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.     

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.     

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.     

根管治疗后牙体修复的治疗方案选择

冠部修复的质量是影响根管治疗后患牙预后的重要因素之一。如何根据患牙的具体情况选择最适合的修复方式,一直以来存在争议。本文介绍了根管治疗后冠部修复的目的与时机,选择修复方式需考虑的因素及具体修复方案的选择等,对近年来关于根管治疗后牙齿修复的研究进展进行分析,旨在为临床决策提供指导。     

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.     

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。     

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。     

两种桩系统修复对根管治疗牙强度影响的有限元应力分析

目的比较两种不同弹性模量的桩修复对根管治疗牙应力分布的影响。方法建立根管治疗后的上颌中切牙分别采用玻璃纤维桩树脂核及铸造镍铬桩核修复的二维有限元模型，牙体预备均保留1．5mm的牙本质肩领。分析受力后的应力分布规律。结果不同材料的桩修复会在根管治疗牙牙根内产生明显不同的应力分布形式。玻璃纤维修复时牙根内的应力分布与天然牙近似，并且整体应力水平较低。铸造镍铬合金桩修复改变了天．然牙原有的应力分布形式，在桩一牙本质界面和桩末端出现了明显的应力集中。结论在选择桩的材料时要考虑其对根管治疗牙应力分布的影响。在保证牙颈部的强度和边缘密合性的同时，选择与牙本质弹性模量相近的桩可以减少根折的可能。     

Clinical and microbiological effects of different restorative materials on the periodontal tissues adjacent to subgingival class V restorations

OBJECTIVES: The relationship between subgingival dental restorations and periodontal health has been thoroughly investigated for many years. However, longitudinal data on the subgingival microflora features after the placement of well-finished subgingival restorations are still lacking. Therefore, this study compares the short-term clinical and microbiological features occurring in the gingiva after the completion of different subgingival restorations. MATERIAL AND METHODS: Sixteen systemically healthy subjects, 10 males and six females (ages: 31.7-45.8 years; mean age 39.3+/-5.1 years), who were non-smokers and were positive for the presence of three cervical abrasion/erosion defects to be restored in three different adjacent teeth were enrolled in this study. The cervical abrasion/erosion defects were each restored by using one of three different materials: amalgam, glass ionomer cement, or composite resin. Immediately before class V cavity preparations and restorations (baseline), clinical monitoring and subgingival plaque sampling were performed in the mid-buccal aspect of each experimental restored tooth and in one adjacent sound, non-treated, control tooth. These procedures were repeated every 4 months over the following 1 year. RESULTS: Throughout the study, the clinical parameters recorded did not change significantly in any of the experimental groups, and no differences were detected among them at each clinical session. Over this time, no significant changes in the composition of the subgingival microflora were observed in amalgam, glass ionomer cement, and control groups. Conversely, in the composite resin group, there was a significant increase in the total bacterial counts, and a significant (p<0.05) decrease in Gram-positive, aerobic bacteria, which was associated with a significant (p<0.05) increase in the Gram-negative, anaerobic microbiota. CONCLUSIONS: Over a 1-year observation period, amalgam, glass ionomer cement, and composite resin subgingival restorations do not significantly affect the clinical parameters recorded. However, composite resin restorations may have some negative effects on the quantity and quality of subgingival plaque.     

Resistance to fracture of crowned endodontically treated premolars restored with ceramic and metal post systems.

OBJECTIVES: The objective of this study was to assess the resistance to fracture of crowned endodontically treated premolars with varying ceramic and metal post systems under simulated occlusal load. METHOD AND MATERIALS: The study consisted of 60 extracted intact premolars with similar root diameter and length. Teeth were divided equally into 4 groups (n = 15) and prepared for posts and cast crowns as follows: group 1 = preformed metal post, composite core, and cast crown; group 2 = cast post and core and cast crown; group 3 = zirconia post, composite core, and cast crown; and group 4 = zirconia post and heat-pressed ceramic core and cast crown. All prepared teeth had 2 mm of sound dentin on which the cast crowns were cemented. A continuous load (kg) was applied by an Instron testing machine to the buccal cusp at a 30-degree angle to the long axis of each tooth at a crosshead speed of 2 mm/min until failure. One-way analysis of variance with Scheffe test was used to statistically compare the differences between groups. RESULTS: Mean failure loads (in newtons) for the 4 test groups were as follows: 1,103.3 (group 1), 1,234.5 (group 2), 826.6 (group 3), and 870.6 (group 4). No significant difference in failure load values was found among all tested groups (F[3,59] = 2.05; P >.05). The primary mode of failure (85%) in all groups was an oblique radicular fracture, either apical to the post or at the post level. Horizontal fracture (15% to 20%) of the root and post was found in groups 3 and 4. CONCLUSION: Within the limitations of this study, varying ceramic and metal post systems did not affect the failure resistance of teeth restored with full-coverage cast metal crowns, under simulated occlusal load.     

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.     

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.     

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.     

In vivo fractures of endodontically treated posterior teeth restored with amalgam

Abstract The cumulative survival rate (retention of both cusps) and the fracture pattern of 1639 endodontically treated posterior teeth were assessed in a retrospective study. All teeth had an MO/DO or an MOD cavity restored with amalgam without cuspal overlays. The 20-year survival rate of teeth with an MO/ DO cavity was markedly higher than that of teeth with an MOD cavity. The lowest survival rate was found for the upper premolars with an MOD cavity: 28% of these teeth fractured within 3 years after endodontic therapy, 57% were lost after 10 years, and 73% after 20 years. Generally, the cusp most prone to fracture was the lingual one, and lingual fractures caused significantly more damage to the periodontal tissues than did facial or total crown fractures. The severity of periodontal damage increased with posterior location of the tooth. By far the most serious failures, irrespective of the cavity type, were found for the upper second molar, as 10 of 29 fractures led to extraction. It is concluded that amalgam, especially in MOD cavities, is an unacceptable material for restoration of endodontically treated posterior teeth if used without cuspal overlays.     

Stress analysis of endodontically treated anterior teeth restored with different types of post material

Finite element analysis was performed to evaluate stress distribution in maxillary central incisors treated endodontically and restored with a post and an all-ceramic crown. Tensile stress at tooth root was analyzed using two-dimensional finite element models with different post diameters and lengths. One post length was 1/3 of the root (short), while the other was 2/3 of the root (long); one post diameter was 1/3 of the root (narrow), while the other was 2/3 of the root (wide). The following combinations were used for posts and cores: gold alloy cast post and core, commercial stainless steel post and resin core, and fiber post and resin core. Results showed that the fiber post produced less stress on the root dentin around the post tip than did the metal posts. This finding thus suggested that to reduce the stresses that cause root fracture, a long, thin fiber post should be used.     

Fracture resistance of endodontically treated premolars restored with ormocer and packable composite

In this study, mesiodistocclusal (MOD) cavity preparations of endodontically treated maxillary premolars that were enlarged to size #50 were restored using three restorative materials (one ormocer, one packable composite, and one high-copper amalgam) and two application techniques (with or without coronal radicular technique). Copper rings were filled with self-curing polymethylmethacrylate resin and the teeth were placed into resin up to the level of the CEJ. The teeth were grouped according to the restorative material and technique, mounted in a Universal Testing 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. The group restored with packable composite without radicular extension showed the highest resistance to fracture (p < 0.05). Both groups restored with amalgam were significantly weaker than all the other groups (p < 0.05).     

Fatigue performance of endodontically treated premolars restored with direct and indirect cuspal coverage restorations utilizing fiber-reinforced cores

Clinical Oral Investigations - The aim of this in vitro study was to investigate the fatigue survival and fracture behavior of endodontically treated (ET) premolars restored with different types of...     

Long-term clinical evaluation of fracture and pulp injury following glass–ionomer cement or composite resin applied as a base filling in teeth restored with amalgam

The aim of this research was to analyse the long-term clinical behaviour of two dental materials applied as filling under silver amalgam restorations: glass-ionomer cement (GIC) and composite resin with adhesive system (CR). In this study, 117 posterior teeth (29 premolars and 88 molars) were selected with carious lesions which resulted in great loss of dentin and cusps with unsupported enamel. After caries removal, cavities were prepared and totally filled with GIC or with CR. In a following visit, new cavities were prepared, leaving the employed filling material as a base and support for the enamel, which were then restored with silver amalgam. Restorations were evaluated periodically after 6 months and up to 5 years. Both fracture and pulpal involvement rates were low. Although differences could be observed in the behaviour of the materials, statistical survival estimation showed that the performances of GIC and CR as filling material were similar. There was a significant association both between kind of tooth (molar or premolar) and long-term survival of the restorations; and between degree of unsupported enamel and the same long-term survival. Our results confirmed that the technique in which GIC or CR are used as filling under silver amalgam restorations is clinically acceptable.     

预成钛合金螺纹桩保留残根的临床修复观察

目的观察钛合金螺纹桩对残根残冠的修复效果。方法对2002年~2009年5月份期间采用钛合金螺纹桩加双固化树脂核修复的病例进行复诊观察并用预定标准评价修复效果。根据患牙的牙位、余留牙体组织量、桩与牙根的直径比及桩在根管内的密合程度对复诊的病例进行分组比较。结果复诊病例共40例,有49颗修复牙,门诊复诊病例23例共25颗修复牙。失败病例中桩折断两例,桩脱落三例。失败病例均发生在余留牙体组织量不理想组。结论螺纹桩在余留牙体组织量理想的情况下可以获得满意修复效果,在牙体缺损较多的情况下修复效果欠佳。