Zirconia Copings Research Articles

34. Marginal fit of metal ceramic copings fabricated with slm technique and cad cam fabricated zirconia copings

34. Marginal fit of metal ceramic copings fabricated with slm technique and cad cam fabricated zirconia copings

Evaluation of Stress Distribution in Endodontically Weakened Teeth Restored with Different Crown Materials: 3D-FEA Analysis.

This study evaluated the stress distribution in endodontically treated teeth, weakened (W) or not weakened (NW), restored with different materials of prosthetic crown using 3D-FEA. Models of a maxillary canine were constructed based on micro-CT images and divided into the groups: G1 (control) - sound tooth; G2 to G7 - endodontically treated teeth restored with glass fiber post (GFP); which G2 to G4 simulated NW root and G5 to G7 simulated W root. For crown material the teeth were restored with: G2 and G5: metallic coping and ceramic veneering, G3 and G6: zirconia coping and ceramic veneering, G4 and G7: alumina coping and ceramic veneering. Load of 180 N was applied at the incisal third of lingual surface at 45º. Models were supported by the periodontal ligament (x=y=z=0). The von Mises stress (VMS) values were calculated. The W teeth presented higher VMS at coping when compared to NW teeth and group G1 showed lower VMS value. For crown material, for both W or NW teeth, increasing VMS was found at metallic, zirconia and alumina coping, respectively. Metallic coping showed a better performance despite its unfavorable esthetics, suggesting as an appropriate material for prosthetic restoration of endodontically treated teeth.

Esthetic abutment design for angulated screw channels: A technical report

Angulated screw channel system abutments (ASCs) have recently been introduced to address the problem with visible screw access that may compromise esthetics. ASCs allow the screw access to be modified up to 25 degrees relative to the implant axis. However, a widened channel, which may cause thinning of the facial ceramic, is needed at the implant screw head to allow for proper engagement of the screwdriver. This technical report introduces a custom titanium insert design, the Satoshi Sakamoto (SS) abutment. The SS abutment consists of a custom titanium metal insert and zirconia coping in which the access hole is located in an esthetic position with an ASC system. The SS abutment results in a crown with more normal crown dimensions that also provides more space for the soft tissues. This SS abutment design allows clinicians to obtain screw-retained restorations with optimal esthetics and mechanical strength.

Retention force of removable partial dentures with different double crowns.

The aim of the study was to compare the retentive behaviors of double crowns with different designs and material compositions before and after artificial aging. Six pairs of double crowns were fabricated: telescopic crowns 0° made of high-noble metal (group A) or non-precious metal (group B), telescopic zirconia copings with secondary crowns made of electroplated gold 2° (group C), crowns with friction pins 2° made of non-precious metal (group D) or zirconia (group E), and conical crowns 6° made of high-noble metal (group F). Retention forces were assessed before and after artificial aging, and after axial and non-axial loading. Initially, specimens in group D (13.9N), B (12.5N), and E (12.2N) exhibited the highest retention forces. Retention forces in groups A (9.6N), C (7.4N), and F (6.0N) were statistically significantly lower than those of the other groups (p<0.05). After artificial aging, double crowns with additional retention elements exhibited the highest retention forces. The largest retention force losses were evident in groups A (70%), B (64%), C (39%), and F (47%). Double crowns with different designs and made of different materials exhibited different retention forces and different long-term retentive behavior. The highest retention force losses were evident in double crowns with more extended surface contact, such as telescopic crowns. Telescopic crowns with additional retention elements were more resistant to wearing than double crowns without additional retention elements. An additional clinical benefit might be the quick and easy possibility of enhancing retention.

Internal Fit and Marginal Gap Evaluation of Zirconia Copings Using Microcomputed Tomography: An In Vitro Analysis.

The purpose of this in vitro study was to measure the marginal and internal fit of single-unit all-ceramic zirconia copings (ZCs) fabricated through three different computer-aided design/computer-assisted manufacture (CAD/CAM) systems using microcomputed tomography (microCT). A total of 10 ZCs were produced for each experimental group. Scanning of the stainless steel (SS) model with its respective copings was conducted with a SkyScan machine. DataViewer software was used to acquire cross-sectional images. Locations of cross-sections for all specimens were standardized to reduce errors. Seven different cross-section locations were selected: four transverse and three sagittal. Adobe Photoshop CS3 was used for the measurements. One-way analysis of variance and Tukey post hoc test were used for the statistical analysis for each group. In addition, t test (α = .05) was used to compare values at each measurement location for the different groups. The results of this study show significant differences in the precision of fit of the experimental groups at the axio-occlusal transition (AOT) location, with a significant gap present in the DeguDent CAD/CAM System compared to the other two systems. Tukey test results indicate a significant difference in the marginal gap between the DeguDent CAD/CAM System and KaVo Everest Dental CAD/CAM System (P = .004). In addition, there is a significant difference in gap size values in the sagittal sections distal to the midline between the DeguDent CAD/CAM System and the Lava Ultimate CAD/CAM System (P = .002). The different CAD/CAM systems showed a clinically acceptable internal fit and marginal adaptation. Different levels of fit were found between the experimental groups. Marginal adaptation was the best in all experimental groups. The gap at the AOT area varied among the three groups, with the DeguDent CAD/CAM System showing the greatest value.

The effective design of zirconia coping on titanium base in dental implant superstructure.

Zirconia exhibits good tissue compatibility and nontoxicity, making it a widely used esthetic replacement material for implant abutments. To avoid abutment-fracture, the parts composed of zirconia with a bonded metal component connected to the implant can be used. The purpose of this study was to design titanium and zirconia components with high fracture resistance at the zirconia component's edge line. Three edge line designs of the titanium base and zirconia sleeve were made: chamfer, shoulder, and back-taper. To assess the strength of the abutment design, static loads were applied vertically and 30 degrees from the vertical axis. A test of tensile strength was also performed after chewing simulation. Conventional zirconia components mounted on a chamfer-type titanium base showed significantly lower fracture resistance than shoulder and back-taper types. This study suggests that to improve the durability of zirconia abutments with a titanium base, a back-tapered edge design is recommended.

Marginal Fit Comparison of Hot Isostatic Pressed and Non-Hot Isostatic Pressed Zirconia Copings with Three Different Marginal Finish Lines Fabricated with Two Different CAD-CAM Systems

Marginal Fit Comparison of Hot Isostatic Pressed and Non-Hot Isostatic Pressed Zirconia Copings with Three Different Marginal Finish Lines Fabricated with Two Different CAD-CAM Systems

Dimensional changes from the sintering process and fit of Y-TZP copings: Micro-CT analysis

ObjectiveTo evaluate the dimensional changes from the sintering process of Y-TZP and relate them to the fit of zirconia copings. MethodsThe sintering shrinkage rate (SSR) was obtained from the measurement of geometric specimens (4×4×2mm). Thirty-six zirconia copings made using CAD/CAM were equally divided into three groups (n=12): ZMAX — IPS e.max ZirCAD (Ivoclar Vivadent, Liechtenstein); ZYZ — InCeram YZ (Vita Zahnfabrik, Germany); and ZK — Zirklein (Zirklein, Brazil). The copings were scanned in micro-CT before and after sintering so that SSR was obtained. The SSR of geometrical specimens and copings was compared to each other and those the manufacturers reported (ANOVA-2 and Tukey, p≤.05). The copings were settled on an abutment and taken to the micro-CT to evaluate their marginal and internal fit. The data enabled the statistical comparison (ANOVA-2 and Tukey, p≤.05) between groups and measurement sites and between the fit obtained with that stipulated by the CAD/CAM software (80μm) (Dunnett test, p≤.05). ResultsAll groups showed statistical differences between the SSR the manufacturer reported and those obtained experimentally and between the SSR of the geometric specimens and copings. In general, the SSR of the copings showed no uniformity. There was no statistical difference among the groups for marginal fit, with differences only for internal fit and between the different regions measured. The fit obtained experimentally differed from the internal space determined in the CAD/CAM software. SignificanceThe lack of uniformity of sintering shrinkage might lead to a non-uniform internal fit of Y-TZP copings.

Effect of Margin Designs on the Marginal Adaptation of Zirconia Copings.

ObjectiveThe aim of this in vitro study was to investigate the effect of Shoulder versus Chamfer margin design on the marginal adaptation of zirconia (Zr) copings.Materials and Methods40 extracted molar teeth were mounted in resin and prepared for zirconia crowns with two margin preparation designs (20=Shoulder and 20=Chamfer). The copings were manufactured by Cercon® (DeguDent GmbH, Germany) using the CAD/CAM system for each tooth. They were tried on each tooth, cemented, thermocycled, re-embedded in resin and were subsequently cross sectioned centrally into two equal mesial and distal halves. They were examined under electron microscope at 200 X magnification and the measurements were recorded at 5 predetermined points in micrometers (µm).ResultsThe overall mean marginal gap for the two groups was found to be 206.98+42.78µm with Shoulder margin design (Marginal Gap=199.50+40.72µm) having better adaptation compared to Chamfer (Marginal Gap=214.46+44.85µm). The independent-samples t-test showed a statistically non-significant difference (p=.113) between the means of marginal gap for Shoulder and Chamfer margin designs and the measurements were recorded at 5 predetermined points for the two groups.ConclusionsThe Chamfer margin design appeared to offer the same adaptation results as the Shoulder margin design.

Dislodgement Resistance of Zirconia Copings Cemented onto Zirconia and Titanium Abutments.

To determine the effect of the cement type and abutment material on the tensile strength required to dislodge zirconia copings. Two experimental groups of abutments were prepared: (1) titanium abutments (n = 30) and (2) zirconia abutments (n = 30). Sixty zirconia copings (custom designed) were fabricated using 3-dimensional computer-assisted design to have a 6-mm projection above the abutment to accommodate a hole, through which a wire was inserted to attach the zirconia coping to a universal testing machine. Each abutment was placed onto an implant analog embedded in acrylic resin blocks to fit onto the universal testing machine. The zirconia copings were cemented onto the abutments with a provisional luting agent, zinc phosphate (ZP) cement, and adhesive resin cement, and after 5500 thermocycles, a tensile force was applied at a crosshead speed of 0.5 mm/min. The removal force was recorded for each specimen. Two-way analysis of variance (ANOVA) and 1-way ANOVA were used for the statistical analysis (P < 0.05). The mean forces necessary to remove the zirconia copings from titanium abutments were 6.52, 83.09, and 251.18 N for temporary cement, ZP cement, and resin cement, respectively. For zirconia abutments, the required forces were 17.82, 116.41, and 248.72 N. The abutment material had no effect on retention, but the cement type affected the retention of the zirconia copings.

EFFECT OF MARGIN DESIGNS AND PORCELAIN VENEERING ON ACCURACY OF BI LAYERED ZIRCONIA CROWN

Statement of problem: Degree of marginal discrepancy determines effectively success and failure of fixed restorations.Purpose: To evaluate the effect of porcelain veneering techniques on the marginal fit of bi- layered zirconia crown using four marginal designs.Materials and Methods: A 40 Plaster replicas were made from two master dies and divided into two main groups (20 for each) according to type of finish line. Each group subdivided into two subgroups (10 for each) to obtain the following groups {A1} shoulder without cervical collar {A2} shoulder with 1 mm cervical collar. {B1} chamfer without cervical collar {B2} chamfer with 1 mm cervical collar. Zirconia blanks were milled using CAD/CAM system to produce 40 zirconia copings. Then, Veneering of the copings was done. Vertical gap distances were measured at 18 predetermined points. Results: Veneering with porcelain exhibited statistical significant difference in mean values of marginal gap in both group {A1} and {B1}, while veneering with porcelain did not exhibit significant difference in both group {A2} and {B2} in comparison with the pre veneering state. Correlations based on the finish line design exhibited significant difference in mean values of marginal gap between all tested groups. Correlations based on presence or absence of cervical zirconia collar did not exhibited statistical significant difference between tested groups. On other hand, there were significant differences in mean values of marginal gap between tested groups in post veneering state, at the level of P value < 0.05. Conclusions: Marginal fit of the final crowns with chamfer finish lines were better than that with shoulder, however, veneering with porcelain significantly raised marginal gap distance of crowns with collarless shoulder and chamfer preparations, while in that designs with cervical collar, veneering was not significantly affected on the marginal gap distance for both finish line designs

Fracture resistance of zirconia-based all-ceramic crowns after bur adjustment.

Intra-oral grinding is often required to optimize occlusion of all-ceramic restorations. The effect of burs of different grit size on the fracture resistance of veneered zirconia crowns was investigated in this study. Forty-eight standardized zirconia copings were produced. The ceramic veneer was designed with a positive ellipsoidal defect on the palatal aspect of the crowns. To simulate adjustment of dental restorations by burs, this palatal defect was removed by use of three different diamond-coated burs with grit sizes 46, 107, or 151μm (fine, medium, or coarse, respectively). Each different grit size of bur was used to grind 16 crowns. All crowns were then polished and surface roughness was measured. Half of the specimens underwent thermomechanical aging (10,000 thermocycles between 6.5°C and 60°C) and 1.2 million cycles of chewing simulation (F=108N). A linear regression model was computed to test the effect of aging and grinding grit size at a level of significance of α=0.05. Fracture loads increased with decreasing grit size. Grit size and aging had a significant effect on the fracture resistance of the crowns. Use of fine and coarse burs for intra-oral adjustments resulted in different fracture resistance of veneered zirconia crowns. Coarse burs should be avoided in the final stage of grinding before polishing.

Influence of space size of abutment screw access channel on the amount of extruded excess cement and marginal accuracy of cement-retained single implant restorations

Statement of problemThe detrimental effect of extruded excess cement on peri-implant tissue has been well documented. Although several techniques have been proposed to reduce this effect by decreasing the amount of extruded cement, how the space size of the abutment screw access channel (SAC) affects the amount of extruded cement and marginal accuracy is unclear. PurposeThe purpose of this in vitro study was to evaluate the effect of the size of the unfilled space of the abutment SAC on the amount of extruded excess cement and the marginal accuracy of zirconia copings. Material and methodsTwelve implant replicas and corresponding standard abutments were attached and embedded in acrylic resin blocks. Computer-aided design and computer-aided manufacturing (CAD-CAM) zirconia copings with a uniform 30-μm cement space were fabricated by 1 dental technician using the standard method. The copings were temporarily cemented 3 times at different sizes of the left space of the SAC as follows: the nonspaced group (NS), in which the entire SAC was completely filled, the 1-mm-spaced group (1MMS), and the 2-mm-spaced group (2MMS). Abutments and crowns were ultrasonically cleaned, steam cleaned, and air-dried. The excess cement was collected and weighed. To measure the marginal accuracy, 20 measurements were made every 18 degrees along the coping margin at ×300 magnification and compared with the pre-cementation readings. One-way ANOVA was calculated to determine whether the amount of extruded excess cement differed among the 3 groups, and the Tukey test was applied for multiple comparisons (α=.05). ResultsThe mean weights (mg) of extruded excess cement were NS (33.53 ±1.5), 1MMS (22.97 ±5.4), and 2MMS (15.17 ±5.9). Multiple comparisons showed significant differences in the amount of extruded excess cement among the 3 test groups (P<.001). The mean marginal discrepancy (μm) of the pre-cemented group (29.5 ±8.2) was significantly different (P<.01) from that of the NS (72.3 ±13.7), the 1MMS (70.1 ±19), and the 2MMS group (70.1 ±18.8). No significant differences were found in marginal accuracy among the 3 test groups (P=.942). ConclusionsWithin the limitations of this in vitro study, leaving a 2-mm space in the SAC reduced the amount of extruded excess cement by 55% in comparison with the nonspaced abutments. However, no effect was found on the marginal accuracy of zirconia copings.

Effect of coping thickness and background type on the masking ability of a zirconia ceramic

Statement of problemThe masking ability of zirconia ceramics as copings is unclear. PurposeThe purpose of this in vitro study was to evaluate the effect of coping thickness and background type on the masking ability of a zirconia ceramic and to determine zirconia coping thickness cut offs for masking the backgrounds investigated. Material and methodsThirty zirconia disks in 3 thickness groups of 0.4, 0.6, and 0.8 mm were placed on 9 backgrounds to measure CIELab color attributes using a spectrophotometer. The backgrounds included A1, A2, and A3.5 shade composite resin, A3 shade zirconia, nickel-chromium alloy, nonprecious gold-colored alloy, amalgam, black, and white. ΔE values were measured to determine color differences between the specimens on the A2 shade composite resin background and the same specimens on the other backgrounds. The color change (ΔE) values were compared with threshold values for acceptability (ΔE=5.5) and perceptibility (ΔE=2.6). Repeated measures ANOVA, the Bonferroni test, and 1-sample t tests were used to analyze data (α=.05). ResultsMean ΔE values ranged between 1.44 and 7.88. The zirconia coping thickness, the background type, and their interaction affected the CIELab and ΔE values (P<.001). ConclusionsTo achieve ideal masking, the minimum thickness of a zirconia coping should be 0.4 mm for A1 and A3.5 shade composite resin, A3 shade zirconia, and nonprecious gold-colored alloy, 0.6 mm for amalgam, and 0.8 mm for nickel-chromium alloy.

Evaluation of the marginal fit of CAD-CAM zirconia copings: Comparison of 2D and 3D measurement methods

PurposeThe purpose of this in vitro study was to compare the marginal fit of zirconia copings by using 2 different measurement methods: a triple optical scan method and a silicone replica method. Material and methodsSixty zirconia copings fabricated by computer-aided design and computer-aided manufacture (CAD-CAM) systems were studied for the marginal fit. For the replica method, the thickness of the light-body silicone layer of the discrepancy was assessed using light microscopy and image analysis software. The triple-scan optical method was performed to obtain a digital three-dimensional map of the marginal fit and analyzed marginal fit measurement values. For each method, the reliability of the measurement was tested, and a nonparametric analysis was then performed to compare the marginal fit values as measured by the 2 evaluation methods (α=.05). ResultsIntraclass correlation coefficients and repeatability coefficients revealed good repeatability for both of the evaluation methods. However, the triple-scan method produced a smaller marginal fit than the replica method (P<.001) for the entire group studied. ConclusionsAlthough both methods showed good repeatability, the triple-scan method was more reliable.

Effect of the Unfilled Space Size of the Abutment Screw Access Hole on the Extruded Excess Cement and Retention of Single Implant Zirconia Crowns.

To evaluate in vitro the effect of the size of the unfilled space of the abutment screw access hole on the amount of extruded excess cement and the retention of zirconia copings. Twelve dental implant replicas were attached to the corresponding abutments and embedded in acrylic resin blocks. A total of 36 CAD/CAM zirconia copings were fabricated by one technician using the standard technique. Abutments were divided into group I: the entire screw access channel was completely filled (nonspaced); group II: 1-mm-spaced; and group III: 2-mm-spaced. The copings were air-abraded and temporarily cemented under constant load of 60 N for 10 minutes. The excess cement was calculated as the difference between the post-cementation and post-excess-removal weights using a digital scale. Retention test was performed by a universal testing machine at a 0.5 mm/min crosshead speed. The ultimate force and tensile strength required for separation were recorded. One-way ANOVA and Tukey's test were used for statistical analysis at p ˂ 0.05. The average amount of extruded cement in groups 1, 2, and 3 was 33.48 ± 1.55, 23.05 ± 5.48, and 15.58 ± 5.98 mg, respectively. Multiple comparisons showed significant differences in the amount of extruded excess cement between the three groups (p ˂ 0.001). The maximum load at decementation in groups 1, 2, and 3 was 98.8, 87.5, and 88.6 N, respectively. Groups 1, 2, and 3 separated at 6.90 ± 1.2, 6.12 ± 0.7, and 6.21 ± 0.9 MPa, respectively, with no significant differences between them. The amount of extruded excess cement was reduced by more than half when a 2-mm space of the screw access hole was left unfilled in comparison to the nonspaced counterpart. The retention of zirconia copings was not affected by the reported technique.

The effect of veneering on the marginal fit of CAD/CAM-generated, copy-milled, and cast metal copings.

This in vitro study investigated the marginal fit of metal and zirconia copings before and after veneering on dies with shoulder/chamfer (s/c) finish lines. Using CAD/CAM, ten (n=10) each s/c zirconia (NZ) copings and ten (n=10) each s/c metal (MM) copings were generated. As controls, ten (n=10) each s/c zirconia copings were copy-milled (ZZ) and ten (n=10) each s/c metal copings were cast (CC). The vertical marginal discrepancy of the copings was measured at 20 predefined spots of the circular shoulder and chamfer finish lines in microns (μm) before and after a first and a second veneering firing using a stereomicroscope at ×40 magnification. Data were statistically analyzed, and the comparisons of CAD/CAM-milled (NZ, MM), copy-milled (ZZ), and cast (CC) copings before and after veneering were made at a significance level of p<0.05. Gap width at s/c finish lines of ZZ was (91±11/100±28) and increased significantly (109±21/141±18) after the first firing (ZZ1). NZ showed significantly smaller gaps than ZZ (36±6/46±12) and (NZ1) after the first firing (61±16/71±29). Gap widths of CC groups (36±8/25±4) were not significantly different from NZ but were significantly lower after the (CC1) first veneering firing (40±8/42±7). MM copings showed gap values similar to NZ. Second firings did not significantly increase gaps in all groups except ZZ2 of chamfer finish line. Veneering increased the marginal gap width of copings. Within the limits of this in vitro study, aesthetic ceramic veneering of CAD/CAM-generated copings caused a statistically significant but tolerable loss of marginal fit precision.

Influence of veneering technique and veneer-coping thickness on fracture toughness of implant retained veneered Y-TZP zirconia crowns

The aim of the study is to investigate the influence of veneering technique and veneer-coping thickness on the fracture toughness of implant retained zirconia crowns. Eighty zirconia copings are fabricated, half of which have 0.5 mm and the other half 1 mm thickness. Each 0.5 mm and 1 mm thickness coping is veneered to overall thickness of 3 and 4 mm using layering and hot press methods. Metal ceramic crowns with veneer-coping thickness of 2.5/0.5 mm are used as controls. All specimens are cemented to implant abutments using zinc oxide eugenol cement and tested using a micro-indenter. Crack lengths for specimens are evaluated to calculate fracture toughness using a formula. Results are analyzed using ANOVA. Veneer-coping thickness of 2.5/0.5 (5:1) and 3.5/0.5 (7:1) show significantly better (p = 0.001) fracture toughness as compared to V/C thickness of 2/1 (2:1) and 3/1 (3:1) for implant retained zirconia crowns. Metal ceramic crowns show significantly higher fracture toughness (p = 0.01) as compared to zirconia crowns of similar veneer/coping thickness. Veneering technique did not influence fracture toughness of zirconia crowns and hot-pressing is a viable technique for veneering Zr copings. Higher veneer-coping ratios i.e. thicker veneer and thinner copings, of zirconia crowns demonstrate better fracture toughness.

Influence of Restorative Materials on Color of Implant-Supported Single Crowns in Esthetic Zone: A Spectrophotometric Evaluation.

Restorations of 98 implant-supported single crowns in anterior maxillary area were divided into 5 groups: zirconia abutment, titanium abutment, and gold/gold hue abutment with zirconia coping, respectively, and titanium abutment with metal coping as well as gold/gold hue abutment with metal coping. A reflectance spectrophotometer was used to evaluate the color difference between the implant crowns and contralateral/neighboring teeth, as well as the color difference between the peri-implant soft tissue and the natural marginal mucosa. The mucosal discoloration score was used for subjective evaluation of the esthetic outcome of soft tissue around implant-supported single crowns in the anterior zone, and the crown color match score was used for subjective evaluation of the esthetic outcome of implant-supported restoration. ANOVA analysis was used to compare the differences among groups and Spearman correlation was used to test the relationships. A gold/gold hue abutment with zirconia coping was the best choice for an esthetic crown and the all-ceramic combination was the best for peri-implant soft tissue. Significant correlation was found between the spectrophotometric color difference of peri-implant soft tissue and mucosal discoloration score, while no significant correlation was found between the total spectrophotometric color difference of implant crown and crown color match score.

Fracture resistances of zirconia, cast Ni-Cr, and fiber-glass composite posts under all-ceramic crowns in endodontically treated premolars.

PURPOSEThe aim of the present study was to evaluate the fracture resistances of zirconia, cast nickel-chromium alloy (Ni-Cr), and fiber-composite post systems under all-ceramic crowns in endodontically treated mandibular first premolars.MATERIALS AND METHODSA total of 36 extracted human mandibular premolars were selected, subjected to standard endodontic treatment, and divided into three groups (n=12) as follows: cast Ni-Cr post-and-core, one-piece custom-milled zirconia post-and-core, and prefabricated fiber-glass post with composite resin core. Each specimen had an all-ceramic crown with zirconia coping and was then loaded to failure using a universal testing machine at a cross-head speed of 0.5 mm/min, at an angle of 45 degrees to the long axis of the roots. Fracture resistance and modes of failure were analyzed. The significance of the results was assessed using analysis of variance (ANOVA) and Tukey honest significance difference (HSD) tests (α=.05).RESULTSFiber-glass posts with composite cores showed the highest fracture resistance values (915.70±323 N), and the zirconia post system showed the lowest resistance (435.34±220 N). The corresponding mean value for the Ni-Cr casting post and cores was reported as 780.59±270 N. The differences among the groups were statistically significant (P<.05) for the zirconia group, as tested by ANOVA and Tukey HSD tests.CONCLUSIONThe fracture resistance of zirconia post-and-core systems was found to be significantly lower than those of fiberglass and cast Ni-Cr post systems. Moreover, catastrophic and non-restorable fractures were more prevalent in teeth restored by zirconia posts.