Fracture resistance of structurally compromised root filled bovine teeth restored with accessory glass fibre posts

Aim  To evaluate the mechanical behaviour of structurally compromised root filled bovine roots after restoration with accessory glass fibre posts.
Methodology  Fifty roots of bovine teeth received conventional post preparations with a cervical diameter of 3.5 mm. The roots were assigned to five groups ( n  = 10): group MP – cast metal post, group GP – glass fibre post and group AGP – glass fibre post plus accessory glass fibre posts. In groups GP-R and AGP-R (similar to groups GP and AGP), 2 mm of coronal tooth structure were left intact. All groups were subjected to an elastic limit assay and tested in an universal machine for fracture resistance. Repeated measures anova were performed to examine differences in fracture resistance; fracture modes were analysed by Fischer's exact test.
Results  The mean fracture resistance values (kgf) were 61.8 (MP), 63.1 (GP), 55.5 (AGP), 56 (GP-R) and (53.1) AGP-R. No statistically significant difference was found between groups. The Fisher's exact test indicated significant differences ( P  < 0.05) in the fracture mode amongst groups MP, GP and AGP, indicating 100%, 50% and 10% of catastrophic fractures, respectivelly.
Conclusions  The use of accessory glass fibre posts affected the fracture mode favorably: 90% of fractures in group AGP were in the coronal third.     

Influence of post system and remaining coronal tooth tissue on biomechanical behaviour of root filled molar teeth

AIM: To investigate ex vivo the influence of post system and amount of remaining coronal tooth tissue on the fracture resistance, fracture mode and strain of root filled molar teeth. Methodology: Seventy mandibular human molar teeth were divided into seven groups (n = 10), one control (sound teeth) and six experimental groups resulting from the interaction between the two study factors: post system (Pa, post absence; Gfp, glass fibre post; Cmp, cast Ni-Cr alloy post and core) and amount of remaining coronal tooth tissue (Fe, 2 mm of ferrule; NFe, no ferrule). Teeth in the experimental groups were restored with metal crowns. For the strain gauge test, two strain gauges per sample were attached on the buccal and proximal root surfaces, and the samples of each group (n = 5) were submitted to a load of 0-100N. Fracture resistance (N) was assessed in a mechanical testing device (n = 10). Strain gauge and fracture resistance data were analysed by two-way anova (3 × 2) followed by the Tukey's HSD and Duncan's test (α = 0.05). The failure mode was evaluated using an optical stereomicroscope and classified according to the location of the failure. Results: The absence of ferrule was associated with lower fracture resistance regardless of the post system. Groups restored with glass fibre post and cast Ni-Cr alloy post and core had similar fracture resistance and higher values than groups without posts, regardless of the remaining coronal tooth tissue. Teeth with no ferrule and cast Ni-Cr alloy post and core resulted in catastrophic fractures and those with no ferrule and glass fibre post or no ferrule and post absence resulted in restorable failures. Buccal strain was higher in sound teeth and lower in teeth without posts. Glass fibre post insertion decreased the buccal strain compared to the teeth with ferrule and absence of post. CONCLUSIONS: Two millimetre of ferrule had a significant influence on cusp strain, fracture resistance and failure mode. The glass fibre post was as effective as the cast Ni-Cr alloy post and core in the restoration of root filled molars regardless of the remaining tooth tissue. Absence of a post decreased the fracture resistance and increased the cusp strain.     

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。     

Effect of ferrule height and glass fibre post length on fracture resistance and failure mode of endodontically treated teeth

The purpose of this study was to evaluate the combined effect of ferrule height and post length on fracture resistance and failure mode of endodontically treated teeth restored with glass fibre posts, composite resin cores and crowns. Ninety human maxillary central incisors were endodontically treated and divided into three groups (n = 30) according to the ferrule heights: 4, 2 and 0 mm, respectively. Post spaces in each group were prepared at 2/3, 1/2 and 1/3 of the root length (n = 10). The specimens were received fibre posts, composite resin core build up and cast metal crowns. After thermocycling, compressive static load was applied at an angle of 135° to the crowns. Two‐way analysis of variance showed significant differences in the failure load in the ferrule height groups, no significant differences in post length groups and no significant interaction between ferrule heights and post lengths. More restorable failure modes were observed.     

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。     

Effects of post system and length on the strain and fracture resistance of root filled bovine teeth

Aim To investigate ex vivo the effects of different post systems and lengths on the strain and fracture resistance of root‐filled teeth. Methodology One hundred and thirty‐five bovine incisors were sectioned 15 mm from their apices, root‐filled and divided into three groups (n = 45): fibreglass post; prefabricated steel post; cast post and core. Each group was divided into three subgroups (n = 15) according to the post length: 5.0 mm; 7.5 mm; 10.0 mm. All teeth were restored with metal crowns. For strain‐gauge measurement, two strain gauges per sample were used. The fracture resistance (N) was measured and the data were analysed with two‐way analyses of variance, followed by the Tukey’s HSD test (α = 05). Results For all posts, decreased lengths resulted in increased microstrain values. However, the fibreglass posts were associated with lower increases when compared with cast post and cores and prefabricated steel posts, which showed microstrain values two times higher when the post length was 5.0 mm. The two‐way analyses of fracture resistance values revealed that post length was statistically significant for the metal posts and not significant for the fibreglass post. The fracture mode analysis indicated that all groups tended to demonstrate root fractures in groups restored with metal posts and resin core fractures in groups restored with fibreglass posts. Conclusions The cast post and core when the length was 10.0 mm had the highest fracture resistance; however, the fibreglass post was effective with the three post lengths, with higher fracture resistance than metal posts when the length was 5.0 mm.     

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。     

Effect of length post and remaining root tissue on fracture resistance of fibre posts relined with resin composite

To investigate the influence of post length and amount of remaining root tissue on the fracture resistance of roots restored with fibre posts relined with resin composite. Ninety upper canine teeth were divided into nine groups (n = 10). The post spaces were prepared resulting in different lengths, as follows: group 2/3, preparations with lengths of 10 mm; group 1/2, preparations with lengths of 7·5 mm; and group 1/3, preparations with lengths of 5 mm. Each group was divided into 3 subgroups according to amount of remaining root tooth tissue (2, 1 mm or 0·5 mm of thick root). Fibre posts relined with resin composite were cemented, and all teeth were restored with metal crowns. The samples were submitted to the fracture resistance test in a universal testing machine, at an angle of 135° and speed of 0·5 mm min^?1. Failure modes were observed and the data of fracture resistance were submitted to the anova and Tukey's (α = 0·05). No statistically significant difference in fracture resistance was found among different post lengths (P > 0·05). Remaining dentin thickness of 2 and 1 mm did not differ statistically in fracture resistance (P > 0·05), which was higher than of 0·5 mm dentin thickness (P < 0·05). A prevalence of repairable failure was observed in all groups. It can be concluded that the length of fibre post relined with resin composite did not influence fracture resistance, but thickness was an important factor for the restoration of endodontically treated teeth.     

Fracture resistance of the buccal cusps of root filled maxillary premolar teeth restored with various techniques

AIM: To compare the cusp fracture resistance of teeth restored with composite resins and two post systems. METHODOLOGY: Eighty extracted single-rooted human maxillary premolars were randomly assigned to eight groups (n = 10). Group 1 (control) did not receive any preparation. From groups 2 to 8, the teeth were root filled and mesio-occluso-distal (MOD) cavities were prepared. Group 2 remained unrestored. Group 3 was restored with packable resin composite using a single-step adhesive. Group 4 was restored with packable resin composite using a single-step adhesive and a thin layer of flowable resin composite. Group 5 was restored with packable resin composite using a total-etch two-step adhesive. Group 6 was restored with ormocer resin composite using a total-etch two-step adhesive. Group 7 was restored with an endodontic glass fibre post and hybrid resin composite using a total-etch two-step adhesive. Group 8 was restored with an endodontic zirconium post and hybrid resin composite using a total-etch two-step adhesive. The teeth were then mounted in a universal testing machine, the buccal cusp loaded (30 degrees ) until fracture, and the data analysed statistically. RESULTS: Group 1 had the greatest fracture resistance, and group 2 the poorest. Groups 5-8 had significantly greater (P < 0.05) fracture resistance than groups 3 and 4. No significant differences were found between groups 3 and 4, or amongst groups 5-8 (P > 0.05). CONCLUSIONS: For root filled maxillary premolars with MOD cavities, adhesive resin composite restorations, with and without glass and zirconium posts, increased the fracture resistance of the buccal cuSPS. A total-etch two-step adhesive increased significantly fracture resistance more than a one-step adhesive. For the one-step adhesive, an additional layer of flowable resin composite did not enhance fracture resistance.     

两种桩核系统在上颌前牙残冠残根修复中的临床研究

目的：比较铸造金属桩核与玻璃纤维桩核修复上颌前牙残冠残根的临床效果。方法：随机选取16～50岁的病例128例共150个上颌前牙残冠残根进行修复,其中64个牙制作铸造金属桩核,86个牙制作玻璃纤维桩核,桩核完成后均行烤瓷熔附金属全冠修复。结果：经过0.5～2.5年的随访观察,铸造金属桩组出现7个牙根折,3个牙修复体松动脱落,1个牙慢性尖周炎复发,成功率为82.81%。玻璃纤维桩组出现2个牙根折,1个牙修复体松动脱落,1个牙窦道溢脓,成功率为95.35%。经χ2检验,两组的差异有显著性。结论：玻璃纤维桩核修复上颌前牙残冠残根具有更好的临床效果。     

铸造桩表面喷砂处理对牙根抗折性能影响的体外实验研究

目的：研究铸造桩表面喷砂处理对牙根抗折性能的影响。方法：20颗近期拔除的单根第一前磨牙,根管治疗后于釉牙骨质界冠方1.5mm截冠,随机分为2组,铸造桩核及金属全冠修复。实验组铸造桩粘固前表面喷砂处理,对照组不作处理。试件包埋于丙烯酸树脂块中,在电子万能实验机上进行测试。结果：对照组牙根折裂强度为2.773±0.357kN,实验组牙根折裂强度为3.113±0.357kN,2组间差异具有统计学意义（P〈0.05）。结论：对铸造金属桩表面进行喷砂处理,可以提高桩核冠修复后牙根的抗折强度。     

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目的比较两种不同材料桩核系统修复漏斗形残根后牙齿抗折性能。方法选择2006年11月至2007年5月山东省无棣县中心医院拔除的牙周病患者完整上颌第一中切牙20颗,截冠后行完善根管治疗,模拟临床情况,根管口磨除部分牙体组织后形成漏斗形残根。然后随机分成两组,分别采用镍铬合金桩、玻璃纤维桩两种不同材料的桩核冠修复。所有样本包埋后,置于电子万能测试机上进行牙根抗折性能的测试。结果牙根抗折强度镍铬合金桩核组小于玻璃纤维桩核组(P<0.01)。结论在漏斗形残根保存修复中,玻璃纤维桩核系统应该为一种较好的选择方式。     

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。     

纤维桩和金属桩修复喇叭状残根抗折性研究

目的：比较纤维桩和铸造金属桩修复重塑后喇叭状残根的抗折性能。方法：选择离体上颌中切牙16个,分为A、B两组,每组各8个,将标本制备成喇叭状根管,并用复合树脂重塑根管。A组用铸造金属桩核修复,B组用纤维桩及复合树脂核修复。两组标本经铸造全冠修复后,放置在电子万能试验机上,与牙长轴135°方向静态加载,直至牙齿折裂,记录加载负荷和折裂模式。结果：铸造桩核组的折裂强度为（0．591±0．094）kN,纤维桩组的折裂强度为0．489±0．081kN,经统计学处理,差异有显著性（P〈0．05）。铸造桩核组8个中6个为破坏性修复;纤维桩组均为可修复性折裂。经统计学处理,两组有显著性差异（p〈0．05）。结论：喇叭状残根经根管重塑后,选择纤维桩联合复合树脂核修复更有利于保护薄弱残根。     

A new classification system for the restoration of root filled teeth

The aim of this report is to (i) review the current literature on the status of root filled teeth, (ii) analyse the most important factors in decision‐making, (iii) discuss the current restorative concepts, and (iv) classify both the evidence and clinical practice in a way that seeks to be clear, understandable and helpful for clinicians. Restoration of root filled teeth represents a challenge for the clinician and remains a controversial subject. The guidelines describe a new classification that is drawn from evidence presented in the literature and also from clinical expertise‐based reviews. It describes five categories of teeth.