Statement of problem: Very little is known about the resistance to fracture of endodontically treated teeth restored with newly developed esthetic post systems.
Purpose: This in vitro study compared the effect of 1 Titanium and 3 esthetic post systems on the fracture resistance and fracture patterns of crowned, endodontically treated teeth.
Methods: A total of 40 recently extracted human maxillary canines with their crowns removed were endodontically treated. Four groups of 10 specimens were formed. Teeth were restored with Titanium (Filpost), quartz fiber (DT Light-Post), glass fiber (ParaPost White) and Zicronia (Cosmopost) posts and numbered as groups 1, 2, 3 &4, respectively. All posts were cemented with Single Bond dental adhesive system and dual-polymerizing RelyX ARC adhesive resin cement. All teeth were restored with composite cores, and metal crowns were fabricated and cemented with glass ionomer cement. Each specimen was imbedded in acrylic resin and then secured in a universal load testing machine. A compressive load was applied at a 130-degree angle to the long axis of the tooth until fracture, at a crosshead speed of 1mm / min. One-way analysis of variance and a Tukey test were used to determine the significance of the failure loads between groups (P<.001). A non-parametric X² test was conducted for evaluation of the mode of failure (P<.001).
Results: The mean failure loads (kg) were 66.95, 91.20, 75.90, and 78.91 for groups 1 – 4, respectively. Teeth restored with quartz fiber posts (group 2) exhibited significantly higher resistance to fracture (P<.001) than the other 3 groups. Teeth restored with glass fiber and zirconia posts (groups 3 and 4) were statistically similar (P<.05). Fractures that would allow repair of the tooth were observed in groups 2 and 3, whereas unrestorable, catastrophic fractures were observed in groups 1 and 4 (P<.001).
Conclusion: Within the limitations of this study, significantly higher failure loads were recorded for root canal treated teeth restored with quartz fiber posts (DT Light-Post). Fractures that would allow repeated repair were observed in teeth restored with quartz fiber and glass fiber posts.

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.
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 (DT Light-Post-RTD/ France), glass fiber ER DentinPost/Brasseler-Komet, Germany), glass fiber plus zirconia (EasyPost, Dentsply-Maillefer, Switz.), and zirconia (CosmoPost, Ivoclar-Vivadent, Liechtenstein). 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.
Conclusions: 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).

Objectives: In endodontically treated teeth, because of extensive structural defects, the risk of fracture is increased. For reconstruction of coronal structure posts provide retention. Composite fiber posts were recently introduced to dentistry. This study compared the fracture strength of maxillary central incisors restored by metalic, fiber-reinforced composite and ceramic posts.
Methods: 30 human maxillary central incisors were used. The crown of each incisor was cut off 1 mm coronally to C.E.J. perpendicular to long axis of the tooth by metal disc. Root canals of teeth were prepared for posts after RCT. Specimens were embedded in autopolymerizing acrylic resin 4 mm below the CEJ and then tested in a universal testing machine (Zwick-Germany). A compressive load was applied at 130 degrees to the long axis until fracture, at a cross-head speed of 0.5 mm/min. Fracture loads were recorded. All data collected were analyzed statistically using the ANOVA and LSD tests.
Results: The mean and standard deviation (S.D.) of failure loads (in Newtons) were 765 +/- 113/265 N, 790+/- 95/34 N, 614+/- 105/32 N for glass-fiber, ceramic and metallic groups, respectively.ANOVA test detected statistically significant differences between all groups. Teeth restored with fiber and ceramic posts exhibited significantly higher resistance to fracture than with titanium posts. Teeth restored by fiber and ceramic posts were statistically similar by LSD test. The highest proportion of undesirable fractures was seen with titanium posts.
Conclusion: Usage of fiber and ceramic posts are preferable to titanium posts. Because of more undesirable fractures in the ceramic group than fiber group, use of the latter posts are recommended overall.

Objectives: Evaluate the mechanical resistance of roots restored with prefabricated posts.
Materials and Methods: 40 sound upper human central incisors had the crown removed and the roots were endodontically treated. After 24 hours, the root canals were prepared using low rotation, going 2/3 or ½ down the depth of the root, and were divided into 4 groups (n=10). Group A: 10 roots were prepared on 2/3 of the depth for the cementation of the Unimetric Post (Dentsply/Maillifer) (UNI) using Clearfil LinerBond 2V and Panavia F (Kuraray Co. Japan), according to manufacturers instructions; Group B: 10 roots were prepared ½ down into the root canal for cementation with the same system as Group A; Group C: 10 roots were prepared on 2/3 of the depth for the cementation of the AESTHETI-POST (AES: RTD/Bisco) using ALL-BOND 2 (Bisco) and Post Cement HI-X (Bisco); Group D: 10 roots were prepared ½ down into the root canal for cementation with the same system as Group C. Three mm of the post were left outside of the root canal, on the cervical portion, to allow the fixation of the core restoration with composite resin (Z250-3M/ESPE, USA). Simulating preparation for a crown. The specimens underwent compression at 450 on a universal testing machine, at a speed of 0.5 mm/min. until fracture.
Results: The mean values of load obtained at fracture (Group A=93.4 Kgf, Group B=88.4 Kgf, Group C=95.7 Kgf, Group D=96.3 Kgf) were statistically tested using ANOVA two-way test. All groups showed statistically similar results (p>0.05).
Conclusion: the different preparation depths of the root canals did not influence the results of the strength tests.

The development of adhesive cements and prefabricated post system (PPS) provides us a conservative alternative to the traditional cast post –core in the reconstruction of endodontically treated teeth. However, the fracture strength of the core/tooth structures continues to be an object of doubts and discussions. The study aimed at evaluating the “in vitro” fracture strength of roots of restored inferior incisor bovine teeth. Thirty bovine teeth and ten human teeth were selected to constitute 4 groups (n=10); group 1) PPS Cosmopost (Ivoclar) + Syntac + Variolink II (Vivadent); group 2) PPS C-Post + All Bond 2 + Post Cement HI-X (Bisco, Inc., USA); group 3) PPS ÆSTHETI-POST +All Bond 2 + Post Cement HI-X (Bisco, Inc., USA); and the group 4) (control group) human incisor teeth prepared for metal ceramic crown. The roots all the same length (15 mm), were embedded into acrylic resin blocks with a film (0.2 mm) of vinyl polysiloxane to simulate the periodontal ligament. The core was build up with composite (7.250 – 3M USA) through a custom transplant matrix. After 24 hours storage (H20/37ºC) the specimens were submitted to the comprehensive test in Richie universal testing machine.

Group	Average	SD
Cosmopost \ Variolink	87.30 MPa	±13.5814
C-Post – AB2 \ HI-X	67.35 MPa	±18.5305
ÆsthetP + AB2 \ HI-X	80.30 MPa	±19.1038
Human Teeth	97.63 MPa	±37.4461

The statistical analysis of the data (ANOVA) revealed no significant difference (p>0.05) among the fracture strength averages of the four groups. The values obtained from the pre-fabricated post systems gave us results are similar to those obtained with natural teeth.

Objectives: To investigate the fracture characteristics of devitalized teeth restored with posts of different materials and length.
Methods: Sixty intact extracted incisors of similar size were chosen and sectioned 2mm coronal to the CEJ. The root canals were instrumented and obturated. Three different post systems were tested: stainless steel post (SB), glass-fiber post (GF), and carbon-fiber post (CF). The teeth were prepared to post lengths of 5 and 10 mm with the appropriate reamers for each post system. Composite cores of a standardized size were constructed over the cemented posts and Ni-Cr ceramic crowns were fabricated with a 1.5 mm ferrule length. The teeth were stored for 24 hours, thermocycled 1500 times (5-55¢XC). The tooth-crown assembly was mounted with a jig in a universal Instron testing machine and loaded at a crosshead speed of 0.5 mm/minute until failure. The teeth were then inspected under a stereoscope and SEM for fracture patterns.
Results: The 10 mm/SB group had the lowest failure load (930 N), and was significantly different from the 5 mm/SB (1339 N) and 10 mm/GF group (1271 N). There was no significant difference in the failure loads among the fiber post groups, and in the failure toughness among six groups. Oblique fracture was the dominant pattern in all groups. Teeth restored with posts of the same material demonstrated similar fracture location and directions. Under SEM observation, cracked dentinal tubules were found in the lingual aspects of the SB posts. Over half of the specimens in the metal post groups exhibited fracture planes passing through the apex of the post.
Conclusions: Use of a 10 mm metal post did not improve the fracture strength of the restored devitalized teeth. Fiber posts provide more uniform stress distribution, which may prevent fracture at the apical end of the post. The fracture patterns of the teeth were associated with the post materials, while the post length had little influence on either the fracture strength or patterns of the teeth.

Abstract/conclusions: The purpose of this study was to evaluate the influence of endodontic and restorative procedures on fracture resistance of teeth, and to compare the incidence of root fracture in teeth with clinical crowns removed that were restored with three different types of post and a composite core build-up. Seven groups of 10 extracted maxillary canines were used. A control group had only a crown preparation, but no endodontic treatment. Three groups had endodontic treatment, crown preparation, and the access restored. Three groups had endodontic treatment, the crown totally removed, a tapered, parallel, or carbon post (Composipost) placed, and a composite build-up. All specimens were subjected to a 45-degree load at 0.5 mm/min until failure occurred. The force at failure and the location of fracture were recorded. The groups with post and composite build-ups failed at significantly lower force than the teeth in which the crowns had not been removed. There were no significant differences in the amount of force required to produce failure among the three groups with different posts and a composite build-up. The group restored with the Composipost had no root fractures, whereas there were five fractures (50%) in each of the parallel and tapered post groups.

Purpose:Fatigue resistance of post and cores is critical to the long term behavior of restored nonvital teeth. The purpose of this in vitro trial was to evaluate the influence of the post material's physical properties on the adaptation of adhesive post and core restorations after cyclic mechanical loading.
Methods: Composite post and cores were made on endodontically treated deciduous bovine teeth using 3 anisotropic posts (made of carbon, quartz, or quartz-and-carbon fibers) and 3 isotropic posts (zirconium, stainless steel, titanium). Specimens were submitted to 3 successive loading phases--250,000 cycles at 50 N, 250,000 at 75 N, and 500,000 at 100 N--at a rate of 1.5 Hz. Restoration adaptation was evaluated under SEM, before and during loading (margins) and after test completion (margins and internal interfaces). Six additional samples were fabricated for the characterization of interface micromorphology using confocal microscopy.
Results: Mechanical loading increased the proportion of marginal gaps in all groups; carbon fiber posts presented the lowest final gap proportion (7.11%) compared to other stiffer metal-ceramic or softer fiber posts (11.0% to 19.1%). For internal adaptation, proportions of debonding between dentin and core or cement varied from 21.69% (carbon post) to 47.37% (stainless steel post). Debonding at the post-cement interface occurred only with isotropic materials. Confocal microscopy observation revealed that gaps were generally associated with an incomplete hybrid layer and reduced resin tags.
Conclusions: Regardless of their rigidity, metal and ceramic isotropic posts proved less effective than fiber posts at stabilizing the post and core structure in the absence of the ferrule effect, due to the development of more interfacial defects with either composite or dentin.

Objectives: The objective of this study was to observe the biomimetic behavior of the fiber resin post and cast post in the cervical stress level of central incisors submitted to the fatigue test. A group of non-posted tooth was also evaluated.
Methods: Thirty six recently extracted upper central incisors were selected. The teeth were divided in three groups. G1 – Cast post and core. G2 – Fiber resin post and composite core G3 – without post and core. Post was introduced 2/3 of the root. All groups were endodontically treated and received a full cast crown. G1 e G2 were cut 1mm to the cervical limit. G3 was just restored with composite resin. For the fatigue test, the teeth were mounted in epoxy supports with a simulation of the periodontal ligament. The angle of test was 45º . An Instron 4444 (Universal Test Machine) was used for the compressive fatigue test. The maximum load was 60N. After the fatigue test, the groups were thermocycled and immersed in ethylene blue die for 24 hrs.
Results: were obtained after teeth sectioning. The Kruskal-Wallis test was used. The average for each group was G1-3.0, G2-1.7, G3-4.6. A significant difference was observed (p<0,05) (T=16.25 and p=0,0003.) G2 had the best result.
Conclusion: the study suggests that teeth with fiber resin post better resists the fatigue test than teeth with cast post or without post, under the specific conditions of the study.

Objectives: The present study was designed to test the null hypothesis that there is no difference in the fracture resistance of pulpless teeth restored with different types of post-core systems and full coverage crowns.
Methods: Extracted human upper premolars were restored with a fiber post, prefabricated metallic post or cast metallic post-core. Teeth with full crown preparations without post-core restorations served as a control. All teeth were restored with full coverage crowns. A 90-degree vertical or 45-degree oblique load was applied to the restored teeth with a crosshead speed of 0.5mm/min, and the fracture loads and mode of fracture were recorded.
Results: Under the condition of vertical loading, the fracture load of teeth restored with the cast metallic post-cores was greatest among the groups (two-factor factorial ANOVA and Scheffe's F test, P < 0.05). All fractures in teeth restored with all types of post-core systems propagated in the middle portions of roots, including the apices of the posts. Under the condition of oblique loading, the fracture load of teeth restored with pre-fabricated metallic posts was significantly smaller than that in other groups. Two-thirds of fractures in the fiber post group propagated within the cervical area, while most fractures in other groups extended beyond the middle of the roots.
Significance: From the results of the present investigations, it was concluded that under the conditions of vertical and oblique loadings, the combination of a fiber post and composite resin core with a full cast crown is most protective of the remaining tooth structure

Abstract/conclusions: This in vitro study evaluated the fracture resistance of bovine teeth with prefabricated carbon fiber posts (Composipost). Fourteen bovine teeth having similar lengths and dimensions were mounted in an acrylic resin block having a simulated periodontal ligament. The post space was prepared using two calibrated drills that provided an 8.5-mm post length. The prefabricated carbon fiber post was luted with a resin luting agent, and the core was made using the system's autopolymerizing resin core material. A crown was luted to each prepared tooth. Each test specimen was intermittently loaded (250 N) at an angulation of 45 degrees to the long axis of the tooth at a frequency of 2 loads per second. Four of the roots had an incomplete longitudinal fracture after loading. The results of this study were compared to a previous study by the authors that had been conducted under similar conditions. The failure rates of the two types of posts from the previous study (prefabricated parallel-sided posts (Para-Post) and tapered, individually cast posts) were significantly higher (Logrank test; P <.02) than those of the carbon fiber posts.

The most recent application of fiber-reinforced composites involves their use as post and core systems to restore endodontically treated teeth. Even though this last application has been advertised and been used clinically by many dentists, there is very little information regarding the physical properties of these posts.
Objectives: The purpose of this study was to compare the fracture resistance and mode of failure of endodontically treated teeth restored with fiber-reinforced composite posts.
Methods: Ninety maxillary central incisors were divided into eight experimental groups and one control group of 10 samples each. Teeth from the two experimental groups called "Narrow" and "Flared" canals were restored with Fiber-Kor, Lucent Anchors and Ribbond posts using two different cementation techniques. Specimens were loaded to failure using an Instron machine.
Results: Statistical analysis using two-way ANOVA revealed no significant difference between flared and narrow canals in mean load to failure between the post systems except for the Ribbond posts. For the narrow canal, the mean load ranged from a low of 4.55 (±1.49) Kg for the Ribbond Standard to a high of 12.9 (±1.64) Kg for the Lucent Anchors while for the flared canal the low mean was 9.04 (±1.76) for Fiber-Kor and the high of 12.87 Kg was equal for both Lucent Anchors and Ribbond Standard. Overall, the ParaPost control group had the highest load value (18.33 ±3.27 Kg). No root fractures occurred in any of the experimental groups.
Conclusions: Results from the study suggest that the mode of failure or deflection of the fiber reinforced composite posts is protective to the remaining tooth structure. Considering the high risk of fracture and the possibility of re-treatment of endodontically treated teeth, the use of these new post systems seems to represent a conservative option when restoring debilitated root canals.

Background: Many post systems are available to clinicians, yet no consensus exists about which one is better in restoring endodontically treated teeth.
Purpose: This study evaluated the fracture strength of teeth with flared canals and restored with two fiber-reinforced resin systems (glass fiber: FRC Postec [Ivoclar Vivadent, Schaan, Liechtenstein]; quartz fiber: D.T. Light-Post (Bisco/RTD), and one custom cast base metal (Ni-Cr) post and core system.
Methods: Thirty anterior teeth had their crowns removed below the cemento-enamel junction and were endodontically treated. The canals were prepared for post fixation, and the canal walls were flared using a taper diamond bur. The prepared roots were randomly divided into three groups according to the post system. All posts were cemented with an adhesive resin cement. For the fiber-reinforced resin posts, cores were built up using microhybrid composite. Metallic crowns were luted using zinc phosphate cement. Specimens were loaded at 45 degrees in a universal testing machine at a crosshead speed of 0.5 mm/min until failure. The mode of failure was classified as repairable or nonrepairable.
Results: Teeth restored with cast posts had fracture strength twice that of teeth restored with resin posts. Fiber-reinforced resin posts failed at a compressive force comparable to clinical conditions, but all failures were repairable.
Conclusions: Fracture strength and mode of failure in anterior teeth with flared canals varied according to the type of post used to support a crown.

Statement of problem: The survival of pulpless teeth restored with a post and core system is a controversial issue. Purpose: This study compared the fracture resistance of 2 types of restorations: teeth restored with prefabricated carbon-fiber (Composipost) posts and composite cores to cast dowel-core restored teeth.
Methods: A total of 44 recently extracted sound premolars were randomly distributed into 2 equal groups: group I, restored with prefabricated carbon-fiber post and a composite core; and group II, with custom-cast type III gold alloy post and cores. The size and shape of the posts were identical in the 2 groups. All teeth were fully covered with a nonprecious cast crown. Fracture resistance was measured by applying a point force at 45 degrees to the long angle of the tooth.
Results: Mean fracture threshold was 103.7 + 53.1 kg for group I versus 202.7 + 125.0 kg for group II (differences significant with P = .003). In group II, however, fracture nearly always affected the tooth itself, whereas in group I, the post-core nearly always failed first.
Conclusions: Significantly higher fracture thresholds were recorded for the cast post and core group. Teeth restored with cast posts typically showed fracture of the tooth, although at loads rarely occurring clinically.

Adhesion between the resin composite and the radicular dentin structure serves an important role by supporting both the core and the superstructure. The aim of this in-vitro study was to investigate the efficacy of two dentin bonding systems and two resin composites on the fracture resistance of pulpless teeth and to determine the effect of the post. Root canal instrumentation was performed for twenty mandibular first premolars and divided into four groups: 1. experimental dentin bonding system (EXP) self-cured resin composite (Clearfil Fll, Kuraray: Fllk; 2. EXP/dual-cured resin composite (Clearfil DC CORE, Kuraray: DC); 3. commercial dentin bonding system (ED primer and Clearfil Photo Bond, Kuraray: ED)(Fll:4 ED/DC. Slowly increasing forces were applied perpendicular to the longitudinal tooth axis in an Instron testing machine with a crosshead speed of 0.5 mm/min. until the root fractured. Results [mean SD (Kgl)] were compared with those previously obtained for with and without the C-POST) (Osada et al. JDR 79: 628.2000) using two-way ANOVA and Scheffe test.

	EXP/Fll	EXP/DC	ED/Fll	ED/DC
	(n-5)
No Post	24.4±2.1	25.8±6.6	22.6±3.9	21.2 ±8.1
With C-POST	46.2±21.2	33.6±4.6	26.4±9.6	33.3±13.1
Without C-POST	38.4±12.7	53.2±11.9	47.7±12.9	33.0±13.7

There was no significant difference in the dentin bonding system/resin composite combinations. When the post was present, the fracture resistance was significantly improved (p<0.01), probably due to reinforcing and supporting of the resin composite core.

Objectives: This research was performed to determine the strength of a selection of endodontic single fiber posts (D T Light-Post, RTD, St Egreve, France) and multiple combinations of new fiber posts recently introduced onto the market.
Methods: Ten specimens for each group of four single posts and seven different combinations of new smaller posts were tested. Single or combinations of these new posts were cemented in an endodontic resin block and loaded at an angle of 45° in universal testing machine (Triaxial Tester T400 Digital) to the long axis using a crosshead speed of 1 mm/min until specimen failure.
Results: The strength of all combinations of new fiber posts were in the same range reported for DT single posts tested. Statistical analyses (ANOVA) of these data did not show significant difference between DT1, DT2 single posts and combinations of new posts, which have their section area corresponding to DTs at 6mm from the tip.
Conclusions: The multiple combinations of these new posts under investigation reported strength analogous to the single posts, which are largely used and tested in clinical practice for years.

Summary: The aim of this in vitro study was to compare the fracture resistance and marginal adaptation of all-ceramic incisor crowns with all-ceramic posts, glass–fiber-reinforced posts and titanium posts as well as a control without any post. Three groups of eight maxillary incisors were restored with an all-ceramic post, a fiber-reinforced composite (FRC) post, a titanium post and a further group was restored without posts. Composite cores were provided and all-ceramic crowns were adhesively luted. After artificial ageing, the fracture resistance of the restored teeth was determined. The marginal adaptation of the restorations at the interfaces between cement-tooth and cement-crown was evaluated with scanning electron microscopy using replica specimen before and after ageing. The restored teeth without posts [270N (235/335)] showed no significantly different fracture strength compared with teeth with the titanium system [340N (310/445)]. The all-ceramic posts [580N (425/820)] and the FRC posts [505N (500/610)] both provided a significant higher fracture resistance than the teeth without posts. Prior to ageing, all materials showed <5% separation at the margins cement-tooth or cement-crown ('marginal gap'). After ageing, the interfaces of all systems deteriorated to values between 6 and 14% marginal gap. The greatest marginal gap was found with the titanium system (14%) at the interface cement-crown and with the all-ceramic posts (12%) at the transition between cement-tooth. Regarding fracture resistance and the marginal adaptation, the all-ceramic and FRC posts may be considered as an alternative to the commonly used titanium post restorations.

The elastic modulus of the restorative material is important in restoring endodontically treated teeth. This study aimed to compare the fracture resistance and failure patterns of 90 mandibular molars restored using resin composites with or without fiber posts, with respect to the number of residual cavity walls. Five restoration types were performed corresponding to different wall defects (groups 1-5). Groups were divided in two subgroups corresponding to the use or absence of fiber posts. Teeth were loaded and resistance of specimens was measured as the axial compressive load to cause fracture and macroscopic fracture patterns were observed. One way ANOVA revealed a significant difference in fracture resistance (p < 0.001). Tukey post hoc test also revealed significant differences between groups as samples restored with fiber posts exhibited mostly restorable fractures. It was concluded that the resistance of endodontically treated mandibular molars restored with composite resins is mainly affected by the number of residual walls. Using fiber-reinforced posts optimized fracture patterns.

Abstract: 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 non-restorable. 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/non-restorable) was found to be significant (χ2 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 non-restorable to restorable patterns. This study suggests that the placement of fiber posts is necessary to improve fracture resistance even under full-coverage crowns.

This study evaluated the influence of the cementation length of glass fiber-reinforced composite (FRC) on the fatigue resistance of bovine teeth restored with an adhesively cemented FRC. Thirty roots of single-rooted bovine teeth were allocated to 3 groups (n = 10), according to the ratio of crown length/root length (post cementation length): group 1 = 2/3, group 2 = 1/2, and group 3 = 1/1. The roots were prepared, the fiber posts (FRC Postec Plus) were cemented, and the specimens were submitted to 2 million mechanical cycles. After fatigue testing, a score was given based on the number of fatigue cycles until fracture, and data were submitted to statistical analysis. All specimens were resistant to fatigue. Taking into account the methodology and results of this study, the evaluated fiber posts can be cemented based on the ratio of crown/root at 1/1. Further clinical studies must be conducted to verify this ratio

Objectives: The restoration of severely damaged teeth that have lost support at the coronal portion of the root canal is very difficult. The aim of this study was the evaluation of different methods of root reinforcement by dual-cure composite and various types of non-metallic posts.
Methods: We performed root canal therapy on 60 maxillary central incisors. The teeth were divided into five groups, and specimens from three groups were prepared to simulate the teeth with flared canals. In the 1st group, no weakening was done. In the 2nd group, the compromised area of the root canal was obturated with gutta percha. In the 3rd group, universal DT Light-Posts were used in the root canal to 8 mm below the margin of the palatal wall, after which the height of the DT post was regulated in the canal pulp chamber space so that it would not be under direct load. The post was then cemented with dual-cure composite. In the 4th and 5th groups, the same procedures were done; however, clear and opaque posts, with shapes and dimensions similar to those of DT Light-Posts, were used. In all groups, the access cavity was restored with light-curing composite resin to 0.5 mm under the margins. After being mounted, all specimens were pressed in an Instron machine. At fracture, the amount of force was recorded.
Results: The highest resistance to fracture belonged to group 1 and the lowest to group 2. The results showed that there was a significant statistical difference, and a Duncan analysis showed that the differences of resistance to fracture were significant in all groups except among groups 3, 4, and 5.
Conclusion: The use of dual-cure composite resin and non-metallic DT Light-Posts can significantly increase the resistance-to-fracture of root-treated maxillary central incisors with thin root walls.

Objectives: The purpose of study was to evaluate the potential of intraradicular reinforcement of layered adhesion technique and two different types of post in structurally compromised roots. Methods: Root canal therapies were done on 48 extracted similar maxillary incisors. The samples were divided to 4 groups. In three groups for simulation of specimens to weakened teeth, instrumentation was done 5mm apical to CEJ from access cavity. In positive control group that weakening was not done, restoration of access cavity was done with composite resin (Z100, 3M dental product, USA) and dentin bonding agent (Single bond, 3M dental product, USA). In second group access cavity of the weakened teeth was restored only with composite resin and dentin bonding agent to the level of CEJ. In third group weakened cervical area were reinforced with a dual cure composite (Bis-Core, BISCO, INC, USA) and translucent quartz fiber post (Light-Post, RTD, France) In the fourth group, the weakened cervical area was reinforced with dual cure composite and cast post with similar morphologic properties. Access cavity in the last two groups were restored with composite resin, then all specimens were tested in an instron machine. Results: The mean fracture load for the 4 groups were 170.12, 71.40, 129.36, and 116.6 kgf respectively. The differences between first group and others (P value=0), second group and others (P value=0) were significant. There was no significant differences between third and forth group (P value =0.103), but the rate of restorable fractures (pattern of fracture) was significantly different between these two groups.
Conclusions: It is concluded that the use of post, dentin bonding agent and a composite resin in a root with thin walls will reinforce the weakened tooth but the type of the post will influence on the final result.

Purpose:To develop a laboratory model aimed at duplicating the failure process of post and core restorations. The load pattern applied was to be repetitive (fatigue) and multivectorial. To determine and compare the resistance under fatigue loading of seven endodontic post/natural root combinations: stainless steel-, titanium-, ceramic-, composite-fiber/epoxy-, two glass-fiber/epoxy- and glass-fiber/acrylic posts.
Methods: The repetitive, alternating and multivectorial intraoral force pattern was reproduced by subjecting the specimens to the rotating cantilever beam test. To this end, the samples were designed as rotation-symmetric structures comprising a root, a post, periodontal ligament- and bone analogs and a restoration analog. The following posts were tested: Unimetric-Ti, Unimetric-SS, Biopost, Composipost, Easypost, DT Light-Post, Everstick post. The samples were spun around their long axes while being clamped into a revolving collet on one end and loaded normal to their long axis on the other end. The aim was to determine the load level at which 50% of the specimens survived- and 50% fractured before 10E6 cycles. The 50% means were determined using the staircase procedure.
Results: In increasing order of magnitude, the resistances to fatigue loading were as follows: Biopost, Unimetric-Ti, Unimetric-SS, Composipost, Easypost, Everstickpost, DT Lightpost.
Significance: The fatigue resistance of the two fibrous posts with the highest fatigue resistance was twice that of any of the ceramic or metal posts.

Objectives: Determine if the fabrication and technology of four post systems modify the stress distribution to canals.
Methods: The stress distributing characteristics associated `with the installation and function of D. T. Light-Post (Quartz fiber, RTD), EasyPost (Glass fiber, Dentsply), Reforpost (Angelus) and Unimetric Post (Steel post, Dentsply) as a control group were determined with a 2-dimensional photoelastic stress analysis using a circular polariscope. Standardized 11 mm in length canals were prepared in PSM-5 (Measurements Group, Raleigh ;N.C) photoelastic sheets material with increasing sizes acrylic drills. All the posts were cemented with resin cement (Bifix QM, Voco, Germany). Then the posts were loaded vertically and with a 26 degrees inclined load at 20, 30,40,50 and 60 kilograms. The posts were photographed (Olympus 5050 Digital Camera) by use of the circular polariscope in the loaded and unloaded state. Qualitative measurement of the number (magnitude) and the closeness (concentrate) of the fringes were made.
Results: The steel preformed post showed the higher stress magnitudes at the vertical and lateral loading. It showed stress concentration at the apical and at each post thread. The pre-stressed fiber post at the vertical load showed the least magnitude and concentration of stress in the surrounding photoelastic material. At lateral loads fiber-glass EasyPost and pre-stressed quartz fiber post showed similar behaviors.
Conclusions: Stress distribution surrounding post cemented in canals, done in photoelastic material, is related with the fabrication material and with the fabrication technology of the posts.

Objectives: Determine if the fabrication and technology of four post systems modify the stress distribution to canals.
Methods: The stress distributing characteristics associated `with the installation and function of D. T. Light-Post (Quartz fiber, RTD), EasyPost (Glass fiber, Dentsply), Reforpost (Angelus) and Unimetric Post (Steel post, Dentsply) as a control group were determined with a 2-dimensional photoelastic stress analysis using a circular polariscope. Standardized 11 mm in length canals were prepared in PSM-5 (Measurements Group, Raleigh ;N.C) photoelastic sheets material with increasing sizes acrylic drills. All the posts were cemented with resin cement (Bifix QM, Voco, Germany). Then the posts were loaded vertically and with a 26 degrees inclined load at 20, 30,40,50 and 60 kilograms. The posts were photographed (Olympus 5050 Digital Camera) by use of the circular polariscope in the loaded and unloaded state. Qualitative measurement of the number (magnitude) and the closeness (concentrate) of the fringes were made.
Results: The steel preformed post showed the higher stress magnitudes at the vertical and lateral loading. It showed stress concentration at the apical and at each post thread. The pre-stressed fiber post at the vertical load showed the least magnitude and concentration of stress in the surrounding photoelastic material. At lateral loads fiber-glass EasyPost and pre-stressed quartz fiber post showed similar behaviors.
Conclusions: Stress distribution surrounding post cemented in canals, done in photoelastic material, is related with the fabrication material and with the fabrication technology of the posts.

Objective: Determine if the cement interface thickness and fabrication material of five post system modify the stress distribution to flared canals.
Methods: The stress distributing characteristics associated with installation and function of Cast Post (Ni-Cr), Para-post (Steel post, Coltene-Whaladent), Integrapost (Titanium post, Premier), Mooser Post (Steel-post, Maillefer) and DT-Light Post (Quartz fiber post, RTD, France) were determined with a two-dimentional photoelastic stress analysis using a circular polariscope ( Photoelastic Inc ).Standardized enlarged canals were prepared in PSM-5 ( Measurements Group, Raleigh ;N.C) photoelastic sheets material with increasing sizes acrylic drills (Orico,Germany). All the posts were cemented with resin cement (Duo-Link, Bisco Inc).The cast post was made closely adapted to the canal walls and cemented with the same cement .Then the posts were loaded vertically and with a 35 degrees inclined load at 10,20 and 30 kilograms. Then the posts were photographed (Olympus 5050 Digital Camera) by use of the circular polariscope in the loaded and unloaded state. Qualitative measurement of the number (magnitude) and the closeness (concentrate) of the fringes were made.
Results: The cast post with thinner cement interface showed the higher stress magnitudes at the vertical and lateral loading. All the metallic preformed post showed high stress concentration at the apical and cervical zones for the loads respectively .The fiber post at the vertical and lateral load showed the least magnitude and concentration of stress in the surrounding photoelastic material.
Conclusions: The stress distribution surrounding posts cemented in flared canals, done in photoelastic material, is related with the fabrication material of the post and with the thickness of the cement interface.

Objectives: The aim of this study was to compare three types of post and core systems and analyze the stress magnitude within the root.
Methods: Two-dimensional photoelastic simulation models of endodontic treated upper central incisors were fabricated with epoxy resin sheets (6 mm of thickness). Models were 10 times the life size. The post and core systems were divided in three different types, build-up method using only composite resin (R), build-up method using composite resin in combination with a glass fiber post (R+F), and a cast post and core (C). The equivalent ratio of elastic modulus for composite resin, dentin, glass fiber post, and metal were considered for all the parts (5:1). The models were observed in a transmission polariscope with the same loading force (400 N) on 45 degrees palatal direction. The measured points were the buccal margin area of the root and the surrounding area of the apex of the post, which used to present the higher stress concentration area. The isochromatic fringe patterns and the stress distribution in the tooth simulation models were analyzed.
Results: In the buccal margin area of the root, R, R+F and C showed 3.1 fringe order, 1.4 fringe order, and 2.4 fringe order, respectively. For the surrounding area of the apex of the post, R, R+F and C showed 0.45 fringe order, 0.80 fringe order, and 1.0 fringe order, respectively.
Conclusion: The stress concentration in the buccal margin area of the root had a higher distribution, compared with the surrounding area of the apex of the post. Resin +Fiber post model had the lowest stress concentration in the buccal margin area of the root.

Objectives: Post-and-core is a perfect restoration method for residual crown or root of pulpless teeth. More and more emphasis has been placed on how to avoid tooth fracture and maintain esthetic appearance without reducing strength and retention. This study shows that the new developed fiber-reinforced composite post (FRC) used successfully for several years, because of their strength and relative flexibility, ease of placement or ease of removal. The purpose of this study was to analyze the effect of two modulus elasticity material posts on root stress distribution by using three-dimensional photoelastic analysis.
Methods: The photoelastic models were divided into four groups according to posts material and loading. The roots stress distribution, which restored with FRC posts and Ni-Cr alloy posts, was analyzed by three-dimensional photoelastic analysis.
Results: The material of posts influenced the root stress distribution significantly. The greater stress concentration was found at apex of Ni-Cr alloy posts with high modulus, the stress was evenly in FRC posts groups. Conclusions: The study concluded that the modulus of posts material influenced the root stress distribution significantly. The FRC posts which modulus was closed to teeth could protect roots from fracture.

Summary / conclusions: The effect of different anatomic shapes and materials of posts in the stress distribution on an endodontically treated incisor was evaluated in this work. This study compared three post shapes (tapered, cylindrical and two-stage cylindrical) made of three different materials (stainless steel, titanium and carbon fiber on Bisphenol A-Glycidyl Methacrylate (Bis-GMA) matrix).Two-dimensional stress analysis was performed using the Finite Element Method. A static load of 100N was applied at 45 degrees inclination with respect to the incisor's edge. The stress concentrations did not significantly affect the region adjacent to the alveolar bone crest at the palatine portion of the tooth,regardless of the post shape or material. However, stress concentrations on the post/dentin interface on the palatine side of the tooth root presented significant variations for different post shapes and materials. Post shapes had relatively small impact on the stress concentrations while post materials introduced higher variations on them. Stainless steel posts presented the highest level of stress concentration, followed by titanium and carbon/Bis-GMA posts.

Objectives: fractures of restored pulpless teeth can be influenced by many factors, including type or design of the post, or the occlusal load and its direction. The purpose of this study is to use finite element analysis to investigate the effect of different posts used for restoring endodontically treated teeth according to different elastic moduli and direction of the occlusal load.
Methods: a 3-dimensional finite element model, including the periodontal ligament, was constructed in a mesio-distal cross sectional view of a mandibulary premolar. Tooth was fully restored with a cast crown, as occurs in clinical practice. The standard model was composed of 80000 elements and 130000 nodes. Elastic modulus and Poisson's ratio of different components, along with the coordinate and geometry of each node and element were entred into a computer. Four different posts (length: 14 mm – diameter : 1.2 mm ; 3 metallic : stainless, titanium, gold – 1 non-metallic : carbon fiber) were investigated according to three different composite core materials. The effect of a 300 MPa load on vertical, 30 degrees and 45 degrees oblique direction was tested. Analysis program (IDEAS, version n°6) was used to solve the stress analysis problem.
Results: stress distribution in the root depends on the elastic modulus and on the direction of the occlusal load. Elastic modulus of the core is less significant than elastic modulus of the post.
Conclusion: the effect of the post on stress distribution varies according to the direction of the load : in a vertical load, gold and carbon fiber posts generate lower stresses in the root than other metallic posts. In a 30 or 45 degrees oblique load, best results are obtained with a carbon-fiber post.

Objective: Fractures of restored pulpless teeth can be influenced by many factors, including type or design of the post, or the occlusal load and its direction. The purpose of this study is to use finite element analysis to investigate the effect of different posts used for restoring endodontically treated teeth, according to different elastic moduli and the direction of occlusal load.
Methods: a 3-dimensional finite element model, including the periodontal ligament, was constructed in a mesio-distal cross sectional view of a mandibular premolar. The tooth was fully restored with a cast crown, as occurs in clinical practice. The standard model was composed of 80000 elements and 130000 nodes. Elastic modulus and Poisson’s ratio of different the components, along with the coordinate and geometry of each node and element were entered into a computer. Four different posts (length: 14mm, diameter: 1.2mm) 3 metallic (stainless, titanium gold) and one non-metallic (carbon fiber) were investigated according to three different composite core materials. The effect of a 300MPa load on vertical, 30 degrees and 45 degrees oblique was tested. Analysis program (IDEAS, Version 6) was used to organize the stress analysis data.
Results: Stress distribution in the root depends on the elastic modulus and the direction of the occlusal load. Elastic modulus of the core is less significant than the elastic modulus of the post.
Conclusions: The effect of the post on stress distribution varies according to the direction of the load. In a vertical load, gold and carbon fiber posts generate lower stresses in the root than other metallic posts. In a 30 or 45 degree oblique load, the best results are obtained with a Carbon fiber post.

Objectives: Endodontically treated teeth become brittle as a result of moisture loss and have a greater incidence of fracture than vital and healthy teeth. The difference between the elastic modulus of dentin and the post material may be a source of stress in the root structures. The aim of the study was to analyse the mechanical behaviour of a teeth restored with prefabricated glass fiber posts and composite core vs cast post and core through 3D finite element analysis.
Methods: Models have more than 1,5 million elements and an average loading force of 200 N was used to simulate biting forces in the two different occlusal conditions. First condition represents so called normal occlusion with tripodal occlusal contact. Second condition represents malocclusion with single contact on the palatal cusp. The load vectors were applied in the direction normal to the surface in order to simulate the contact with antagonistic teeth.
Results: Endodontic posts take some of the stresses on themselves and values are smaller on the surface of the tooth. In the case of normal occlusion stress distribution is the same for sound and restored tooth, dissimilarity exsists in the values od stresses. Significantly higher tensile stress values were recorded for the cast post and core restored tooth. At the root furcation, tensile stress appeared only in the restored tooth. In the case of normal occlusion, tensile stress at root furcation occurs only in the model with cast post and core.
Conclusions: Cast posts resulted in significantly higher stress values. Tensile stresses are much harmful for the tooth tissue and this type of stress occurs at the root furcation only in the restored tooth, esspecially in the cast post and core.

Objectives: Post and core applications are generally used in the restoration of endodontically treated teeth. The stress distribution during masticatory function in a tooth restored with a post and core can cause root fracture. The different mechanical behavior of post and dentine is a critical parameter for the load transmission. In order to minimize the rigidity difference between the post and the dentine, a new kind of post was developed. The aim of this study was to analyze the mechanical behavior of a new polymeric composite post reinforced with glass fibers. A natural tooth was considered as a reference model.
Methods: The 3D finite element method (FEM) was selected to perform the stress analysis of the two-rooted first maxillary premolar restored with glass fiber posts. Composite resin was used as the core material and full porcelain crowns covered the model. Four noded tetrahedral were applied in the description of the tooth morphology, resulting in 1,684,512 elements and 246,510 nodes with 739,539 degrees of freedom. A total force of 200N was applied.
Results: The greatest stresses were observed in the palatal cervical region (-16.126MPa) and in the intraradicular parts of the post (-23.898MPa). In the cervical region, the mean high-intensity compressive stress areas were more extensive in the natural tooth (-175.222 MPa).
Conclusions: The glass fiber composite post induces a stress field similar to that of the natural tooth, except in the cervical region, where the tooth has higher compressive stresses.

Objective: To investigate the stress distribution of periodontally involved teeth restored with different posts using finite element analysis.
Methods: 2-D models of a maxillary central incisor consisting of a PFM crown, composite core, parallel post, dentin, gutta percha, periodontal ligament, and cortical/trabecular bone were constructed using ANSYS v9.0 software. The posts tested were stainless steel (SS), carbon fiber (CF), and glass fiber (GF) at 10mm and 5mm lengths into the root canals. The alveolar bone level was set either as intact periodontium or with bone loss even with the apical end of short post. All materials were assumed to be linearly elastic and isotropic except CF and GF posts which were orthotropic. Teeth were subjected to two different loads: the first a 70N force on the incisal tip; the second a 100N force on the lingual surface of crown at a 145 degree angulation.
Results: With the 70N load the stress distribution patterns were similar among the groups. For the 100N load at 145 degrees, the models representing periodontal bone loss showed higher von Mises stress over the middle part of root periphery and around the post ends compared to the intact periodontium groups. In the intact periodontium groups, the stress around the crown margins was higher than the middle of the root. The SS post exhibited higher stress levels than the other posts only around the apical end of the post. The SS/5mm group with periodontal bone loss exhibited the greatest stress (334 MPa) on the dentin around the ends of posts.
Conclusion: Teeth with posts and periodontal bone loss generate higher stress concentrations with an increased risk of root fracture. The major difference in stress distribution between rigid and non-rigid posts is primarily around the apical ends of the posts.

Abstract/conclusions: Most coronal radicular reconstructions are made of cast inlay core metals or prefabricated metal posts covered in composite. The differences in the mechanical properties of these elements create a heterogeneous mass with inconsistent mechanical behavior. Studies using the Finite Element Method have shown the biomechanical disturbances casued by the inclusion of materials with a modulus of elasticity that is superior to that of dentine (ie, nickel, chrome, zircon, etc). The use of materials with a modulus of elasticity close to that of dentine does not disturb the flow of stress inside the root. To our knowledge, only a composite material structured with programmable mechanical properties would be capable of producing both high mechanical performance and a modulus of elasticity adapted to dentine values. The Composipost / C-POST, made of carbon epoxy, accommodates the demands of the dentine, as well as the in vitro stress linked to the prosthesis. The internal structure, consisting of long high-performance carbon fibers, unidirectionally and equally stretched, confers a totally original behavior that is adapted to clinical objectives. In addition, the C-POST has a fracture resistance superior to most metals.

Objectives: A comparative study on the stress distribution in the dentine and cement layer of an endodontically treated maxillary incisor has been carried out by using Finite Element Analysis (FEA). The role of post and cement rigidity on reliability of endodontic restorations is discussed.
Methods: A 3D FEM model (13,272 elements and 15,152 nodes) of a central maxillary incisor is presented. A chewing static force of 10 N was applied at 125° angle with the tooth longitudinal axis at the palatal surface of the crown. Steel, carbon and glass fiber posts have been considered. The differences in occlusal load transfer ability when steel, carbon and glass posts, fixed to root canal using luting cements of different elastic moduli (7.0 and 18.7 GPa) are discussed.
Results and significance: The more stiff systems (steel and carbon posts) have been evaluated to work against the natural function of the tooth. Maximum Von Mises equivalent stress values ranging from 7.5 (steel) to 5.4 and 3.6 MPa (respectively, for carbon posts fixed with high and low cement moduli) and to 2.2 MPa (either for glass posts fixed with high and low cement moduli) have been observed under a static masticatory load of 10 N. A very stiff post works against the natural function of the tooth creating zones of tension and shear both in the dentine and at the interfaces of the luting cement and the post. Stresses in static loading do not reach material (dentine and cement) failure limits, however, they significantly differ leading to different abilities of the restored systems to sustain fatigue loading. The influence of the cement layer elasticity in redistributing the stresses has been observed to be less relevant as the post flexibility is increased.

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

Oliviera, L.C.A., Candido, M.S.M., Duarte, S., Oliviera, S.A.G., Comparative study of stress distribution in upper incisors; biometric behavior of post systems. AADR Abstract #0548, 2003 (www.dentalresearch.org)

Objective: this work proposes a study about the distribution of mechanical stresses in the radicular dentin restored with different post systems, by means of Photoelastic and Finite Element techniques. This analysis is conducted for the following post systems: carbon fiber, fiberglass, zirconium, stainless steel, titanium and cast metal (Cu-Al alloy) and the healthy tooth (control). The computer analysis and numerical results were validated by laboratory experimental data (Photoelastic).
Methods: For this purpose, representative 2-dimensional models were of the upper central incisor were built for both methods. These models were subject to a 100N load applied at the tip of the crown, at 450 from the axis along the tooth. These results are expressed in terms of the Von Mises and Sy stresses and the fringe order, for the Finite Element and photoelastic methods, respectively.
Results: Through the analysis of these results, it can be concluded that significant stress distributions arise between the 6 different post systems tested, so that those made of zirconium, stainless steel, titanium and cast metal produced high stress concentration at the post/dentin interface region. In the cases of carbon fiber and fiberglass, on the other hand, the stress distribution along the radicular surface is uniform, lacking stress concentration areas.
Conclusion: The zirconium, stainless steel, titanium and cast metal posts present mechanical properties which are different from those of the tooth structure, resulting in significant alterations over the mechanical behavior of the dental structure. The non-metallic posts comply more satisfactorily with the requirements necessary to provide a mechanical behavior more similar to that of the dental structure, the compatibility among the mechanical properties found in these systems and the dentin providing a biometric behavior, reducing the risk of failure or fracture of the root.

Objective: this work proposes a study about the distribution of mechanical stresses in the radicular dentin restored with different post systems, by means of Photoelastic and Finite Element techniques. This analysis is conducted for the following post systems: carbon fiber, fiberglass, zirconium, stainless steel, titanium and cast metal (Cu-Al alloy) and the healthy tooth (control). The computer analysis and numerical results were validated by laboratory experimental data (Photoelastic).
Methods: For this purpose, representative 2-dimensional models were of the upper central incisor were built for both methods. These models were subject to a 100N load applied at the tip of the crown, at 450 from the axis along the tooth. These results are expressed in terms of the Von Mises and Sy stresses and the fringe order, for the Finite Element and photoelastic methods, respectively.
Results: Through the analysis of these results, it can be concluded that significant stress distributions arise between the 6 different post systems tested, so that those made of zirconium, stainless steel, titanium and cast metal produced high stress concentration at the post/dentin interface region. In the cases of carbon fiber and fiberglass, on the other hand, the stress distribution along the radicular surface is uniform, lacking stress concentration areas.
Conclusion: The zirconium, stainless steel, titanium and cast metal posts present mechanical properties which are different from those of the tooth structure, resulting in significant alterations over the mechanical behavior of the dental structure. The non-metallic posts comply more satisfactorily with the requirements necessary to provide a mechanical behavior more similar to that of the dental structure, the compatibility among the mechanical properties found in these systems and the dentin providing a biometric behavior, reducing the risk of failure or fracture of the root.

Objective: Composite resin core materials in conjunction with various kinds of prefabricated posts are gaining in popularity. However, it is not yet clear, which kind of material is most suitable for the post. The aim of this study was to evaluate the influence of the prefabricated post on stress distributions in an abutment tooth restored with composite resin by 3-dimensional finite element analysis.
Methods: Four 3-dimensional finite element models of an endodonticaly treated premolar were made. In these four models, posts and cores were built up with composite resin and four types of prefabricated post; glass fiber post (GFP), Titanium post (TIP), Zirconia post (ZRP), and Stainless steel post (STP). In all the models, an occlusal force similar to chewing beef jerky, was applied to the center of occlusal surface (lingual direction: 24N,distal direction:29N, apical direction:164N), which was measured with a small 3-dimensional occlusal force meter. Then Von Mises stress distributions within the root were calculated.
Results: In all models, there were similar distributions of stress concentration at the apical area. However, in the dentin of the root around the end of the prefabricated posts, there were differences in stress concentration. The magnitudes of stress in this area for GFR, TIP, ZRP and STP were 11.5 Mpa, 12.6 MPa, 12.0 MPa, and 14.9 MPa respectively.
Conclusion: Within the limitations of this experiment, GFR was indicated to be most suitable since this model showed lower stress values, which means less possibility of root fracture.

In this work the mechanical response to external applied loads of a new glass fiber reinforced endodontic post is simulated by finite element (FE) analysis of a bidimensional model. The new post has a cylindrical shape with a smooth conical end in order to adequately fit the root cavity, and to avoid edges that could act as undesired stress concentrators. Mechanical data obtained by three-point bending tests on some prototypes fabricated in the laboratory are presented and used in the FE model. Under various loading conditions, the resulting stress component fields are hence compared with those obtained in the case of two commercial endodontic posts (i.e. a cast metal post and a carbon fiber post) and with the response of a natural tooth. The gold cast post-and-core produces the greatest stress concentration at the post-dentin interface. On the other hand, fiber-reinforced composite posts do present quite high stresses in the cervical region due to their flexibility and also to the presence of a less stiff core material. The glass fiber composite shows the lowest peak stresses inside the root because its stiffness is much similar to dentin. Except for the force concentration at the cervical margin, the glass fiber composite post induces a stress field quite similar to that of the natural tooth

Objectives: Endodontically treated teeth with flared root canal are frequently found for many reasons and the prognosis of post and core restoration are also unpredictable. Reinforcing techniques that weaken the tooth had been introduced, however, the suitable methods are still questioning. The aim of this study is to investigate the stress distribution in root dentin and restorative materials.
Methods: The 2 –dimensional Finite Element models of flared root canals (Maxillary central incisors) with ten restorative techniques were performed, using MSC/Nastran for Windows. Three evaluated parameters: reinforcing or non-reinforcing the flared root canal, reinforcing materials (composite resin and reinforced glass ionomer) and the post materials (gold alloy type III, Ni-Cr alloy, stainless steel, and carbon fiber) were investigated. All materials were assumed to be homogeneous, isotropic, linearly elastic. The load (150N) was applied on the lingual surface of metal-ceramic crown; 130 degrees to the tooth axis.
Results: The results showed that maximal tensile stress in dentin were reduced in the reinforcing models. Reinforcement with composite resin provided less maximum tensile strength than that with reinforced glass ionomer. Higher elastic modulus of posts, such as Ni-Cr alloy showed more maximum tensile stress at post apex, but less stress concentration at flared dentin compared with posts with lower elastic modulus.
Conclusions: From this FEA study, reinforcement of flared root canal with composite resin and carbon fiber post showed favorable stress distribution in restoring the teeth with flared root canal.

Objectives: The aim of this study was to compare the dye penetration under repeated loading using Cyclic Loading Machine, which stimulated masticatory system, and to evaluate the fracture aspects of different post systems.
Methods: 25 single rooted incisors were divided into 5 groups; Cast posts, Para post, FRC Postec, CosmoPost, and endodontically treated teeth. Each post was cemented with DUOLINK (Bisco, U.S.A.), and core build-up was done using LIGHT-CORE (Bisco,U.S.A). Nittoflon Tape (Nitto Co. Japan) was used to simulate the periodontal ligaments. The load of 9.8N at 1 Hz for 50,000 cycles was applied to the angle of 45 degrees to the long axis of the tooth in 0.5% Fuchsine Basic solution on the Cyclic Loading Machine. After the fracture aspects were observed, the ratio of dyed surface area to the total root surface area was evaluated by Image Analyzer(Image Pro 4.0, U.S.A.) and statistically analyzed with Kruskal-Wallis Test and Duncan's Multiple Range Test at P=0.05. Results: The cast post showed the largest microleakage, while those of FRC Postec, Para post, CosmoPost were significantly lower(P<0.05). The fracture lines of FRC Postec and CosmoPost were limited to the upper 1/3 of the root, while those of cast post and Para post were extended to middle 1/3 of the root.
Conclusions: In view point of microleakage, FRC Postec, CosmoPost, and Para post showed less value. However, considering the fracture aspects together, the results indicate that FRC Postec and CosmoPost were meaningful clinically.

Objectives: The purpose of this study was to develop and evaluate a non-destructive test system that could test concurrently fatigue and microleakage.
Methods: A new multi-purpose computer-operated impact machine was designed and used in combination with a modified fluid filtration apparatus to evaluate concurrently both core integrity and post microleakage in the same sample. Crowns of single rooted teeth were removed and the roots were randomly assigned to five groups (n=10) and restored with the following post systems: one metallic group-Titanium ParaPost (TP) cemented with zinc phosphate, and four non-metallic groups- CosmoPost (CO), C-POST (CP), Esthetic C-POST (EC), and FiberKor Posts (FK). All non-metallic posts were cemented with resin cement. Tetric Ceram was used for composite core for all groups. Samples were imbedded in an acrylic resin mold, connected to the filtration system and the baseline/control microleakage was measured. Samples were then placed in a positioning jig in the fatigue testing machine and subjected to 100,000 impacts at 45 degrees to the long axis of the root with a force of 55N at a frequency of 3HZ. After 60,000 impacts, the samples were subjected to 1,000 thermocycles (60KT) between 50C and 550C. Microleakage of the post systems was measured at 30K, 60K, 60KT and 100K cycles.
Results: All samples showed no detectable displacement of any core. Mean +/-SD microleakage in microliters significantly increased in all groups as samples were subjected to increased impacts and thermocycling. The metallic group (TP) showed a statistically significant increase in microleakage (p<0.05) when compared to the non-metallic groups (CO, CP, EC and FK) at the conclusion of the study.
Conclusions: The test design was successful in performing both fatigue loadings and microleakage measurements in the same sample using core integrity and prefabricated post microleakage as test parameters.

The purpose of this study was to evaluate a new nondestructive test system, which could test concurrently fatigue and microleakage. Fifty, single-rooted teeth were restored with one of the following posts systems and a composite core: titanium ParaPost cemented with zinc phosphate cement; CosmoPost; C-Post; Esthetic C-Post; and FiberKor post, all cemented with resin cement. Samples were embedded and placed in a positioning jig. They were impacted at 45 degrees to the long axis of the tooth with a force of 55 N at a frequency of 3 Hz for a total of 100,000 impacts. After 60,000 impacts, samples were thermocycled. Core integrity and post microleakage were evaluated periodically throughout the 100,000 impacts. Samples showed no detectable displacement of any of the cores, but the metallic group showed a statistically significant increase in microleakage (p < 0.05) at the conclusion of the study compared with the nonmetallic groups.

Statement of problem: Several new esthetic dowel systems are available for the restoration of endodontically treated teeth, but little is known about how effectively these dowels seal the restored teeth.
Purpose: The purpose of this in vitro study was to compare microleakage of 3 esthetic, adhesively luted dowel systems with a conventional dowel system.
Methods: The root canals of 41 human intact single-rooted extracted teeth were prepared using a step-back technique. The teeth were randomly divided into 4 experimental groups (n=10), and 1 tooth served as a positive control. The decoronated roots were obturated with gutta-percha using lateral condensation. Roots were restored with 1 of the following dowel systems according to the manufacturer's instructions: (1) stainless steel dowels (ParaPost), (2) glass fiber dowels (Snowpost), (3) resin-supported polyethylene fiber (Ribbond) dowels, or (4) zirconia dowels (Cosmopost). Using a fluid filtration method, coronal leakage of the specimens along the dowel space and root canal restorative material was measured. Fluid movement measurements were made at 2-minute intervals for 8 minutes to measure the presence of voids existing in the obturated canals, at 1 week, 3 months, and 6 months following dowel insertion. A repeated-measures analysis of variance (ANOVA) was used to analyze logarithmic transformations of data (time and dowel material) for significant differences. The Tukey HSD test and paired 2-tailed tests were used to perform multiple comparisons (alpha=.05).
Results: The data indicated that the leakage values varied according to the dowel system used (P<.01). There was significant interaction between dowel systems and time of testing (P<.01). The sealing ability of zirconia dowels decreased over time (P<.01), but sealing abilities of stainless steel and resin-supported polyethylene fiber dowels remained constant (P>.05). The sealing ability of glass fiber dowels increased at 3 months (P=.032) and remained constant over the next 3 months (P=.758). Statistically, resin-supported polyethylene fiber and glass fiber dowels showed the lowest coronal leakage when compared with stainless steel and zirconia dowels at all time periods (P<.01). There were no significant differences between resin-supported polyethylene fiber and glass fiber dowels at any time period. The initial leakage measurement in zirconia dowel and stainless steel dowels were similar (P=.914), but became significantly different at 3 and 6 months (P<.01).
Conclusions: Resin-supported polyethylene fiber dowels and glass fiber dowels tested exhibited less microleakage compared to zirconia dowel systems. The latter system should be further evaluated because of its unacceptable level of leakage.

Aim: The determination of the influence of non-metallic posts on the stress distribution to the supporting tissues.
Method: Two 3D models were created: one intact maxillary incisor and one reconstructed with post (ceramic, carbon fiber and glass fiber). The compressive load (30daN) was applied to an angle of 45 degrees on the palatal surface of the crown. The Algor software computed the stress for each model comparing the maximum registered intensity, localization and concentration into the dento-periodontal complex.
Results: The fiber reinforced posts induced lower stress peak inside the root, the von Mises stress in the teeth reconstructed with carbon and glass fiber post being similar to that recorded in a tooth without post. The ceramic post produced the greatest stress concentration in the middle third of the root, this behavior supporting the potential risk of the vertical root fractures registered "in vivo".
Conclusions: The fiber reinforced posts are more suitable for the clinical longevity of the tooth, representing the best choice to reconstruct an endodontically treated tooth.

Objectives: This study was to compare the fracture resistance and failure mode of natural teeth with endodontically treated teeth, with and without post systems that have different shapes and components.
Methods: Total 45 human mandibular incisors were divided into 9 groups; natural teeth (A), root canal treated teeth without post (B), and teeth with their crowns removed and restored with seven kinds of post systems. Each post was cemented with dual-cured resin cement, DUOLINKTM (Bisco) and core build-up was done with light-cured composite, LIGHT-CORETM (Bisco), except cast posts. Each specimen was embedded in acrylic resin with periodontal ligament simulation and shear load was applied using universal testing machine (Z020, Zwick) at a crosshead speed of 5 mm/min. After test, the fracture aspects were evaluated by naked eye and SEM.
Results: The followings are the data of fracture resistance and they were analyzed by Kruskal-Wallis test and Duncan's multiple range test at P=0.01 (unit: N). Standard deviations are in parenthesis.

A	B	Cast post	Parapost (Whaledent)	Parapost fiber white (Whaledent)	Filpost (Filhol Dental)	C-post (Bisco)	FRC Postec (Ivoclar)	Cosmo post (Ivoclar)
		46% Au alloy (parallel)	S-S (parallel)	Glass fiber (parallel)	Titanium (taper)	Carbon fiber (taper)	Glass fiber (taper)	Zirconia (taper)
974.0a (80.0)	838.6b (80.9)	642.4c (102.3)	639.8c (44.8)	542.4d (40.0)	551.8d (58.2)	556.4d (31.3)	508.8d (59.4)	501.6d (39.8)

The highest fracture resistance was recorded for Cast post and Para post (P<0.01). In failure mode, C-post and FRC Postec showed favorable aspects with few cracks around apical third.
Conclusions: The carbon and glass fiber posts with tapered shape resulted in good failure mode, in spite of their lower strength than metal post, meaning the possibility of re-treatment.

Aims: This work studied how prefabricated intra-radicular post material affects the mechanical performance of restored teeth. The effect of using two different materials (glass fiber and stainless steel) with significantly different elastic moduli was studied.
Methods: A combined theoretical and experimental method was used; first, an experimental fracture strength test was performed on 6 extracted human maxillary central incisors. The teeth were de-coronated, treated endodontically and restored-30 with glass fiber posts (Parapost Fiber White; Coltene/Whaledent, Cuyahoga Falls, OH, USA) and 30 with stainless steel posts (ParaPost; Coltene/Whaledent, Cuyahoga Falls, OH, USA). The data were recorded and the results compared using an ANOVA test. Then, the Finite Element technique was used to develop a model of the restored tooth. For both post systems, the model allowed for the study of the stress distribution patterns on the restored tooth under external loads.
Results: For teeth restored with stainless steel posts, a significantly lower failure load was found, as compared with those teeth restored with glass fiber posts (520N versus 803N). The estimated distributions confirmed a worse mechanical performance on teeth restored using stainless steel posts, with a high stress concentration due to the significant difference between the elastic moduli of the steel and the surrounding materials (207GPa versus 18.6GPa).
Conclusion: Within the limitations of this study, post systems where the elastic modulus of the post is similar to that of the dentin and core, have a better biomechanical performance. Moreover, the failure mode for these fiber post systems will allow for further repair.

Objectives: To compare in vitro failure modes of fiber reinforced post systems with prefab metal and cast post systems.
Methods: The literature was searched using MEDLINE, with the year limits 1984-2002/6 for dental articles written in English, German or Dutch. Key words: (post or core or build-up or dowel) and (teeth or tooth) not (implant or orthodontic or periodontal or primary teeth). The following steps were conducted: 1) Inclusion of abstracts describing post-core techniques to reconstruct endodontically treated teeth and their mechanical characteristics (strength, fracture, failure, resistance, survival, retention, leakage, seal). Descriptive studies or reviews were excluded. 2) Inclusion if in vitro studies on fracture resistance of single rooted human teeth restored with prefab fiber posts and composite cores. 3) Failure mode categorization. Favorable failures were defined as repairable failures including adhesive failures, and fractures above bone simulation. Unfavorable were non-repairable, vertical root fractures. Steps 2) and 3) were conducted using the Aim, Materials and Methods and Results of the articles. All assessments were done by 2 operators. Consensus was reached in case of disagreement. Kappa’s were used for observer agreement. Percentages of favorable failures of the post systems were compared using Wilcoxon Signed Rank Test.
Results: MEDLINE identified 1237 articles. Results of each step: inclusion of 203 articles (Kappa=0.86) of which 21 dealt with fibers, 2) inclusion of 8 articles (Kappa=0.62) of which 6 dealt with failure mode of carbon fibers, 3) failure mode categorization per system (Kappa=0.99). Favorable failures occurred significantly more with the carbon fiber reinforced posts than with the prefab metal (n=11, p=0.05, z=1.96) and respectively, the cast post groups (n=8, p=0.02, z=2.39).
Conclusions: These results suggest a more favorable failure mode of the Carbon fiber post systems compared with prefab metal and cast post systems. Comparative studies of the different post systems are scarce

Objectives: To evaluate fracture resistance of metal-ceramic crown restored incisors with different post-and-core systems.
Methods: Selected 40 intact maxillary central incisors were endodontically treated and then randomly assigned to four groups of 10 teeth each. Teeth in Group A were prepared to root canal with 10 mm in length, 1.6 mm in diameter and restored with fiber-reinforced posts (Snowpost, Carbotech) and composite cores. Same final preparation but root canal with 1.5 mm in diameter was achieved for teeth in the other three groups. Teeth in Group B were restored with prefabricated titanium alloy posts (ParaPost, Coltene-Whaledent) and composite cores and teeth in Group C were restored with cast nickel-chromium post-cores. The posts were luted with a composite resin luting system, and metal-ceramic crowns were restored and cemented with the same luting system for all of the teeth in Group A, B and C. The other 10 teeth were restored with cast nickel-chromium post-cores and metal-ceramic crowns as a control, which were cemented with glass-ionomer cement. All restored teeth were thermocycled for 5000 cycles (5 degrees C/55 degrees C) as a fatigue test. The tooth was loaded in a universal testing machine at an angle of 135 degrees to the long-axis at the incisal edge with a crosshead speed of 1.5 mm/min until fracture. Fracture loads (N) and modes (repairable or catastrophic) were recorded. One-way ANOVA and SNK test were used to determine the significance of the failure loads between groups. Chi-square test was conducted for evaluation of the fracture mode.
Results: The fracture loads from Group A, B, C and control group were (534.4 +/- 145.7) N, (499.8 +/- 168.9) N, (412.6 +/- 99.3) N, (337.4 +/- 121.2) N, respectively. A significant difference was existed among four groups (P < 0.05). The fracture loads of Group A and Group B were significantly higher than control group (P < 0.05). The repairable mode of fracture observed from Group A to control group was 80%, 40%, 20% and 30%, Group A had a significantly higher number of repairable fractures than those of the other groups (P < 0.05).
Conclusions: Within the limitations of this study, fiber-reinforced post has an excellent fracture resistance, and can be recommended as an alternative to cast post-cores, especially for incisor esthetic restoration

Carbon fiber reinforced carbon (CFRC) in the form of a prefabricated post has recently been developed and is theoretically acceptable for consideration in an endodontic post-retained crown system. This study compared four different types of postcore system cemented into 40 extracted anterior human teeth. The test groups consisted of CFRC posts cemented with a composite resin luting agent, and used with either a cast gold alloy core (Group B) or a composite resin core (Group C). Two existing post-core techniques were used as controls for comparison with the CFRC groups. One control was a prefabricated wrought precious alloy post having a cast gold alloy core, and cemented with zinc phosphate cement (Group A). The other was a prefabricated stainless steel post with a composite resin core, and cemented with a composite resin luting agent (Group D). All specimens were restored with a gold alloy crown and tested to failure with an obliquely applied compressive load at 130 degrees in an Instron using a cross-head speed of 5 cm min-1. The results showed that post-retained crowns using a prefabricated CFRC post exhibited properties comparable with, and in some cases better than, those of existing prefabricated posts. The mode of failure of specimens restored with a CFRC post was more favourable to the remaining tooth tissue than was that of specimens restored with a metallic post.

Objectives: This study evaluated the deformation of endodontically treated teeth with 3 different post systems at 4 simulated clinical stages. Methods: Extracted human anterior maxillary teeth (n=30) were used and randomly assigned to 3 groups (i.e. post systems): fiber-reinforced epoxy resin posts –Group 1 (ER DentinPost), zirconium oxide ceramic posts –Group 2 (ER CeraPost) and titanium posts –Group 3 (ER Titan post) (all from Komet, Brasseler GmbH, Lemgo, Germany). A series of endodontic treatments was applied and after each single procedure the teeth were loaded (3.75N) and the deformation was assessed using Speckle pattern interferometry. The following treatments were applied: a) no treatment (control), b) access preparation and initial root canal instrumentation (Kerr files ISO 40), c) post preparation (Size 110) and d) cementation of the posts (gr. 1+2: resin bonded / Gr. 3: zinc phosphate cement).
Results: Access preparation (with root canal instrumentation) and post preparation significantly increased the deformation under loading (p<0.05 - one-way ANOVA and post-hoc Scheffé test). All posts reduced the deformation of the teeth but the levels were significantly different: titanium posts - 0.38±0.02µm > zirconium oxide ceramic posts - 0.45±0.02µm > fiber-reinforced epoxy resin posts - 0.53±0.03µm (p<0.05).
Conclusion: It can be concluded that a) the increase of stability corresponds to the mechanical properties of the post materials and that b) the fiber-reinforced epoxy resin posts can almost preserve the deformation pattern of teeth without a post. This might be favorable in view of studies showing a high incidence of unrestorable root fractures in case of post materials with mechanical properties significantly different from the properties of root dentine.

Resistance to lateral loading is critical for clinical success of the post/core assembly.
Objective: The purpose of this in-vitro study was to evaluate the load resistance and failure mechanism of glass fiber and metal retained core build-ups.
Methods: Following the removal of the clinical crown, gutta percha was used to restore canals prepared to size 40 in 60 extracted human anterior teeth. After storage in water for 1 week at 370C, post preparations were made to a depth of 9mm and parallel ParaPost, FiberKleer and FiberKor posts and tapered FiberKleer and D.T. Light Post were cemented using Bond-1 adhesive and Lute-It cement. Using a gelatin capsule matrix a core was fabricated using Build-It resin. A flat area was prepared on the core at a 45º angle to the lingual/occlusal aspect of the post/core/tooth assembly. The specimens were stored in water for 24 hours at 370C, thermocycled and loaded to failure at a crosshead speed of 1mm/min in an Instron testing machine.
Results: Mean load at failure (in Newtons) and failure pattern for each group are presented below.

Post	Load (N)	Failure Mode
Parapost	563.5 ± 119.3	7 root fracture, 3 core failures
Parallel FiberKleer	376.9 ± 77.9 a	10 core failures
Tapered FiberKleer	373.8 ± 45.2 a	1 root fracture, 7 core failures, 2 post debonds,
Parallel FiberKor	368.0 ± 69.7 a	9 core failures, 1 post debond
Tapered D.T. Light	246.7 ± 81.4	10 core failures

ANOVA and post hoc LSD tests revealed significant differences in load failure (p<0.05). Groups with a similar letter are statistically similar (p>0.05).
Conclusion: Metal posts generated the highest resistance to failure of the post/core assembly but also the highest root fracture.

Objectives: The objective of this study was to compare the fracture resistance and mode of failure of endodontically treated teeth restored with three different post systems at two lengths.
Methods: Seventy human single-rooted premolars were endodontically treated and sectioned at the buccal CEJ. Teeth were randomly distributed into groups of ten and assigned to one of seven treatment groups. Three different pre-fabricated posts, Parapost XP, Light-Post and Snowlight, were cemented at either 5 or 10 mm into a post space and standardized composite cores fabricated. A composite core group with no post served as a control. Samples were stored for 24 hours in 100% humidity at 37°C and were subsequently loaded at 90° to the longitudinal axis until ultimate failure occurred. An initial failure load and mode of failure were also recorded and analyzed using two-way ANOVA. Results: The average initial failure loads at 10 mm in Newtons were: Parapost XP 170.05 ± 60.08; Light-Post 123.29 ± 46.64; Snowlight 70.43 ± 32.26. The average initial failure loads at 5 mm were: Parapost 111.08 ± 49.84; Light-Post 64.25 ± 33.83; Snowlight 62.85 ± 18.47. The control group value was 40.24 ± 9.52. Core debonding from the tooth interface was the mode of initial failure for all samples.
Conclusions: Parapost XP samples had significantly higher initial and ultimate failure loads than Light-Post or Snowlight samples at each of the two respective post lengths. Results indicate that stainless steel post provides better support for a core than glass or quartz fiber-reinforced post when a 90° load is applied. The glass and quartz fiber-reinforced post were not found to be significantly different for providing fracture resistance at 90° load angle. Root fractures upon ultimate failure occurred in 25% of the Parapost XP samples and no root fractures occurred in any other group.

Purpose: The purpose of the investigation was to compare the performances of teeth restored with quartz-fiber, carbon-quartz fiber, and zirconium-dioxide posts covered with all-ceramic crowns when subjected to a cyclic loading tests performed in a wet environment.
Materials and Methods: Forty single-rooted human lower premolars having similar dimensions were endodontically treated and mounted in acrylic resin blocks with a simulated periodontal ligament. The teeth were divided into three experimental groups and one control group. Post holes 8 mm long were prepared in the roots of the experimental groups in which quartz fiber (Aestheti-Plus), carbon-quartz fiber (Aestheti-Post), and zirconium dioxide (Cerapost) posts were cemented. In the control group, no posts were used. The crown buildup was made with composite resin. The teeth were covered with all-ceramic crowns and intermittently loaded an at angle of 45 degrees to the long axis of the tooth at a frequency of two loads per second.
Results: Only one failure (root fracture + post fracture), was observed in each of the fiber post groups, while in the zirconium dioxide post group, six failures were observed (one crown fracture and 5 root fracture + post fractures). The Kaplan-Meier analysis of the three experimental groups showed that the survival rate of zirconium dioxide posts was significantly lower than that of both types of fiber post. All the experimental groups showed a survival rate higher than that of the control group.
Conclusion: Fiber posts reduced to a minimum the risk of root fractures of teeth restored with composite cores and Empress crowns under the present experimental conditions (intermittent loading in a wet environment)

Purpose: The purpose of the investigation was to compare the performances of teeth restored with quartz-fiber, carbon-quartz fiber, and zirconium-dioxide posts covered with all-ceramic crowns when subjected to a cyclic loading tests performed in a wet environment.
Materials and Methods: Forty single-rooted human lower premolars having similar dimensions were endodontically treated and mounted in acrylic resin blocks with a simulated periodontal ligament. The teeth were divided into three experimental groups and one control group. Post holes 8 mm long were prepared in the roots of the experimental groups in which quartz fiber (Aestheti-Plus), carbon-quartz fiber (Aestheti-Post), and zirconium dioxide (Cerapost) posts were cemented. In the control group, no posts were used. The crown buildup was made with composite resin. The teeth were covered with all-ceramic crowns and intermittently loaded an at angle of 45 degrees to the long axis of the tooth at a frequency of two loads per second.
Results: Only one failure (root fracture + post fracture), was observed in each of the fiber post groups, while in the zirconium dioxide post group, six failures were observed (one crown fracture and 5 root fracture + post fractures). The Kaplan-Meier analysis of the three experimental groups showed that the survival rate of zirconium dioxide posts was significantly lower than that of both types of fiber post. All the experimental groups showed a survival rate higher than that of the control group.
Conclusion: Fiber posts reduced to a minimum the risk of root fractures of teeth restored with composite cores and Empress crowns under the present experimental conditions (intermittent loading in a wet environment)

The elastic modulus of the restorative material is important in restoring endodontically treated teeth. This study aimed to compare the fracture resistance and failure patterns of 90 mandibular molars restored using resin composites with or without fiber posts, with respect to the number of residual cavity walls. Five restoration types were performed corresponding to different wall defects (groups 1-5). Groups were divided in two subgroups corresponding to the use or absence of fiber posts. Teeth were loaded and resistance of specimens was measured as the axial compressive load to cause fracture and macroscopic fracture patterns were observed. One way ANOVA revealed a significant difference in fracture resistance (p < 0.001). Tukey post hoc test also revealed significant differences between groups as samples restored with fiber posts exhibited mostly restorable fractures. It was concluded that the resistance of endodontically treated mandibular molars restored with composite resins is mainly affected by the number of residual walls. Using fiber-reinforced posts optimized fracture patterns.

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.
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).
Conclusions: 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.

The aim of this study was to evaluate the fracture strength and mode of failure of endodontically treated teeth reconstructed with glass fiber reinforced posts. Twenty maxillary central incisors, extracted for periodontal reasons, were divided in 2 groups: gr. 1 - glass fiber posts, and gr.2 - control (endodontically treated but without posts). All samples were embedded in resin blocks and mounted in stainless steel cylinders for the compressive test. The force was applied on oral surface of the crown, until the failure occurred. The compressive loads at failure were recorded and compared with the statistical method Student t. The mode of failure of the specimens were also evaluated. The statistical analysis of the force values showed no significant difference between the groups. In conclusion, because of their low Young's modulus, the non-metallic posts made of resin composite reinforced with glass fibers have a protective effect on the dental tissues, the recorded mode of failure being very similar with the control group.