In vitro evaluation of the retention of zirconia-based ceramic posts luted with glass ionomer and resin cements

The retention of zirconia-based ceramic posts (CosmoPost system) luted with glass ionomer and resin cements was evaluated. Thirty-two extracted, caries-free, unrestored teeth were selected and stored in chlorhexidine and water solution. The teeth were endodontically treated and randomly assigned to two groups (n=16). Each tooth was decoronated and prepared to a depth of 10.0 mm from root surface to receive a 1.4 mm diameter zirconium dioxide post. Each group had posts cemented with either glass ionomer cement (Fuji I) or resin cement (Variolink II). The post/teeth specimens were embedded in resin blocks and subjected to tensile testing. The tensile force required to dislodge the cemented posts in a tensile testing machine was recorded. The mean stress values of both groups were analyzed for statistical differences using ANOVA and Student's t-test. Significance level was set at 5%. Mean peak forces at failure (N) and standard deviation for the tested cements were the following: Fuji I = 121.8 (+/-17.4) and Variolink II = 228.1 (+/-36.8). Posts luted with the resin cement presented statistically significant higher tensile bond strength than those retained with glass ionomer (p<0.05). It may be concluded that zirconia posts cemented with resin-based cement (Variolink II) failed at statistically significant higher values compared to those cemented with glass ionomer cement (Fuji I). Regardless of the cement type, the posts failed adhesively at the cement/post interface when subjected to a tensile force.     

Fracture resistance of teeth restored with two different post-and-core designs cemented with two different cements: an in vitro study. Part I.

OBJECTIVE: The purpose of this in vitro study was to investigate fracture resistance in teeth restored with cast post and cores with and without ferrule and using two different luting cements. METHOD AND MATERIALS: Forty intact maxillary premolars were endodontically treated after their crowns were removed at 2.00 mm from the cementoenamel junction. Specimens were embedded in acrylic resin blocks in aluminum cylinders, 4.00 mm apical to the cementoenamel junction. Twenty specimens were ferruled, and half of the posts and cores were cemented with zinc-phosphate cement, while the other half was cemented with resin cement. The same procedures were followed for the nonferruled group. Loads were applied at an angle of 45 degrees and measured with a universal testing machine. ANOVA and Tukey test were used for statistical analyses; a significance level was established at 5%. RESULTS: Ferruled specimens showed greater resistance than nonferruled ones, regardless of the cement used. There was no statistical difference between the group of specimens cemented with resin cement and without ferrule and the ferruled groups. The non-ferruled group with zinc-phosphate cement showed the poorest results. CONCLUSION: A 2.00-mm cervical ferrule is important for fracture resistance of restored teeth, and resin cement has a better performance.     

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

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

Rigid versus Flexible Dentine-like Endodontic Posts—Clinical Testing of a Biomechanical Concept: Seven-year Results of a Randomized Controlled Clinical Pilot Trial on Endodontically Treated Abutment Teeth with Severe Hard Tissue Loss

Introduction

This is the first clinical long-term pilot study that tested the biomimetic concept of using more flexible, dentine-like (low Young modulus) glass fiber–reinforced epoxy resin posts (GFREPs) compared with rather rigid, stiff (higher Young modulus) titanium posts (TPs) in order to improve the survival rate of severely damaged endodontically treated teeth.

Methods

Ninety-one subjects in need of postendodontic restorations in teeth with 2 or less remaining cavity walls were randomly assigned to receive either a tapered TP (n = 46) or a tapered GFREP (n = 45). The posts were adhesively luted using self-adhesive resin cement. The composite core build-ups were prepared ensuring a circumferential 2-mm ferrule. The primary endpoint was a loss of restoration for any reason. To study group differences, the log-rank test was calculated (P < .05). Hazard plots were constructed.

Results

After 84 months of observation (mean = 71.2 months), 7 restorations failed (ie, 4 GFREPs and 3 TPs). The failure modes were as follows: GFREP:root fracture (n = 3), core fracture (n = 1) and TP:endodontic failure (n = 3). No statistical difference was found between the survival rates (GFREPs = 90.2%, TPs = 93.5%, P = .642). The probability of no failure was comparable for both post materials (risk ratio; 95% confidence interval, 0.965–0.851/1.095).

Conclusions

When using self-adhesive luted prefabricated posts in severely destroyed abutment teeth with 2 or less cavity walls and a 2-mm ferrule, postendodontic restorations achieved high long-term survival rates irrespective of the post material used (ie, glass fiber vs titanium).     

Reinforcement effect of adhesively luted fiber reinforced composite versus titanium posts.

OBJECTIVE: The aim of the present study was to investigate the influence of the rigidity of different post materials (titanium versus glass fiber reinforced composite [FRC]) on the fracture resistance of endodontically treated teeth (ETT). METHOD: Forty-eight caries-free maxillary central incisors were randomly assigned to six groups (n=8). After endodontic treatment, teeth of four groups were flattened 2mm above and two groups at the cemento-enamel junction (CEJ). As control, specimens of one group received neither composite build-up nor post, and teeth were left empty (E). In another group only a resin composite build-up was placed (C). In two groups, both titanium and FRC posts were inserted. One group with titanium (2/T) and FRC (2/FRC) post received a 2mm deep ferrule preparation. For one group with titanium (0/T) and FRC (0/FRC) post no ferrule design was provided. All-ceramic crowns were adhesively luted on all specimens. Specimens were exposed to thermomechanical loading and finally statically loaded until failure. RESULTS: The median fracture load values (min-max) were: E=317 (242-404); C=387 (335-475); 0/FRC=352 (0-440); 2/FRC=502 (326-561); 0/T=420 (0-548), 2/T=517 (416-653). Statistically significant differences were computed between E, C, 2/FRC, 0/T and 2/T; between C, 2/FRC and 2/T; between 0/FRC, 2/FRC and 2/T; between 0/T and 2/T regarding maximum fracture load. SIGNIFICANCE: Fracture resistance of ETT is not influenced by the rigidity of the post material. The combination of ferrule preparation and endodontic post results in higher load resistance after TML than any other build-up design.     

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

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

Fracture resistance of teeth restored with 2 different post-and-core designs fixed with 2 different luting cements: an in vitro study. Part II.

OBJECTIVE: The purpose of this in vitro study was to investigate fracture resistance in teeth restored with cast posts and cores with and without ferrule and using 2 different luting cements. METHOD AND MATERIALS: Forty intact extracted maxillary premolars were endodontically treated after their crowns were removed 2 mm from the cementoenamel junction. Specimens were embedded in acrylic resin blocks, in aluminum cylinders, 2.00 mm apical to the cementoenamel junction. Twenty specimens were ferruled. Within this group, half of the posts and cores were cemented with zinc phosphate cement, while the other half were cemented with resin cement. The same procedures were followed for the nonferruled group. The posts and cores were cast in gold alloy. Specimens were placed in a universal testing machine, and loads were applied at an angle of 45 degrees and a rate of 1 mm/min until the teeth fractured. Analysis of variance and Tukey tests were used for statistical analysis; level of significance was established at 5%. RESULTS: There was no association between type of cement and cervical ferrule; ferruled specimens showed greater resistance than nonferruled ones, regardless of the cement used. CONCLUSION: A 2-mm cervical ferrule improves fracture resistance of restored teeth, but the type of luting cement used does not seem to affect resistance.     

Is adhesive cementation of endodontic posts necessary?

Recently, the appropriate, durable bond of adhesive systems and composite resin cements to retain endodontic posts was challenged. The question arises whether it would be possible to place glass fiber posts in a less technique sensitive conventional nonadhesive approach. The influence of nonadhesive, self-adhesive, and etch-and-rinse systems on load capability of postendodontic restorations was studied. Human maxillary central incisors were divided into 4 groups (n = 10). Teeth were endodontically treated and restored by using glass fiber posts luted with different cements/composite resin combinations: (1) RelyX Unicem (3M ESPE, Seefeld, Germany)/Clearfil Core (Kuraray Europe, Duesseldorf, Germany), (2) RelyX Unicem/LuxaCore, (3) zinc phosphate cement/Clearfil, and (4) LuxaCore (DMG, Hamburg, Germany)/Clearfil. A 2 mm-ferrule preparation was performed. All specimens received adhesively luted all-ceramic crowns and were exposed to thermal cycling and mechanical loading before subsequent static loading. Significant differences between the experimental groups regarding load capability and fracture patterns were observed. The conventional non-adhesive post cementation is less reliable to withstand simulated functional forces compared to adhesive approaches.     

Fracture resistance of endodontically-treated teeth restored using three root-reinforcement methods

AIM: The aim of this in vitro study was to compare the fracture resistance of endodontically-treated anterior teeth with their roots reinforced using three different restorative methods. METHODS AND MATERIALS: Forty sound maxillary human central incisors were randomly assigned to four groups (n=10). The crowns of the teeth were removed at a level 2 mm incisal to the cementoenamel junction (CEJ). After root canal therapy, flared canals were simulated in three groups. In the first, second, and third groups the flared canals were reinforced with resin composite (RCO) (Clearfil DC Core Automix), two Reforpins (REF), and a resin cement (RCE) (Panavia F 2.0), respectively. In the fourth (DEN) group flared canals were not created. The same size fiber reinforced composite (FRC) posts were cemented with resin cement (Panavia F 2.0) in all groups. After post cementation and restoration of the teeth crown with a core build-up composite (Clearfil Photo Core), the roots of the teeth were embedded in acrylic resin blocks up to 1 mm below the CEJ. The samples were loaded in an Instron testing machine with a crosshead speed of 0.5 mm/min at a 45 angle to the long axis of the tooth on the palatal surfaces until failure occurred. Data were analyzed using the Kruskal-Wallis, Mann-Whitney, and Chi-square tests (p=0.05). RESULTS: Significant differences were found between fracture resistance in all of the groups (P<0.05) with the exception being among the RCO and REF groups. The least mean value 230 (130) N and the highest mean value 830 (220) N were shown in the fracture resistance of the RCE and DEN groups, respectively. CONCLUSION: Reforpin can be used as an alternative to resin composite for internal reinforcement of weakened roots according to the results of this study. For reinforcement of flared canals, fiber posts along with Reforpin or resin composite proved to have higher fracture resistance than resin cement. Non flared canals had the highest fracture resistance.     

Effect of ferrule height and glass fibre post length on fracture resistance and failure mode of endodontically treated teeth

The purpose of this study was to evaluate the combined effect of ferrule height and post length on fracture resistance and failure mode of endodontically treated teeth restored with glass fibre posts, composite resin cores and crowns. Ninety human maxillary central incisors were endodontically treated and divided into three groups (n = 30) according to the ferrule heights: 4, 2 and 0 mm, respectively. Post spaces in each group were prepared at 2/3, 1/2 and 1/3 of the root length (n = 10). The specimens were received fibre posts, composite resin core build up and cast metal crowns. After thermocycling, compressive static load was applied at an angle of 135° to the crowns. Two‐way analysis of variance showed significant differences in the failure load in the ferrule height groups, no significant differences in post length groups and no significant interaction between ferrule heights and post lengths. More restorable failure modes were observed.     

桩核对根管治疗牙修复后强度的影响

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

Retention of quartz-fibre endodontic posts with a self-adhesive dual cure resin cement

This study examines retention of a quartz-fibre endodontic post cemented in extracted human teeth using two cement types. Fifty-four extracted buman central incisor teeth were prepared for a tapered quartz-fibre post. Posts were cemented in 28 teeth using conventional resin cement (RelyX ARC), and 26 teeth using self-adhesive resin cement (RelyX Unicem). Posts were cyclically-loaded. Bond strengths were tested and dependability assessment was carried out. Although there was no significant difference in Weibull modulus between groups (p < 0.05), greater dependability was displayed by RelyX Unicem group. Easy application and greater dependability of self-adhesive cement may improve bonding of fibre-based posts in root canals.     

Effect of post type and restorative techniques on the strain and fracture resistance of flared incisor roots

Restoring flared endodontically treated teeth continues to be a challenge for clinicians. This study evaluated the effect of post types and restorative techniques on the strain, fracture resistance, and fracture mode of incisors with weakened roots. One hundred five endodontically treated bovine incisors roots (15 mm) were divided into 7 groups (n=15). The two control groups were (C) intact roots restored with Cpc (cast posts and core) or Gfp (glass fiber posts). The five experimental groups were (F) flared roots restored with GfpAp (Gfp associated with accessory glass fiber posts), GfpRc (anatomic Gfp, relined with composite resin), and GfpRcAp (anatomized Gfp with resin and accessory glass fiber posts). All teeth were restored with metal crowns. Mechanical fatigue was performed with 3x10(5)/50 N. Specimens were loaded at 45o, and the strain values (μS) were obtained on root buccal and proximal surfaces. Following that, the fracture resistance (N) was measured. One-way ANOVA and Tukey's HSD tests (α=0.05) were applied, and failure mode was checked. No significant difference in strain values among the groups was found. Cpc presented lower fracture resistance and more catastrophic failures in flared roots. Gfp associated with composite resin or accessory glass fiber posts seems to be an effective method to improve the biomechanical behavior of flared roots.     

Effect of different ferrule designs on the fracture resistance and failure pattern of endodontically treated teeth restored with fiber posts and all-ceramic crowns

Objective

This study investigated the effect of different ferrule heights on endodontically treated premolars.

Materials and Methods

Fifty sound mandibular first premolars were endodontically treated and then restored with 7-mm fiber post (FRC Postec Plus #1 Ivoclar-Vivadent) luted with self-polymerized resin cement (Multilink, Ivoclar Vivadent) while the coronal section was restored with hybrid composite core build-up material (Tetric Ceram, Ivoclar-Vivadent), which received all-ceramic crown. Different ferrule heights were investigated: 1-mm circumferential ferrule without post and core (group 1 used as control), a circumferential 1-mm ferrule (group 2), non-uniform ferrule 2-mm buccally and 1-mm lingually (group 3), non-uniform ferrule 3-mm buccally and 2-mm lingually (group 4), and finally no ferrule preparation (group 5). The fracture load and failure pattern of the tested groups were investigated by applying axial load to the ceramic crowns (n=10). Data were analyzed statistically by one-way ANOVA and Tukey’s post-hoc test was used for pair-wise comparisons (α=0.05).

Results

There were no significant differences among the failure load of all tested groups (P<0.780). The control group had the lowest fracture resistance (891.43±202.22 N) and the highest catastrophic failure rate (P<0.05). Compared to the control group, the use of fiber post reduced the percentage of catastrophic failure while increasing the ferrule height did not influence the fracture resistance of the restored specimens.

Conclusions

Within the limitations of this study, increasing the ferrule length did not influence the fracture resistance of endodontically treated teeth restored with glass ceramic crowns. Insertion of a fiber post could reduce the percentage of catastrophic failure of these restorations under function.     

Survival of extensively damaged endodontically treated incisors restored with different types of posts-and-core foundation restoration material

Statement of problem

Which post-and-core combination will best improve the performance of extensively damaged endodontically treated incisors without a ferrule is still unclear.

Effect of ferrule and post placement on fracture resistance of endodontically treated teeth after fatigue loading

Objectives

To evaluate the influence of the ferrule effect (1) and the fibre-post placement (2) on the fracture resistance of endodontically treated teeth subjected to cyclic fatigue loading.

Methods

40 extracted single-rooted upper pre-molars were sectioned at the CEJ (groups a and b) or 2 mm above the CEJ (groups c and d), and subsequently endodontically treated. After 24-h water storage at 37 °C, specimens were restored according to four build-up approaches (n = 10 per group): (a) NF–NP (no ferrule, no post), (b) NF–P (no ferrule, fibre-post), (c) F–NP (ferrule, no post) and (d) F–P (ferrule, fibre post). RelyX Posts (3M-ESPE) were used in groups NF–P and F–P, and were cemented with Panavia F 2.0 (Kuraray). A standardized composite core was built, after which specimens were restored with an all-ceramic crown (IPS Empress CAD, Ivoclar-Vivadent) Specimens were fatigued by exposure to 1,200,000 cycles using a chewing simulator (Willytech). All specimens that survived fatigue loading were fractured using a universal loading device (Micro-Tester, Instron). A two-way analysis of variance was used to determine the statistical significance of the factors ferrule and post on fracture resistance.

Results

Only one NF–NP specimen failed under fatigue. The ferrule effect significantly enhanced the fracture resistance of the restored teeth, regardless the use of a post (p = 0.003). F–NP obtained the highest fracture resistance (758.52 ± 121.89 N), which was not significantly different from F–P (647.58 ± 132.95 N); NF–NP presented the lowest fracture resistance (361.52 ± 151.69 N). For all groups, only ‘repairable’ failures were recorded.

Conclusions

Avoiding extra-removal of sound tooth structure, rather than placing a fibre post, can protect endodontically treated teeth against catastrophic failure. However, when any ferrule can be preserved, a fibre-post may improve the retention and fatigue resistance of the restoration.     

Fracture resistance of endodontically treated teeth restored with composite posts

STATEMENT OF PROBLEM: 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 used clinically by many dentists, there is very little information regarding the physical properties of these post systems. PURPOSE: The purpose of this study was to compare the effect of 3 fiber-reinforced composite post systems on the fracture resistance and mode of failure of endodontically treated teeth. MATERIAL AND METHODS: Ninety maxillary central incisors were divided into 8 experimental groups and 1 stainless steel (ParaPost) control group of 10 specimens each. Eighty teeth were assigned to 2 main experimental groups called "narrow" and "flared" canals. For the narrow canal group, post spaces were prepared with the corresponding reamer to restore the teeth with FibreKor, Luscent anchors, and Ribbond posts of 1.5 mm, 1.6 mm, and 2.0 mm in diameter, respectively. For the flared canals group thin-walled canals were simulated. Teeth for the flared canals were restored with the same posts but were cemented into tapered 2 mm wide canals created with a tapered diamond bur. Prefabricated posts (FibreKor and Luscent anchors) for narrow and flared canals were cemented with an autopolymerized resin cement and a flowable composite, respectively, whereas customized Ribbond posts were luted with a light-polymerized flowable composite for both canal types. An additional set of 20 Ribbond posts with coronal portions of variable size and shape referred to as "Ribbond nonstandardized" were also prepared and evaluated. Specimens were loaded to failure (kg) with a universal testing machine at a crosshead speed of 0.05 cm/min until failure occurred. Data were analyzed with analysis of variance and Student t tests (P<.05). RESULTS: Statistical analysis revealed no significant difference between flared and narrow canals in mean load to failure between the post systems except for the Ribbond posts (P<.01). 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 Luscent anchors. For the flared canal the low mean was 9.04 (+/-1.76) kg for FibreKor and the high was equal for both Luscent anchors and Ribbond standard, 12.87 (+/-2.69) and 12.87 (+/-3.54), respectively. Overall, the ParaPost control group had the highest load value (18.33 +/- 3.27 kg) (P<.05). Ribbond nonstandardized had a mean load to failure of 24.91 (+/-11.53) Kg for the narrow canal group and 31.95 (+/-11.98) kg for the flared canal. Results from these groups were excluded from the statistical analysis because of the uncontrolled core sizes and high standard deviations. No root fractures occurred in any of the experimental groups. CONCLUSION: Results from the study show that the load to failure of the stainless steel posts were significantly stronger than all the composite posts studied. However, the mode of failure or deflection of the fiber-reinforced composite posts is protective to the remaining tooth structure.     

Effect of restoration method on fracture resistance of endodontically treated maxillary premolars

PURPOSE: The aim of the present study was to compare the fracture resistance of endodontically treated maxillary premolars with mesio-occlusodistal (MOD) cavities restored using various restorative materials and luting agents. MATERIALS AND METHODS: Eighty extracted human maxillary premolars satisfying certain predetermined criteria were subjected to seven different restoration methods (10 premolars per method). After endodontic treatment, an MOD cavity was prepared in each specimen, and restoration was carried out by one of the following methods: group 1 = control (intact premolars); groups 2 and 3 = restoration using a photo-cure resin composite with and without bonding, respectively; groups 4 and 5 = restoration using a cast-metal inlay with zinc phosphate and adhesive resin cements, respectively; groups 6 and 7 = restoration using a cast-metal onlay with zinc phosphate and adhesive resin cements, respectively; and group 8 = restoration using a hybrid resin onlay. A fracture test was conducted to determine the fracture resistance and fracture mode of each specimen. RESULTS: Fracture resistance was greatest for teeth restored using a cast-metal onlay cemented with adhesive resin cement, but those fractures that did occur were generally unrestorable. Fracture resistance of teeth restored using a cast-metal inlay was also high. Fracture resistance for teeth restored using a resin composite was significantly lower, but the majority of these fractures were restorable. CONCLUSION: Endodontically treated maxillary premolars with MOD cavities could be successfully restored by cast onlay and inlay restorations luted with adhesive resin cement, but their failure mode was often unfavorable.     

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

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

Randomized controlled clinical pilot trial of titanium vs. glass fiber prefabricated posts: preliminary results after up to 3 years

PURPOSE: This randomized parallel-group clinical pilot study aimed to compare the clinical outcome of prefabricated rigid titanium to glass fiber endodontic posts when luted with self-adhesive universal resin cement. MATERIALS AND METHODS: Ninety-eight patients in need of postendodontic restoration were assessed for eligibility. Ninety-one patients met the selection criteria and were randomized and allocated to 2 intervention groups. Forty-five participants were treated using a titanium post and 46 participants received a glass fiber post, each in combination with composite core buildups for postendodontic restoration. All posts had a diameter of 1.4 mm and a length of 13 mm and were cemented 8 mm within the root canal with self-adhesive universal resin cement. A circumferential ferrule of 2 mm was always provided. Surgical crown lengthening was necessary in 13 cases. Patients were observed in intervals of 3, 6, 12, 24, and 36 months after post placement. RESULTS: After 24 to 36 months (mean +/- SD: 27.9 +/- 5.6) of observation following post placement, 1 tooth was extracted because of changes of the prosthetic treatment plan. No failures were observed among the 88 patients with follow-up data. CONCLUSIONS: Both titanium and glass fiber reinforced composite posts result in successful treatment outcomes after 2 years. The material combination used seems to be appropriate in the short term for cementing endodontic posts, irrespective of the post material.