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

Comparative evaluation of fracture resistance of endodontically treated teeth with wedge shaped non-carious cervical lesions using different types of esthetic post: An in vitro study

Introduction

Background of the study: Conventionally, postcore and crown foundation systems have been employed for restoring endodontically treated teeth (ETT).

Aim

The aim of this study was to evaluate and compare the fracture resistance of ETT with wedge-shaped noncarious cervical lesions (NCCLs) using different types of esthetic posts.

Technique

Forty maxillary first premolars possessing two root canals have been randomly divided into four groups (n = 10). Thirty tooth specimens were used to generate buccal wedge-shaped NCCLs. Zirconia and prefabricated fiber posts have been cemented in Groups III and IV. In universal testing machine, the palatal cusp has been subjected to nonaxial compressive stress at 30° angle with crosshead speed of 0.5 mm/min till fracture occurred. (1) Group I - composite resin core (CRC), (2) Group II - NCCLs + CRC, (3) Group III - NCCLs + PFC + CRC, and (4) Group IV - NCCLs + custom-made zirconia post + CRC.

Results

A one-way analysis of variance/Kruskal-Wallis test was employed to compare the outcome variables between the study groups, which showed Group III's fracture resistance was noticeably greater than Group I. Finally, there has been a substantial difference (P < 0.0001) between Group IV and all other groups.

Conclusion

Maxillary premolars with NCCLs that were repaired endodontically utilizing PFCs showed higher fracture resistance than maxillary premolars without posts.

Experimental investigation and finite element analysis on the durability of root-filled teeth treated with multisonic irrigation

OBJECTIVE

This study compared the fracture load, stress distribution, and survival probability under cyclic loading of extensively restored teeth treated with multisonic irrigation with those treated with conventional instrumentation, with or without a post.

METHODS

Mesial-occlusal-distal cavities were prepared in 30 human mandibular premolars. The teeth were randomly divided into 3 groups of 10 based on the endodontic and restorative procedures: (1) Root canal treatment (RCT) followed by resin composite restoration (control group), (2) RCT followed by a glass fiber post restoration (conventional group), and (3) minimal instrumentation plus multisonic irrigation followed by resin composite restoration (GW group). All groups were restored with full-coverage crowns. The samples were subjected to step-stress cyclic loading until fracture and then scanned using micro-CT to identify the fracture modes. FEA was conducted to evaluate the failure-causing stresses.

RESULTS

The mean fracture loads for the control, conventional, and GW groups were 1700 ± 176 N, 1760 ± 97 N, and 1760 ± 70 N, respectively. The respective numbers of cycles to failure were 39461 ± 6634, 41261 ± 3965, and 40151 ± 3127. There was no significant difference in the fracture load or number of cycles to failure among the groups (p > 0.05). This was supported by the FEA results which showed similar critical stress values in the three groups.

SIGNIFICANCE

The multisonic irrigation system led to a comparable fracture load and durability in extensively restored premolars as conventional RCT with or without a fiber post.

Fracture resistance, 3-dimensional finite element analysis, and safety factors for five post-and-core restorations with crowns placed in the noncircular-shaped canals of premolars

STATEMENT OF PROBLEM

Restoring endodontically treated premolars with noncircular canals presents a significant challenge.

PURPOSE

The purpose of this study was to compare the in vitro fracture resistance and the finite element computational calculation-based stress and safety factor of noncircular-shaped, endodontically treated premolars restored with 5 different prefabricated and custom computer-aided design and computer-aided manufactured post-and-core systems.

MATERIAL AND METHODS

Fifty single-rooted oval-shaped canal maxillary premolars were endodontically treated and post spaces were prepared. The specimens were divided into 5 categories on the basis of the post-and-core system used: Group CN composite resin core without a post, Group CF prefabricated fiber-reinforced composite resin post and composite resin core, Group IC interpenetrating phase composite post-and-core, Group LS lithium disilicate post-and-core, and Group ZR zirconia post-and-core. Lithium disilicate crowns were fabricated and cemented on the 5 different post-and-core systems and subjected to a fracture resistance test using a spherical indenter with static loading. Differences in fracture resistance were evaluated using a 1-way analysis of variance (ANOVA) (α=.05). The 3-dimensional finite element method was used to determine the von Mises stress and safety factors, defined as the ratio of the material's strength to the von Mises stress experienced, within different compartments of the restored tooth model.

RESULTS

In the in vitro fracture resistance test, the mean ±standard deviation fracture loads of the 5 groups were 2144 ±515 N, 1801 ±600 N, 1690 ±312 N, 1612 ±545 N, and 1487 ±600 N, respectively and were statistically similar (P=.078). All specimens within the ZR group exhibited restorable fractures. In contrast, only 30% of the CN group specimens showed restorable fractures. The incidence of restorable fractures in the CF, IC, and LS groups was 70%, 80%, and 70%, respectively. Although all groups showed similar maximum von Mises stress and stress distribution, safety factors in the models varied significantly. The ceramic crown was the weakest component in the LS and ZR groups, with much lower safety factors than dentin and post-and-core regions. Additionally, the CN group's wider dentin area had a demonstrably lower safety factor.

CONCLUSIONS

Endodontically treated noncircular-shaped canal premolars showed minimal effect on fracture resistance regardless of post type. However, for teeth with sufficient ferrule, using any post-and-core system significantly reduced the incidence of nonrestorable fractures compared with just a coronal foundation restoration, with custom zirconia offering the potential of achieving a restorable outcome after fracture.

Comparative Evaluation of Fracture Resistance and Failure Modes in Endodontically Treated Teeth Restored With Zirconia-Reinforced Lithium Silicate and Cast Metal Alloys: An In Vitro Study

Introduction This study evaluates the mechanical performance of a new all-ceramic material, zirconia-reinforced lithium silicate (ZLS), as a restorative material for the rehabilitation of endodontically treated teeth with severe coronal destruction. Material and methods Sixty extracted mandibular first premolars of similar size and shape were collected, and root canal treatment and tooth preparation were performed. They were divided into six groups as follows: Group 1 A - ZLS post and core, Group 1 B - ZLS one-piece dowel crown, Group 1 C - ZLS endocrown, Group 2 A - Cast post & core with metal crown, Group 2 B - Cast one-piece dowel crown, Group 2 C - Metal endocrown. After etching and bonding, all restorations were cemented with dual-cure resin cement. All specimens were loaded until failure in a Universal Testing Machine. Fracture analysis and failure modes analysis were conducted through visual examination. For statistical analysis, a one-way ANOVA test was used to analyze fracture resistance values. Results Within Group 1, the mean fracture resistance was highest for the ZLS post and core (610 N), followed by the ZLS endocrown (450 N) and the ZLS one-piece dowel crown (356 N), respectively, and this difference was statistically significant (P < 0.05). An inter-group comparison using an unpaired t-test showed a significant difference between the ZLS post and core (1A) and the Cast post and core (2A) (P < 0.05). Conclusion ZLS restorations have great potential to be used as an alternative to cast metal restorations for the restoration of severely damaged endodontically treated teeth.

Fracture resistance and failure mode of endodontically treated premolars reconstructed by different preparation approaches: Cervical margin relocation and crown lengthening with complete and partial ferrule with three different post and core systems

PURPOSE

To assess the fracture resistance and failure mode of endodontically treated premolars reconstructed by different preparation approaches: cervical margin relocation (CMR) and crown lengthening (CL) with complete ferrule (CLF) and partial ferrule (CLPF) with three different post and core systems.

MATERIALS AND METHODS

In this in vitro study, 100 maxillary premolars were assigned to the following 10 groups according to their preparation approach and type of post and core system (n = 10): (I) control (intact teeth), (II) prefabricated fiber post (PFP) and composite core with CMR (PFP-CMR), (III) polyethylene fiber-reinforced composite (PEFRC) with CMR (PEFRC-CMR), (IV) casting post (CP) and core with CMR (CP-CMR), (V) PFP-CLPF, (VI) PEFRC-CLPF, (VII) CP-CLPF, (VIII) PFP-CLF, (IX) PEFRC-CLF, and (X) CP-CLF. After thermomechanical loading, the fracture resistance and failure mode were assessed. Data were analyzed statistically (α = 0.05).

RESULTS

In all post and core systems, the CLPF approach had lower fracture resistance than CMR (p < 0.05); CLF showed higher fracture resistance than CLPF only in the PFP system (p = 0.038). In PEFRC and CP systems, the difference between CLF and CLPF was not significant (p > 0.05). No significant difference was found in fracture resistance of different post and core systems with the same preparation approach (p > 0.05). CLPF showed the highest frequency of favorable, and CLF showed the highest frequency of unfavorable fractures.

CONCLUSION

CLPF yielded lower fracture resistance than CMR. The difference in fracture resistance was not significant between CLF and CMR but the frequency of unfavorable fractures was higher in CLF than in other groups.

Anatomic CAD-CAM post-and-core systems: A mastication simulation study

STATEMENT OF PROBLEM

Few studies have investigated the differences among various post-and-core systems under mastication simulation. Comparing these systems while simulating the clinical environment should provide a more accurate assessment of their performance.

PURPOSE

The purpose of this in vitro study was to evaluate the fatigue resistance of conventional cast metal and prefabricated fiber post systems with computer-aided design and computer-aided manufacture (CAD-CAM) prefabricated nonmetal post-and-core systems.

MATERIAL AND METHODS

Forty freshly extracted human maxillary premolars were endodontically treated and divided into 4 subgroups (n=10) according to the material: cast metal, zirconia, fiber-reinforced composite resin, prefabricated fiber post. The post-and-core materials were manufactured either conventionally or milled with CAD-CAM technology. All specimens were exposed to simultaneous mastication simulation (1.2 million cycles) and thermocycling (10 000 cycles at 5 °C to 55 °C) and analyzed based on failure of specimens. Data were analyzed by using the Kaplan-Meier survival analysis and Cox-regression (α=.05).

RESULTS

Both cast metal and zirconia post-and-core groups had similar fatigue resistance (P>.05) but significantly higher fatigue resistance than the fiber-reinforced groups (P<.05). Fiber-reinforced composite resin and prefabricated fiber post did not survive the mastication simulation, fracturing between 504 000 and 752 000 cycles, with fractures occurring in the cervical portion of the tooth.

CONCLUSIONS

Cast metal and zirconia post-and-core systems had improved physical properties with high resistance to fatigue when compared with fiber-reinforced post-and-core systems.

In Vitro Effect of the Length of Relocated Cervical Margin with Casting Post and Core, Prefabricated Fiber Post, and Polyethylene Fiber with a Composite Core on Fracture Resistance and Marginal Integrity

Objective

This study aimed to assess the effect of length of the relocated cervical margin with casting post and core (CP), prefabricated fiber post and composite core (PFP), and polyethylene fiber-reinforced composite (PEFRC) on fracture resistance and marginal integrity.

Materials and Methods

In this in vitro study, 70 sound human maxillary premolars were divided into seven groups according to the type of post and core system and length of the relocated cervical margin (n = 10): control (no preparation), PFP-3, PEFRC-3, CP-3 with 3 mm of cervical margin relocation (CMR), PFP-6, PEFRC-6, and CP-6 (with 6 mm of CMR). The samples were restored with zirconia crowns (except the control group). Epoxy resin replicas were fabricated before and after thermomechanical loading. Marginal integrity was assessed at the luting cement-core, core-tooth, and luting cement-enamel interfaces under a scanning electron microscope (SEM) (×200). Fracture resistance and failure mode were subsequently assessed. Data were analyzed by independent t-test, paired t-test, ANOVA, Tukey-Games Howell, Mann-Whitney, Kruskal-Wallis, Wilcoxon, Mann-Whitney with Bonferroni correction, and Fisher-Freeman-Halton tests (α = 0.05).

Results

The marginal integrity of the groups with 3 mm of CMR followed the following order: PEFRC > PFP > CP at all interfaces (P  < 0.05). In 6-mm CMR groups, this order was CP < PFP = PEFRC at the luting cement-core and (CP < PEFRC) = PFP at the core-tooth interface. No significant difference was found in fracture resistance when comparing the 3-mm CMR groups with each other (P  > 0.05). PFP-6 showed higher FR than CP-6 (P  < 0.001). PEFRC-6 had no significant difference with PFP-6 and CP-6 (P  > 0.05). In each post and core system, 3-mm CMR groups showed higher marginal integrity and fracture resistance (P  < 0.05).

Conclusion

Increasing the length of the relocated cervical margin decreased the marginal integrity and fracture resistance of all three systems of CP, PFP, and PEFRC.

Assessment of CAD/CAM Fabrication Technologies for Post and Core Restorations-A Narrative Review

The primary objective of this study is to conduct a comprehensive review of the existing literature that discusses research on post and core restorations, covering aspects such as their composition, manufacturing methods, and clinical effectiveness. The methodology employed in this review encompasses the implementation of a well-defined search strategy, the establishment of criteria for inclusion and exclusion, and the selection of relevant studies to summarize their findings. To gather relevant literature published between 1993 and 2023, the research team conducted separate searches on PubMed, Web of Science, and Embase databases. In total, 168 titles were initially retrieved from these electronic databases. By applying the predefined exclusion criteria, the researchers identified 73 articles that specifically address the conventional and computer-aided design/computer-aided manufacturing (CAD/CAM) technologies employed in post and core restorations. These treatments are commonly employed to restore teeth that have received endodontic therapy and subsequently experienced loss of dental structure. The development of computerized technology for the creation of customized posts and cores has emerged as a straightforward and efficient alternative to traditional methods. The review synthesizes papers discussing the techniques and materials involved in CAD/CAM-based construction of post and cores. It explores strategies for restoring endodontically treated teeth, highlighting both direct and indirect approaches. Commonly mentioned materials include zirconia, composite resin, and hybrid ceramics. Despite the limited literature on CAD/CAM post and core procedures, the review emphasizes the necessity of further research to assess long-term outcomes and efficacy. Additionally, it suggests including implications for future research and clinical recommendations to enhance the depth and practical relevance of the review.

Fracture resistance of endodontically treated teeth, restored with two post-core systems in different post space diameters (in vitro study)

BACKGROUND

Fracture resistance of post-core restoration depends on the design of the post, post diameter, post length, the type of adhesive cement used along with material of the core. Despite the different studies concerning the effect of post space diameter on the fracture resistance of endodontically treated teeth, more information regarding fracture resistance and the effect of different post space systems/materials and diameters is required.

AIM OF THE STUDY

This study aimed to evaluate fracture resistance of endodontically treated teeth, restored with two post-core systems in different post space diameters.

MATERIALS AND METHODS

Twenty freshly extracted maxillary central incisors were collected for this study. They were randomly divided into four groups according to intracanal post and its diameter. Group GN (glass-fiber post of 10-mm length and 1.3-mm diameter with composite core), group GW (glass-fiber post of 10-mm length and 1.75-mm diameter with composite core), group ZN (custom-made zirconia one-piece post-core of 10-mm length and 1.3-mm diameter) and group ZW(custom-made zirconia one-piece post-core of 10-mm length and 1.75-mm diameter). Fracture resistance for all samples was evaluated using the universal testing machine under a static load. The data was collected and statistically analyzed using One-Way ANOVA test. Modes of failure were assessed using stereomicroscope for each group.

RESULTS

The highest mean fracture resistance was recorded in group GW (638.7 ± 285.1 N), followed by group ZW (598.5 ± 127.6 N), then GN group (442.8 ± 65.38 N). The lowest mean fracture resistance was recorded in group ZN (435.3 ± 117.3 N). One-Way ANOVA test revealed that there was no statistically significant difference in fracture resistance values among the groups.

CONCLUSION

Post space diameter had an impact over the fracture resistance of endodontically treated teeth. Modulus of elasticity of post material had a major effect on the fracture resistance and mode of failure along with the restorability of the restored tooth. However, there was no statistically significant difference among the tested groups.

Fracture strength of endocrown maxillary restorations using different preparation designs and materials

PURPOSE

This study investigated the impact of preparation design and material types on fracture strength in maxillary premolars endocrowns after thermodynamic aging.

MATERIALS AND METHODS

Eighty two-rooted maxillary premolar crowns underwent endodontic treatment (N = 80, n = 10). The teeth were categorized into ten groups (4-mm deep with no intracanal extension lithium disilicate glass ceramic & multilayer zirconia endocrowns (LE0 & ZE0); 4-mm deep with 4-mm intracanal extension in one canal (LE1 & ZE1); 4-mm deep with 2-mm intracanal extensions in both canals (LE2 & ZE2); flat overlays with no endocore (LO & ZO); glass fiber reinforced post & core and crown (LC & ZC)). After cementation, all specimens were subjected to 1500 thermocycles and 1,200,000 chewing cycles with an axial occlusal load of 49 N. A static loading test was performed at a non-axial 45° loading using a universal testing machine and failure modes (Type I: restoration debonding; Type II: restoration fracture; Type III: restoration/tooth complex fracture above bone level; Type IV: restoration/tooth complex fracture below bone level) were evaluated using a stereoscope. Data were ananalzed using 2-way ANOVA and Tukey's tests (alpha = 0.05).

RESULTS

The endocrowns manufactured from multilayered zirconia and pressed lithium disilicate glass ceramic exhibited a fracture load ranging between 1334 ± 332 N and 756 ± 150 N, with ZC presenting the highest and LE2 the lowest values. The differences were not statistically significant (p > 0.05).

CONCLUSION

All endocrowns tested in this study performed similar considering the different designs and materials tested. The distribution of fracture modes did not differ significantly depending on the design of the restoration and the type of material used.

Current Insights on Fiber Posts: A Narrative Review of Laboratory and Clinical Studies

PURPOSE

The aim of this study was to review the literature related to the clinical performance and laboratory findings regarding fiber posts, as well as the cementation technique employed with their use.

MATERIALS AND METHODS

A literature search was performed using an electronic database, PubMed/Medline, between 2010 and 2023. The terms used were "intra coronal post, fiber post, post cementation, and post length". Titles and abstracts were initially screened, and a full-text assessment was conducted for those that fulfilled the inclusion criteria. The reference list of the collected papers was also screened for further relevant citations.

RESULTS

In this work, 135 potentially eligible studies were analyzed. Titles and abstracts of 90 studies followed the inclusion criteria and were selected for a full-text assessment, resulting in 50 studies selected. Moreover, additional studies from relevant citations were included, totaling 57 studies.

CONCLUSION

According to the laboratory and clinical studies revised, the survival rate between fiber and prefabricated and cast metal posts was similar, and failures were mainly related to the loss of retention. The intra-canal post length of less than two-thirds of the root length presented successful results when ferrule was present. Furthermore, the ferrule increased the longevity of teeth restored with fiber posts. Additionally, the use of a surface treatment protocol for fiber posts and the adhesive cementation technique both contributed to the clinical success and longevity of the intra-canal post.

Conventional cast vs. CAD/CAM post and core in a fully digital chairside workflow - An in vivo comparative study of accuracy of fit and feasibility of impression taking

OBJECTIVES

Clinical data for CAD/CAM post and cores (PC) is still scarce, even though developments in digital dentistry have improved dental treatment in many aspects. Therefore, the purpose of this in vivo study was to compare CAD/CAM PC fabricated in a fully digital chairside workflow to conventional cast PC (CPC) according to the accuracy of fit and the impression taking. The null hypothesis was that there is no significant difference between CAD/CAM PC and CPC.

METHODS

The study was conducted on 30 teeth in 25 patients receiving a CPC during their prosthetic treatment plan. On each tooth a conventional and a digital post impression were taken. Subsequently, one CPC following a conventional and one CAD/CAM PC following a digital workflow were fabricated. Both PC were tried-in intraorally and assessed according to a standardised evaluation sheet. The deviation between the two impression methods was evaluated by superimposing the datasets in a 3D analysis software. Statistical analysis for pairwise comparison was conducted according to Wilcoxon and median test with a significance level of p = 0.05.

RESULTS

CAD/CAM PC performed significantly better compared to CPC according to accuracy of fit (p = 0.022) and feasibility of impression taking (p < 0.001). The deviation between post impression methods increased from "coronal" to "apical". Between "coronal"/"middle" no significant difference (p = 0.158) was detected, whereas the pairwise comparison between the other measurement categories showed significant differences (p = 0.002, p < 0.001).

CONCLUSIONS

The null hypothesis was rejected since CAD/CAM PC performed significantly better and the deviation between the post impression methods showed significant differences.

CLINICAL SIGNIFICANCE

By using intraoral scanners (IOS) teeth can be restored with customised CAD/CAM PC in a single session. Within the limitations of this study the fully digital chairside workflow led to superior accuracy of fit of PC and higher feasibility of impression taking than the conventional workflow for CPC.

Comparative Stress Analysis of Custom-Made PEEK Dental Post-Cores versus Conventional Post-Cores in Incisor Restorations: A Finite Element Study

BACKGROUND We conducted a finite element analysis to evaluate stress levels in incisor teeth restored with custom polyetheretherketone (PEEK) dental post-cores compared to conventional post-cores. MATERIAL AND METHODS Using micro-computed tomography (μCT) imaging data, a 3D model of a maxillary incisor was created. For each material type, 3D mesh models were developed via specialized software. Two post diameters, 2.5 mm and 3.5 mm, were considered. Five different post materials were examined: Unfilled polyetheretherketone (Group UP); Glass fiber-reinforced polyetheretherketone (Group GP); Carbon fiber-reinforced polyetheretherketone (Group CP); Metal (Group M); and Zirconia ceramic (Group Z). Each model underwent finite element analysis, after which the von Mises equivalent stress values were determined. RESULTS For models involving both wide and narrow diameter posts across the crown, crown cement, post cement, and dentin, PEEK posts (Group UP, GP, and CP) exhibited higher von Mises stress values than Groups Z and M. However, the reverse trend was noticed in the post model itself. In the post cement model, stress values appeared similar only for the narrow-diameter post groups. Notably, results for Groups Z and M were largely consistent with each other. CONCLUSIONS PEEK posts, which have a lower modulus of elasticity, demonstrated different stress values when contrasted with zirconia and metal posts. As the post diameter expanded, the residual dentin decreased, influencing the stress values among various materials. Further in vitro and clinical examinations are essential to comprehensively understand PEEK posts.

Fibre-reinforced Cad/CAM post and cores: The new "gold standard" for anterior teeth with extensive coronal destruction?-A fully digital chairside workflow

Objectives

Since one-third of persons suffer a dental trauma, treatment of anterior teeth using post and core (PC) is becoming important. In teeth with extensive destruction, cast PC (CPC) remain the "gold standard", even though they lead to aesthetic impairment and have a mismatching elastic modulus to that of dentin. Prefabricated fibre-reinforced posts have elastic modulus similar to that of dentin but the accuracy of fit and mechanical stability are worse. This study was aimed to evaluate the deviation and mechanical performance of fibre-reinforced CAD/CAM PC (FRPC) fabricated in a fully digital chairside workflow, compared to those of CPC.

Methods

On 30 teeth, a PC preparation was conducted, and a conventional and digital post impression were taken with an intraoral scanner. Fifteen teeth each were treated with CPC and FRPC, respectively. The deviation was evaluated by superimposing the datasets of the digitalised stone models and digital post impressions. Decementation and root fracture during chewing simulation were analysed by microscopy and X-ray. Statistical analysis was performed by pairwise comparison and Kaplan-Meier analysis.

Results

The median deviation for the "coronal", "middle" and "apical" were 14.5, 18.0 and 113.7 μm, respectively. The pairwise comparison for "coronal"/"middle" showed no significance (p = 0.465), whereas that for "coronal"/"apical" and "middle"/"apical" showed highly significant differences (p < 0.001). After chewing simulation, five decementations and two root fractures were detected for CPC. For FRPC, neither decementation nor root fracture were documented.

Significance

Within the limitations of this study, FRPC performed significantly better than CPC.

Outcome of teeth restored with CAD/CAM zirconium dioxide post-cores: a retrospective study with a follow-up period of 3-6 years

Statement of problem

Computer aided design/computer aided manufacturing (CAD/CAM) zirconia post-cores is one of the options of post crown restoration materials due to their esthetic properties and superior mechanical strength. However, the clinical effect on aesthetics and strength properties is unclear due to the lack of results of their long-term follow-up.

Purpose

This retrospective clinical study aims to analyze the survival rate, clinical manifestations, and failure factors after CAD/CAM zirconia post-core restoration.

Material and methods

Clinical and radiographic examinations were performed on 342 patients with 400 teeth for 3–6 years postsurgical follow-up examination. The patients were all received CAD/CAM zirconia post-cores and all-ceramic crowns at the Department of Prosthodontics in the public hospital. The retrospective outcomes were conducted after zirconia post restoration, including survival rate by Kaplan–Meier analysis and findings of manifestations and failure factors. The effects of gender and dental position on survival rate were analyzed by Cox–Mantel Test.

Results

This study retrospectively evaluated 261 teeth from 229 patients with a 35% drop-out rate. The survival rate was 96.0%, and the success rate was 92.4%. According to the tooth position classification, the survival rate was 100% for 101 anterior teeth, 95.4% for 69 premolars, and 88.3% for 91 molars. According to gender, the survival rate of the male group was 92.3%, while that of the female group was 98.0%, with a significant difference (P < 0.01). The complications included crown fracture (1.9%) periapical inflammation (1.9%), crown debonding (1.1%), percussion abnormal (1.9%) and root fracture (0.8%).

Conclusions

Within the limitations of this retrospective study, it can be concluded that CAD/CAM zirconia post-cores are clinically promising. Compared with the posterior teeth, CAD/CAM zirconia post-cores are more suitable for anterior teeth.

Customized Post and Cores Fabricated with CAD/CAM Technology: A Literature Review

Post and core restorations are a widely accepted method to restore endodontically treated teeth with compromised tooth structure. The use of computerized technology to fabricate customized post and cores is a simple and quick alternative to conventional methods. A literature search was conducted, and a summary of articles describing fabrication techniques and materials used to fabricate post and cores with computer-aided design and computer-aided manufacturing (CAD/CAM) has been provided. Several techniques have been reported to restore endodontically treated teeth with CAD/CAM post and cores, including direct and indirect methods. Zirconia, composite resin, and hybrid ceramic were the most commonly reported materials. Published reports on CAD/CAM post and core are limited; however, further studies are needed to investigate the long-term outcome of this treatment.

Comparison of stress distribution between zirconia/alloy endocrown and CAD/CAM multi-piece zirconia post-crown: three-dimensional finite element analysis

OBJECTIVES

This study aimed to evaluate a digital multi-piece zirconia post-crown to restore a mandibular second molar with extensive coronal loss and limited restoration space, and to compare the stress distribution between endocrowns made of zirconia or alloy and CAD/CAM multi-piece zirconia post-crowns.

MATERIAL AND METHODS

Four three-dimensional finite element analysis models of a mandibular second molar with extensive coronal loss and limited restoration space were created as follows: (A) intact molar; (B) zirconia endocrown restored molar; (C) multi-piece post-crown restored-molar with tapered nail; (D) multi-piece post-crown restored molar with T-shaped nail. Models C and D were divided into two subgroups according to the material type: C1/D1, zirconia; C2/D2, NiCr alloy. The maximum modified von Mises failure criterion (mvM) stresses were calculated, and the stress distribution was recorded to analyze the effects of the restoration and material types on the biomechanical properties of dentin and prosthesis.

RESULTS

The maximum mvM stress of dentin in model B (33.80 MPa) was lower compared with models C (C1, 37.81 MPa; C2, 36.36 MPa) and D (D1, 36.34 MPa; D2, 34.97 MPa) under vertical load, but the opposite was observed under oblique load. The highest mvM stress was concentrated in the nail region located in the root canal, and the T-shaped nail values were greater than the tapered nail, whereas model D with T-shaped nail showed a lower mvM stress level in dentin compared with Model C with tapered nail.

CONCLUSIONS

The digital multi-piece zirconia post-crown is a potential approach to restore mandibular second molars with extensive coronal loss and limited restoration space.

CLINICAL RELEVANCE

The digital multi-piece zirconia post-crown has potential to restore mandibular second molars with extensive coronal loss and limited restoration space using an innovative approach.

Influence of Conventional Polymer, Hybrid Polymer and Zinc Phosphate Luting Agents on the Bond Strength of Customized Zirconia Post in Premolars-An In-Vitro Evaluation

The aim was to identify the influence of conventional polymeric resin based cement (RC), hybrid polymer modified glass ionomer (RMGIC) and Zinc phosphate cement (ZPC) on the pull out strength of the customized zirconia post in premolars. Access cavity and root canals were performed in sixty premolar teeth with the standardized crown down technique (ProTaper Universal, Dentsply). Post space impressions were scanned, and the pre-sintered Zenostar Zr Translucent blanks (Weiland Dental, Pforzheim) were milled with the Opera-system to form the post. All prepared specimens were divided equally in three groups based on the cement type employed for luting as follows: group A: ZPC; group B (GC Fuji PLUS Capsule): RMGIC; group C (and RC (3M RelyX ARC). Ten specimens in each group were thermocycled (TC) at 5 and 55 °C in distilled water baths (40,000 cycles). Pull out bond strength was assessed using a universal testing machine at 0.5 mm/min. The means and standard deviations were compared using ANOVA and Tukey Kramer multiple comparisons tests. A significant difference among the cement groups as well as between TC and non-thermocycled (NTC) groups (p < 0.05) was observed. The highest tensile stress was demonstrated among group C (Resin, 69.89 ± 4.81 (NTC), 64.06 ± 4.36 (TC)) with the least in group A, (zinc phosphate, 43.66 ± 5.02 (NTC), 37.70 ± 5.10 (TC)) for both groups. Group A presented with 100% adhesive bond failures, followed by 80% in group C and 70% in group B, respectively. A similar outcome was observed in the TC group for the cement; however, unlike the NTC group, the TC group showed more cohesive failures compared to the NTC mixed failure. Dual cure polymer based cement demonstrated higher bond strength and efficient adhesive bonding of the customized Zr post with root dentine compared to zinc phosphate (non-polymeric) and RMGIC (hybrid polymer). Thermocycling compromised Zr post adhesive bonding to root dentin.

Structural integrity of extracted teeth restored using three different post-and-core systems: An in vitro comparative study

Aim

The objective of the study was to assess the in vitro fracture resistance of endodontically treated teeth restored using different post-and-core materials.

Materials and methods

Extracted human mandibular premolars (n = 36) were extracted teeth and equally distributed into four (4) treatment groups: cast metal post-and-core, milled zirconia post-and-core, pre-fabricated post with composite resin core and control group. These samples were then each subjected to the load to fracture test using a universal testing machine. Fracture resistance data were compared among groups by analysis of variance and Fisher’s exact test.

Results

The highest mean fracture resistance value was observed in the zirconia post-and-core treatment group (1567.26 ± 317.66 N), followed by the cast metal (1355.92 ± 621.56 N) and lastly the pre-fabricated post with composite resin core (725.67 ± 251.05 N) treatment group. Differences among groups were not statistically significantly different (P = 3.77).

Conclusion

Endodontically treated mandibular premolars with a zirconia post-and-core system exhibited the highest robustness against structural failure based on its mean fracture resistance value. In addition, extracted teeth restored with cast post-and-core resisted a greater stress load than those restored with fiber-reinforced posts. Zirconia showed a more favorable fracture mode than the other restorations.

Fracture strength of endodontically treated premolars restored with different post systems and metal-ceramic or monolithic zirconia crowns

The purpose of this study was to investigate the fracture strength of endodontically treated human maxillary premolars (ETP) restored with posts and metal ceramic (MC) or monolithic zirconia (MZ) crowns. Sixty ETP were randomly divided into 3 groups. Teeth in control group (C) received a resin filling. ETP in the MC group were restored with prefabricated metal posts, composite cores and MC crowns while in the MZ group with glass-fiber posts, composite cores and MZ crowns. Half of the specimens were loaded at a 135° angle and half under axial loading until fracture. The fracture modes were divided in repairable and irreparable using optical microscopy. Mean fracture strength was significantly higher for MC than for MZ crowns and control group only under axial loading. The distribution of repairable and irreparable failures presented no significant differences. Crown placement significantly improved the fracture strength of ETP irrespectively of post and crown type.

Evaluation of stress distribution in an endodontically treated tooth restored with four different post systems and two different crowns- A finite element analysis

Aim and objectives

The study evaluated the stress distribution in an endodontically treated tooth with four different post systems and restored with two different prosthetic crown materials using finite element analysis (FEA).

Material and methods

A total of eight 3D FEA models of maxillary central incisor were created and divided into two groups; group porcelain fused to metal (PFM) crown (n = 4) and group PEEK crown (n = 4). The endodontically treated tooth was restored using four different post materials such as fiber-reinforced composite (FRC), carbon fiber-reinforced polyetheretherketone (CFR-PEEK), glass fiber reinforced polyetheretherketone (GFR-PEEK) and polyetherketoneketone (PEKK) and composite resin core. A static load of 100 N was applied and von Mises stress was calculated. The stress ratio in dentin was analyzed by using the Mohr-Coulomb failure theory.

Results

In dentin, under the applied forces for both, PFM group and PEEK group, it was observed that CFR-PEEK post exhibited minimum von Mises stress while PEKK post exhibited maximum von Mises stress values. The result obtained showed that low stresses were detected using CFR-PEEK post than FRC, GFR-PEEK, and PEKK posts.

Conclusion

Stress observed in dentin, when CFR-PEEK post was used was lesser in comparison to the FRC post. It was noted that PEEK crown and the PFM crown showed similar effect in dentin in stress generation. Hence, PEEK crown can be used as an alternative to the PFM crown.

Fracture Resistance and Failure Mode of Custom-made Post-and-cores of Polyetheretherketone and Nano-ceramic Composite

Clinical Relevance

Custom-made post-and-cores of polyetheretherketone (PEEK) and nano-ceramic composite showed good fracture resistance and failure mode. Clinicians should be aware that these materials might be an efficient alternative for post-and-cores, because they promote esthetics while reducing the risk of root fractures.

SUMMARY

Purpose: The purpose of this study was to evaluate the fracture resistance and failure mode of custom-made post-and-cores manufactured with different esthetic materials.

Methods and Materials: A total of 48 mandibular premolar extracted teeth were selected, endodontically treated, and prepared to receive the posts. Specimens were randomly divided into four groups (n=12/group): group 1, polyetheretherketone (PEEK, Degos; G1); group 2, nano-ceramic composite (Lava Ultimate, 3M ESPE; G2); group 3, cast metal post (NiCr alloy, control; G3); group 4, fiberglass post (Whitepost, FGM, control; G4) customized with a nano-hybrid resin composite (Z250, 3M ESPE). Experimental post-and-cores (G1 and G2) were manufactured with a computer-aided design/computer-aided manufacturing system. All posts were cemented with self-adhesive resin cement (Rely X U200, 3M ESPE), and specimens were stored in distilled water at 37°C for 60 days. A universal testing machine was used to measure the fracture resistance (0.5 mm/min at an angle of 45° to the long axis of the tooth). Fractures were classified as repairable or catastrophic. One-way analysis of variance with Tukey post hoc and χ2 tests for independence and Bonferroni adjustments were applied (α=0.05).

Results: The fracture resistance values (mean ± SD, in newtons) were 379.4 ± 119.8 (G1), 506.4 ± 138 (G2), 939.6 ± 146.5 (G3), and 449.6 ± 66.5 (G4). Only G3 exhibited a significant difference (p&lt;0.05). The χ2 test showed an association between failure mode and post-and-core material [χ2(3) = 23.65; p&lt;0.001]. After Bonferroni adjustment, only G3 presented a higher than expected incidence of catastrophic failures (p&lt;0.001). In the remaining groups, most failures were repairable and related to debonding.

Conclusions: Customized post-and-cores of PEEK and nano-ceramic composites exhibited good mechanical performance. Their fracture resistance was comparable to that observed for fiberglass customized posts, yet lower than that for cast metal posts. For PEEK post-and-cores, in particular, additional studies are needed to improve adhesiveness and reduce the risk of debonding.

A comparison of the fracture resistance of premolars without a ferrule with different post systems

STATEMENT OF PROBLEM

Which type of post improves the performance of endodontically treated mandibular premolars without a ferrule remains unclear.

PURPOSE

The purpose of this in vitro study was to compare the restoration of endodontically treated mandibular premolars without a ferrule by using different post systems.

MATERIAL AND METHODS

Thirty extracted mandibular premolars were endodontically treated, and their crowns removed. They were divided into 3 groups with different post systems (n=10): zirconia ceramic posts (ZRPs), fiber posts (FPs), and bundled glass fiber-reinforced composite resin posts (GTPs). After post placement and core fabrication, computer-aided design and computer-aided manufacture (CAD-CAM) lithium disilicate crowns were cemented. The specimens were subjected to thermocycling and mastication simulation before a fracture test in a universal testing machine. The maximum load at which the fracture occurred was recorded, and the fractured specimens were examined by using an optical microscope. The data were analyzed for statistical differences with a 1-way ANOVA and the Tukey honestly significant difference post hoc test (α=.05).

RESULTS

No statistically significant difference in fracture strength was found among the groups (P=.970). From the light microscopy examination, catastrophic failure was observed in all specimens, and there was no failure of the ceramic crowns.

CONCLUSIONS

Based on the findings of this in vitro study, the choice of post material with a low or high modulus of elasticity did not prevent catastrophic failures in endodontically treated teeth without a ferrule.

Fracture Resistance of Tilted Premolars Restored with Different Post-Core Systems

Aims and Objective:

To assess the effect of root tilt on the fracture resistance and failure pattern of endodontically-treated premolars restored with different post-core systems.

Materials and Methods:

Ninety endodontically-treated premolars were mounted in acrylic blocks with 0°, 12°, and 24° axial root tilt. Teeth in each group were restored in three subgroups with cast post-core, readymade metal posts and composite cores, and fiber post and composite cores. Crowns of all teeth were prepared coinciding with the long axis of the acrylic blocks to receive all-ceramic crowns. All restored teeth were stressed to record the maximum load at failure and the associated failure pattern. The collected data were statistically analyzed using two-way ANOVA, Tukey's, and Kruskal–Wallis tests at α = 0.05 on past software to detect any differences between subgroups.

Results:

Analysis of the collected data indicated significant differences between the tested subgroups (ANOVA, P = 3.86). Further analysis showed significant difference between all test subgroups and the control (Tukey's, P < 0.05). In general, teeth with 0° tilt seemed more resistant to fracture than the tilted ones. For all groups, teeth restored with fiber post and composite cores (SG3) were more resistant to fracture compared to other post-core systems (SG1 and SG2) (Tukey's, P < 0.05). The root fracture was the most commonly seen mode of failure.

Conclusions:

Root tilting usually affects the fracture resistance of teeth restored with post-core systems. The fiber post and composite cores seemed to be the best choice to restore teeth with different root tilting possibilities.