界垂直与牙体长轴截冠。分别行铸造镍铬合金桩核、铸造镍铬合金桩树脂核及玻璃纤维桩树脂核＋金属全冠修复。在万能测试机进行力学测试,记录最大载荷和断裂模式。结果：3组的抗折强度分别为292.06±155.51N、439.89±89.55N和284.98±133.56N,铸造镍铬合金桩树脂核组明显高于另外2组,差异具有统计学意义。铸造镍铬合金桩均导致牙根垂直折裂,玻璃纤维桩10颗桩折,2颗桩折合并唇侧颈1/3折裂。结论：无箍作用时应充分利用树脂与牙体的粘结作用,高强度的铸造镍铬合金桩较玻璃纤维桩能更好地抵抗外力,结合高强度的树脂核强度更大。     

牙本质肩领对纤维桩修复效果影响的研究进展

在众多的桩核修复材料中,纤维桩以其优良的物理性能、机械性能和美学特性得到越来越多的临床应用,牙本质肩领的设计形态对于纤维桩修复后的固位、稳定、牙根抗折性能等方面具有重要意义,本文就牙本质肩领对纤维桩修复效果影响的研究进展作一综述.     

桩核对牙冠完整的上颌第一前磨牙的应力影响

目的:采用有限元法比较不同桩核或有无桩核修复牙冠完整的上颌第一前磨牙时牙体组织的应力情况.方法:采用New Tom锥形束CT扫描获取数据,建立四种三维有限元模型,加载偏舌侧45°角的150N力.结果:在桩尖区钴铬合金桩核修复时应力集中,VoMises应力峰值39.3MPa比对照组14.2MPa增加176.8％;纤维桩核修复时应力均匀,VonMises应力峰值16.7MPa比对照组14.2MPa增加17.6％,钴铬合金桩核修复最大主应力峰值13.4MPa是纤维桩核修复9.3MPa的1.44倍;用树脂材料直接充填时(无桩核)应力与对照组基本一致.结论:与钴铬合金桩核相比,纤维桩核更适合上颌第一前磨牙修复;在牙冠部有足够牙体组织时,直接由树脂材料充填开髓洞型后行全冠修复是可行的.     

多桩烤瓷冠修复磨牙弯曲根管的残根

目的探讨采用多桩桩冠修复的方式来保留中、重度弯曲根管磨牙残根的可行性。方法应用多桩桩冠修复技术修复弯曲根管的磨牙残根。结果自2005年以来,共治疗了33例患者的41颗弯曲根管的磨牙残根,3年后随访,其成功率达85.4%。结论在严格掌握修复适应证的基础上,严格操作并采用减小力等措施,该技术修复弯曲根管磨牙残根是一种简便、有效的方法。     

Influence of type of luting cement used with all-ceramic crowns on load capability of post-restored endodontically treated maxillary central incisors

Adhesive luting of the final restorations is supposed to support the overall strength of post-endodontically restored teeth. For evaluating adhesive vs conventional cementation, the load capability of adhesively restored endodontically treated teeth (ETT) with glass fibre-reinforced composite posts (GFRCP), resin composite cores and all-ceramic crowns was determined. Thirty-two caries-free human upper, central incisors were randomly assigned to four groups, endodontically treated and cut 2 mm above the cemento-enamel junction. All teeth were restored with GFRCP, composite core build-ups and all-ceramic crowns. All-ceramic crowns were cemented with zinc phosphate cement (I), glass ionomer cement (II), and a self-adhesive resin cement (III and IV). After thermo-mechanical loading, the specimens were loaded to fracture. Maximum load capability F _max and fracture patterns were compared using non-parametric statistics. Median values for the maximum load capability F _max (minimum/maximum) in [N] were: I = 503 (416/1,038), II = 442 (369/711), III = 502 (326/561) and IV = 518 (416/652). No statistically significant differences were found for F _max (p = 0.761) and fracture patterns (p = 0.094) between the experimental groups. The type of cementation of all-ceramic crowns, whether self-adhesive or conventional, appears to have no impact on the load capability of ETT restored with GFRCP and composite core build-ups.     

Long-term survival of endodontically treated,maxillary anterior teeth restored with either tapered or parallel-sided glass-fiber posts and full-ceramic crown coverage

Objectives

This retrospective study investigated the clinical effectiveness over up to 8 years of parallel-sided and of tapered glass-fiber posts, in combination with either hybrid composite or dual-cure composite resin core material, in endodontically treated, maxillary anterior teeth covered with full-ceramic crowns.

Methods

The study population comprised 192 patients and 526 endodontically treated teeth, with various degrees of hard-tissue loss, restored by the post-and-core technique. Four groups were defined based on post shape and core build-up materials, and within each group post-and-core restorations were assigned randomly with respect to root morphology. Inclusion criteria were symptom-free endodontic therapy, root-canal treatment with a minimum apical seal of 4 mm, application of rubber dam, need for post-and-core complex because of coronal tooth loss, and tooth with at least one residual coronal wall. Survival rate of the post-and-core restorations was determined using Kaplan–Meier statistical analysis.

Results

The restorations were examined clinically and radiologically; mean observation period was 5.3 years. The overall survival rate of glass-fiber post-and-core restorations was 98.5%. The survival rate for parallel-sided posts was 98.6% and for tapered posts was 96.8%. Survival rates for core build-up materials were 100% for dual-cure composite and 96.8% for hybrid light-cure composite.

Conclusions

For both glass-fiber post designs and for both core build-up materials, clinical performance was satisfactory. Survival was higher for teeth retaining four and three coronal walls.     

The effect of different full-coverage crown systems on fracture resistance and failure pattern of endodontically treated maxillary incisors restored with and without glass fiber posts

The aim of this study was to compare the fracture resistance and failure pattern of endodontically treated maxillary incisors restored using composite resin with or without fiber-reinforced composite (FRC) posts under different types of full-coverage crowns. The null hypothesis tested was that fracture resistance and the failure pattern of these teeth were not affected by the use of FRC posts or by the type of full-coverage crown. One hundred twenty maxillary incisors were endodontically treated and divided into 4 groups of 30 each. Each group was divided into two subgroups: restoration with or without fiber post. PFM crowns were placed in group 1, Empress II crowns in group 2, SR Adoro crowns in group 3, and Cercon crowns in group 4. Fracture tests were performed by loading specimens to fracture. Data were analyzed with two-way analysis of variance (alpha = 0.05). The type of crown was not a significant factor affecting fracture resistance (p = 0.4), whereas the presence of a post was (p = 0.001). Both the presence of post and the type of crown had a significant influence on the proportion of restorable versus unrestorable fractures. Although prosthodontics textbooks do not generally advocate the placement of fiber posts in endodontically treated incisors, the results of this study indicate that the use of fiber posts in such teeth increases their resistance to fracture and improves the prognosis in case of fracture.     

上颌双侧中切牙外伤行冠延长术后的修复设计

目的：比较上颌双侧中切牙外伤行冠延长术后,不同修复设计对牙槽骨应力及牙齿动度的影响。方法：通过逆向工程技术建立齿冠延长术后不同骨下降高度的三维有限元模型,并将其设计为单冠、二联冠、三联冠、四联冠修复;然后用三维有限元法分析降低不同牙槽骨高度对桩核冠修复后牙槽骨应力分布及牙齿动度的影响。结果：随着牙槽骨高度的降低,所有修复形式组的牙槽骨应力及牙齿位移都有所上升,其中单冠修复组的增加幅度最大;当骨高度下降1 mm和2 mm时,单冠和3种联冠修复均能满足牙周潜力的要求;而骨下降高度为3 mm时,单冠修复组的应力值超过了牙周潜力的范围,二联冠修复接近牙周潜力,三联冠及四联冠修复均小于牙周潜力。结论：去骨高度在2 mm以内时,单冠和二联冠修复均可,但二联冠可以降低手术后造成的不利影响;当去骨高度为3 mm时,必须采用联冠修复,最好选用三联冠修复。     

牙体缺损程度对后牙桩核冠修复牙本质应力影响的三维有限元分析

目的:比较上颌第一磨牙不同程度牙体缺损桩核冠修复后牙本质应力分布情况,探讨牙体剩余量与牙本质应力分布之间的关系。方法:通过磨片法建立上颌第一磨牙桩核冠有限元模型,比较上颌第一磨牙4种不同程度牙体缺损桩核冠修复后的牙本质应力分布情况。结果:后牙牙体水平向缺损量超过其牙冠牙体量1/2时,牙本质应力峰值较高,缺损量在牙冠牙体量1/2以内,对应力峰值无显著影响。结论:当水平向牙体剩余量大于1/2时,剩余牙体组织所受应力较大,上颌第一磨牙的腭根根分叉处是根折的危险区域。     

Influence of core material on fracture resistance and marginal adaptation of restored root filled teeth

Aim To investigate ex vivo the influence of direct placement core materials on the fracture strength and marginal adaptation of root filled maxillary central incisors restored with glass fibre‐reinforced posts, various core materials and all‐ceramic crowns. Methodology Forty‐eight human maxillary incisors were root filled. Posts were placed and teeth restored with composite cores and crowns (n = 8). Six core materials were examined after thermal cyclic and mechanical loading (TCML). Fracture force was determined under static loading. The marginal adaptation at the interfaces between cement‐tooth and cement‐crown were categorized as ‘intact margin’ or ‘marginal gap’ using scanning electron microscopy. Statistical analysis was undertaken with the Mann–Whitney U‐test (α = P ≤ 0.05). Results Median fracture strength varied between 204 N (low viscous experimental core) and 1094 N (Multicore). No difference in fracture resistance was found with varying viscosity of the core material. The layering technique improved the fracture performance (P = 0.059) to a minor degree. Crowns with dedicated core materials (Rebilda 1063 N; Multicore 1094 N) had a significantly higher fracture resistance than crowns with a conventional restorative material (Tetric Ceram 509 N). Significantly poorer marginal adaptation before TCML was found for the layering technique at the tooth–cement interface and for all experimental cores after TCML. At the crown–cement interface significant differences in marginal adaptation could be determined between Multicore‐layered core (P = 0.002) and Multicore‐Rebilda (P = 0.001) after TCML. Conclusions The fracture strength of post and core restorations was dependent on the core material and bonding system. Marginal adaptation was influenced by the method of application of the core material and by TCML.     

纤维桩表面处理对其修复后牙根抗折裂强度的影响

目的评价不同的纤维桩表面处理方法对纤维桩修复后牙根抗折裂性能的影响。方法将24根纤维桩平均分为喷砂组、过氧化氢酸蚀组和未处理组（对照组）,分别将其黏固于24颗经过桩道预备的离体牙内,树脂成核,然后行金属全冠修复。模拟口腔环境将样本进行冷热循环和循环加载,然后置于电子万能实验机上测试其抗折裂强度,记录样本折裂时的力值以及折裂模式。结果纤维桩表面处理组的牙根抗折裂强度均大于未处理组（P<0.05）,而喷砂和过氧化氢处理组之间的牙根抗折裂强度的差异无统计学意义（P>0.05）。各组的折裂模式均以根颈1/3处折裂为主。结论喷砂和过氧化氢酸蚀处理均能提高纤维桩加树脂核修复后的牙根的抗折裂强度。     

上颌前磨牙薄弱根管桩核冠修复的有限元应力分析

目的 建立上颌单根前磨牙正常根管和薄弱根管4种桩核冠修复方式的三维有限元模型,并进行应力分析,为临床前磨牙薄弱根管的修复提供参考.方法 正常上颌单根前磨牙,通过micro-CT扫描、MIMICS、GEOMAGIC、ANSYS等软件建立正常根管、薄弱根管及其4种修复方式的有限元模型,采用有限元分析软件ANSYS计算分析...     

两种材料桩冠修复前牙残冠和残根的临床效果观察

目的 观察铸造金合金核桩冠和玻璃纤维核桩冠修复前牙残冠残根的临床效果。方法 选取72例(18~52岁)前牙残冠残根患者,共计120颗患牙,经过完善的根管治疗后随机分为2组:A组60颗患牙,使用铸造金合金核桩冠;B组60颗患牙,使用玻璃纤维核桩冠;同时每一组又分为有牙本质肩领组和无牙本质肩领组。全部患牙均用贵金属烤瓷全冠恢复牙体外形。观察2组患者的修复成功率。结果 随访24个月后,铸造金合金核桩冠组和玻璃纤维核桩冠组修复成功率相似,但在有牙本质肩领和无牙本质肩领时铸造金合金核桩冠组和玻璃纤维核桩冠组修复成功率相差较大。结论 牙体组织残留量及所选核桩材料与修复成功率密切相关。?