Fracture resistance of endodontically treated teeth restored with composite posts

STATEMENT OF PROBLEM: The most recent application of fiber-reinforced composites involves their use as post and core systems to restore endodontically treated teeth. Even though this last application has been advertised and used clinically by many dentists, there is very little information regarding the physical properties of these post systems. PURPOSE: The purpose of this study was to compare the effect of 3 fiber-reinforced composite post systems on the fracture resistance and mode of failure of endodontically treated teeth. MATERIAL AND METHODS: Ninety maxillary central incisors were divided into 8 experimental groups and 1 stainless steel (ParaPost) control group of 10 specimens each. Eighty teeth were assigned to 2 main experimental groups called "narrow" and "flared" canals. For the narrow canal group, post spaces were prepared with the corresponding reamer to restore the teeth with FibreKor, Luscent anchors, and Ribbond posts of 1.5 mm, 1.6 mm, and 2.0 mm in diameter, respectively. For the flared canals group thin-walled canals were simulated. Teeth for the flared canals were restored with the same posts but were cemented into tapered 2 mm wide canals created with a tapered diamond bur. Prefabricated posts (FibreKor and Luscent anchors) for narrow and flared canals were cemented with an autopolymerized resin cement and a flowable composite, respectively, whereas customized Ribbond posts were luted with a light-polymerized flowable composite for both canal types. An additional set of 20 Ribbond posts with coronal portions of variable size and shape referred to as "Ribbond nonstandardized" were also prepared and evaluated. Specimens were loaded to failure (kg) with a universal testing machine at a crosshead speed of 0.05 cm/min until failure occurred. Data were analyzed with analysis of variance and Student t tests (P<.05). RESULTS: Statistical analysis revealed no significant difference between flared and narrow canals in mean load to failure between the post systems except for the Ribbond posts (P<.01). For the narrow canal, the mean load ranged from a low of 4.55 (+/-1.49) kg for the Ribbond standard to a high of 12.9 (+/-1.64) kg for the Luscent anchors. For the flared canal the low mean was 9.04 (+/-1.76) kg for FibreKor and the high was equal for both Luscent anchors and Ribbond standard, 12.87 (+/-2.69) and 12.87 (+/-3.54), respectively. Overall, the ParaPost control group had the highest load value (18.33 +/- 3.27 kg) (P<.05). Ribbond nonstandardized had a mean load to failure of 24.91 (+/-11.53) Kg for the narrow canal group and 31.95 (+/-11.98) kg for the flared canal. Results from these groups were excluded from the statistical analysis because of the uncontrolled core sizes and high standard deviations. No root fractures occurred in any of the experimental groups. CONCLUSION: Results from the study show that the load to failure of the stainless steel posts were significantly stronger than all the composite posts studied. However, the mode of failure or deflection of the fiber-reinforced composite posts is protective to the remaining tooth structure.     

Impact resistance of crowned endodontically treated central incisors with internal composite cores

Abstract The impact fracture resistance of crowned endodontically treated teeth with composite cores but without posts, that had either no coronal dentin remaining or a 1mm dentin collar was compared to that of unrestored, caries free teeth. The teeth were struck mid-labially to simulate a common trauma situation using a pendulum device and fracture1 resistance determined by calculation of absorbed energies. No significant difference was found between the intact teeth and the-crowned root treated teeth with composite core and a 1mm dentin collar. Crowned loot treated teeth with a composite core but no coronal dentin had significantly reduced fracture resistance (p < 0.05). Teeth with the dentin collar mainly fractured obliquely from the bueeal crown margin to a point coincident with the simulated alveolus, representing a clinical situation which would allow retention rather than extraction of the tooth.     

Fracture resistance and primary failure mode of endodontically treated teeth restored with a carbon fiber-reinforced resin post system in vitro

PURPOSE: This study was undertaken to characterize the fracture resistance and mode of fracture of endodontically treated incisors restored with cast post-and-core, prefabricated stainless steel post, or carbon fiber-reinforced composite post systems. MATERIALS AND METHODS: Ten endodontically treated teeth restored with each technique were subjected to a compressive load delivered at a 130-degree angle to the long axis until the first sign of failure was noted. The fracture load and the mode of fracture were recorded. RESULTS: The failure loads registered in the three groups were not significantly different. Between 70%, and 80% of teeth from any of the three groups displayed fractures that were located above the simulated bone level. CONCLUSION: The use of carbon fiber-reinforced composite posts did not change the fracture resistance or the failure mode of endodontically treated central incisors compared to the use of metallic posts.     

Fracture resistance of endodontically treated teeth restored with three different prefabricated esthetic posts

Purpose: This study was undertaken to evaluate the role of composition of prefabricated esthetic posts in fracture resistance of endodontically treated teeth in vitro. Materials and Methods: Thirty human, single‐rooted teeth (maxillary central incisors and canines) with similar root dimensions, extracted for therapeutic reasons, were used in this study. The crowns were removed below the cementoenamel junction to obtain a standard root length of 17 mm. The roots were endodontically treated following the conventional manual technique and randomly assigned to three groups (n = 10) according to the post used: Aestheti‐Post, Bisco, Schaumberg, Illinois; FibreKor Post, Jeneric/Pentron, Wallingford, Connecticut; and CosmoPost, Ivoclar Vivadent, Schaan, Liechtenstein. The root canals were rendered patent, and the root preparations were standardized through flaring with the manufacturers' drills included in the respective kits. The posts were cemented with an adhesive system and a resin cement (All‐Bond 2 and C & B, Bisco, respectively), according to the manufacturers' directions. Composite resin (Tetric Ceram, Ivoclar Vivadent) crowns were built up using a preformed polyester matrix, and the specimens were mounted in metallic rings with cold‐cure acrylic resin and kept in saline solution at 4°C for 24 hours. Fracture resistance was then determined using an EMIC DL‐2000 universal testing machine. The crosshead speed was 0.5 mm/min with the 45‐degree compressing load at the middle third of the crown. Data were analyzed using one‐way analysis of variance and Tukey'stest (p<.001). Results: Mean fracture resistance was as follows: Aestheti‐Post, 83.5 kgf; FibreKor Post, 85.7 kgf; and CosmoPost, 36.5 kgf. The fracture strength of CosmoPost was significantly lower than that of the other posts. Teeth restored with CosmoPost had post fractures, and in three specimens, those were associated with root fractures. Teeth restored with the other two posts presented fractures on the composite crowns. CLINICAL SIGNIFICANCE Compared with ceramic posts, carbon‐fiber and glass‐fiber prefabricated esthetic posts provide endodontically treated teeth higher fracture resistance.     

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。     

离体前磨牙3种修复方法的抗力研究

［摘要］目的 探讨离体前磨牙根管充填后不同修复方法对牙体抗折性能的影响因素。 方法60颗离体下颌前磨牙随机分为4组,A组为空白对照组,B、C、D组分别按同一标准根管治疗后,牙冠统一制备成近中洞型（MO）备用,B组采用复合树脂修复,C组采用全瓷嵌体修复,D组采用高强度纤维复合树脂修复。四组样本通过负荷加载（加载头与牙齿长轴呈135°,横梁位移速度1 mm/min）,实验记录各样本折裂时的最大负荷值,并观察其折裂模式。 结果 A组折裂负荷值最高(1 413.91±95.93)N,D组其次 (1324.66±88.56)N,B组折裂负荷值最低(796.57±118.85)N, C组(961.05±101.45)N, A组与D组负荷值差异无统计学意义（P>0.05）,其余组间均有统计学差异（P＜0.05））;折裂模式D组与其它3组有统计学差异（P＜0.05）,其余组间均无统计学差别（P>0.05）。 结论 高强度纤维复合树脂修复,可以明显提高修复体的折裂负荷值,折裂模式也更有优势。     

In vivo fractures of endodontically treated posterior teeth restored with enamel-bonded resin

Abstract The cumulative survival rate of 190 endodontically treated posterior teeth were assessed in a retrospective study; all teeth had an MO/DO or an MOD cavity restored with a composite resin without cuspal overlays after previous acid-etching of the enamel. In contrast to our previous study on endontically treated posterior teeth restored with amalgam, the survival rate of the MOD resin-restored teeth was equal to that of MO/DO teeth. Teeth restored with a light-activated resin had a much lower survival rate than teeth restored with a chemically-activated material, the cause presumably being that the light-activated resins were insufficiently irradiated. Nearly 25% of the teeth had been restored with a microfilled resin for anterior use and these teeth had a lower survival rate than had teeth restored with a macrofilled or hybrid resin. It was also found that a beveling technique did not decrease the fracture rate while the use of an intermediate layer of low-viscosity resin resulted in a significant improvement.     

Fracture resistance of roots prosthetically restored with intra‐radicular posts of different lengths

Summary The purpose of this study was to assess the fracture resistance of roots that were prosthetically restored with intra‐radicular posts of different lengths. Forty‐five bovine incisors were sectioned 17 mm from their apices, endodontically treated and randomly divided into three experimental groups: GI, fibreglass posts luted at a depth of 12 mm; GII, 8 mm and GIII, 4 mm. All posts were luted with dual resin cement. Resin composite cores were prepared with standardized measurements, 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, until fracture occurred. The data, in MPa, were submitted to the analysis of variance (anova ) followed by Tukey’s test (α = 0·01). No statistically significant difference (P > 0·01) was found between GI (129·72 ± 12·14) and GII (154·3 ± 12·08), which presented the highest fracture resistance values. Group GIII (100·5 ± 8·07) showed lower fracture resistance (P < 0·01) when compared with GI and GII. Within the limitations of this study, it was concluded that the post lengths influenced the fracture resistance of prosthetically restored roots. These results suggest that it is not necessary to perform excessive intra‐radicular post‐space preparation to improve the fracture resistance of roots.     

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.     

Fracture resistance and stress distribution in endodontically treated maxillary premolars restored with composite resin.

PURPOSE: The aim of this study was to evaluate the effect of endodontic and restorative treatment on the fracture resistance of posterior teeth. MATERIALS AND METHODS: Fifty intact premolars were selected and randomly placed into five groups (n = 10): G1, intact teeth (control); G2, mesial-occlusal-distal (MOD) preparation; G3, MOD preparation restored with composite resin (Z-250, 3M ESPE); G4, MOD preparation and endodontic treatment; and G5, MOD preparation, endodontic treatment, and composite resin restoration. The specimens were submitted to an axial compression load in a mechanical test machine (EMIC), at a speed of 0.5 mm/min. Fracture patterns were analyzed at four levels. Five 2D numerical models were created by Ansys 10.0 for finite element analysis (FEA). RESULTS: Mean values of compressive strength for all groups were (Kgf): G1 (83.6 +/- 25.4); G2 (52.7 +/- 20.2); G3 (82.1 +/- 24.9); G4 (40.2 +/- 14.2); G5 (64.5 +/- 18.1). Statistical analysis (ANOVA and Tukey's test) showed that fracture resistance of G1 was significantly higher than that of G5, G2, and G4. Resistance of G3 was also higher than that of G2 and G4. Results showed that the tooth resistance is completely maintained when MOD preparation is restored with composite resin and partially recovered when MOD preparation associated with an endodontic access is restored in the same way. The endodontic treatment and composite resin restoration influenced stress distribution in the dental structure. CONCLUSIONS: Composite resin restoration plays an important role in recovering tooth strength. With regard to fracture mode, restoration and endodontic treatment increased the incidence of periodontal involvement, which was demonstrated by association with the finite element mechanical test method.     

Resistance to fracture of restored endodontically treated teeth

Abstract Endodontically treated teeth were restored by 8 different methods. Copper rings were filled with commercial hard setting cement and the teeth were placed into the cement to the level of the cemento-enamel junction. The teeth were grouped according to restorative methods, mounted in an Instron T.T. machine and subjected to a slowly increasing compressive force until fracture occurred. The force of fracture for each tooth was recorded and the results in the various groups compared. All teeth fractured in a similar manner, irrespective of restorative method used. Preparation of a post space in the roots significantly weakened the teeth. Cementation of a steel parapost with zinc oxyphosphate cement did not significantly strengthen the teeth. Filling the post space and the access cavity with a composite resin following acid etching of the root canal and cavity walls strengthened the teeth more than other methods used to restore them. This finding may be of clinical importance, for instance in the restoration of endodontically treated young teeth with incomplete root formation and wide root canals.     

Fracture resistance and failure patterns of endodontically treated mandibular molars restored using resin composite with or without translucent glass fiber posts

The elastic modulus of the restorative material is important in restoring endodontically treated teeth. This study aimed to compare the fracture resistance and failure patterns of 90 mandibular molars restored using resin composites with or without fiber posts, with respect to the number of residual cavity walls. Five restoration types were performed corresponding to different wall defects (groups 1-5). Groups were divided in two subgroups corresponding to the use or absence of fiber posts. Teeth were loaded and resistance of specimens was measured as the axial compressive load to cause fracture and macroscopic fracture patterns were observed. One way ANOVA revealed a significant difference in fracture resistance (p < 0.001). Tukey post hoc test also revealed significant differences between groups as samples restored with fiber posts exhibited mostly restorable fractures. It was concluded that the resistance of endodontically treated mandibular molars restored with composite resins is mainly affected by the number of residual walls. Using fiber-reinforced posts optimized fracture patterns.     

Evaluation of fracture resistance of endodontically treated teeth restored with composite resin along with fibre insertion in different positions in vitro

This study was carried out to compare the different techniques of placement of polyethylene fibre (Ribbond) on reinforcement of endodontically treated teeth with MOD cavities in vitro. Forty extracted human premolars were randomly assigned to four groups (n = 10). Teeth in Groups I–IV received root canal treatment and a MOD cavity preparation, with gingival cavosurface margin 1.5 mm in coronal to cementoenamel junction. Group I served as no fibre group, Group II as occlusal fibre group, Group III as base fibre group and Group IV as dual‐fibre group (occlusal and base both). Subsequent to restoring with composite resin and thermocycling, a vertical compressive force was applied at a cross‐head speed of 0.5 mm min^?1 using universal testing machine until fracture. Data were analysed using one‐way analysis of variance and Tukey's post hoc tests. Fracture resistance was significantly highest in dual‐fibre group (P < 0.001) as compared with other groups. The highest favourable fracture rate was observed in the base fibre group (70%). This study concluded that the use of polyethylene fibre inserted over or under the restoration significantly increased the fracture strength of the root canal‐treated teeth and maximum fracture resistance was observed when cavity was restored using dual‐fibre technique.     

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。     

Fracture resistance of endodontically treated molars restored with extensive composite resin restorations

STATEMENT OF PROBLEM: When cuspal coverage is required, there is no evidence that indirect composite resin restorations are superior to direct restorations in terms of biomechanical behavior. PURPOSE: The purpose of this in vitro study was to compare the fracture resistance of cusp-replacing direct and indirect composite resin restorations in endodontically treated molars. MATERIAL AND METHODS: Forty-five human mandibular molars were selected and divided into 3 groups (n=15): DIR specimens, restored with direct composite resin (Estelite Sigma) restorations; IND specimens, restored with indirect composite resin (Estelite Sigma) restorations, and control specimens, which remained intact. Endodontic treatment was performed using NiTi ProTaper rotary instruments, and teeth were filled using lateral condensation of gutta-percha and sealer. Extensive Class II MO cavities were prepared, and the 2 mesial cusps were reduced, allowing a 2-mm layer of composite resin. All teeth were prepared to the same dimensions, considering reasonable human variation. Specimens were loaded to failure and the fracture loads were recorded (N). The mode of fracture was determined using a stereomicroscope and classified as favorable or unfavorable failure. The data were subjected to a Kruskal-Wallis test, multiple-comparison Mann-Whitney test, and a chi-square test (alpha=.05). RESULTS: Significant differences (P<.001) were observed between the control group and both DIR and IND groups. However, no significant difference was found between the DIR and IND groups. The chi-square test did not show a significant difference in the frequencies of favorable/unfavorable failure modes among the 3 groups (P=.981). CONCLUSIONS: No significant difference was observed in the fracture resistance of endodontically treated molars restored to original contours with an extensive cusp-replacing direct or indirect composite resin restoration.     

Fracture resistance of endodontically treated teeth restored with bonded amalgam and full crowns

The use of dentin bonding prior to placement of core build-up restorations has been shown to reduce microleakage and reinforce remaining tooth structure. However, information is lacking about the influence a core build-up has on the fracture resistance of crowned teeth. The purpose of this in-vitro study was to compare the influence of three types of core build-ups on the fracture resistance of crowned teeth.