Advertisement

Comparison of Fracture Resistance between Cast Posts and Fiber Posts: A Meta-analysis of Literature

Published:October 26, 2012DOI:https://doi.org/10.1016/j.joen.2012.09.026

      Abstract

      Introduction

      The aim of this study was to compare the fracture resistance of cast posts versus the fracture resistance of fiber posts by means of meta-analysis when they were used in the restoration of endodontically treated teeth.

      Methods

      MEDLINE, Cochrane Controlled Trials Register, China National Knowledge Infrastructure, and China Biology Medicine disc were used in the literature search. Two independent reviewers assessed the titles and abstracts of all articles that were found according to the predefined inclusion criteria. Relevant articles were acquired in full-text form. Data in these studies were independently extracted. Standardized mean differences of included studies were combined and analyzed by using meta-analysis.

      Results

      Thirteen studies met the inclusion criteria. There was considerable heterogeneity among these studies. The standardized mean difference of the combined data was 0.64 (95% confidence interval, 0.08–1.20; P < .001), indicating that the cast post group displayed significantly higher fracture resistance than the fiber post group.

      Conclusions

      On the basis of the current best available evidence, we concluded that cast posts had higher fracture resistance than fiber posts.

      Key Words

      It has been suggested that endodontically treated teeth (ETT) are more brittle and may fracture more easily than vital teeth (
      • Carter J.M.
      • Sorensen S.E.
      • Johnson R.R.
      • et al.
      Punch shear testing of extracted vital and endodontically treated teeth.
      ,
      • Sokol D.J.
      Effective use of current core and post concepts.
      ).The loss of tooth structure from caries or trauma also makes ETT more susceptible to fracture. To improve the fracture resistance of ETT, post and core techniques are clinically necessary to restore ETT. Because the choice of an appropriate post material is crucial to successful restoration, much research has been focused on this subject. Different in vitro systems were measured, and researchers compared their fracture resistance to find the optimal system. Various kinds of post material were involved in fracture tests. Fiber posts and cast metal posts were 2 common types among the tests. In several studies, the results were inconsistent or conflicting (
      • Stricker E.J.
      • Göhring T.N.
      Influence of different posts and cores on marginal adaptation, fracture resistance, and fracture mode of composite resin crowns on human mandibular premolars: an in vitro study.
      ,
      • Ni C.W.
      • Chang C.H.
      • Chen T.Y.
      • et al.
      A multiparametric evaluation of post-restored teeth with simulated bone loss.
      ). Thus, their clinical relevance was limited.
      The most widely used method to evaluate the fracture resistance of ETT is load testing. In this method, all specimens (restored with post-core) are exposed to continuous loading from specific machines. After the occurrence of teeth fractures, the fracture loads were recorded. The higher the fracture loads were, the more resistant the teeth were when restored with the tested post. Thus we usually compared fracture resistance of variable post material through their fracture loads.
      The aim of this study was to compare the fracture load of ETT restored with either a cast post or a fiber post in loading test. The null hypothesis was that there would be no difference in fracture load between these test groups. We used meta-analysis to process the data, which is a reliable method of synthesizing published information and providing direct evidence to clinical practice (
      • Borenstein M.
      • Hedges L.V.
      • Higgins J.P.T.
      • et al.
      Introduction to Meta-analysis.
      ).

      Materials and Methods

       Literature Search

      Studies in vitro that compared different fracture resistance of cast posts and fiber posts were identified. These trials were conducted in humans. The search strategy for detecting literature was used to search MEDLINE (Table 1) and Cochrane Controlled Trials Register from 1995–2011. A similar search was undertaken on China National Knowledge Infrastructure and China Biology Medicine from 2001–2011. Languages were restricted to English and Chinese.
      Table 1MEDLINE Search Strategy
      No.Search historyResults
      1Root canal therapy OR dental pulp devitalization OR endodontically treated teeth16,598
      2Post and core technique3,014
      3Tooth fractures4,750
      41 AND 2 AND 3333
      5Limits: humans, English, Chinese, publication date from 1995–2011241

       Inclusion Criteria

      Two reviewers independently assessed and selected the studies on the basis of certain inclusion criteria (Table 2).
      Table 2Inclusion Criteria
      1. All studies must be randomized controlled trials.
      2. All specimens were single-root, freshly extracted adult teeth that were free of root-surface caries, fractures, and previous restorations.
      3. All specimens had similar size (length, buccolingual and mesiodistal extension).
      4. All specimens were kept moist before use.
      5. After standard root canal therapy, all specimens had regular post space preparation.
      6. A simulated periodontal ligament was established on root surfaces with a layer of silicone material. The finish line of the crown was maintained 2 mm coronal to the embedding material to simulate normal biologic width.
      7. The fracture loads were recorded with the unit of force (newton, N).

       Data Extraction

      Data extracted from each study independently included the name of the first author, year of publication, the number of specimens, the mean force and standard deviation (SD) of fracture load (N), the height of ferrule, tooth type, and loading type.

       Meta-analysis

      Continuous data were expected for the fracture load of cast posts and fiber posts. To compare continuous data, a calculation of the standardized mean difference (SMD) was conducted. We defined the SMD as the difference in mean between cast posts and fiber posts divided by a pooled standard deviation. The I2 of Higgins and Thompson (
      • Higgins J.P.
      • Thompson S.G.
      Quantifying heterogeneity in a meta-analysis.
      ) was used to assess heterogeneity among studies. I2 describes the proportion of total variation attributable to between-study heterogeneity as opposed to random error or chance. In the presence of substantial heterogeneity I2 (>50%) (
      • Higgins J.P.
      • Thompson S.G.
      • Deeks J.J.
      • et al.
      Measuring inconsistency in meta-analyses.
      ), the random effect model (REM) was adopted as the pooling method; otherwise, the fixed effect model (FEM) was used as the pooling method, both along with a 95% confidence interval (CI). Funnel plots were used to show the publication bias. The meta-analysis was performed by using software Revman 4.2.8 provided by the Cochrane Collaboration (http://www.cc-ims.net/RevMan). The level of statistical significance was set at .05.

      Results

       Data Summary of Included Studies

      Thirteen articles met the inclusion criteria. Of these, 8 studies were published in English and 5 studies in Chinese. Human premolars were used as specimens in 6 studies, central incisors in 5 studies, and canines in 3 articles. For the cast metal material, Ni-Cr alloy was used in 9 studies and noble alloy in 3 studies, and the last one gave no detail statement. In the aspects of the fiber posts, glass fiber posts were used in 11 studies, carbon fiber posts in 2 studies, and quartz fiber posts in 1 study. Of these articles, 2 studies investigated the effect of ferrule on the fracture resistance of ETT restored with cast or fiber posts. Five studies investigated the fracture load of ETT with ferrule. Three studies had trials of ETT without ferrule, and 3 articles made no clear statement of the ferrule. When it came to the testing technique, 9 studies applied static loading to the specimens. Three studies used chewing simulation method to test the fracture load. Only 1 study applied gradual cyclic loading for testing the failure values.

       Meta-analysis

      The thirteen studies (
      • Stricker E.J.
      • Göhring T.N.
      Influence of different posts and cores on marginal adaptation, fracture resistance, and fracture mode of composite resin crowns on human mandibular premolars: an in vitro study.
      ,
      • Ni C.W.
      • Chang C.H.
      • Chen T.Y.
      • et al.
      A multiparametric evaluation of post-restored teeth with simulated bone loss.
      ,
      • Maccari P.C.
      • Cosme D.C.
      • Oshima H.M.
      • et al.
      Fracture strength of endodontically treated teeth with flared root canals and restored with different post systems.
      ,
      • Raygot C.G.
      • Chai J.
      • Jameson D.L.
      Fracture resistance and primary failure mode of endodontically treated teeth restored with a carbon fiber-reinforced resin post system in vitro.
      ,
      • Aghdaee N.A.
      • Darban J.G.
      • Mohajeri A.
      Fracture strength in restored teeth before and after load cycling: an in vitro study.
      ,
      • Meng Q.F.
      • Chen Y.M.
      • Guang H.B.
      • et al.
      Effect of a ferrule and increased clinical crown length on the in vitro fracture resistance of premolars restored using two dowel-and-core systems.
      ,
      • Dorriz H.
      • Alikhasi M.
      • Mirfazaelian A.
      • et al.
      Effect of ferrule and bonding on the compressive fracture resistance of post and core restorations.
      ,
      • Qing H.
      • Zhu Z.
      • Chao Y.
      • et al.
      In vitro evaluation of the fracture resistance of anterior endodontically treated teeth restored with glass fiber and zircon posts.
      ,
      • Zhang Q.
      The Fracture Resistance of Flared Root Canal Tooth Restored with Different Post Systems.
      ,
      • Chen L.
      • Qin Y.
      The fracture resistance of flared root canal tooth restored with different post systems.
      ,
      • Hou X.
      Effect of crown lengthening and ferrule placement on static load failure of teeth restored with different post-cores systems.
      ,
      • Hou X.
      • Gao X.
      • Yang P.
      • et al.
      Fracture resistance of residual teeth restored with two different post and core systems.
      ,
      • Zha W.
      • Zhang H.
      • Bian J.
      Research of fracture resistance of flared root restored with fiber post and cast post-core.
      ) were heterogeneous (χ2 = 63.04, degrees of freedom = 14, P < .001, I2 = 77.8%). Thus, REM was used for combining study estimates. The total SMD was 0.64 (95% CI, 0.08–1.20). The test of overall effect showed that P < .001, and it indicated cast posts had significantly higher fracture resistance than fiber posts (Fig. 1). Funnel plot showed a little asymmetry in the bottom part of the figure (Fig. 2). The forest plot displayed the heterogeneity between studies, and we found 2 articles with opposite results (Fig. 1). After we deleted these articles, we processed the residual studies' estimates and got a new result (χ2 = 16.84, degrees of freedom = 12, P = .16, I2 = 28.7%). The residual studies were homogeneous (Fig. 3). Thus, FEM was used to combine study estimates. The new SMD was 0.98 (95% CI, 0.70–1.25). The test of overall effect showed that P < .001 (Fig. 3). Although 2 heterogeneous results were deleted, the result still showed that cast posts had significantly higher fracture resistance than fiber posts. We made a new funnel plot of the residual 11 studies; it showed asymmetry in the left bottom of the graph. We found one study had more remarkable SMD than the others (Fig. 4).
      Figure thumbnail gr1
      Figure 1Forest plot of all included studies.
      Figure thumbnail gr2
      Figure 2Funnel plot of all included studies.
      Figure thumbnail gr3
      Figure 3Forest plot of residual studies after deletion of 2 heterogeneous studies.
      Figure thumbnail gr4
      Figure 4Funnel plot of residual studies after deletion of 2 heterogeneous studies.

      Discussion

       Level of Evidence

      Randomized controlled trials are considered the most reliable method for experimental design (
      • Coward D.D.
      Partial randomization design in a support group intervention study.
      ) because they can minimize confounders and maximize control over the trial environment (
      • Begg C.B.
      • Mazumdar M.
      Operating characteristics of a rank correlation test for publication bias.
      ). Randomized controlled trials are also high in the hierarchy of quality of evidence (
      • Greenhalgh T.
      Getting Your Bearings (What Is This Paper About?): How to Read a Paper—The Basics of Evidence Based Medicine.
      ) and can establish the most convincing causal relationship compared with other types of clinical studies, eg, cohort, case-control, and cross-sectional survey. All the included studies were described as randomized, but none of them were described as double-blind. Only 4 of them provided the information about the methods used in random allocation.

       Heterogeneity

      The forest plot (Fig. 1) showed heterogeneity existed between the included studies. This heterogeneity disappeared after we deleted 2 studies with opposite results (Fig. 3). Thus, these 2 studies might cause the heterogeneity. Both studies showed the cast posts group had lower fracture resistance than the fiber posts group (
      • Ni C.W.
      • Chang C.H.
      • Chen T.Y.
      • et al.
      A multiparametric evaluation of post-restored teeth with simulated bone loss.
      ,
      • Chen L.
      • Qin Y.
      The fracture resistance of flared root canal tooth restored with different post systems.
      ). The result was contrary to the total estimates. After we investigated these deleted studies (
      • Ni C.W.
      • Chang C.H.
      • Chen T.Y.
      • et al.
      A multiparametric evaluation of post-restored teeth with simulated bone loss.
      ,
      • Chen L.
      • Qin Y.
      The fracture resistance of flared root canal tooth restored with different post systems.
      ), we found they both had distinct differences from other studies. For instance, one of these studies used a tooth with weak dentin wall at the root cervix (the thickness was 0.5 mm) (
      • Chen L.
      • Qin Y.
      The fracture resistance of flared root canal tooth restored with different post systems.
      ). For other studies, the thickness of the dentin wall at the cervix was no less than 1 mm. The weakened root cervix might have higher stress concentration at the interface between the post and the healthy dentin. When the tooth was restored with post that had the lower modulus of elasticity (eg, fiber post), the tooth strength was increased. Meanwhile, the tooth that was restored with cast post might easily be subject to fracture (
      • Akkayan B.
      • Gulmez T.
      Resistance to fracture of endodontically treated teeth restored with different post systems.
      ,
      • Fokkinga W.A.
      • Kreulen C.M.
      • Vallittu P.K.
      • et al.
      A structured analysis of in vitro failure loads and failure modes of fiber, metal, and ceramic post-and-core systems.
      ). This explained the lower fracture resistance that was acquired from the cast post group in one of the heterogeneous studies (
      • Chen L.
      • Qin Y.
      The fracture resistance of flared root canal tooth restored with different post systems.
      ). Another heterogeneous study (
      • Ni C.W.
      • Chang C.H.
      • Chen T.Y.
      • et al.
      A multiparametric evaluation of post-restored teeth with simulated bone loss.
      ) used composite resin endocrowns to restore the teeth. The other studies all used cast metal crowns. The lower fracture resistance of cast post may be explained by the stiffer core material, which did not follow the deformation of the composite resin crowns under load. This may have led to critical strain on inner crown surfaces and to fractures of these crowns. Therefore, the cast post group showed lower fracture resistance.

       Publication Bias

      Publication bias is the tendency that positive studies are more likely to be published than negative ones. It could falsely skew the conclusion of meta-analysis in either direction. Funnel plots can test whether publication bias exists (
      • Glasziou P.
      Systematic Reviews in Health Care: A Practical Guide.
      ,
      • Sutton A.J.
      Methods for Meta-analysis in Medical Research.
      ). We included only published randomized controlled trials in our meta-analysis, which could have increased the risk of publication bias by neglecting nonrandomized studies or unpublished articles. The risk of publication bias would be further enhanced by searching only 4 electronic databases. The language restriction also caused the bias. After we deleted 2 heterogeneous studies, we obtained a new funnel plot (Fig. 4). Although the new graph displayed good symmetry, it had an isolated point at the right bottom. According to the SMD, we found the corresponding study (
      • Maccari P.C.
      • Cosme D.C.
      • Oshima H.M.
      • et al.
      Fracture strength of endodontically treated teeth with flared root canals and restored with different post systems.
      ). It had a higher value for the SMD. This study investigated glass fiber post and quartz fiber post, and the comparison between these materials showed no significant difference. Thus, we combined the data of these subcategories when we extracted the data from the included studies. This might have caused the deviation that appeared in the funnel plot.

       Testing Technique

      Various technique modes are used in testing fracture resistance of ETT. The most widely used type is the linear compressive (static) loading in a common universal material testing machine until failure happens. Because of its efficiency (low costs, not time-consuming), static loading becomes a frequently applied technique that simulates clinical load conditions in a simplistic way. However, this method cannot consider other factors influencing the survival of materials such as fatigue stresses or aging. It cannot replicate the fracture pattern that occurred clinically (
      • Kelly J.R.
      Clinically relevant approach to failure testing of all-ceramic restorations.
      ). Different types of dynamic loading with different cycle counts with or without simultaneous thermocycling and with or without additional static loading until failure occurs have been described. The most frequent dynamic load test is the chewing simulation introduced by Krejci et al (
      • Krejci I.
      • Reich T.
      • Lutz F.
      • et al.
      An in vitro test procedure for evaluating dental restoration systems: 1—a computer controlled mastication simulator.
      ) as the computer-controlled mastication simulation. As modification, an applied load of 30 N with 10,000 thermocycles was specified (
      • Butz F.
      • Lennon A.M.
      • Heydecke G.
      • et al.
      Survival rate and fracture strength of endodontically treated maxillary incisors with moderate defects restored with different post-and-core systems: an in vitro study.
      ,
      • Heydecke G.
      • Butz F.
      • Strub J.R.
      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.
      ,
      • Heydecke G.
      • Butz F.
      • Hussein A.
      • et al.
      Fracture strength after dynamic loading of endodontically treated teeth restored with different post-and-core systems.
      ). Later, an intermittent loading was described by Isidor and Brondum (
      • Isidor F.
      • Brondum K.
      Intermittent loading of teeth with tapered, individually cast or prefabricated, parallel-sided posts.
      ). A load of 250 N is applied at a frequency of 2 per second (
      • Isidor F.
      • Odman P.
      • Brondum K.
      Intermittent loading of teeth restored using prefabricated carbon fiber posts.
      ,
      • Mannocci F.
      • Ferrari M.
      • Watson T.F.
      Intermittent loading of teeth restored using quartz fiber, carbon-quartz fiber, and zirconium dioxide ceramic root canal posts.
      ). This protocol was also modified to applied load peaks of 70 N at a 1.5-Hz frequency with additional thermocycling and a 4-kg load at 72 cycles per minute (
      • Libman W.J.
      • Nicholls J.I.
      Load fatigue of teeth restored with cast posts and cores and complete crowns.
      ). A disadvantage of the intermittent loading is that if no failure happens during the cycling (most cycling was stopped after 400,000 N), a comparison with studies that used load-to-failure testing is impossible. Another testing technique introduced by Strand et al (
      • Strand G.V.
      • Tveit A.B.
      • Gjerdet N.R.
      • et al.
      Marginal ridge strength of teeth with tunnel preparations.
      ) uses a gradual cycling dynamic force with a frequency of 2 Hz, initially varying between 50 and 100 N for 500 cycles. Then the force is varied in increments of 50 N and 500 cycles until failure occurs. As with static loading, this method can be applied in a universal material testing machine (eg, Instron, Norwood, MA), which is less time-consuming and expensive. In our investigation, 9 included studies used static loading. Three studies used chewing simulation method to test the fracture load. Only 1 study applied gradual cyclic loading for testing the failure values. The testing method of dynamic loading is closer to clinical conditions. It was stated that clinically, the process leading to restoration failure is caused by repeated stress application during mastication. Therefore, the numerous load cycles that are applied to specimens were essential to simulate the clinical conditions (
      • Wiskott H.W.
      • Nicholls J.I.
      • Belser U.C.
      Effect of tooth preparation height and diameter on the resistance of complete crowns to fatigue loading.
      ). The differences in the testing techniques affect the comparison between various post materials. Most studies found significant differences between cast posts and fiber posts when they applied static loading to the specimens in vitro. Otherwise, some studies discovered that the dynamic loading type showed no significant difference in the comparison of various post materials (
      • Xible A.A.
      • de Jesus Tavarez R.R.
      • de Araujo Cdos R.
      • et al.
      Effect of cyclic loading on fracture strength of endodontically treated teeth restored with conventional and esthetic posts.
      ,
      • Hu S.
      • Osada T.
      Resistance to cyclic fatigue and fracture of structurally compromised root restored with different post and core restorations.
      ).
      However, in vivo, there are additional factors such as changing force directions in mastication that cannot be simulated in the dynamic loading procedures. An ideal testing method should not only imitate natural loading mechanisms but should also produce failure modes similar to those in vivo. On the basis of the present study, we need a standard testing design to eliminate methodological bias that could cause conflicting results and clinical recommendations.

       Fracture Pattern

      All included articles had descriptions about the fracture pattern of the teeth restoration in detail. In relation to this aspect, all results were consistent with each other except one study (
      • Raygot C.G.
      • Chai J.
      • Jameson D.L.
      Fracture resistance and primary failure mode of endodontically treated teeth restored with a carbon fiber-reinforced resin post system in vitro.
      ). The results demonstrated that teeth with cast posts had catastrophic failures, such as oblique or horizontal fractures in the middle third of the root or vertical fractures of the root (
      • Ni C.W.
      • Chang C.H.
      • Chen T.Y.
      • et al.
      A multiparametric evaluation of post-restored teeth with simulated bone loss.
      ,
      • Meng Q.F.
      • Chen Y.M.
      • Guang H.B.
      • et al.
      Effect of a ferrule and increased clinical crown length on the in vitro fracture resistance of premolars restored using two dowel-and-core systems.
      ,
      • Qing H.
      • Zhu Z.
      • Chao Y.
      • et al.
      In vitro evaluation of the fracture resistance of anterior endodontically treated teeth restored with glass fiber and zircon posts.
      ). However, the failures that occurred with the fiber posts were repairable, such as fractures at the cervical third of roots or the cores (
      • Ni C.W.
      • Chang C.H.
      • Chen T.Y.
      • et al.
      A multiparametric evaluation of post-restored teeth with simulated bone loss.
      ,
      • Meng Q.F.
      • Chen Y.M.
      • Guang H.B.
      • et al.
      Effect of a ferrule and increased clinical crown length on the in vitro fracture resistance of premolars restored using two dowel-and-core systems.
      ,
      • Qing H.
      • Zhu Z.
      • Chao Y.
      • et al.
      In vitro evaluation of the fracture resistance of anterior endodontically treated teeth restored with glass fiber and zircon posts.
      ) that presented similar behavior. One possible explanation is that fiber posts have a modulus of elasticity similar to that of dentin, which facilitates stress dissipation. For the fiber post groups, the space between the dentin canal walls and the post was wider and filled with resin cement in opposition to the cast posts that were molded to adjust the post shape to the canal walls. Thus, the thicker resin cement layer for fiber posts might have acted as stress absorption when tooth was under occlusal force. Therefore, the less force will be focused in the root. It also increases the ability of force to spread so the risk of root fracture will decrease.

       Post Selection

      This article reviewed the literature to compare the differences in fracture resistance between 2 kinds of post materials. When it comes to the selection of posts in clinical conditions, we should consider all factors that would influence the survival of restoration. Two included studies investigated the ferrule effect on the fracture resistance. Both studies concluded that the existence of ferrule can significantly improve the fracture resistance of ETT. The amount of remaining coronal tooth structure is also a critical factor in determining the post selection (
      • Nishimura Y.
      • Tsubota Y.
      • Fukushima S.
      Influence of cyclic loading on fiber post and composite resin core.
      ). The bulk of the tooth above the restorative margin should be necessary to achieve resistance form (
      • Barkhordar R.A.
      • Radke R.
      • Abbasi J.
      Effect of metal collars on resistance of endodontically treated teeth to root fracture.
      ). The results of in vitro (
      • Sidoli G.E.
      • King P.A.
      • Setchell D.J.
      An in vitro evaluation of a carbon fiber based post and core system.
      ,
      • Stockton L.W.
      • Williams P.T.
      Retention and shear bond strength of two post systems.
      ) and in vivo studies (
      • Bergman B.
      • Lundquist P.
      • Sjogren U.
      • et al.
      Restorative and endodontic results after treatment with cast posts and cores.
      ) indicate that fiber posts can be used when ample coronal dentin remains and the crown is well supported by remaining tooth structure (
      • Bergman B.
      • Lundquist P.
      • Sjogren U.
      • et al.
      Restorative and endodontic results after treatment with cast posts and cores.
      ); otherwise, cast posts may be used when there is moderate-to-severe tooth loss. The bonding of a post to the tooth structure can improve the prognosis of the post-core restored tooth by increasing post retention (
      • Mannocci E.
      • Ferrari M.
      • Watson T.F.
      Intermittent loading of teeth restored using quartz fiber, carbon-quartz fiber and zirconium dioxide ceramic root canal posts.
      ) and by reinforcing the tooth structure (
      • Saupe W.A.
      • Gluskin A.H.
      • Radke Jr., R.A.
      A comparative study of fracture resistance between morphologic dowel and cores and a resin-reinforced dowel system in the intraradicular restoration of structurally compromised roots.
      ). It has been stated that reinforcement of the tooth is due to the stress distribution characteristics of the bonding materials (
      • Saupe W.A.
      • Gluskin A.H.
      • Radke Jr., R.A.
      A comparative study of fracture resistance between morphologic dowel and cores and a resin-reinforced dowel system in the intraradicular restoration of structurally compromised roots.
      ). Of the cements available, zinc phosphate cement is the one that has been used frequently. Newer adhesive resin luting agents are advocated for the luting of posts in comparison with the traditional cements. It was reported that resin luting agents showed good adhesion to fiber posts (
      • Mannocci E.
      • Ferrari M.
      • Watson T.F.
      Intermittent loading of teeth restored using quartz fiber, carbon-quartz fiber and zirconium dioxide ceramic root canal posts.
      ).
      Because a wide variety of factors would influence the survival of posts, the clinician should be selective in choosing the post system that best fits the individual needs of each tooth.

      Acknowledgments

      The authors thank Chongqi Jia and Jiawei Tian for their assistance in processing the data.
      The authors deny any conflicts of interest related to this study.

      References

        • Carter J.M.
        • Sorensen S.E.
        • Johnson R.R.
        • et al.
        Punch shear testing of extracted vital and endodontically treated teeth.
        J Biomech. 1983; 16: 841-848
        • Sokol D.J.
        Effective use of current core and post concepts.
        J Prosthet Dent. 1984; 52: 231-234
        • Stricker E.J.
        • Göhring T.N.
        Influence of different posts and cores on marginal adaptation, fracture resistance, and fracture mode of composite resin crowns on human mandibular premolars: an in vitro study.
        J Dent. 2006; 34: 326-335
        • Ni C.W.
        • Chang C.H.
        • Chen T.Y.
        • et al.
        A multiparametric evaluation of post-restored teeth with simulated bone loss.
        J Mech Behav Biomed Mater. 2011; 4: 322-330
        • Borenstein M.
        • Hedges L.V.
        • Higgins J.P.T.
        • et al.
        Introduction to Meta-analysis.
        John Wiley & Sons, Ltd, Padstow, UK2009
        • Higgins J.P.
        • Thompson S.G.
        Quantifying heterogeneity in a meta-analysis.
        Stat Med. 2002; 21: 1539-1558
        • Higgins J.P.
        • Thompson S.G.
        • Deeks J.J.
        • et al.
        Measuring inconsistency in meta-analyses.
        BMJ. 2003; 327: 557-560
        • Maccari P.C.
        • Cosme D.C.
        • Oshima H.M.
        • et al.
        Fracture strength of endodontically treated teeth with flared root canals and restored with different post systems.
        J Esthet Restor Dent. 2007; 19: 30-37
        • Raygot C.G.
        • Chai J.
        • Jameson D.L.
        Fracture resistance and primary failure mode of endodontically treated teeth restored with a carbon fiber-reinforced resin post system in vitro.
        Int J Prosthodont. 2001; 14: 141-145
        • Aghdaee N.A.
        • Darban J.G.
        • Mohajeri A.
        Fracture strength in restored teeth before and after load cycling: an in vitro study.
        J Calif Dent Assoc. 2011; 39: 300-307
        • Meng Q.F.
        • Chen Y.M.
        • Guang H.B.
        • et al.
        Effect of a ferrule and increased clinical crown length on the in vitro fracture resistance of premolars restored using two dowel-and-core systems.
        Oper Dent. 2007; 32: 595-601
        • Dorriz H.
        • Alikhasi M.
        • Mirfazaelian A.
        • et al.
        Effect of ferrule and bonding on the compressive fracture resistance of post and core restorations.
        J Contemp Dent Pract. 2009; 10: 1-8
        • Qing H.
        • Zhu Z.
        • Chao Y.
        • et al.
        In vitro evaluation of the fracture resistance of anterior endodontically treated teeth restored with glass fiber and zircon posts.
        J Prosthet Dent. 2007; 97: 93-98
        • Zhang Q.
        The Fracture Resistance of Flared Root Canal Tooth Restored with Different Post Systems.
        Shandong University, Jinan, China2007
        • Chen L.
        • Qin Y.
        The fracture resistance of flared root canal tooth restored with different post systems.
        Chinese Journal of Practical Stomatology. 2008; 5: 300-301
        • Hou X.
        Effect of crown lengthening and ferrule placement on static load failure of teeth restored with different post-cores systems.
        Shandong University, Jinan, China2007
        • Hou X.
        • Gao X.
        • Yang P.
        • et al.
        Fracture resistance of residual teeth restored with two different post and core systems.
        Chinese Journal of Prosthodontics. 2007; 8: 133-135
        • Zha W.
        • Zhang H.
        • Bian J.
        Research of fracture resistance of flared root restored with fiber post and cast post-core.
        J Clin Stomatol. 2009; 25: 228-229
        • Coward D.D.
        Partial randomization design in a support group intervention study.
        Western Journal of Nursing Research. 2002; 24: 406-421
        • Begg C.B.
        • Mazumdar M.
        Operating characteristics of a rank correlation test for publication bias.
        Biometrics. 1994; 50: 1088-1101
        • Greenhalgh T.
        Getting Your Bearings (What Is This Paper About?): How to Read a Paper—The Basics of Evidence Based Medicine.
        2nd ed. BMJ Publishing Group, London2001 (39–55)
        • Akkayan B.
        • Gulmez T.
        Resistance to fracture of endodontically treated teeth restored with different post systems.
        J Prosthet Dent. 2002; 87: 431-437
        • Fokkinga W.A.
        • Kreulen C.M.
        • Vallittu P.K.
        • et al.
        A structured analysis of in vitro failure loads and failure modes of fiber, metal, and ceramic post-and-core systems.
        Int J Prosthodont. 2004; 17: 476-482
        • Glasziou P.
        Systematic Reviews in Health Care: A Practical Guide.
        Cambridge University Press, New York2001
        • Sutton A.J.
        Methods for Meta-analysis in Medical Research.
        John Wiley, New York2009
        • Kelly J.R.
        Clinically relevant approach to failure testing of all-ceramic restorations.
        J Prosthet Dent. 1999; 81: 652-661
        • Krejci I.
        • Reich T.
        • Lutz F.
        • et al.
        An in vitro test procedure for evaluating dental restoration systems: 1—a computer controlled mastication simulator.
        Schweiz Monatsschr Zahnmed. 1990; 100: 953-960
        • Butz F.
        • Lennon A.M.
        • Heydecke G.
        • et al.
        Survival rate and fracture strength of endodontically treated maxillary incisors with moderate defects restored with different post-and-core systems: an in vitro study.
        Int J Prosthodont. 2001; 14: 58-64
        • Heydecke G.
        • Butz F.
        • Strub J.R.
        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.
        J Dent. 2001; 29: 427-433
        • Heydecke G.
        • Butz F.
        • Hussein A.
        • et al.
        Fracture strength after dynamic loading of endodontically treated teeth restored with different post-and-core systems.
        J Prosthet Dent. 2002; 87: 438-445
        • Isidor F.
        • Brondum K.
        Intermittent loading of teeth with tapered, individually cast or prefabricated, parallel-sided posts.
        Int J Prosthodont. 1992; 5: 257-261
        • Isidor F.
        • Odman P.
        • Brondum K.
        Intermittent loading of teeth restored using prefabricated carbon fiber posts.
        Int J Prosthodont. 1996; 9: 131-136
        • Mannocci F.
        • Ferrari M.
        • Watson T.F.
        Intermittent loading of teeth restored using quartz fiber, carbon-quartz fiber, and zirconium dioxide ceramic root canal posts.
        J Adhes Dent. 1999; 1: 153-158
        • Libman W.J.
        • Nicholls J.I.
        Load fatigue of teeth restored with cast posts and cores and complete crowns.
        Int J Prosthodont. 1995; 8: 155-161
        • Strand G.V.
        • Tveit A.B.
        • Gjerdet N.R.
        • et al.
        Marginal ridge strength of teeth with tunnel preparations.
        Int Dent J. 1995; 45: 117-123
        • Wiskott H.W.
        • Nicholls J.I.
        • Belser U.C.
        Effect of tooth preparation height and diameter on the resistance of complete crowns to fatigue loading.
        Int J Prosthodont. 1997; 10: 207-215
        • Xible A.A.
        • de Jesus Tavarez R.R.
        • de Araujo Cdos R.
        • et al.
        Effect of cyclic loading on fracture strength of endodontically treated teeth restored with conventional and esthetic posts.
        J Appl Oral Sci. 2006; 14: 297-303
        • Hu S.
        • Osada T.
        Resistance to cyclic fatigue and fracture of structurally compromised root restored with different post and core restorations.
        Dent Mater J. 2005; 24: 225-231
        • Nishimura Y.
        • Tsubota Y.
        • Fukushima S.
        Influence of cyclic loading on fiber post and composite resin core.
        Dent Mater J. 2008; 27: 356-361
        • Barkhordar R.A.
        • Radke R.
        • Abbasi J.
        Effect of metal collars on resistance of endodontically treated teeth to root fracture.
        J Prosthet Dent. 1989; 61: 676-678
        • Sidoli G.E.
        • King P.A.
        • Setchell D.J.
        An in vitro evaluation of a carbon fiber based post and core system.
        J Prosthet Dent. 1997; 78: 5-9
        • Stockton L.W.
        • Williams P.T.
        Retention and shear bond strength of two post systems.
        Oper Dent. 1999; 24: 210-216
        • Bergman B.
        • Lundquist P.
        • Sjogren U.
        • et al.
        Restorative and endodontic results after treatment with cast posts and cores.
        J Prosthet Dent. 1989; 61: 105
        • Mannocci E.
        • Ferrari M.
        • Watson T.F.
        Intermittent loading of teeth restored using quartz fiber, carbon-quartz fiber and zirconium dioxide ceramic root canal posts.
        J Adhes Dent. 1999; 1: 153-158
        • Saupe W.A.
        • Gluskin A.H.
        • Radke Jr., R.A.
        A comparative study of fracture resistance between morphologic dowel and cores and a resin-reinforced dowel system in the intraradicular restoration of structurally compromised roots.
        Quintessence Int. 1996; 27: 483-491