桩核修复与牙根抗折裂强度

桩核修复在残根残冠保存中占据十分重要的地位,桩核的设计与牙根抗折强度有着密切关系。本文将就桩修复材料、剩余牙本质、根管预备、桩核形态、黏结等与桩修复牙抗折裂强度之间的关系进行讨论。     

玻璃陶瓷高嵌体和金属全冠修复根管治疗后下颌前磨牙的抗折强度

目的:比较玻璃陶瓷高嵌体和金属全冠修复经根管治疗后的下颌前磨牙的牙体抗折强度。方法:选择45颗完整的下颌前磨牙,经根管治疗后,随机分为3组。A组以流体树脂垫底,树脂充填作为对照组;B组和C组以流体树脂垫底后,牙体均预备为MOD洞型。B组以树脂充填后,再进行牙体预备,以钴铬合金金属全冠修复;C组牙体预备,以玻璃陶瓷高嵌体黏结修复。将3组标本用万能实验机垂直加载,直至标本发生纵裂,记录各样本牙裂时的最大载荷数值与折裂模式。采用SPSS13.0软件包对数据进行统计学分析。结果:A、B、C组的平均抗压载荷值分别为(234.44±44.36)、(267.11±65.55)、 (314.91±33.67) N。2个实验组与对照组相比差异均有显著性(P<0.05);B组的抗压载荷值高于C组,差异有显著性(P<0.05)。3组样本牙折裂模式两两比较,结果显示组间差异均有显著性(P<0.05)。结论:玻璃陶瓷高嵌体是保护经根管治疗后的下颌前磨牙的较好方法。     

两种桩核修复系统对残根抗折性能的影响

目的：比较2种不同弹性模量的桩核系统对根管治疗后残根抗折强度的影响。方法：20颗下颌前磨牙在釉牙骨质界处截冠后随机平均分为2组,分别进行玻璃纤维桩＋树脂核（FPC）＋金属冠修复和铸造镍铬桩核（CPC）＋金属全冠修复。实验标本包埋于树脂块中,在电子万能测力机上以1mm/min的速度加载直至断裂。结果：2组的断裂强度分别为2.39±0.55KN和3.06±0.27KN,差异有显著性（P〈0.05）。可修复性断裂多见于FPC组,而不可修复性的破坏多见于CPC组（P〈0.05）。结论：传统的铸造桩核系统适用于剩余牙根条件良好,有足够抗力形,同时咀嚼力量较大的患牙,而玻璃纤维桩则有利于薄弱牙根的保存。     

漏斗状根管治疗牙重塑后不同桩核系统修复的抗折性研究

目的比较漏斗状根管治疗牙在根管重塑前后不同桩核系统修复的抗折强度及牙折形式。方法采用两因素三水平的析因设计。选择45颗近期拔除的上颌中切牙,随机分为9组,每组5颗。分别按照根管重塑因素和桩核系统因素的三个水平交互组合进行处理。样本进行破坏性力学试验,记录瞬间力值及牙折形式。结果根管重塑因素对抗折强度具有显著性影响（P〈0.05）,桩核系统因素对抗折强度不产生明显影响（P〉0.05）,两种因素之间无交互作用（P〉0.05）。结论根管重塑可显著提高漏斗状根管治疗牙桩核系统修复后的抗折强度。重塑后的漏斗状根管治疗牙,不同桩核系统修复后的抗折强度无显著性差异。     

循环加载对不同桩核修复后牙体抗折强度的影响

目的 用循环加载的方式模拟核桩冠修复一段时间后的状况,比较不同桩核修复后牙体的抗折强度,了解其远期修复效果。方法 15颗下颌离体前磨牙随机分为3组,分别为铸造金属桩核组（A组）、玻璃纤维加强复合树脂桩核组（B组）、树脂充填组（C组）,每组5个试件。所有试件在完成桩核修复后均做金属冠修复,经过300 000次循环加载和1 000次5~55 ℃冷热循环后,再在力学测试机上测试试件的抗折强度,记录试件断裂时的力值和试件破坏形式。结果 B组和C组抗折强度显著高于A组（P<0.05）。A组主要为不可修复性折裂,其他两组主要为可修复性折裂。结论 临床修复残根残冠时,可以优先考虑纤维桩加树脂核修复或者树脂充填修复。     

牙本质肩领形态对氧化锆桩核修复抗折强度影响的研究

目的：评价不同牙本质肩领形态的尖牙行一体式氧化锆桩核修复后的抗折强度.方法：选择50颗新近拔除的上颌尖牙,随机分为5组,每组10颗,根管治疗后根据牙本质肩领的缺损程度对样本进行分类处理,各组的设计方案为：A组,保留高度为2.0mm的完整牙本质肩领作为对照组;B组,去除唇侧牙本质肩领;C组,去除近中及唇侧牙本质肩领;D组,只保留远中牙本质肩领;E组,磨除整个牙本质肩领.使用万能材料测试机对样本进行抗折强度测试,所得结果采用SPSS 13.0软件对样本的抗折强度进行单因素方差分析和组间两两比较的q检验分析,检验水准α=0.05.结果：5组样本的抗折强度如下：A组1026.30±139.01N,B组878.20±105.67N,C组845.70±100.56N,D组710.20±96.91N,E组686.00±89.91N.其中B组与C组、D组与E组组间比较差异无统计学意义（P＞0.05）,其余各组间比较差异均有统计学意义（P＜0.05）.结论：一体式氧化锆桩核修复时,保存唇舌侧牙本质肩领对提高患牙的抗折强度有重要意义.     

可塑纤维桩修复对根管治疗牙抗折强度的影响

目的比较不同桩修复离体牙对修复体整体抗折强度的影响。方法将32颗上颌前磨牙行根管治疗并从唇侧釉牙骨质界上2 mm处截断后随机分为4组,A组采用镍铬金属铸造桩核加铸造冠修复,B组采用Tenax FiberWhite纤维桩、树脂核加铸造冠修复,C组采用EverStick可塑纤维桩单根（直径1.5 mm）、树脂核加铸造冠修复,D组采用EverStick可塑纤维桩双根（直径1.5 mm和1.2 mm）、树脂核加铸造冠修复。所有离体牙均由自凝树脂包埋,电子万能试验机加载头与牙体长轴成45°,以1 mm/min的加载速度加载直至试件任何部分折裂,记录读数并观察修复体折裂模式。结果A、B、C、D组间修复体的整体抗折强度差异无统计学意义（P>0.05）。各纤维桩组牙体折裂位置较铸造桩更接近牙颈部。结论尽管可塑纤维桩自身的弯曲强度较低,但是修复离体牙后整体抗折强度较高,可以满足临床要求。各纤维桩组折裂模式较铸造桩组更有利于修复体失败后的再修复。     

桩核直径和材料种类对根管治疗后牙齿抗折强度的影响

目的：本研究的目的为评估不同直径的铸造纯钛桩和玻璃纤维桩对根管治疗后牙齿抗折强度的影响。方法：选择50颗新近拔除的上颌中切牙,根管治疗后将样本完全随机分为5组（n=10）：A组：1．35mm铸造纯钛桩;B组：1．5mm铸造纯钛桩;C组：1．375mm预成玻璃纤维桩;D组1．5mm预成玻璃纤维桩;E组：树脂修复。采用万能材料测试机对样本的抗折强度进行测试,对实验结果进行统计分析并进行断裂模式分析。结果：5组样本的抗折强度如下：A组404．22±73．92N,B组488．17±78．68N,C组280．32±45．23N,D组317．53±50．87N,E组222．76±38．67N。其中C组与D组组问两两比较差异无统计学意义∽〉0．05）,其余各组间比较差异均有统计学意义（p〈0．05）。铸造纯钛桩主要表现为不可修复的根中或根尖损伤,而预成玻璃纤维桩主要表现为可修复的根颈部损伤或桩折。结论：铸造纯钛桩核修复上颌中切牙表现为较高的抗折强度,可承受较大载荷,而玻璃纤维桩核修复对牙根的破坏小,有利于患牙的再治疗。     

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。     

四种桩钉对无髓牙抗折力影响的比较

目的：比较四种桩钉下无髓牙的抗折力，评价阶梯形核桩钉对无髓牙抗折力的影响。方法：将28个离体上前牙随机分成4组，按常规制作核桩钉及金属全冠，试件分别放置在设计的根部夹具上测试。结果：研制的柱状阶梯形核桩钉及螺纹形核桩钉对无髓牙的抗折力与南京产合金种牙钉无显著差异(P＞0．05)。前三组与杭州产牙用根管钉组有非常显著差异(P＜0.01)且高于该组。结论：研制的螺纹形和柱状阶梯形核桩钉在无髓牙抗折力方面能满足临床要求。     

Fracture resistance of crowned incisors with different post systems and luting agents

This study evaluated the fracture resistance of crown-restored incisors with different post-and-core systems and luting cements. Fifty intact maxillary central incisors were randomly assigned to five groups of 10 teeth each. Group 1 was restored with fibre posts (Snowpost) luted with an adhesive composite resin cement (Panavia F). Group 2 was restored with titanium alloy posts (Parapost) luted with the resin cement, and Group 3 with titanium alloy posts and a glass-ionomer cement (Fuji I). Composite cores (Clearfil Photocore) were built up in groups 1, 2 and 3. Group 4 was restored with cast post-and-cores luted with the resin cement, and group 5 with the cast post-and-cores and the glass-ionomer-cement served as a control group. All teeth were restored with metal-ceramic crowns. After thermal stressing, the specimen was then secured in a universal testing machine. Fracture loads and modes were recorded. One-way ANOVA and a Tukey test were used to determine significant differences between the failure loads of groups. Chi-square test was conducted for evaluation of the fracture modes. The fracture loads of groups 1 and 2 were significantly higher than that of the control group (P<0.05). Group 1 had a significantly higher number of repairable fractures than the other four groups (P<0.001). Within the limitations of this study, the results suggest that fibre posts can be recommended as an alternative to cast and prefabricated metallic posts. Composite resin cement cannot significantly improve fracture resistance of metallic post and crown-restored incisors.     

Effect of fibre post length and adhesive strategy on fracture resistance of endodontically treated teeth after fatigue loading

Objectives

To evaluate the effect of the length of fibre-posts¹ and type of adhesive cement² on the fracture resistance of endodontically treated teeth, after fatigue loading.

Methods

Eighty extracted upper pre-molars were sectioned at the CEJ and endodontically treated. After 24 h of water storage at 37 °C, RelyX Posts (3M-ESPE) were cemented with Panavia F 2.0 (Kuraray) or RelyX Unicem (3M-ESPE). A standardized composite core was built. Specimens were divided into four groups depending on the post–core ratio: (A) 2/1 (control); (B) 3/2; (C) 1/1 (small diameter); (D) 1/1(large diameter) and submitted to 1,200,000 cycles using a chewing simulator (Willytech). Immediately afterwards, all specimens that survived fatigue loading were fractured using a universal loading device (Micro-tester, Instron). Data were analysed with ANOVA.

Results

Four percent of the specimens failed during fatigue loading. The length of the post into the root affected the fracture resistance. The statistical outcome varied according to the inclusion of specimens failed during fatigue loading. However, the control group always had the lowest fracture resistance. The type of adhesive cement did not affect the fracture resistance. A prevalence of not-repairable failures was observed in specimens restored with the longest posts, whilst shorter posts led to more repairable failures.

Conclusions

Shortening the post length and the ensuing preservation of more tooth structure, offer the potential for reparability through an in-built fail safe mechanism and may thus reduce the occurrence of catastrophic failures.     

Influence of type of final restoration on the fracture resistance and fracture mode of endodontically treated premolars with occluso-mesial cavities

IntroductionThe aim of this study was to compare the fracture resistance of endodontically treated premolars after the application of three restorative materials (i.e., direct composite, indirect composite, and computer aided design/computer aided manufacturing CAD/CAM ceramic inlays) to restore a conservative occluso-mesial cavity preparation.Materials and methodssixty sound maxillary premolars were divided into four experimental groups; group A: the control group, where neither root canal treatment nor preparation were performed; group B: teeth were restored with a direct Filtek Z250 composite restorative material; group C: teeth were restored with an indirect inlay Filtek Z250 composite restorative material; group D: teeth were restored with IPS E.Max CAD/CAM monolithic ceramic inlays. Access cavities and root canal treatment procedures were conducted using standard techniques. Then, the cavities were restored with direct composite restorative materials following manufacturer’s instructions. Each group received mesial-occlusal cavities and restored according to the designated group.Teeth from all groups were exposed to a thermocycling regimen of 500 cycles in water baths at 5–55 °C. Then, each specimen was mounted on a special fixture on a computer controlled Instron Universal Testing Machine. An axial compressive load was applied to the palatal cusp up to failure at an angle of 45°. The force was applied at the rate of 2 mm/min until visible or audible evidence of fracture was observed. The force at fracture was measured in MPa, and the fracture mode was recorded as either favorable [restorable adhesive fracture above the cemento-enamel junction (CEJ)] or unfavorale (non-restorable fractures under CEJ). The obtained data were analyzed using the SPSS version 21.0 statistical software. One-way ANOVA and Tukey's test were used to compare the mean values of maximum load of the four groups. Pearson's Chi-square test was used to compare the distribution of failure mode among the four groups. The p-value of ≤ 0.05 was used to report the statistical significance of results.     

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.     

不同桩核和箍结构与牙根抗力的实验研究

目的研究不同材料桩核及箍结构对牙体抗折强度的影响。方法32颗完整离体下颌第一前磨牙于颊侧釉牙骨质界上1mm处截冠,制备残根模型;按桩核材料及箍结构不同分为四组:铸造桩核无箍结构组(A1组)、铸造桩核有箍结构组(A2组)、纤维桩无箍结构组(B1组)、纤维桩有箍结构组(B2组)。所有试件自铸造全冠颈缘完成线下2mm包埋于自凝塑料内,电子万能试验机以与牙长轴成150°、横梁位移速度1.0mm/min于颊尖顶加载,测定断裂载荷并进行统计学分析(а=0.05)。结果四组试件的折裂载荷均值(KN)依次为:1.46±0.45、1.07±0.21、1.13±0.30、1.02±0.27。铸造桩核无箍结构组表现出显著高的折裂载荷(P<0.05)。桩核材料对试件的破损模式亦有显著的影响(P<0.05)。结论残根桩核修复时,采用牙冠延长术设计2mm高的箍结构,降低了修复后牙体的抗力;使用预成纤维桩联合复合树脂核修复有利于保护残根。     

The effect of luting media on the fracture resistance of a flame sprayed all-ceramic crown

Objectives: This in vitro study investigated the effect of selected luting media on the fracture resistance of a flame-sprayed all-ceramic crown.

Methods: Three groups of 10 human upper premolar teeth were prepared for crowning using a standardised technique. Flame sprayed crowns were fabricated and cemented onto the preparations using zinc phosphate (ZPC), glass polyalkenoate (GPC) or composite luting cement (CLC). During crown seating, a pressure perfusion system simulated pulpal fluid outflow equivalent to 300 mm of H₂O. Compressive fracture resistance was determined for each group using a Universal Testing Machine with a crosshead speed of 1 mm min⁻¹. A group of unrestored teeth acted as a control.

Results: The fracture resistance of the groups ranked as follows: ZPC>CLCGPC=unrestored teeth. The difference between the fracture resistance of ZPC and CLC groups and the control group was statistically significant. The mode of fracture between the luted crowns and natural crowns was markedly different.

Conclusions: When tested in compression, a new, flame-sprayed all-ceramic crown, when luted in place using ZPC, GPC or CLC, could produce strengths comparable to or greater than natural unrestored teeth. The luting agent used significantly affected the recorded fracture loads.     

Effect of different ferrule designs on the fracture resistance and failure pattern of endodontically treated teeth restored with fiber posts and all-ceramic crowns

Objective

This study investigated the effect of different ferrule heights on endodontically treated premolars.

Materials and Methods

Fifty sound mandibular first premolars were endodontically treated and then restored with 7-mm fiber post (FRC Postec Plus #1 Ivoclar-Vivadent) luted with self-polymerized resin cement (Multilink, Ivoclar Vivadent) while the coronal section was restored with hybrid composite core build-up material (Tetric Ceram, Ivoclar-Vivadent), which received all-ceramic crown. Different ferrule heights were investigated: 1-mm circumferential ferrule without post and core (group 1 used as control), a circumferential 1-mm ferrule (group 2), non-uniform ferrule 2-mm buccally and 1-mm lingually (group 3), non-uniform ferrule 3-mm buccally and 2-mm lingually (group 4), and finally no ferrule preparation (group 5). The fracture load and failure pattern of the tested groups were investigated by applying axial load to the ceramic crowns (n=10). Data were analyzed statistically by one-way ANOVA and Tukey’s post-hoc test was used for pair-wise comparisons (α=0.05).

Results

There were no significant differences among the failure load of all tested groups (P<0.780). The control group had the lowest fracture resistance (891.43±202.22 N) and the highest catastrophic failure rate (P<0.05). Compared to the control group, the use of fiber post reduced the percentage of catastrophic failure while increasing the ferrule height did not influence the fracture resistance of the restored specimens.

Conclusions

Within the limitations of this study, increasing the ferrule length did not influence the fracture resistance of endodontically treated teeth restored with glass ceramic crowns. Insertion of a fiber post could reduce the percentage of catastrophic failure of these restorations under function.     

玻璃纤维桩修复不同缺损程度前牙抗折裂性能的比较

将离体上前牙进行根管治疗后分为4 组,使用玻璃纤维桩修复后测试抗折裂强度.结果显示:牙本质肩领为2 mm组抗折裂强度较高.     

两种桩系统修复对根管治疗牙强度的影响

目的比较两种不同弹性模量的桩系统对根管治疗牙修复后强度的影响。方法20颗近期拔除的完整人上颌中切牙,根管治疗后随机分成两组,每组10颗。组一进行玻璃纤维桩ParaPost Fiber white(Coltene/ whaledent Inc)、复合树脂核及铸造全冠修复。组二进行铸造镍铬桩核及铸造全冠修复。每组牙均保留1.5mm的牙本质肩领(Ferrule)。实验标本包埋于自凝树脂块中,固定在DCS5000材料试验机上。加栽头以1mm/min的速度,与牙长轴成130°进行加载直至标本断裂。断裂强度采用独立样本t检验,断裂方式采用Fisher’s精确概率法(P <0.05)。结果组一断裂强度为43.406±18.959kg,组二33.680±9.675kg,差异无显著性(P>0.05)。可修复性断裂方式见于玻璃纤维桩核,而不可修复性的破坏多见于铸造镍铬桩核组(P<0.001)。结论在牙体预备保留1.5mm牙本质肩领(Ferrule)的情况下,两种不同弹性模量的桩对根管治疗牙桩核加全冠修复后的强度影响无差异,可修复性的破坏见于弹性模量与牙本质近似的玻璃纤维桩组。