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.     

Fracture resistance of endodontically treated premolars with fibre-reinforced composite restorations

This study investigated the fracture resistance and failure mode of endodontically treated premolars restored with a glass fibre-reinforced composite resin. Endodontically treated maxillary premolars were divided in 4 groups: group O: occlusal access opening restored with direct composite; group O+: as group O but with fibre reinforcement; group MOD: occlusal access opening and mesio-distal (MOD) cavity restored with direct composite; group MOD+: as group MOD but with additional fibre reinforcement. Pairwise comparisons of the fracture force among all groups was performed (95% confidence level). Fractures were classified in 4 groups depending on the type of fracture. Group O was the strongest (452.7N) and group MOD the weakest (292.4N). Fracture resistance was significantly different among all groups, except between groups O+ and MOD+. The majority of the unreinforced teeth displayed unfavourable fractures, while the reinforced teeth displayed more favourable fractures. The incorporation of glass fibre weakened endodontically treated but otherwise intact premolars; premolars with MOD restorations were stronger if reinforced with fibres. Fibre reinforcement led to more favourable fractures.     

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.     

Fracture resistance of endodontically treated maxillary premolars restored with CAD/CAM ceramic inlays

STATEMENT OF PROBLEM: Endodontically treated posterior teeth are more likely to fracture compared to posterior teeth with vital pulps. Reinforcement with an extracoronal restoration that covers the cusps is the most commonly recommended method for reducing the risk of fracture. It is not known whether bonded intracoronal restorations without cuspal coverage will reduce the risk of fracture. PURPOSE: The aim of this in vitro study was to investigate whether reinforcement of endodontically treated premolars with MOD preparations could be achieved by insertion of bonded CAD/CAM ceramic inlays. MATERIAL AND METHODS: Forty-five extracted maxillary premolars were equally distributed among 3 groups (END, CER, CTR). In group END (n=15), root canals were enlarged with a rotary NiTi system and obturated with heat-softened gutta-percha around a plastic carrier (Thermafil). After filling of the endodontic access cavities with autopolymerizing composite resin (Luxacore), standardized MOD cavity preparations were made and CAD/CAM ceramic inlays (CEREC) were fabricated and then bonded to the teeth with composite resin (Tetric) and an adhesive system (Syntac Classic). In group CER (n=15), teeth without endodontic treatment were restored with bonded inlays (CEREC). Sound premolars served as controls (group CTR, n=15). Teeth were then thermal cycled (1445 cycles, dwell time: 30 seconds, 5 degrees /55 degrees C). An eccentric load was applied on the buccal incline of the palatal cusp in a universal testing machine until cusp fracture (N). Fracture load was evaluated with the Mann-Whitney test, and type of fracture, with a chi-square analysis (alpha=.05). The type of fracture was determined by visual inspection: type I - supragingival fracture within the palatal cusp; type II - fracture below cemento-enamel junction of palatal cusp; and type III - fracture of palatal cusp and central portion of the tooth exposing the root canal cavity. RESULTS: No significant difference was found among the 3 groups with respect to load required for fracture. Mean fracture load +/- SD was recorded as follows: 291.6 +/- 113.7 N for group END, 363.2 +/- 140.3 N for group CER, and 296.5 +/- 170.5 N for group CTR. Regarding fracture modes, significantly more teeth from group END exhibited fractures of type III and II compared with control specimens. CONCLUSION: Teeth restored with bonded CAD/CAM ceramic inlays (CEREC) fractured with a significantly higher number of severe fractures compared to the control group.     

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.     

不同基牙设计对CAD/CAM全瓷修复体抗折强度的影响

目的 研究不同CAD/CAM全瓷修复体修复根充后前磨牙的抗折强度。方法 收集21颗因正畸拔除的上颌第一前磨牙,制备近面及舌尖缺损洞型。样品分为3组,第1组为直接树脂充填组;第2组为保留缺损组;第3组为纤维桩核组,然后利用IPS e.max CAD全瓷修复体进行修复,采用Rely X U200树脂黏结剂进行黏固。对所有样品进行抗折强度测试,采用光学显微镜观察样品的断裂类型。采用SPSS 15.0软件包对数据进行统计学分析。结果 纤维桩核组全瓷修复体的抗折强度显著大于树脂充填组和保留缺损组。第1组和第2组以修复体破裂为主,第3组除修复体破裂外,还发生牙体组织破裂。结论 对于伴有功能牙尖缺损的前磨牙,建议采用纤维桩核+全瓷冠进行修复。     

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。     

Fracture resistance of thermal cycled and endodontically treated premolars with adhesive restorations

STATEMENT OF PROBLEM: Cavity preparations have routinely been associated with decreased fracture strength of restored teeth. PURPOSE: The purpose of this study was to evaluate the influence of endodontic treatment and thermal cycling on the fracture resistance of teeth restored with ceramic or composite resin inlay restorations. MATERIAL AND METHODS: One hundred sound, maxillary premolars were selected. Twenty intact teeth served as a control group. Eighty teeth were prepared with MOD cavity preparations; half of them were also endodontically treated. Inlay restorations were prepared with composite resin (Filtek Z250) or feldspathic ceramic (Vitadur Alpha). Half of the specimens for each group were submitted to thermal cycling (500 cycles, between 5 and 55 degrees C, dwell time of 30 seconds). The specimens were subjected to compressive axial loading using a steel ball. Data were analyzed using 3-way ANOVA and post hoc Tukey's test (alpha=.05). RESULTS: Except for those teeth restored with ceramic without endodontic treatment and thermal cycling, no other group achieved fracture strength similar to sound teeth. Ceramic and composite resin restorations provided similar resistance to fracture. There was a significant interaction between endodontic therapy and thermal cycling (P<.001). In the nonthermal cycled groups, endodontically treated teeth showed significantly lower fracture resistance (P<.001). All experimental groups had similar fracture strength when submitted to thermal cycling. CONCLUSIONS: Both restorative techniques provided similar fracture resistance. Endodontic treatment decreased the fracture resistance of nonthermal cycled specimens, while thermal cycling decreased the fracture resistance of nonendodontically treated specimens.     

Resistance to fracture of restored endodontically treated premolars

Abstract Endodontically treated premolars were restored using 5 different methods. Copper rings were filled with commercial hard-setting cement and the teeth were placed into the cement up to the level of the cemento-enamel junction. The teeth were grouped according to restorative method, mounted in an Instron TT machine and the buccal walls subjected to a slowly increasing compressive force until fracture occurred. The force of fracture of the walls of each tooth was recorded and the results in the various groups compared. All teeth fractured in a similar manner irrespective of the restorative method used. The resistance to fracture of the teeth increased significantly when MOD cavities in the teeth were acid etched prior to the restoration with a composite resin. The use of a bonding agent after acid etching did not further increase the resistance to fracture of the premolars restored with a resin. The acid etch composite resin technique was as effective in preventing fractures of the teeth when 2 mm of the resin was removed and replaced with an amalgam as when the entire cavities were filled with the resin material.     

不同修复方法对邻[牙合]缺损的下颌前磨牙根管治疗术后抗折性能影响的研究

目的：比较不同修复方法对邻[牙合]缺损的下颌前磨牙根管治疗术后抗折强度的影响。方法：将50颗离体下颌前磨牙随机分为A、B、C、D、E五组,每组10颗。A组（对照组）：完整离体牙,不做任何处理。其它四组（实验组）样本牙经根管治疗并制备邻骀缺损。B组：光固化树脂直接充填;C组：树脂充填＋铸造全冠修复;D组：铸造桩核＋铸造全冠修复;E组：纤维桩树脂核＋铸造全冠修复。所有样本牙在电子万能试验机上以与牙体长轴成30°角、lmm／min速度加载直至样本折裂,记录样本折裂时的载荷数值与折裂模式,对数据进行统计分析。结果：A、B、C、D、E组的折裂载荷分别为（952．93±102．03）、（383．97±46．31）、（733．51±54．94）、（604．76±123．73）和（893．44±87．08）N。五组之间两两比较,只有A、E两组之间差异无统计学意义,其余差异均有统计学意义;A、B、C、D、E组产生不可修复性折裂（根折位于包埋树脂平面以下）的样本数分别为0、2、1、9、3,其中D组牙体的折裂模式与其它三组差异均存在统计学意义,剩余三组间两两比较差异无统计学意义。结论：纤维桩树脂核联合全冠修复可作为邻[牙合]缺损的前磨牙根管治疗术后的优选修复方式。     

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。     

Fatigue behavior of endodontically treated premolars restored with different fiber-reinforced designs

ObjectivesThe aim was to investigate the fatigue survival and marginal-gap inside the root-canal of endodontically treated (ET) premolars reinforced by various fiber-reinforced post-core composites (FRCs). Moreover, composite-curing at different depths in the canal was evaluated.Methods170 intact upper-premolars were collected and randomly divided into ten groups (n = 15). One group served as control (intact-teeth). After endodontic procedure standard MO cavities were prepared and restored with different post-core fiber-reinforced materials and designs. Three-group (A1-A3) were restored with either packable and flowable short fiber-reinforced composite (SFRC) core or conventional composite-core. Two-group (B1-B2) were restored with SFRCs as short post (3 mm) and core. Four-group (C1-C4) were restored with SFRCs as post (6 mm) and core with or without unidirectional FRC posts (individually-made or conventional). After completing the restorations, teeth from Group C1-C4 (n = 5/group) were sectioned and stained. Specimens were viewed under a stereo-microscope and the percentage of microgaps within the root-canal was calculated. Fatigue-survival was measured using a cyclic-loading machine in the rest of the specimens.ResultsApplication of flowable SFRC as luting-core material with individually-made FRC post (Group C3) did not differ from intact-teeth regarding fatigue-survival (p > 0.05). The rest of the groups produced significantly lower survival (p < 0.05) compared to intact-teeth. Post/core restorations made from packable SFRC (Group C1) had a lower microgap (19.1%) at the examined interphase in the root-canal than other groups.SignificanceThe restoration of ET premolars with the use of individually-made FRC post and SFRC as luting-core material showed promising achievement regarding fatigue-resistance and survival.     

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.     

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.     

Fracture resistance of endodontically treated anterior teeth restored with four post-and-core systems.

OBJECTIVE: The purpose of this study was to evaluate the fracture resistance and the mode of failure of endodontically treated teeth restored with four post-and-core systems. METHOD AND MATERIALS: Forty intact human incisors were randomly divided into four groups. Teeth from each group received endodontic therapy and one of four post-and-core systems: serrated, parallel-sided, cast post and core; serrated, parallel-sided, prefabricated post and resin-composite core; carbon-fiber-reinforced (CFC) post and resin-composite core; and ceramic post and resin-composite core. A full-coverage metal crown was fabricated and cemented onto each tooth. Each specimen was subjected to a compressive load at a 45-degree angle to its axis until failure. The failure load was recorded and compared statistically. The mode of failure of the specimens was analyzed. RESULTS: There was no significant difference in the failure loads among groups. More catastrophic root fracture was detected in the group restored with ceramic posts and resin-composite cores. CONCLUSION: The fracture resistance of endodontically treated teeth restored with these four post-and-core systems could be accepted clinically. Unfavorable tooth fracture was shown in all groups.     

Resistance to fracture of endodontically treated premolars restored with glass ionomer cement or acid etch composite resin

MOD cavity preparations in 64 endodontically treated premolars were restored using four different methods. Copper rings were filled with commercial hard-setting cement and the teeth were placed into the cement up to the level of the cementoenamel junction. The teeth were grouped according to restorative method, mounted in an Instrom T.T. machine, and the buccal walls subjected to a slowly increasing compressive force until fracture occurred. The force of fracture of the walls of each tooth was recorded and the results in the various groups compared. All teeth fractured in a similar manner irrespective of the restorative method used. The resistance to fracture of the teeth was the same when they were restored with glass ionomer cement as a base over which an amalgam or composite resin was placed or with acid-etched resin. When the entire cavities were filled with glass ionomer cement the resistance to fracture of the teeth decreased significantly compared with the acid etch resin technique.     

根管治疗后上颌前磨牙直接粘接修复的应力分布

目的 通过有限元法分析根管治疗后牙齿直接粘接修复的应力分布,为临床选择修复方法提供理论依据.方法 利用微型CT扫描信息,建立因正畸治疗拔除的年轻男性上颌第二前磨牙三维有限元模型,模拟根管治疗后远中验面缺损的4种不同直接粘接修复方法(G3:单纯粘接修复;G4:腭尖覆盖修复;G5:全验面覆盖修复;G6:远中验面覆盖),以完整牙(G1)和缺损未修复牙(G2)作为对照.在两牙尖斜面上加载200 N的轴向载荷,分析各组修复后牙齿的应力分布情况及安全因子的大小.结果 G1 ～ G6组总体拉应力峰值依次为106、383、287、56、62和95 MPa;G3 ～ G6组修复体安全因子依次为5.46、1.38、1.43及1.73,粘接层安全因子依次为0.33、0.52、5.16及2.11.结论 综合牙齿应力分布和安全因子因素,全(牙合)面或保留一侧完整边缘嵴的(牙合)面覆盖修复方式优于单纯粘接修复和腭尖覆盖的修复方式.