In vitro fracture behavior of maxillary premolars with metal crowns and several post-and-core systems

The in vitro fracture behavior of severely damaged premolars, restored with metal crowns with limited ferrule and several post-and-core systems, was investigated. Crowns of maxillary premolars were removed and canals were prepared with Gates Glidden drills and with Parapost drills. Groups of 11 samples were each treated with cast post-and-cores (Parapost XP, Wironium Plus) (group 1), prefabricated metal posts (Parapost XH) (group 2), prefabricated glass fiber posts (Parapost FiberWhite) (group 3), and custom-made glass fiber posts (EverStick Post) (group 4). Posts and composite cores and metal crowns in groups 2, 3, and 4 were adhesively cemented. Post-and-cores and crowns in group 1 were cemented with phosphate cement. Thermocycling was performed (6,000x, 5-55 degrees C). Two static load tests (30 degrees ) were applied. During the first load test (preloading) no failures occurred. Failure modes from the second load test were categorized into favorable and unfavorable failures. Mean failure loads among the four groups (group 1, 1,845 N; group 2, 1,718 N; group 3, 1,812 N; and group 4, 1,514 N) were not significantly different. Unfavorable failures were root fractures and favorable failures were postcrown displacements. No differences in frequencies of unfavorable/favorable failures were seen among the groups. The results suggest that different post-and-core systems have no influence on the fracture behavior of severely damaged premolars restored with metal crowns with limited ferrule.     

Fracture strength of teeth with flared root canals restored with glass fibre posts

OBJECTIVE: To investigate the fracture strength and pattern of failure of teeth with weakened roots reconstructed by different procedures. METHODS: In an in vitro study root posts were placed in 50 endodontically treated canines, divided into 5 groups (n=10) as follows: cast metallic post; glass fibre post with smaller diameter than the root canal; glass fibre post with smaller diameter than the root canal + glass fibre strips; glass fibre post with smaller diameter than the root canal + accessory glass fibre posts; anatomical post (glass fibre post with smaller diameter than the root canal, relined with low viscosity composite resin). Posts were luted with resin cement and the coronal portion of posts was constructed with composite resin. Metallic crowns were cemented on the posts. Specimens were submitted to compressive load in a universal testing machine. Fracture strength values of each group were compared. RESULTS: Fracture strength values were for Groups 1-5 respectively: 1087.06; 745.69; 775.41; 920.64; 876.12kgf, with significant differences between Groups 1 and 2 and between Groups 1 and 3 (p<0.05). Observed patterns of fracture were: Group 1 - 100% of roots fractured; Groups 2 and 4 - variable fracture modes; Group 3 - 60% of fractures occurred in the cervical root third; Group 5 - 50% of failures occurred in the coronal portion of the post. CONCLUSIONS: The fracture strength of teeth with cast metallic posts, teeth with anatomical posts or teeth with glass fibre posts combined with accessory posts was similar. All teeth restored with cast metallic posts presented fractures and were unfavourable to maintenance of the remaining tooth structure. Teeth with fibre posts (Groups 2 to 5) presented variable fracture modes; however, the maximum percentage of unfavourable fractures was 30%.     

Fracture behavior of structurally compromised non-vital maxillary premolars restored using experimental fiber reinforced composite crowns

PURPOSE: To study the fracture behavior of direct resin composite crowns with or without experimental fiber reinforcement. METHODS: Clinical crowns of single-rooted maxillary premolars were cut off at the cemento-enamel junction. Canals were prepared with Gates Glidden drills up to size 4. No additional post-space preparations were made. Roots were embedded in acrylic and canal entrances were standardized (depth 2 mm, diameter 1.75 mm). Three groups of 14 samples were treated as follows: (1) custom-made glass FRC post (EverStick Post); fibers 5 mm deep in the canal, (2) similar post-system as (1) with incorporation of a new type of glass fiber fabric, (3) no fiber reinforcement (control). Posts were cemented with resin cement (Panavia F). Resin composite crowns (Filtek Z250) were made using an anatomically formed mold. Static load until fracture was applied using a universal loading device with a cylindrical bar (diameter 2 mm) with a crosshead speed of 5 mm/minute (loading angle: 30 degrees to the tooth long-axis). Failure modes were categorized as favorable and unfavorable failures. RESULTS: There was no significant difference in mean failure loads among the four groups (P > 0.05). Favorable failures occurred significantly more often in Group 2 than in the other groups (P < 0.05). The results suggest that an incorporated glass fiber fabric does not affect the load-bearing capacity of resin composite complete crowns on structurally compromised and non-vital premolars. Incorporation of a glass fiber fabric, however, has a beneficial effect on the failure mode.     

In vitro fracture behaviour of composite crowns with and without posts

The failure load and failure mode of severely damaged endodontically treated maxillary premolars were examined within a laboratory study. The premolars were divided into 4 groups. The first of which was restored with prefab metal posts, the second with prefab fibre posts and the third with custom-made fibre posts; all 3 receiving direct resin crowns. In a 4th (control) group no post-space preparation was performed and no posts were placed; a direct resin composite complete crown was made. After thermocycling, all specimens were statically loaded in a universal test machine until failure, under an angle of 30 degrees. There was no significant difference between the mean failure loads. Failure was merely due to unfavourable, non-repairable fractures (ending below the simulation of bone level). This study suggests that posts are not necessarily required to increase the failure load of direct resin composite crowns, however, clinical studies are necessary to confirm these findings.     

Load-bearing capacity of human incisor restored with various fiber-reinforced composite posts

Objectives

The aim of this study was to evaluate the load-bearing capacity and microstrain of incisors restored with posts of various kinds. Both prefabricated titanium posts and different fiber-reinforced composite posts were tested.

Methods

The crowns of human incisors were cut and post preparation was carried out. The roots were divided into groups: (1) prefabricated serrated titanium posts, (2) prefabricated carbon fiber-reinforced composite posts, (3) individually formed glass fiber-reinforced composite posts with the canal full of fibers, and (4) individually formed “split” glass fiber-reinforced composite posts. The posts were cemented and composite crowns were made. Intact human incisors were used as reference. All roots were embedded in acrylic resin cylinders and stored at room temperature in water. Static load was applied under a loading angle of 45° using a universal testing machine. On half of the specimens microstrain was measured with strain gages and an acoustic emission analysis was carried out. Failure mode assessment was also made.

Results

The group with titanium posts showed highest number of unfavorable failures compared to the groups with fiber-reinforced composite posts.

Significance

With fiber-reinforced composite posts the failures may more often be favorable compared to titanium posts, which clinically means repairable failures.     

Effect of different all-ceramic crown system on fracture resistance and failure pattern of endodontically treated maxillary premolars restored with and without glass fiber posts

Endodontically treated teeth are traditionally restored with a crown to prevent fracture. The aim of this study was to compare the fracture resistance and failure modes of endodontically treated maxillary premolars treated with or without a fiber post and restored with different types of crowns. Eighty human maxillary premolars were selected. After root canal treatment, the teeth were embedded in resin blocks and divided into four groups. Samples received MOD cavity preparations and were divided into two subgroups: with and without fiber posts and restored using porcelain fused to metal, lithium disilicate, fiber-reinforced composite, or zirconia crowns. The specimens were vertically loaded in the central fossa using a universal loading machine until failure, and the maximum breaking loads were recorded. Samples were perfused with Indian ink to highlight the fracture lines and the mode of failure that was classified as restorable or nonrestorable. Even without post, all crown designs resisted vertically applied forces beyond those that may be encountered in the mouth. Two-way analysis of variance revealed the use of a fiber post (p = 0.007) and the type of crown (p < 0.001) significantly affected the restorability of fractured teeth. The relationship between placing or not placing the post and the type of failure (restorable/nonrestorable) was found to be significant (chi(2) test, p = 0.002). Although post placement resulted in higher fracture resistance values, these were significant for Empress II crowns only. The results suggest that the posts could contribute to the reinforcement and strengthening of pulpless maxillary premolars. With respect to failure modes, placement of fiber posts improved the fracture from nonrestorable to restorable patterns. This study suggests that the placement of fiber posts is necessary to improve fracture resistance even under full-coverage crowns.     

An in vitro study of the fracture resistance and the incidence ofvertical root fracture of pulpless teeth restored with six post-and-coresystems

STATEMENT OF PROBLEM: Posts and cores are often required with pulpless teeth to provide retention and resistance form for complete crowns. Nevertheless, conventional posts may increase the potential for root fracture. PURPOSE: This study compared the resistance to vertical root fracture of extracted teeth treated with post-core systems that were modified with polyethylene woven fibers (Ribbond) with those treated with conventional post-and-core systems. MATERIAL AND METHODS: Canal instrumentation was performed for 60 maxillary central incisors, and complete crown preparations were made. The coronal portion of each tooth was amputated, and 6 post-and-core systems were studied. Specimens were mounted in acrylic resin blocks with a layer of polyvinyl siloxane covering the roots. Loads were applied at an angle of 130 degrees and measured with a universal testing machine. Results were analyzed statistically with 1-way analysis of variance with Student-Newman-Keuls grouping and chi-square analysis. RESULTS. Cast posts and cores resulted in significantly higher failure thresholds than all others, except for prefabricated, comparably sized, parallel-sided posts with composite cores. All failures in the group with cast posts involved fracture of the teeth, whereas 70% of the teeth with comparably sized parallel-sided posts and composite cores failed as a result of tooth fractures and 30% experienced core fractures. The woven fiber post-core system was significantly lower in strength than all others, and exhibited significantly fewer vertical root fractures. CONCLUSIONS: Polyethylene woven fiber and composite resin without a prefabricated post resulted in significantly fewer vertical root fractures, but mean failure load was the lowest. Smaller diameter prefabricated posts combined with the polyethylene woven fiber and composite cores improved resistance to failure. Traditional cast posts and cores were the strongest of the 6 post-core systems.     

Fracture strength of teeth restored with all-ceramic posts and cores.

OBJECTIVE: The purpose of this in vitro investigation was to evaluate the fracture strength of endodontically treated teeth restored with different all-ceramic posts and cores. METHOD AND MATERIALS: Seventy-two endodontically treated human maxillary central incisors were divided into 3 groups with 24 teeth each and restored with 1 of the following methods: prefabricated zirconia ceramic posts and resin composite buildups; zirconia ceramic posts and copy-milled alumina ceramic cores (2-piece technique), or copy-milled all-ceramic posts and cores made from a zirconia-reinforced glass-infiltrated alumina ceramic (1-piece technique). Each group was divided into 3 subgroups of 8 samples each, consisting of teeth that did not receive crown restorations and were stored for 60 days, teeth restored with all-ceramic crowns and stored for 60 days, and teeth restored with all-ceramic crowns and subjected to 1.2 million loading cycles with 30 N in a chewing simulator. RESULTS: The mean fracture strengths ranged from 205 to 522 N. Prefabricated zirconia posts and resin composite buildups showed a statistically significantly lower fracture strength after chewing simulation than teeth restored with prefabricated zirconia posts and alumina ceramic cores. CONCLUSION: All-ceramic posts and cores made with the 2-piece technique showed promising fracture strengths under the tested conditions.     

不同桩核系统及根管重塑对漏斗形根管下颌前磨牙抗折特性的研究

目的探讨不同桩核及根管重塑对漏斗形根管下颌前磨牙抗折特性的影响。方法将36颗离体下颌前磨牙随机分为A、B、C、D共4组,每组9颗。A、B、C组设为实验组,预备成漏斗形根管,A组用预成玻璃纤维桩复合树脂核修复,B组用预成钛合金平行螺纹桩复合树脂核修复,C组用复合树脂根管重塑铸造桩核修复;D组（对照组）采用正常根管预备,行铸造桩核修复。桩核修复后,4组均行铸造全冠修复。在电子万能试验机上以与牙体长轴成30°方向,以1 mm·min-1速度加载至样本折裂,分析4组样本的抗折载荷和折裂模式。折裂模式分为可修复性和不可修复性。对抗折载荷行单因素方差分析,对折裂模式采用Fisher′s确切概率法分析。结果A、B、C、D组的抗折载荷分别为（1.39±0.56）、（1.17±0.40）、（1.21±0.30）、（1.31±0.56）kN,4组间的差异无统计学意义（P>0.05）。A、B、C、D组产生不可修复性折裂的样本分别为6、8、9、9颗,4组间折裂模式的差异也无统计学意义（P>0.05）。结论不同桩核系统对下颌前磨牙漏斗形根管残根的抗折特性没有影响,复合树脂重塑可作为漏斗形根管残根修复的一种选择。     

桩核材料与纤维/树脂复合材料桩钉联合修复无髓牙的抗折性能研究

目的评价3种树脂类桩核材料与高强玻璃纤维/树脂复合材料(FRC)桩钉联合修复无髓牙的抗折性能。方法用FRC桩钉和3种经不同方法处理(热压和未热压)的树脂核(Artglass聚合体、Charisma复合树脂、AB组份复合树脂)联合修复离体无髓牙根,测试1300加载时的破坏载荷。结果Artglass聚合体组的抗折力最高(505.4N),经热压处理后强度明显提高(564.1N) ; Chari~复合树脂组经热压后脆性增加,强度降低(热压前后分别为411.3N和 315.3N); AB组份树脂组经热压后强度明显提高(热压前后分别为358.4N和423.4N)。实验中无1例出现桩钉折断和聚酷冠碎裂。结论不同桩核材料与FRC桩钉联合修复无髓牙的抗折力不同,其中Art乡ass聚合体组的抗折力最高,但是此3组的抗折力均超过了咀嚼过程中前牙的咬合力,树脂核与纤维/树脂复合材料桩钉联合修复无髓前牙残根可以满足临床需要。     

Fracture resistance of crowned incisors with different post systems and luting agents

This study evaluated the fracture resistance of crown-restored incisors with different post-and-core systems and luting cements. Fifty intact maxillary central incisors were randomly assigned to five groups of 10 teeth each. Group 1 was restored with fibre posts (Snowpost) luted with an adhesive composite resin cement (Panavia F). Group 2 was restored with titanium alloy posts (Parapost) luted with the resin cement, and Group 3 with titanium alloy posts and a glass-ionomer cement (Fuji I). Composite cores (Clearfil Photocore) were built up in groups 1, 2 and 3. Group 4 was restored with cast post-and-cores luted with the resin cement, and group 5 with the cast post-and-cores and the glass-ionomer-cement served as a control group. All teeth were restored with metal-ceramic crowns. After thermal stressing, the specimen was then secured in a universal testing machine. Fracture loads and modes were recorded. One-way ANOVA and a Tukey test were used to determine significant differences between the failure loads of groups. Chi-square test was conducted for evaluation of the fracture modes. The fracture loads of groups 1 and 2 were significantly higher than that of the control group (P<0.05). Group 1 had a significantly higher number of repairable fractures than the other four groups (P<0.001). Within the limitations of this study, the results suggest that fibre posts can be recommended as an alternative to cast and prefabricated metallic posts. Composite resin cement cannot significantly improve fracture resistance of metallic post and crown-restored incisors.     

Direct restoration of severely damaged incisors using short fiber-reinforced composite resin

OBJECTIVES: The aim of this in vitro study was to evaluate the static load-bearing capacity and the failure mode of endodontically treated maxillary incisors restored with complete crowns made of experimental composite resin (FC) with short fiber fillers, with and without root canal posts. Further aim was to evaluate the effect of fiber-reinforced composite resin (FRC) on the failure mode of the restoration. MATERIAL AND METHODS: The experimental composite resin (FC) was prepared by mixing 22.5 wt.% of short E-glass fibers (3mm in length) and 22.5 wt.% of semi-interpenetrating polymer network (IPN) resin with 55 wt.% of silane treated silica fillers. The clinical crowns of 30 human extracted maxillary incisors were sectioned at the cemento-enamel junction. Five groups of direct complete crowns were fabricated (n=6); Group A: made from particulate filler composite resin (PFC) (Grandio Caps, VOCO, control), Group B: PFC with fiber post (everStick, StickTeck), Group C: made from PFC with everStick fiber post and FRC-substructure, Group D: made from FC, Group E: made from FC with FRC-substructure. The root canals were prepared and posts were cemented with resin cement (ParaCem Universal). All restored teeth were stored in water at room temperature for 24h before they were statically loaded with speed of 1.0 mm/min until fracture. Data were analyzed using ANOVA (p=0.05). Failure modes were visually examined. RESULTS: ANOVA revealed that restorations made from experimental fiber composite resin had higher load-bearing capacity (349N) (p<0.05) than the control restorations (173N). No significant difference was found in load-bearing capacity between restorations reinforced with FRC-substructure and those without (p>0.05). CONCLUSIONS: Restorations made from short glass fiber containing composite resin with IPN-polymer matrix showed better load-bearing capacity than those made with either plain PFC or PFC reinforced with fiber post.     

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.     

Clinical evaluation of a carbon fibre reinforced carbon endodontic post

This study reports a prospective clinical trial comparing a carbon fibre reinforced carbon (CFRC) endodontic post with a conventional prefabricated post. Twenty-seven single rooted maxillary anterior teeth in 18 patients (nine males and nine females; age range 18-60 years) were restored either with a CFRC post or a wrought precious alloy control. Cast type III gold alloy cores were used in conjunction with both post groups. The CRFC posts (n = 16) were cemented with a composite luting agent and the conventional posts (control) were cemented with zinc phosphate. Four failures were recorded in the CFRC post group at 24, 29, 56 and 87 months, compared with one failure in the control group at 84 months. These results suggest that post-retained crowns utilizing a CFRC material and a composite resin luting agent do not perform as well as conventional wrought precious alloy posts.     

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.     

Effect of post-retained composite restoration of MOD preparations on the fracture resistance of endodontically treated teeth

PURPOSE: The present study aimed to compare the fracture resistance and failure patterns of endodontically treated premolars with MOD preparations restored using different material combinations. The null hypothesis postulated that there was no association between the fracture resistance of endodontically treated premolars and the resin composite materials or the post-and-core system used to build up the restorations. MATERIALS AND METHODS: Eighty single-rooted maxillary premolars were used. After endodontic treatment and preparation of MOD preparations, 8 groups of 10 samples each were created, using the following material combinations: group 1 (control), flowable and microhybrid resin composites; group 2, flowable A; group 3, flowable B; group 4, microhybrid resin A; group 5, microhybrid resin B; group 6, flowable B + microhybrid resin B; group 7, flowable A + microhybrid resin A + post A; group 8, flowable B + microhybrid resin B + post B. Mechanical static fracture tests were performed loading the specimens till fracture. RESULTS: The mean failure loads (N) were 502 (control), 470 (group 7), 445 (group 8), 441 (group 6), 405 (group 5), 364 (group 4), 317 (group 2), and 302 (group 3). Statistically significant differences were found between groups 1 vs 2, 1 vs 3, and 3 vs 7 (p < 0.05). CONCLUSION: The fracture resistance of endodontically treated premolars with MOD preparations was enhanced by the use of the sandwich technique. The samples restored with posts predominantly showed restorable fractures, while teeth restored without posts mostly displayed unrestorable failures.     

Influence of fatigue loading on four post-and-core systems in maxillary premolars.

OBJECTIVE: Clinical studies show a high failure incidence after years of service of endodontically treated premolars, when restored with post-core crowns, especially those with short posts or deficient ferrules. The reason for this can be a deterioration of the luting cement around the post by fatigue from functional loading. In particular, the anatomy of premolars may frequently be incompatible with the application of long endodontic posts. The aim of this study was to evaluate the influence of fatigue loading on the quality of the cement layer between posts with restricted lengths and the root canal wall in premolars. As the stiffness of posts may affect the outcome, post-and-core systems with varying post stiffness were selected. METHOD AND MATERIALS: Four types of post-and-core systems were selected for this study: three prefabricated post systems combined with a resin composite core material and one cast post and core. The three prefabricated posts were titanium posts (Tenax), quartz-fiber posts (Aestheti-Post), and quartz-coated-carbon-fiber posts (Aestheti-Plus). The post-and-core restorations were made on single-rooted, human, maxillary premolars from which the coronal sections were removed at the level of the proximal cementoenamel junction. Following endodontic treatment, a cast post and core (post length 6 mm) was prepared for each tooth individually (direct method) and cemented into the root canal with chemical cure Panavia 21 TC. The prefabricated posts were directly cemented in the root canal and then, after applying a dual-cure adhesive (Clearfil Photobond), built up with a core build-up composite (Clearfil Photocore). For each group (n = 8), half of the specimens were exposed to fatigue loading (10(6) load cycles) almost perpendicular to the axial axis (85 degrees), while the other half was used as the control. Three parallel, transverse root sections of 1.5-mm thickness, were cut from each specimen. These sections were examined by scanning electron microscopy (SEM) to evaluate the cement integrity, while the retention strength of the cemented post sections was determined with a push-out test. RESULTS: Fatigue loading did not cause separation of the buildups from the roots or affect the push-out strength. On a univariate level, only SEM evaluation showed significant differences between the types of post, fatigue loading, and between the levels of root sections. The cement integrity with the titanium post was significantly less than with the other three systems, which did not differ among themselves. The differences could not be explained by differences in stiffness between the posts. CONCLUSION: A composite core build-up material bonded to the dentin and supported by quartz-fiber posts or quartz-coated-carbon-fiber posts, cemented with adhesive cement like Panavia 21 TC, may be a viable alternative for the conventional cast core.     

Influence of the flexural modulus of prefabricated and experimental posts on the fracture strength and failure mode of composite resin cores

The purpose of this study was to evaluate the influence of flexural modulus of non-metal posts on the fracture strength and failure mode of composite resin cores. Thirty-two human premolars were divided into four groups: prefabricated glass fiber post with 1.0 mm diameter and composite resin core (Group PE1.0), that with 1.5 mm diameter and composite resin core (Group PE1.5), experimental post (flexural modulus; 4.25GPa) and composite resin core (Group EX), and preparation for abutment teeth only (Group NT). After a static loading test, the fracture strength and failure mode were recorded. Group NT (1670.81 N) showed higher fracture strength than Groups PE1.0 (866.44 N), PE1.5 (825.19 N) and EX (1075.63 N) (p<0.05). This study showed that the fracture strength of endodontically treated teeth restored with composite resin cores is not influenced by the flexural modulus of non-metal posts.     

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。     

不同桩核金属烤瓷全冠修复后前牙抗剪切力的实验研究

目的 探讨不同桩核系统金属烤瓷全冠修复上颌前牙后修复体抗剪切力的差异.方法 对40颗大小相似的新鲜上颌中切牙行根管充填后截冠,随机分成4组,每组10颗.其中3组分别用纤维增强树脂桩和树脂核、预成钛合金桩和树脂核,铸造镍铬合金桩核修复,桩核与金属烤瓷全冠均用树脂粘接剂粘固;另1组用玻璃离子粘固剂粘固铸造镍铬合金桩核和金属烤瓷全冠作为对照组.经温度循环疲劳实验,用万能力学实验机测试样本牙的抗剪切力,并观测折裂型,进行统计学分析.结果 纤维增强树脂桩组、预成钛合金桩组、铸造桩核组及对照组的抗剪切力分别为(534.4±145.7)N、(499.8±168.9)N、(412.6±99.3)N、(337.4±121.2)N.纤维增强树脂桩组和预成钛合金桩组的抗剪切力大于对照组,差异有统计学意义(P＜0.05);纤维增强树脂桩组中可再修复折裂型样本牙数量多于其他组,差异有统计学意义(P＜0.05).结论 纤维增强树脂桩核金属烤瓷全冠修复有较好的抗剪切力,且折裂型多为可再修复型,修复后残根保存率高.