桩核对根管治疗牙修复后强度的影响

目的　比较不同修复方法对根管治疗牙修复后强度的影响。方法　 6 0个完整拔除的人上中切牙 ,根管治疗后随机分为 5组 ,每组 12个。A组 :完整的根管治疗牙 ;B组 :根管治疗后烤瓷熔附金属 (PFM)全冠修复 ;C组 :牙体预备保留 2 0mm高的牙本质套圈 ,铸造金属桩核及PFM全冠修复 ;D组 :牙体预备无牙本质套圈 ,铸造金属桩核及PFM全冠修复 ;E组 :牙体预备保留 2 0mm高的牙本质套圈 ,Parapost预成桩、复合树脂核及PFM全冠修复。在MTS 810材料试验机上沿与牙长轴成 135度方向加载 ,测试折裂强度。结果采用方差分析。结果　牙体预备保留 2 0mm高的牙本质套圈 ,铸造金属桩核及PFM全冠修复者折裂强度最高 ,为 (1793 5 9± 387 93)N ;完整的根管治疗牙次之 ,为(146 6 6 8± 2 40 11)N ;其余 3组的折裂强度 (95 8 49± 2 86 0 2 )N、(992 98± 2 91 0 0 )N、(994 94± 2 85 0 4)N之间 ,差异无显著性。修复牙有无牙本质套圈 ,其折裂强度间差异有高度显著性 (P <0 0 1)。结论　桩核能否增强根管治疗牙的抗折裂强度与其修复设计有关 ,牙本质套圈可明显增强根管治疗牙的抗折裂能力。     

CELAY全瓷桩核强度的研究

目的:比较Celay 全瓷桩核、铸造金属桩核及Parapost 预成桩复合树脂核修复的根管治疗牙全冠修复后的抗折裂强度。方法:60 个完整拔除的人上中切牙,根管治疗后随机分为5 组,每组12 个。A 组:牙体预备保留210 mm高的牙本质套圈,Celay 桩核;B 组:牙体预备无牙本质套圈,Celay 桩核;C 组:牙体预备保留210 mm 高的牙本质套圈,铸造金属桩核;D 组:牙体预备无牙本质套圈,铸造金属桩核;E 组:牙体预备保留210 mm高的牙本质套圈,Para2post 预成桩,复合树脂核。所有标本皆用Celay 全冠修复。标本在室温下保存于100 %湿度中30 d 后,在MTS 810 材料试验机上沿与牙长轴成45°的方向加载,测试折裂强度。结果:各组的折裂强度间有显著性差异( P < 0101) ,牙体预备保留210 mm高的牙本质套圈时,Celay 桩核与铸造金属桩核的折裂强度显著高于其他三组,其他三组之间无显著性差异,Celay 桩核修复时,有无210 mm高的牙本质套圈其折裂强度有显著性差异( P < 0105) 。结论:在牙体预备保留210 mm高的牙本质套圈时,Celay 桩核的强度可基本满足临床要求而不致发生桩核的折裂。     

The effect of post-core and ferrule on the fracture resistance of endodontically treated maxillary central incisors.

AIM: To evaluate the effect of post reinforcement, post type and ferrule on the fracture resistance of endodontically treated maxillary central incisors. MATERIALS AND METHODS: Sixty central incisor teeth were selected and grouped into six groups, viz. A, B, C, D, E, and F, each consisting of 10 specimens. Group A specimens were not subjected to any restorative treatment. Group B specimens were endodontically treated and crowned. Specimens of groups C and D were restored with custom cast post and core. Specimens of groups E and F were treated with prefabricated titanium post and composite core. Specimens of groups C and E were restored with porcelain-fused metal (PFM) crown having 2 mm ferrule. Specimens of groups D and F were restored with PFM crown having no ferrule. All the specimens were subjected to load (newton, N) on the lingual surface at a 135 degree angle to the long axis with a universal testing machine until it fractured. The fracture load and mode of fracture of each specimen were noted. One-way analysis of variance with Tukey honestly significant difference procedure was employed to identify the significant difference among the groups at 5% level (P < 0.05). RESULTS: There were significant differences among the six groups studied (P < 0.0001). The highest fracture strength was recorded with specimen of group C (1376.7 N). There were significant differences between groups A and D versus groups B, E, and F. There were no significant differences between groups B, E, and F. Cervical root fracture was the predominant mode of failure in all the groups except group A. CONCLUSION: The results showed that endodontically treated teeth restored with custom cast post core were as strong as the untreated group. Teeth restored with custom cast post core were better resistant to fracture than teeth restored with prefabricated titanium post and composite core. Ferrule is more important in custom cast post core than in prefabricated post and composite core.     

In vitro fracture resistance of endodontically treated central incisors with varying ferrule heights and configurations

STATEMENT OF PROBLEM: The in vitro effectiveness of a uniform circumferential ferrule has been established in the literature; however, the effect of a nonuniform circumferential ferrule height on fracture resistance is unknown. PURPOSE: This in vitro study investigated the resistance to static loading of endodontically treated teeth with uniform and nonuniform ferrule configurations. MATERIAL AND METHODS: Fifty extracted intact maxillary human central incisors were randomly assigned to 1 of 5 groups: CRN, no root canal treatment (RCT), restored with a crown; RCT/CRN, no dowel/core, restored with a crown; 2 FRL, 2-mm ferrule, cast dowel/core and crown; 0.5/2 FRL, nonuniform ferrule (2 mm buccal and lingual, 0.5 mm proximal), cast dowel/core and crown; and 0 FRL, no ferrule, cast dowel/core and crown. The teeth were prepared to standardized specifications and stored for 72 hours in 100% humidity prior to testing. Testing was conducted with a universal testing machine with the application of a static load, and the load (N) at failure was recorded. Statistical analysis was performed with a 1-way analysis of variance and the Tukey Honestly Significant Difference test (alpha=.05). The mode of fracture was noted by visual inspection for all specimens. RESULTS: There was strong evidence of group differences in mean fracture strength ( P <.0001). Following adjustment for all pairwise group comparisons, it was found that the lack of a ferrule resulted in a significantly lower mean fracture strength (0 FRL: 264.93 +/- 78.33 N) relative to all other groups. The presence of a nonuniform (0.5 to 2-mm vertical height) ferrule (0.5/2 FRL: 426.64 +/- 88.33 N) resulted in a significant decrease ( P =.0001) in mean fracture strength when compared with the uniform 2-mm vertical ferrule (2 FRL: 587.23 +/- 110.25 N), the group without RCT (CRN: 583.67 +/- 86.09 N), and the RCT-treated tooth with a crown alone (CRN/RCT: 571.04 +/- 154.86 N). The predominant mode of failure was an oblique fracture extending from the lingual margin to the facial surface just below the insertion of the tooth into the acrylic resin. CONCLUSION: The results demonstrated that central incisors restored with cast dowel/core and crowns with a 2-mm uniform ferrule were more fracture resistant compared to central incisors with nonuniform (0.5 to 2 mm) ferrule heights. Both the 2-mm ferrule and nonuniform ferrule groups were more fracture resistant than the group that lacked a ferrule.     

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.     

Survival rate and fracture strength of endodontically treated maxillary incisors with moderate defects restored with different post-and-core systems: an in vitro study

PURPOSE: This study compares the survival rate and fracture strength of endodontically treated maxillary incisors with moderate coronal defects restored with different post-and-core systems after exposure to an artificial mouth. MATERIALS AND METHODS: Sixty-four caries-free human maxillary central incisors were selected for standardized size and quality, endodontically treated, and decoronated 2 mm coronal to the cementoenamel junction. Group 1 was restored with titanium posts and composite cores, group 2 received zirconia posts and a composite core, and in group 3 zirconia posts with a heat-pressed ceramic core were used. Teeth restored with cast posts and cores served as controls. All teeth were prepared and restored with complete cast crowns. All samples were exposed to 1.2 million cycles in a computer-controlled chewing simulator with simultaneous thermocycling. In addition, the samples were loaded until fracture in a static testing device. RESULTS: The survival rates of the different groups were: 94% for titanium/composite, 63% for zirconia/composite, 100% for the all-ceramic post and core, and 94% for the cast post and core. The following mean fracture strengths were obtained: titanium/composite = 425 +/- 155 N, zirconia/composite = 202 +/- 212 N, zirconia/ceramic = 378 +/- 64 N, cast post and core = 426 +/- 178 N. The lower fracture load in the group with zirconia posts and composite cores was statistically significant. The use of zirconia posts resulted in fewer oblique root fractures. CONCLUSION: Prefabricated titanium posts with composite cores, zirconia posts with heat-pressed ceramic cores, and cast posts and cores yield comparable survival rates and fracture strengths for the restoration of crowned maxillary incisors with moderate coronal defects. Survival rates and fracture strengths for zirconia posts with composite cores are significantly lower, so this combination cannot be recommended for clinical use.     

Effect of a crown ferrule on the fracture resistance of endodontically treated teeth restored with prefabricated posts

STATEMENT OF PROBLEM: Root fracture is one of the most serious complications following restoration of endodontically treated teeth. PURPOSE: The purpose of this study was to compare the fracture strengths of endodontically treated teeth using posts and cores and variable quantities of coronal dentin located apical to core foundations with corresponding ferrule designs incorporated into cast restorations. MATERIAL AND METHODS: Fifty freshly extracted canines were endodontically treated. The teeth were randomly divided into groups of 10 and prepared according to 5 experimental protocols. Control group: teeth with custom cast post and core; 0-mm group: teeth without coronal structure (no ferrule); 1-mm, 2-mm, and 3-mm groups: teeth with 1 mm, 2 mm, and 3 mm of remaining coronal tooth structure (1-, 2-, and 3-mm ferrule), respectively. All specimens in 0-mm through 3-mm (noncontrol) groups were restored with a prefabricated post (Screw-Post) and composite resin (Z100) core located superior to the different tooth structure heights. All teeth were restored with complete metal crowns. The fracture resistance (N) was measured in a universal testing machine at 45 degrees to the long axis of the tooth until failure. Data were analyzed by 1-way analysis of variance and Tukey test (alpha=.05). RESULTS: Significant differences (P<.001) were found among the mean fracture forces of the test groups (control group: 818.2 N; 0-mm, 1-mm, 2-mm, and 3-mm groups: 561.0 N, 627.6 N, 745.3 N, and 907.1 N, respectively). When the mode of failure was evaluated, all failures in the control group occurred due to root fracture, and all failures in the 0-mm group occurred due to core fracture. The majority of failures in the other groups occurred due to crown cementation failure. CONCLUSION: The results of this study showed that an increased amount of coronal dentin significantly increases the fracture resistance of endodontically treated teeth.     

Effect of Core Material and Restoration Design on Strength of Endodontically Treated Bovine Teeth: A Laboratory Study

Purpose: The purpose of this study was to evaluate the fracture resistance of bovine teeth restored with one-piece cast core/crowns and no ferrule, compared to teeth restored with amalgam cores and full coverage crowns, with and without a dentine ferrule.
Materials and Method: Thirty bovine incisors were selected and modified to ensure all teeth had axial dentine walls of similar size. The teeth were then randomly allocated to one of the three groups: control group restored with amalgam core and cast crown without ferrule; ferrule group restored with amalgam core and cast crown with a 2-mm dentine ferrule; one-piece group restored with one-piece cast core/crown without ferrule. Each tooth was loaded to the point of fracture.
Results: The mean load resisted by the control group, the ferrule group, and the one-piece group were 1092.5, 1843.5, and 1463.1 N, respectively. The mean load resisted by the ferrule group was significantly greater than the control group ( p < 0.001) and the one-piece cast core/crown group ( p = 0.04). The mean load resisted by the one-piece cast core/crown group was significantly greater than the control group ( p = 0.04).
Conclusions: The maximum load resistance was significantly enhanced by a 2-mm ferrule compared with teeth with no ferrule and teeth restored with one-piece cast core/crowns. Teeth restored with one-piece cast core/crowns were significantly more resistant to loading than teeth restored with amalgam cores and crowns without a ferrule.     

Effect of incomplete crown ferrules on load capacity of endodontically treated maxillary incisors restored with fiber posts, composite build-ups, and all-ceramic crowns: an in vitro evaluation after chewing simulation

OBJECTIVE: The aim of this study was to compare the fracture resistance of endodontically treated maxillary central incisors with incomplete crown ferrules after chewing simulation. MATERIAL AND METHODS: Forty caries-free maxillary central incisors were divided into 4 groups (n = 10). Endodontic treatment was performed. Teeth were decoronated 2 mm above the cemento-enamel junction (CEJ). Group I (control) provided a 360 degrees circumferential 2-mm ferrule. In group II, a 2-mm ferrule was present on the palatal aspect (status after occlusal overload), and in group III on the facial aspect (status after traumatic injury). In group IV, the ferrule was interrupted by bi-proximal cavitations (simulating caries treatment). The teeth received glass fiber reinforced posts and composite core restorations. All-ceramic crowns were adhesively cemented. Specimens were simultaneously exposed to thermal cycling and mechanical loading (1.2 million cycles; 6,000 cycles 5 degrees/55 degrees C) and finally statically loaded until failure in a universal testing machine (crosshead speed = 1 mm/min). For statistical analysis, the Kruskal-Wallis test was applied followed by the Mann-Whitney U-test as post hoc testing. RESULTS: The median fracture load values (min./max.) were: group I = 502 (326/561), group II = 658 (280/827), group III = 899 (396/1176), and group IV = 360 (279/646). Analysis revealed statistically significant differences between test groups, except between groups I and IV and groups II and IV. CONCLUSIONS: The fracture resistance of endodontically and post/core restored teeth is dependent on the degree of tooth conservation. An incomplete crown ferrule is associated with greater variation in load capacity and, despite high fracture values, inclines to fracture.     

Resistance to cyclic fatigue and fracture of structurally compromised root restored with different post and core restorations

The aim of this study was to evaluate the resistance to fracture of endodontically treated teeth with flared canals restored with different post and core restorations under static and cyclic fatigue loadings. Sixty human maxillary central incisors were used. Two main groups (non-ferrule and 1-mm ferrule) were divided into three types of restoration: custom cast post-and-core (MPC), resin composite post-and-core (RCP), and resin composite core in combination with prefabricated carbon fiber post (FRC). Half of each group was subjected to a static loading test, and the other to a cyclic fatigue test. FRC exhibited a significantly higher number of load cycles than the other groups, and MPC showed the highest failure load among the tested groups. However, all FRC and MPC specimens demonstrated unfavorable root fractures. The results of this study suggested that RCP prepared with 1-mm ferrule was the most desirable restoration for structurally compromised roots, as relatively strong resistance to cyclic fatigue and fracture was revealed--given that all RCP specimens demonstrated favorable root fracture.     

不同桩核材料及箍结构对前牙抗折强度的影响

目的研究不同桩核材料及箍结构对前牙抗折强度的影响。方法选取28颗完整上颌中切牙随机分为四组:A1组:剩余釉牙骨质界上8mm牙体组织+镍铬合金桩修复;A2组:剩余釉牙骨质界上8mm牙体组织+低金合金桩修复;B1组:剩余釉牙骨质界上2mm牙体组织+镍铬合金桩修复;B2组:剩余釉牙骨质界上2mm牙体组织+低金合金桩修复。自凝包埋后,固定于生物力学试验机上,测试实验牙的抗折强度并观察其折裂类型,应用SPSS分析软件进行统计学分析。结果各组样本的折裂力值依次为:614.79±39.03N,438.73±28.20N,430.13±32.99N,411.94±47.46N。桩核材料对折裂强度有显著影响(P<0.05);箍结构形式对折裂强度有显著影响(P<0.05)。桩核材料和箍结构形式两个因素之间存在交互效应(P<0.05)。结论①不同桩核材料对桩核冠修复后的牙齿抗折强度有影响。②正常情况下,尽量使用弹性模量较低桩核材料,可在一定程度上改善破坏性牙折的发生率。③箍结构的形式对折裂强度有显著影响。④桩核材料的弹性模量和箍结构的形式两个因素之间存在交互效应。     

An in vitro study evaluating the effect of ferrule length on fracture resistance of endodontically treated teeth restored with fiber-reinforced and zirconia dowel systems

STATEMENT OF PROBLEM: There are few published studies analyzing the effects of different ferrule lengths of endodontically treated teeth in relationship to newly developed fiber-reinforced and zirconia dowel systems. PURPOSE: This in vitro study compared the effect of 3 different ferrule lengths on the fracture resistance and fracture patterns of crowned endodontically treated teeth restored with 4 different esthetic dowel systems. MATERIAL AND METHODS: The crowns of 123 human maxillary canines were removed at the cementoenamel junction and the roots were endodontically treated. Three master tooth models were prepared to ferrule lengths of 1.0 mm, 1.5 mm, and 2.0 mm to produce 3 master analogs. Each root was embedded in autopolymerizing resin with a 0.2-mm layer of silicone impression material to simulate the periodontal ligament. Forty analogs of each master tooth, with ferrule lengths of 1.0 mm, 1.5 mm, and 2.0 mm were produced with copy-milling (Celay system). Each group was further subdivided into 4 groups of 10 specimens each and restored with 4 different esthetic dowel systems (quartz fiber, glass fiber, glass fiber plus zirconia, and zirconia). All dowels were luted with adhesive resin cement (RelyX ARC), restored with composite cores (Valux Plus), and Ni-Cr alloy (Wiron 99) complete crowns. All specimens were loaded at 130 degrees to the long axes in a universal testing machine at a crosshead speed of 1 mm/min until fracture. Fracture patterns were classified as failures above or below the incisal third of the roots. The data were analyzed with 2-way ANOVA and Tukey HSD tests (alpha=.05). A Fisher exact test was conducted for evaluation of the mode of failure (alpha=.05). RESULTS: Mean failure loads (kg) for quartz fiber, glass fiber, glass fiber plus zirconia, and zirconia groups, respectively, with the 3 ferrule lengths were: 1.0-mm ferrule specimens: 98.09 +/- 2.90, 85.36 +/- 2.82, 80.24 +/- 1.88, 70.11 +/- 2.48; 1.5-mm ferrule specimens: 101.0 +/- 2.88, 87.58 +/- 2.83, 89.8 +/- 2.09, 82.71 +/- 2.14; 2.0-mm ferrule specimens: 119.5+/-1.78, 99.84+/-1.23, 98.6 +/- 1.64, 95.42 +/- 1.02. Teeth prepared with 2.0-mm ferrules demonstrated significantly higher fracture thresholds (P<.001). There were no significant differences in fracture patterns. CONCLUSION: Increasing the ferrule length of the endodontically treated teeth from 1 mm to 1.5 mm in specimens restored with quartz-fiber and glass-fiber dowels did not produce significant increases in the failure loads (P=.084, P=.119, respectively). No significant difference was detected between glass-fiber and glass-fiber plus zirconia dowels with 1.5-mm and 2.0-mm ferrules (P=.218, P=.244, respectively). However, fracture thresholds were higher for all 4 dowel systems when the specimens were prepared with a 2.0-mm ferrule length (P<.001).     

不同材质桩核修复漏斗状残根的抗疲劳强度

目的探讨不同材质桩核修复对漏斗状前牙牙根抗疲劳强度的影响。方法30颗离体上颌中切牙均分为无领圈和有领圈2个实验组。各实验组再分为3部分,各5颗样牙。本分别用铸造金属桩核(MPC)、单纯复合树脂桩核(RCP)及预成碳纤维桩联合复合树脂桩核(FRC)进行修复。测定各样本牙疲劳强度并对实验结果进行双因素方差检验(α=0.05)。结果各实验组用FRC修复者与用其他2种材料者相比,均表现出明显高的平均疲劳强度(P<0.05)。预备牙本质领圈可明显提高不同材质桩核修复牙的疲劳强度(P<0.05)。结论FRC在提高前牙牙根抗疲劳强度方面具有明显优点。为提高前牙牙根的抗疲劳强度,预备牙本质领圈是必要的。     

Influence of remaining coronal tooth structure on fracture resistance and failure mode of restored endodontically treated maxillary incisors

Statement of problem

Limited information is available on the effect of an incomplete ferrule because of the varying residual axial wall heights and the volume of residual tooth structure on the fracture resistance of endodontically treated and restored maxillary incisors.

Evaluation of the effect of different ferrule designs on the fracture resistance of endodontically treated maxillary central incisors incorporating fiber posts, composite cores and crown restorations

AIM: The purpose of this study was to evaluate the fracture resistance of endodontically treated maxillary central incisors restored with quartz fiber posts, composite cores, and crowns when different types of ferrule designs were incorporated. METHODS AND MATERIALS: Sixty maxillary incisors were divided into six groups: Group 1 (control): teeth with root canal treatments having a full crown prosthesis; Group 2: teeth with a 2 mm circumferential ferrule; Group 3: teeth with a 2 mm ferrule only in the vestibular region; Group 4: teeth with a 2 mm ferrule only in the palatal region; Group 5: teeth with a 2 mm ferrule in the vestibular and palatal region, having cavities in both proximal areas; and Group 6: teeth with no ferrule. The teeth in the experimental groups were restored with quartz fiber posts-composite cores and full metallic crowns. All experimental teeth were subjected to an increasing compressive force with a crosshead speed of 1 mm/min, until fracture occurred. RESULTS: The median fracture values of groups were as follows: Group 1: 574.4 N, Group 2: 472.4 N, Group 3: 474.3 N, Group 4: 480.7 N, Group 5: 463.1 N, and Group 6: 297.9 N. A statistically significant difference was found between Group 1 and Group 6 (p< 0.01). CONCLUSION: It was concluded different ferrule designs did not have any influence on the fracture resistance of teeth with fiber posts. The results of this study indicate fiber posts can safely be used for their reinforcing properties. Furthermore, there is no significant change in the resistance of teeth with fiber posts regardless of which ferrule design is incorporated. The property of these types of posts is an additional advantage in clinical practice.     

In vitro evaluation of the fracture resistance of anterior endodontically treated teeth restored with glass fiber and zircon posts

STATEMENT OF PROBLEM: The published information is equivocal regarding the fracture resistance of endodontically treated teeth restored with fiber posts. Additionally, little is known about the biomechanical performance of glass fiber and zircon posts. PURPOSE: This in vitro study investigated the fracture resistance of anterior endodontically treated teeth prepared with a 2-mm ferrule, restored with glass fiber and zircon posts and composite resin cores or cast posts and cores. MATERIAL AND METHODS: Twelve matched pairs of teeth were obtained from 4 cadavers, and all were endodontically treated and prepared with a standardized 2-mm ferrule. According to a random number table, the 2 teeth from each matched pair were randomly divided into 2 groups. The test group consisted of 12 specimens restored with a glass fiber and zircon post (Fibio) and composite resin (Durafil) core. Twelve matching specimens restored with a nickel-chromium (NiCr) cast post and core served as the control. Specimens in both groups were cemented with resin cement (Panavia F). After cementation of cast NiCr complete crowns with zinc polycarboxylate cement (ShangChi), the specimens were loaded with an incremental static force at an angle of 135 degrees to the long axis of the root until failure occurred. A paired sample t test was used to compare the fracture resistance (N) of teeth restored with the 2 post-and-core systems (alpha=.05). RESULTS: The mean failure load of paired differences between the 2 groups was -261.3+/-237.3 N. The test group exhibited significantly lower failure loads than the control group (P=.004). All specimens displayed root fractures, most of which were oblique, with cracks initiating from the palatal cervical margin and propagating in a labial-apical direction. CONCLUSION: Within the limitations of this study, the teeth restored with glass fiber and zircon posts demonstrated significantly lower failure loads than those with cast NiCr post and cores. All specimens failed via root fractures.     

桩核修复方法对梭形根管牙断裂强度的影响

目的：比较3种不同桩核修复方法对梭形根管牙断裂强度的影响。方法：30颗近期拔除的上颌中切牙根管治疗后预备成梭形,随机分为3组,每组10颗。Ⅰ组行玻璃纤维桩、Luxacore树脂核和铸造全冠修复;Ⅱ组根管扩大预备后行铸造镍铬桩核和铸造全冠修复;Ⅲ组玻璃离子水门汀重塑根管后行铸造镍铬桩核和铸造全冠修复。Zwick z010型电子万能试验机测试断裂强度。结果：Ⅰ组与Ⅱ组、Ⅲ组试件牙的断裂强度差异有显著性,Ⅱ组与Ⅲ组差异无显著性。结论：梭形根管牙的断裂强度与其修复设计有关,采用玻璃纤维桩及树脂核修复有较高的断裂强度,且断裂方式利于再修复。     

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.     

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。     

Fracture strength and survival rate of endodontically treated maxillary incisors with approximal cavities after restoration with different post and core systems: an in-vitro study

OBJECTIVES: This study compared the fracture strength and survival rate of endodontically treated crowned maxillary incisors with approximal class III cavities and different core build-ups. METHODS: Sixty-four caries free human maxillary central incisors were selected for standardized size and quality, endodontically treated and prepared with approximal cavities 3mm in diameter. Group 1 was restored with titanium posts, group 2 received zirconia posts, in group 3 the root canal was partially filled with a hybrid composite. In the control group, only the access opening was restored. All teeth were prepared for and restored with full cast metal alloy crowns and subsequently exposed to 1.2 million cycles in a computer-controlled chewing simulator with simultaneous thermocycling. In addition, the samples were loaded until fracture in a static testing device. RESULTS: One specimen with composite reinforced root canal did not survive the dynamic load test. The following median fracture strengths in Newtons for the different groups were: titanium post 1038, zirconia 1057, composite resin 750, control (no post) 1171. The fracture load in group 3 (composite resin) was significantly lower (P<0.05) than in the other groups. CONCLUSIONS: The reconstruction of endodontically treated single rooted teeth with approximal cavities can be successfully performed by closure of the endodontic and additional cavities with composite. Cementation of endodontic posts offers comparable but no advantageous fracture resistance. Enlargement of the root canal space after completion of endodontic treatment should be avoided and cannot be compensated for by injection of composite resin. Less catastrophic failures were observed without post reconstruction.