Influence of Ferrule, Post System, and Length on Biomechanical Behavior of Endodontically Treated Anterior Teeth

The effect of ferrule and core material on fracture resistance of endodontically treated anterior teeth restored with ceramic crowns after artificial aging

OBJECTIVES

To assess the influence of ferrule and core type on the fracture strength of endodontically treated anterior teeth (ETAT) and identify the failure mode type and distribution across different core types and ferrule conditions.

METHODS

Sixty extracted human central incisors were endodontically treated, decoronated and divided into two main groups (F=with ferrule, NF=no ferrule). Each main group was further subdivided into three subgroups according to the core material used: direct composite cores (DC), Ribbond fibre-reinforced composite cores (RIB-DC), and glass fibre post (GFP) with direct composite cores (GFP-DC). All specimens received E.max crowns and underwent thermal cycling and cyclic loading. Subsequently, the fracture resistance was tested with static loads applied to the crown restoration. Two-Way ANOVA and Chi square tests identified significant differences among the groups (p < 0.05).

RESULTS

The means and standard deviations (SD) of fracture loads in Newtons (N) for specimens in the F subgroups were RIB-DC: 465.0 (104.20), GFP-DC: 367.6 (79.59), DC: 275.8 (68.48), and in NF subgroups were RIB-DC: 110.8 (24.33), GFP-DC: 95.6 (25.47), DC: 67.4 (7.46). Specimens with ferrule yielded significantly higher fracture loads than those without ferrule (p = 0.0054). In the F groups, fracture loads of specimens with RIB-DC cores were significantly higher than those with GFP-DC (p = 0.0019) and those with DC (p = 0.0001). Moreover, fracture loads for the GFP-DC were significantly higher than those for the DC (p = 0.0026). The GFP-DC specimens showed the highest incidence of catastrophic failures (p = 0.0420).

CONCLUSIONS

Using fibre-reinforced composite (FRC) cores significantly increased fracture resistance in ETAT with ferrule. The failure modes repairable and possibly repairable were dominant in most specimens.

CLINICAL SIGNIFICANCE

When restoring ETAT with insufficient coronal tooth structure, preserving 2 mm of tooth structure ferrule and preparing cores with FRC can increase fracture resistance and reduce the incidence of non-repairable catastrophic fractures of teeth.

Ultrasonic activation of adhesive systems increases bond strength and intratubular penetration of resin cement in root dentin subjected to radiation therapy

OBJECTIVE

This study aimed to evaluate the effect of ultrasonic activation of etch-and-rinse and self-etch adhesive systems on the bond strength of resin cement to irradiated root dentin.

MATERIALS AND METHODS

Eighty human maxillary anterior teeth were distributed into 8 groups (n = 10), according to the type of adhesive system used (etch-and-rinse and self-etch), the ultrasonic activation of the adhesive systems, and the dentin condition (irradiated or non-irradiated - 70 Gy). Endodontic treatment was performed followed by fiberglass post-space preparation. After fiberglass posts' luting, the roots were transversely sectioned on dentin discs and submitted to the push-out bond strength test (0.5 mm/min). The fractured specimens were analyzed under a stereomicroscope and Scanning Electron Microscope (SEM) for failure mode classification. One of the dentin discs was analyzed under SEM to evaluate the characteristics of the adhesive interface.

RESULTS

Irradiated specimens had lower bond strength than non-irradiated specimens (P < 0.0001). Ultrasonic activation of both adhesive systems increased the bond strength of the resin cement to irradiated dentin (P < 0.0001). Radiotherapy significantly affected the failure mode in the middle (P = 0.024) and apical thirds (P = 0.032) (adhesive failure).

CONCLUSION

Non-irradiated specimens had a more homogeneous adhesive interface. When ultrasonically activated, both adhesive systems showed a greater number of resinous tags, regardless of the dentin condition.

CLINICAL RELEVANCE

Ultrasonic activation of adhesive systems is a feasible strategy to enhance fiberglass posts retention in oncological patients.

Biomechanical impact of labiolingual diameter on endodontically treated anterior teeth with crown restoration under occlusal loading

OBJECTIVE

To evaluate the effect of the labiolingual diameter and construction of an endodontically treated (ET) anterior tooth with crown restoration on stress distribution and biomechanical safety under occlusal loading.

METHODOLOGY

Three-dimensional finite element models were generated for maxillary central incisors with all-ceramic crown restorations. The labiolingual diameters of the tooth, defined as the horizontal distance between the protrusion of the labial and lingual surfaces, were changed as follows: (D1) 6.85 mm, (D2) 6.35 mm, and (D3) 5.85 mm. The model was constructed as follows: (S0) vital pulp tooth; (S1) ET tooth; (S2) ET tooth with a 2 mm ferrule, restored with a fiber post and composite resin core; (S3) ET tooth without a ferrule, restored with a fiber post and composite resin core. A total of 12 models were developed. In total, two force loads (100 N) were applied to the crown's incisal edge and palatal surface at a 45° oblique angle to the longitudinal axis of the teeth. The Von Mises stress distribution and maximum stress of the models were analyzed.

RESULTS

Regardless of the loading location, stress concentration and maximum stress (34.07~66.78MPa) in all models occurred in the labial cervical 1/3 of each root. Both labiolingual diameter and construction influenced the maximum stress of the residual tooth tissue, with the impact of the labiolingual diameter being greater. A reduction in labiolingual diameter led to increased maximum stress throughout the tooth. The ferrule reduced the maximum stress of the core of S2 models (7.15~10.69 MPa), which is lower compared with that of S3 models (19.45~43.67 MPa).

CONCLUSION

The labiolingual diameter exerts a greater impact on the biomechanical characteristics of ET anterior teeth with crown restoration, surpassing the influence of the construction. The ferrule can reduce the maximum stress of the core and maintain the uniformity of stress distribution.

7.5- to 11.5-Year Follow-up of the Fracture Removal Treatment for Propagated Crown Fractures

A definitive method to predictably treat propagated longitudinal fractures remains elusive. A proof-of-concept case report series documenting nonsurgical removal of propagated longitudinal fractures has shown up to 5 years of clinical and radiographic success. This installment of the case report series further documents these teeth with 7.5-year to 11.5-year recall evaluations. Three previously reported cases of fracture removal were followed at 11.5 years (1 case), 9.75 years (1 case), and 7.5 years (1 case) after treatment to determine the long-term clinical and radiographic success of nonsurgical fracture removal. This case report series has demonstrated 10-year success (clinically and radiographically) for the treatment of progressive longitudinal fractures. Propagated fractures can be nonsurgically removed and the iatrogenic defect repaired with long-term success providing a foundation for treatment and further investigation.

Stress analysis of horizontal mid-root fracture managed with different intraradicular fixation protocols: A 3D-finite element study

The current study evaluated the stress distribution in a maxillary central incisor with mid-root fracture after splinting with different intra-radicular posts using 3D-finite element analysis (FEA). Five 3D-FEA models were constructed. Model 1 was an intact tooth with no fracture, Model 2: A tooth with a horizontal mid-root fracture, with no treatment. Model 3: Same as model 2, and intraradicular splinting using fiber post. Model 4: Same as model 2 and intra-radicular splinting using Protaper Gold file F3. Model 5: Same as model 2, and with intraradicular splinting with Ribbond. The FEA of all models was done to obtain the maximum Von-Mises stress in the root canal space, the dentin, the periodontal ligament, and the bone. The highest Von Mises stresses for the root canal space and the dentin were found in Model 3, followed by models 4, 5, and 2, and least in Model 1. The Von Mises stress of the periodontal ligament was the least in model 1. The Von Mises stress of bone was higher in all experimental models than in the baseline model. The results suggest that in cases where intra-radicular splinting is indicated, fiber posts and Ribbond are better alternatives to endodontic files due to the lower stresses exerted.

How long must a post be? A retrospective survival analysis on a large cohort with long follow-ups

OBJECTIVES

Post and core (PC) is frequently used, but clinical evidence concerning how long a post must be is scarce. Recommendations in dental literature range from half of the root which should be incorporated, to post space preparations conducted as deep as possible increasing the risk for root perforation thus tooth loss. Therefore, the aim of this retrospective survival analysis is to evaluate the post length as well as the post-clinical crown ratio on a large patient cohort with long follow-ups.

MATERIALS AND METHODS

Overall 1026 PC in 731 patients could be included in this study (2004-2023). The files were analysed due to the parameters post length and post-clinical crown ratio on X-Ray. Furthermore, the influence of the type of covering prosthetic restoration, location, type of tooth, luting material, PC material, bone attachment and therapist was evaluated. The statistical analysis was assessed using Kaplan-Meier (univariate influences) and Cox regression (multifactorial influences).

RESULTS

Survival until extraction as well as decementation was significantly influenced by bone attachment and covering prosthetic restoration. Posts reaching the middle third of the root showed highly significant (p < 0.001) better survival probabilities than those reaching the coronal or apical third. Regarding the post-clinical crown ratio, no significant difference was found for post = crown/post > crown, whereas post

CONCLUSIONS

The post space preparation should not be extended over the middle third of the root, but has to be deep enough to ensure that the post is at least as long as the clinical crown.

CLINICAL SIGNIFICANCE

Against the background of the large sample size and the long follow-ups, the results of this retrospective survival analysis are suitable to give general recommendations regarding how long a post has to be in order to ensure the best survival probability for PC treatment.

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Key Words

• Cox regression
• Kaplan-Meier analysis
• Post length
• Post-clinical crown ratio
• Survival time

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MESH Headings

• Humans
• Retrospective Studies
• Follow-Up Studies
• Post and Core Technique
• Dental Restoration Failure
• Crowns
• Survival Analysis

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Affiliation(s)

Sarah Marie Reich Justus Liebig University, Dental Clinic - Department of Prosthodontics, Schlangenzahl 14, 35392 Giessen, Germany
Kay-Arne Walther Justus Liebig University, Dental Clinic - Department of Prosthodontics, Schlangenzahl 14, 35392 Giessen, Germany
Bernd Wöstmann Justus Liebig University, Dental Clinic - Department of Prosthodontics, Schlangenzahl 14, 35392 Giessen, Germany
Peter Rehmann Justus Liebig University, Dental Clinic - Department of Prosthodontics, Schlangenzahl 14, 35392 Giessen, Germany
Jonas Adrian Helmut Vogler Justus Liebig University, Dental Clinic - Department of Prosthodontics, Schlangenzahl 14, 35392 Giessen, Germany.

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Scientific mapping of hotspots and trends of post and core research based on the Web of Science: A bibliometric analysis

Statement of problem

Post and core (PC) restoration has been widely used to restore endodontically treated teeth. Nevertheless, bibliometric studies focusing on PC research are lacking.

Purpose

The purpose of this bibliometric analysis was to review the general situation and determine the research direction of PC restoration by means of visualization, including the time development, countries, institutions, authors, journals, research categories, and the information of references with the strongest citation burst.

Material and methods

The search was carried out within the topic field of the Web of Science (WoS) database. CiteSpace, VOSviewer, and R language were used to analyze the literature. Bibliometric indicators in terms of title, keyword, reference, publication time, institution, country and citation information were analyzed.

Results

Between 1966 and 2022, dental research on PC trended upward, especially in 2011 and up to 2022. Scholars in Brazil, the United States, and Italy actively participated in PC research. The country that published the most was Brazil. Italy both ranked first in the H-index and average citations per item and had cooperative relations with several countries. The United States ranked first in the world in total citation count. The University of Siena published the most articles. The Journal of Prosthetic Dentistry (JPD) was the major contributing journal. The top three authors in this field were Ferrari M, Goracci C and Naumann M. The largest cooperative network of authors consisted of four Italian scholars. There were six main clusters of research topics on PC through CiteSpace co-citations. In addition, CiteSpace co-citations, CiteSpace Burst detection and VOSviewer keyword analysis showed the most important research interests, such as bond strength, fiber post, fracture resistance, and finite element analysis. Photodynamic therapy is the latest research hotspot. Finally, there were the top 25 references with the strongest citation bursts, which mainly focused on four aspects, namely, studies related to fiber posts, PC bonding strength, finite element analysis, and residual teeth and the ferrule effect.

Conclusions

This bibliometric analysis provides a comprehensive overview of PC research, including the research time, country, institution, author, journal, article clustering, article keywords, and important literature analysis, so that researchers can have a clear understanding of the research situation in this field.

Comparative analysis of the biomechanical behavior of the maxillary central incisors restored with glass fiber post and cast metal post and core submitted to orthodontic forces: A study with finite elements

INTRODUCTION

Different types of intraradicular restorations and their insertion have an impact on teeth biomechanics. This study aimed to analyze the biomechanical behavior of maxillary central incisors restored with glass fiber post (GFP) and cast metal post and core (CMP) subjected to buccolingual and mesiodistal orthodontic forces using the finite element method.

METHODS

Two models of the maxillary central incisor with periodontal ligament, cortical bone, and trabecular bone were made. One of the models included intraradicular restoration with GFP, whereas, in the other, the incisor was restored with CMP. After creating the tridimensional mesh of finite elements, applying 2 orthodontic forces were simulated: 65 g of buccolingual force and 70 g of mesiodistal force. The forces were applied parallel to the palatal plane in the region of the bracket slot, located 4 mm to the incisal edge.

RESULTS

The maximum stresses generated in the GFP-restored root were 3.642 × 10-1 MPa and 4.755 × 10-1 MPa from the buccolingual and mesiodistal forces, respectively. Likewise, the stresses in the CMP restored root were 2.777 × 10-1MPa and 3.826 × 10-1MPa. The radicular area with higher stress on both models was located in the cervical third: on the buccal surface when the buccolingual force was applied and on the mesial surface when the mesiodistal force was applied. The highest stress levels were found on the CMP structure.

CONCLUSIONS

The incisor restored with cast metal post revealed lower stress values transferred to the root than the one restored with GFP. The stresses on the structure of the GFP were lower and more homogeneous than the ones found on the cast metal post. The difference among the stress values in the materials is within a safe margin for using both materials in relation to orthodontic forces.

Mechanical behavior of endodontically treated teeth: A three-dimensional finite element analysis using displacement vector

PURPOSE

This study aimed to analyze the effects of core materials, remaining tooth structures, and interfacial bonding on stress distribution in endodontically treated teeth using finite element analysis (FEA).

MATERIALS AND METHODS

Three-dimensional FEA was conducted using a reverse engineering technique based on maxillary premolars scanned by micro-computed tomography. Six models were generated with or without ferrules and with one of the following three abutment systems: metal core, resin core, or resin core with fiber posts. In each model, bonding and debonding were assumed in the dentin and surrounding structures: bonded and debonded models. The maximum principal stress values were recorded, and stress distribution of the entire restored teeth and dentin was generated. Furthermore, the distribution of the displacement vector of the debonded models was generated.

RESULTS

In comparing the bonded and debonded models, the debonded models showed larger values for tensile stresses than those in bonded models for all abutment models. The models without ferrules rotated around the center of the abutment, whereas those with ferrules did not show remarkable displacement in the analysis.

CONCLUSION

FEA assuming fracture of adhesive interface proved to be an effective method to clarify the significance of ferrules. It prevents stress concentration in dentin by reducing the rotation of the abutment, even when the adhesive fails.

Evaluation of Er:YAG and Er,Cr:YSGG lasers on intraradicular bonding using modified glass fiber tips

The aim of this study was to determine whether erbium laser irradiation emitted by modified glass-fiber tips would improve the intraradicular bonding of fiber posts. Forty human canines were endodontically treated and prepared for fiber-post placement. Roots were divided into five groups (n=8); according to the laser-tip combinations (2,940 nm Er:YAG and 2,780 nm Er,Cr:YSGG). Non-irradiated root canals served as control. Posts were cemented with self-adhesive resin cement and subjected to push-out test. Failure modes were characterized, and intraradicular bonded interfaces were analyzed by SEM and submitted to nanoleakage evaluation. Data were analyzed by two-way ANOVA and Tukey test (α=0.05). No significant differences were observed in cervical and middle sections (p>0.05), while significantly higher bond strengths were observed in apical sections (p<0.05). Laser irradiation reduced adhesive failures, cement-dentin gap formation, and nanoleakage apically. Laser-irradiation protocols employing end- or radial-firing tips improved bonding to apical intraradicular dentin contributing to more uniform bonded interfaces.

Effect of silicone-based sealers on fiber post retention: An in vitro study

PURPOSE

The effect of a silicone-based sealer on fiber post retention has not been the subject of research and remains unclear. This study aimed to evaluate and compare the impact of a silicone-based sealer and an epoxy resin sealer on fiber post retention.

MATERIAL AND METHODS

Forty extracted human mandibular premolars that were caries-free, single-rooted, and possessed straight single canals were the specimens of the present study. Teeth were randomly divided into two groups (n = 20 each). All specimens were prepared using gutta-percha. The sealer used in the first group was Guttaflow 2, while AH26 was used in the second group. Post spaces were prepared immediately after obturation for each specimen. Prefabricated fiber posts were luted in both groups using a self-adhesive resin cement (RelyX-U200). Each specimen was vertically secured using a universal testing machine (Instron Corp.) and a constant pull-out force at a loading rate of 0.5 mm/min was applied until the point of dislodgement. Data were analyzed using t-tests.

RESULTS

A significant difference was found between the mean of maximum loads of the silicone-based sealer and epoxy resin sealer groups (p = 0.0001). The mean maximum load for the epoxy resin sealer group was 194.62 N, while that for the silicone-based sealer group was 111.64 N.

CONCLUSION

Fiber post retention in teeth obturated using silicone-based sealer was inferior to that in teeth obturated with epoxy resin sealer. Therefore, the sealer used during obturation can significantly affect fiber post retention.

Survival of severely compromised endodontically treated teeth restored with or without a fiber glass post

OBJECTIVE

The use of a fiber glass post (FGP) type and choice of FGP diameter to restore endodontically treated incisors without ferrule is controversial. This study evaluated survival rate and failure mode of severely compromised central incisors without ferrule rehabilitated using resin-based composite (RBC) with or without FGP with different diameters.

METHODOLOGY

A total of 60 decoronated bovine incisors without a ferrule were endodontically treated and prepared for 1.4, 1.6, and 1.8 mm diameter FGPs (Whitepost System DC 0.5, Fit 0.4, and DCE 0.5; FGM). Half of the teeth received FGPs cemented using dual-cure resin cement (Allcem Core; FGM), the other half were filled using only bulk-fill RBC (OPUS Bulk Fill; FGM). The crowns were directly restored with RBC. The roots were embedded in polystyrene resin and the periodontal ligament was simulated with polyether impression material. Fatigue testing was conducted under 5 Hz cyclic loading at 30 degrees to the incisal edge, beginning at 50 N (5,000 cycles) as a warmup. After, the load was increased 100 N every 15,000 cycles until fracture occurred. All specimens were subjected to transillumination, micro-CT analysis, and digital radiography before and after fatigue testing. Fracture mode was classified according to severity and repair potential. Data were analyzed with Kaplan-Meier survival test and post hoc log-rank test (α=0.05) for pairwise comparisons.

RESULTS

Using FGP significantly increased the number of cycles to failure, irrespective of FGP diameters (p=0.001). The FGP diameters had no statistically significant effect on cycles to failure or failure mode.

CONCLUSION

Using FGP without ferrule improved survival rate of structurally severely compromised central incisors compared with rehabilitation without FGP. The diameter of the FGPs had no effect on the survival rate and failure mode.

Comparative effectiveness of fiber and metal posts in the restoration of endodontically treated teeth: A systematic review with network meta-analysis

STATEMENT OF PROBLEM

Different varieties of fiber and metal intraradicular posts have been used for the restoration of endodontically treated teeth with insufficient sound tooth structure. Evidence on the comparative efficacy of posts in a clinical setting is insufficient to provide clear clinical guidelines and recommendations.

PURPOSE

The purpose of this systematic review with network meta-analysis was to assess the comparative efficacy of fiber and metal posts used for the restoration of endodontically treated teeth.

MATERIAL AND METHODS

A search was conducted for trials published in Medline, Scopus, PubMed, and Cochrane Central Register of Controlled Trials from inception until November 2022. The study was registered with the International Prospective Register of Systematic Reviews (PROSPERO) (CRD42022384340). A network meta-analysis was performed on data from randomized controlled trials that assessed the comparative efficacy of fiber posts and metal posts for the restoration of endodontically treated teeth. Subgroup analyses were performed to compare all the varieties of fiber and metal posts. The types of posts were ranked according to their efficacy using the Surface Under the Cumulative Ranking (SUCRA) system. The Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) approach was used to assess the level of certainty of evidence.

RESULTS

Twenty-five articles were included in the quantitative analysis. Fiber posts (RR=0.15 [95% CI: 0.06, 0.33]) significantly prevented tooth fracture as compared with no posts. Prefabricated carbon fiber posts (RR=0.06 [95% CI: 0, 0.54]) ranked highest followed by custom glass fiber posts (RR=0.15 [95% CI: 0.04, 0.52]) and prefabricated glass fiber posts (RR=0.22 [95% CI: 0.07, 0.62]) in the outcome of tooth fracture. Metal posts (RR=0.24 [95% CI: 0.12, 0.46]) ranked higher than fiber posts (RR=0.39 [95% CI: 0.27, 0.56]) in the outcome of debonding. Custom gold alloy posts (RR=0.12 [95% CI: 0.03, 0.48]), prefabricated gold alloy posts (RR=0.04 [95% CI: 0.00, 0.87]), and prefabricated titanium posts (RR=0.21 [95% CI: 0.10, 0.45]) had higher rankings in the outcome of debonding or loss of retention of a post followed by custom glass fiber posts (RR=0.37 [95% CI: 0.21, 0.63]) and prefabricated glass fiber posts (RR=0.38 [95%CI: 0.25, 0.58]). Prefabricated glass fiber posts (RR=0.40 [95% CI: 0.20, 0.81]) had statistically significant differences in the outcome of secondary caries. The GRADE approach determined a moderate level of certainty of evidence.

CONCLUSIONS

The use of a fiber post when indicated results in reduced risk of tooth fracture as compared with no post. Prefabricated carbon fiber posts, prefabricated glass fiber posts, and custom glass fiber posts reveal a lower risk of tooth fracture. Overall, the use of prefabricated glass fiber posts had a lower risk of tooth fracture, debonding, and secondary caries. However, more trials with longer follow-up periods are recommended to enhance the certainty of evidence.

Effect of the timing of radiation therapy on the push-out strength of resin cement to root dentine

This study investigated the effect of radiation timing on the bond strength of resin cement to intraradicular dentine. Fifty human teeth were distributed into 5 groups (n = 10): Control (nonirradiated teeth), Before-RCT (teeth irradiated before root canal treatment), After-CH (teeth irradiated after canal preparation and placement of calcium hydroxide intracanal dressing), After-RCT (teeth irradiated after completion of root canal treatment) and After-FPL (teeth irradiated after luting of a glass fibre post). Each tooth received 70 Gy irradiation. The roots were sectioned for push-out strength testing. After-RCT and After-FPL groups had significantly lower push-out strength than the control at the middle third (p < 0.05). Control and After-CH groups had a higher percentage of cohesive dentine failure. Radiotherapy after root canal obturation and post luting adversely affected the adhesiveness of resin cement to intraradicular dentine. Teeth irradiated before root canal treatment and after placement of calcium hydroxide had the best performance.

The Effect of Remaining Coronal Tissue Height on the Fracture Strength of Over-Flared Endodontically Treated Central Incisors Restored Using a Multipost Approach

Objectives

This study aimed to examine the effect of remaining coronal tissue height on the fracture strength of over-flared endodontically treated central incisors restored with multiple prefabricated fiberglass posts using the multipost approach.

Materials and Methods

A total of 40 human central maxillary incisors were examined in this study. The samples were assigned to five groups (n = 8) based on the height of the remaining coronal tissue: with no remaining coronal tissue, 1-mm coronal tissue height (CTH1), 2-mm coronal tissue height, 3-mm coronal tissue height (CTH3), and one intact tooth (IT) group. Following endodontic treatment of an over-flared canal, the postspace depth was 10 mm, and the residual dentin thickness was 1 mm. Two prefabricated fiberglass posts were cemented into the root canal, adopting a multipost approach. The static load was applied at 0.5 mm/min and 135° concerning the tooth's longitudinal axis until a fracture occurred. One-way analysis of variance and the post hoc Tukey's test were performed to analyze the data at a significance level of p < 0.05.

Results

The maximum fracture strength was recorded for IT (control group), while the minimum fracture strength was found for teeth with a coronal tissue height of 1 mm. The differences between IT group and other groups (p < 0.05), as well as the differences between the group with CTH3 and groups without coronal tissue and CTH1, were significant.

Conclusion

In sum, an increase in the height of the remaining coronal tissue (≥3 mm) significantly increased the fracture strength of over-flared endodontically treated central incisors after restoration with prefabricated fiberglass posts by adopting a multipost approach.

Finite element analysis of endodontically treated premolars without ferrule restored with one-piece glass fiber post and core in combination with different inner shoulder retention form systems

OBJECTIVE

The current study was performed to explore the impact of post materials as well as the inner shoulder retention form (ISRF) design on the biomechanical behavior of endodontically treated premolars without ferrule restoration using a method of mathematical three-dimensional (3D) finite element analysis (FEA).

METHODS

Based on the tooth anatomy and our previous research, eight mandibular second premolar FEA models representing different restorative situations were built: teeth with (a) 2.0 mm height ferrule (DF), (b) no ferrule (NF), (c) 0.5 mm width and 0.5 mm depth ISRF (ISRFW0.5D0.5), (d) 0.5 mm width and 1.0 mm depth ISRF (ISRFW0.5D1.0), (e) 0.5 mm width and 1.5 mm depth ISRF (ISRFW0.5D1.5), (f) 1.0 mm width and 0.5 mm depth ISRF (ISRFW1.0D0.5), (g) 1.0 mm width and 1.0 mm depth ISRF (ISRFW1.0D1.0), (h) 1.0 mm width and 1.5 mm depth ISRF (ISRFW1.0D1.5). All groups were restored with prefabricated glass fiber post and resin composite core (PGF), one-piece glass fiber post-and-core (OGF) and cast Co-Cr alloy (Co-Cr) respectively, and the zirconia crown was restored. Load (180N) was subjected to the buccal cusp at 45° to the tooth's long axis. Stress pattern, maximum principal stress values (MPS), and maximum displacement values on root, post and core, cement layer were calculated for each model.

RESULTS

Stress distributions were similar while the values were different among groups. Regardless of restorative approaches, roots restored with PGF showed the highest MPS values, followed by OGF and Co-Cr groups. Regardless of post materials, NF groups resulted in the highest MPS values and maximum displacement values, while ISRF and DF groups exhibited similar results. Compared with PGF groups in association with ISRF, except for OGF with ISRFW0.5D0.5, the remaining OGF groups with ISRF and all Co-Cr groups in association with ISRF presented lower values than that of DF groups. And among different ISRF systems, roots restored with ISRFW1.0D1.0 presented the lowest stress (PGF: 32.96 MPa, OGF: 31.69 MPa, Co-Cr: 29.66 MPa).

CONCLUSIONS

For endodontically treated premolars without ferrule, restored with OGF in combination with ISRF preparation could effectively enhanced its load-bearing capacity. Furthermore, the ISRF with a depth and width of 1.0 mm is recommended.

Finite element analysis of maxillary first molar with mesial-occlusal-distal-palatal defect restored with different post-and-core strategies

Purpose

To explore which restoration strategy generates the most favorable stress distribution in an endodontically-treated maxillary first molar with mesial-occlusal-distal-palatal defect.

Methods

Models with one post in palatal canal (PP), each post in palatal and distobuccal canals (PDP), each post in palatal and mesiobuccal canals (PMP), and each post in all canals (PDMP) were established for an endodontically-treated maxillary first molar with mesial-occlusal-distal-palatal defect either with fiber-reinforced composite (FRC) post or gold alloy cast (GAC) post. A 400-N vertical force and a 225-N lateral force were respectively applied. The Mohr-Coulomb stress ratio (σ_{MC ratio}) in the residual tooth structure (RTS), the resin cement, and the crowns, the tensile stress (σ_t) and compressive stress (σ_c) in the FRC posts, the von-Mises stress ratio (σ_{vM ratio}) in the GAC post-and-cores, and the σ_t and shear stress (σ_s) at the adhesive interfaces were calculated using finite element analysis.

Results

FRC posts generated lower σ_{MC ratio} than GAC posts in the RTS (0.3274-0.3643 vs. 0.3399-0.4118). Among the FRC post groups, the PDMP group got the lowest σ_s at the dentin-post interface (14.92 MPa) and the abutment-crown interface (8.242 MPa) under vertical loading, as well as the lowest σ_{MC ratio} in the RTS (0.3381) and the lowest σ_s at the dentin-post interface (38.00 MPa) under lateral loading.

Conclusions

From the point of stress distribution, placing FRC posts in the palatal, distobuccal, and mesiobuccal canals is the optimal strategy in restoring a severely damaged maxillary first molar, provided that lateral occlusal force is reduced.

Influence of Root Post Materials and Aging on Fracture Strength and Marginal Gap Quality of Ceramic Crowns-An In Vitro Study

The design of and materials for prosthodontic abutments and posts have significant influences on the fracture resistance of restored teeth. This in vitro study compared the fracture strength and marginal quality of full-ceramic crowns as a function of the inserted root posts via simulation of a five-year period of use. Test specimens were prepared from 60 extracted maxillary incisors using titanium L9 (A), glass-fiber L9 (B), and glass-fiber L6 (C) root posts. The circular marginal gap behavior, linear loading capacity, and material fatigue after artificial aging were investigated. The marginal gap behavior and material fatigue were analyzed using electron microscopy. The linear loading capacity of the specimens was investigated using the Zwick Z005 universal testing machine. None of the tested root post materials showed statistically significant differences in marginal width values (p = 0.921), except in the case of marginal gap location. For Group A, there was a statistically significant difference from the labial to the distal (p = 0.012), mesial (p = 0.000), and palatinal (p = 0.005). Similarly, Group B showed a statistically significant difference from the labial to the distal (p = 0.003), mesial (p = 0.000), and palatinal (p = 0.003). Group C showed a statistically significant difference from the labial to the distal (p = 0.001) and mesial (p = 0.009). Linear load capacity reached mean values of 455.8-537.7 N, and micro-cracks occurred after artificial aging, predominantly in Groups B and C. Through the chosen experimental design, it was shown that the root post material and root post length had no influence on the fracture strength of the test teeth before or after artificial aging. However, the marginal gap location depends on the root post material and its length, which is wider mesially and distally and also tends to be greater palatinally than labially.

Effect of bioceramic root canal sealers on the bond strength of fiber posts cemented with resin cements

This study aimed to evaluate the influence of calcium silicate-based sealers on the bond strength of fiber posts using conventional and self-adhesive resin cement. Sixty single-rooted teeth were selected. The canals were prepared with a reciprocating instrument 40.06. The roots were randomly distributed in six groups (n = 10) according to the strategies for root canal filling and fiber posts cementation: AH Plus/RelyX ARC; AH Plus/RelyX U200; Bio C Sealer/RelyX ARC; Bio C Sealer/RealyX U200; Sealer Plus BC/RelyX ARC; and Sealer Plus BC/RelyX U200. The roots were transversally sectioned, and one slice per post-third was obtained. The push-out test was performed at a crosshead speed of 1mm/min. The failure patterns were described after assessment with a stereomicroscope with a 10× magnification. Bond strength was calculated and analyzed using the ANOVA and Tukey test. AH Plus did not influence the bond strength of fiber posts cemented with conventional (RelyX ARC) or with self-adhesive resin cement (RelyX U200). The lowest bond strength values were obtained when calcium silicate-based sealers were associated with conventional resin cement (Bio C Sealer/RelyX ARC and Sealer Plus BC/RelyX ARC). Except for Sealer Plus BC/RelyX ARC, all groups presented lower bond strength at the apical portion compared to the cervical portion of the post. Adhesive failures between cement and post and cement and dentin were predominant (55.3%). Calcium silicate-based sealers decreased the bond strength of fiber posts cemented with conventional resin cement.

Chemical analysis of irradiated root dentin and its interaction with resin cements

OBJECTIVES

To investigate the chemical changes in root dentin submitted to ionizing radiation and how it affects the interaction with resin cements.

MATERIALS AND METHODS

Forty human premolars were randomly divided into two groups (n = 20): non-irradiated and irradiated. They were randomly subdivided according to the type of resin cement (n = 10): conventional (RelyX ARC, 3 M ESPE) or self-adhesive (RelyX U200, 3 M ESPE). After cementation of the fiberglass posts, the roots were sectioned to be analyzed by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and confocal laser scanning microscopy (CLSM). The data obtained from FTIR and Raman were analyzed using two-way ANOVA followed Tukey's test (α = 0.05). For CLSM, a descriptive analysis was performed.

RESULTS

In the FTIR, there was a significant difference between the non-irradiated and irradiated groups for phosphate (p = 0.011), carbonate (p < 0.001), amide III (p = 0.038), and carbonate/mineral ratio (p < 0.001). Regarding the root third, there was a difference for amide I (p = 0.002), mineral/matrix ratio (p = 0.001), and amide I/CH₂ (p = 0.026) between the cervical and the others. Raman spectroscopy revealed no difference between groups for 961/1458 cm^-1 in the diffusion zone. CLSM showed a different interaction pattern for the two cements with the irradiated dentin from the cervical third.

CONCLUSIONS

Ionizing radiation altered the chemical composition of root dentin, especially in the cervical third. The resin cements showed less interaction with the irradiated root dentin.

CLINICAL RELEVANCE

As radiotherapy alters the chemical composition of root dentin, the interaction of resin cement with dentin can compromise the success of rehabilitation with fiberglass posts.

Efficacy of CAD/CAM Glass Fiber Posts for the Restoration of Endodontically Treated Teeth

Objective

The aim of this systematic review was to provide an overview of available scientific evidence regarding the comparative efficacy of computer-aided design (CAD) and computer-aided manufacturing (CAM) glass fiber posts with prefabricated and metal cast posts for the restoration of endodontically treated teeth (ETT).

Methods

This systematic review was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Electronic and manual searches were performed using the PubMed, SciELO, Cochrane, ScienceDirect, Web of Science, and EBSCO databases. The reference lists of the selected papers were reviewed to identify relevant papers. There were no year restrictions, and eligible studies were those in English publications and describing in vitro studies evaluating intraradicular retainers (IRs) for (i) fracture resistance, (ii) bond strength, (iii) adaptation, and (iv) cement layer thickness. Literature reviews, systematic reviews, meta-analyses, case reports, in vitro studies with <8 specimens, and noncomparative trials involving prefabricated or metal cast posts were excluded. The authors of this review independently screened the search results, extracted data, and assessed the risk of bias.

Results

No significant differences were found in fracture resistance between prefabricated and CAD/CAM glass fiber posts or between CAD/CAM glass fiber and metal cast posts, although the latter demonstrated higher fracture resistance than the prefabricated glass fiber posts. Restoration with a full crown was not necessary to increase the fracture resistance in the presence of the ferrule effect. CAD/CAM glass fiber and metal cast posts had higher bond strength, lower nanoleakage, and better adaptation to the root canal.

Conclusions

Despite the heterogeneity of methodologies and results reported, the results of these studies indicated that the CAD/CAM glass fiber and metal cast posts showed greater efficacy in terms of fracture resistance, retention, and adaptation, compared to prefabricated glass fiber posts.

Fatigue performance of endodontically treated premolars restored with direct and indirect cuspal coverage restorations utilizing fiber-reinforced cores

Objectives

The aim of this in vitro study was to investigate the fatigue survival and fracture behavior of endodontically treated (ET) premolars restored with different types of post-core and cuspal coverage restorations.

Materials and methods

MOD cavities were prepared on 108 extracted maxillary premolars. During the endodontic treatment, all teeth were instrumented with rotary files (ProTaper Universal) to the same apical enlargement (F2) and were obturated with a matched single cone obturation. After the endodontic procedure, the cavities were restored with different post-core and overlay restorations (n = 12/group). Three groups (A1–A3) were restored with either conventional composite core (PFC; control) or flowable short-fiber-reinforced composite (SFRC) core with/without custom-made fiber posts and without overlays. Six groups had similar post-core foundations as described above but with either direct PFC (B1–B3) or indirect CAD/CAM (C1–C3) overlays. Fatigue survival was tested for all restorations using a cyclic loading machine until fracture occurred or 50,000 cycles were completed. Kaplan-Meyer survival analysis was conducted, followed by pairwise post hoc comparisons.

Results

None of the restored teeth survived all 50,000. Application of flowable SFRC as luting-core material with fiber post and CAD/CAD overlays (Group C3) showed superior performance regarding fatigue survival (p < 0.05) to all the other groups. Flowable SFRC with fiber post and direct overlay (Group B3) showed superior survival compared to all other direct techniques (p < 0.05), except for the same post-core foundation but without cuspal coverage (Group A3).

Conclusions

Custom-made fiber post and SFRC as post luting core material with or without cuspal coverage performed well in terms of fatigue resistance and survival when used for the restoration of ET premolars.

Clinical relevance

The fatigue survival of direct and indirect cuspal coverage restorations in ET MOD premolars is highly dependent on whether the core build-up is fiber-reinforced or not. The combination of short and long fibers in the form of individualized post-cores seems to offer a favorable solution in this situation.

Effect of calcium silicate-based endodontic sealer on the retention of fiber posts cemented at different time intervals

Objective

To evaluate the effect of BC HiFlow, a new calcium silicate-based endodontic sealer, compared with a resin epoxy-based sealer after 2 different times of cementation on the pull-out bond strength of glass-fiber–reinforced composite posts cemented with a self-adhesive resin cement (RelyX Unicem).

Methodology

Sixty human maxillary central incisors were decoronated, prepared and obturated with gutta-percha and sealer. Roots were distributed into 5 groups according to the sealer and time of post cementation: (1) AH Plus sealer with immediate post fixation, (2) BC HiFlow with immediate post fixation, (3) AH Plus and post fixation after 7 days, (4) BC HiFlow and post fixation after 7 days, and (5) fiber post fixation in canals obturated with gutta-percha only (no sealer). After 1 week of post cementation, the pull-out test was performed and the failure mode was examined under a digital microscope. Data were analyzed using ANOVA followed by Tukey's post hoc and t tests (p < .05).

Results

With immediate post cementation, AH Plus group showed significantly higher pull-out retentive strength than the BC HiFlow and control groups (p = .009 and p < .001, respectively). There was no significant difference between the groups when the posts were cemented 7 days after obturation (p = .726). The time of post cementation had a significant influence on the canals obturated with AH Plus (p = .003). The time did not significantly affect the canals obturated with BC HiFlow (p = .289). The prominent type of failure was mixed mode in all groups.

Conclusion

BC HiFlow sealer did not affect the pull-out bond strength of glass-fiber–reinforced composite posts cemented with a self-adhesive resin cement immediately after or 7 days after obturation. For immediate post cementation, AH Plus increased the pull-out bond in comparison to BC HiFlow.

Effect of Sonic Activation on Push-Out Bond Strength of Fiber Post: An In Vitro Study

This study aimed to evaluate the effectiveness of conventional and sonic activation techniques on push-out bond strength of fiber post cemented with two different monomers containing self-adhesive resin cement (SARC). Four groups (n = 19 each) were made based on the type of SARC (Rely X U200 and Panavia SA) and technique (conventional and sonic activation). After placing the fiber post, each root was sectioned into 2 mm coronal, middle, and apical portions, and a push-out bond strength test was performed using a universal testing machine. The least push-out bond strength (13.0 ± 0.9 MPa) was found in Rely X U200 conventional technique and highest with Panavia SA sonic activation technique (15.4 ± 0.9 MPa). A significant difference was found in push-out bond strength at coronal (p = 0.002), middle (p = 0.002), and apical (p = 0.001) root sections using Rely X U200 cement with sonic activation as compared to the conventional technique. However, no difference (p > 0.05) was noticed between conventional and sonic activation techniques in Panavia SA cement at any root level. Sonic activation can be used as an adjunct with a manual technique to increase bond strength. However, it was noted that 10-MDP monomer containing SARC performed well regardless of techniques.

Comparison of the fracture strength of endodontically treated teeth restored with polyether ether ketone, zirconia and glass-fibre post-core systems

PURPOSE

This study aimed to compare the fracture resistance and fracture mode of maxillary central incisors restored with four different sizes and three different post-core systems.

MATERIALS AND METHODS

One hundred and twenty maxillary incisors were endodontically treated and randomly divided into three groups (12 subgroups). Post cavities for the narrow subgroups were prepared with 1.4-mm-diameter drills in lengths of 7.5 mm (SN) and 10 mm (LN). Post cavities for the wide subgroups were prepared with 1.6-mm-diameter drills in lengths of 7.5 mm (SW) and 10 mm (LW) (n = 10). Group F was restored with glass-fibre post and composite resin core, Group P was restored with custom PEEK post-core and Group Z was restored with custom zirconia post-core. All posts were cemented with a dual-cure resin cement. Zirconia copings were cemented. Specimens were loaded on the palatal surface with a universal testing machine, and the fracture strengths of the teeth were statistically analysed using ANOVA and post hoc Tukey tests.

RESULTS

Statistically significant differences existed between the fracture strengths of the post materials. The highest fracture strength was in Group F, and the lowest was in Group P. Evaluation of the fracture strengths of the post lengths and diameters demonstrated that the short-narrow group of Group Z had the lowest fracture strength (P < .05). The long-wide group of Group F showed the highest fracture resistance. In Group P, no statistically significant difference existed between the post-cores of different dimensions (P > .05). Irreparable fractures were observed mostly in Group Z, and decementation was more common in Group P.

CONCLUSIONS

PEEK post-cores showed sufficient fracture strength for the anterior region, similar to the other two post-core materials. PEEK post-cores showed more decementation and repairable fractures at lower forces, while restoration failure was mostly catastrophic for glass-fibre and zirconia posts.

The resin-matrix cement layer thickness resultant from the intracanal fitting of teeth root canal posts: an integrative review

OBJECTIVE

The aim of this study was to perform an integrative review on the layer thickness and microstructure of resin-matrix cements around custom-made or standard teeth root intracanal posts.

MATERIALS AND METHODS

An electronic search was conducted on the PubMed using a combination of the following scientific terms: intraradicular post, root intracanal post, resin cement, thickness, adaptation, endodontic post, layer thickness, fit, shape, and endodontic core. The literature selection criteria accepted articles published in the English language, up to May 2021, involving in vitro analyses, meta-analyses, randomized controlled trials, and prospective cohort studies.

RESULTS

The search identified 154 studies, of which 24 were considered relevant to this study. The selected studies provided important data considering cement layer thickness, tooth preparation, endodontic post, and type of resin-matrix cement. The anatomical variability of root canal systems, such as the oval- or C-shaped, represents a challenge in dental restoration with tooth root intracanal posts. The fitting of intracanal posts to different root regions is variable resulting in thick and irregular layers of resin-matrix cement. Defects like pores, micro-cracks, and micro-gaps were detected in the resin-matrix cement microstructure and represent spots of stress concentration and fracture. Custom-made tooth root intracanal posts provide a proper fitting and decrease the layer thickness of resin-matrix cement.

CONCLUSIONS

In fact, the layer thickness of resin-matrix cements depends on the fitting of endodontic posts to tooth root canals. An increase of resin cement thickness causes the appearance of defects like pores, micro-cracks, and micro-gaps that can induce stress concentration and fractures at interfaces.

CLINICAL RELEVANCE

The fitting of the endodontic post into the teeth root canal determine the layer thickness of the resin-matrix cement to establish an adequate retention. However, the increase in the thickness of the resin-matrix cement layer can lead to a high number of defects like pores or cracks and therefore decrease the strength of the interface.

Interface analysis after fatigue loading of adhesively luted bundled fiber posts to human root canal dentin

OBJECTIVES

The aim of this study was to assess the fatigue loading behavior and fracture resistance of endodontically treated teeth restored with adhesively luted bundled fiber posts in comparison to solid fiber posts. Image analysis (2D and 3D) was applied to evaluate modes of failure and to characterize susceptible parts of the post-and-core interface.

METHOD

Crowns of 72 human similar-sized central upper incisors were removed and roots received a conventional root canal filling prior to establishing 4 groups of core build-up: No Post group (nP) received a 4 mm deep filling made of composite inside the canal with no dental post, fiber post group (FP) received a conventional solid post, and two experimental groups received bundles of 6 (FB6) or 12 (FB12) 0.3 mm thin fiber posts, respectively. Posts were placed adhesively inside the root canal using a dual-curing build-up composite in combination with a self-etch adhesive, the latter was also used for nP group. Upon completion of core build-ups, all teeth received full-ceramic crowns that recreated the original tooth form. Samples were subjected in a 135° angle to thermo-mechanical loading (TML) for 1.2 Mill. chewing cycles followed by static load tests (fracture resistance). Fracture modes as well as intracanal failure modes with respect to failed interfaces were analyzed using optical and electron microscopy (SEM). Microcomputer tomography (μCT) was used to exemplary compare pre and post TML geometries.

RESULTS

Static load test was significantly different between groups (p < 0.0005; Kruskal-Wallistest). Pairwise comparison showed that the nP group (221 ± 103N) failed at significantly lower forces compared to the FP (454 ± 184N), FB6 (477 ± 250N) and FB12 (478 ± 260N) groups (p ≤ 0,001; Mann-Whitney-U-test). Fracture modes were significantly affected by the presence or absence of a post (p ≤ 0,016; Chi-square test) revealing increased incidence of restorable fractures at the cervical region for nP group. Microscopic analysis revealed more intracanal failures at interfaces between post surfaces and composite for solid posts, whereas fiber bundled posts mostly failed at the interfaces between composite and dentin. Micro-CT analysis showed no alterations of the root-post-and-core structure after TML except slight deformations of occasionally entrapped voids.

CONCLUSION

Fracture resistance and fracture modes were significantly affected by the presence or absence of a post, whereas the investigated post groups did not differ from each other. However intracanal failure revealed differences in adhesive failures between solid fiber posts and bundled fiber posts. Deformations of entrapped voids, revealed by micro-Ct analyses after TML, lead to the assumption that applied forces result in alterations in the regions of voids.

Fatigue failure of anterior teeth without ferrule restored with individualized fiber-reinforced post-core foundations

OBJECTIVES

The aim was to explore the survival of extensively damaged anterior teeth without ferrule restored with different fiber-reinforced composite (FRC) post-core foundations and composite crowns.

MATERIALS AND METHODS

Sixty extracted upper central incisors were decoronated and randomly divided into four groups (n = 15). After endodontic treatment, the specimens were restored with different individualized fiber-reinforced post-core foundations as follows: control group (CTRL): multiple unidirectional FRC-post + dual-cure composite-core, PFC: multiple unidirectional FRC-post + packable short fiber-reinforced composite (SFRC), BPFC: Bioblock technique with only packable SFRC, BFFC: Bioblock technique with only flowable SFRC. After core build-up, the teeth were finalized with adhesively luted CAD/CAM composite crowns. Cyclic isometric loading (5 Hz) was applied at 100 N for 5000 cycles, and then 200 N and 300 N for 15,000 cycles each in a fluid chamber. The specimens were loaded until fracture occurred or when a total of 35,000 cycles were reached. Kaplan-Meyer survival analysis was conducted, followed by pairwise log-rank post hoc comparisons (Mantel-Cox).

RESULTS

The survival rates of the control (8279 cycles) and PFC (6161 cycles) were significantly higher compared to BPFC (3223 cycles) and BFFC (2271 cycles) (p < 0.05). Regarding fracture pattern, nearly all specimens fractured in a restorable manner.

CONCLUSIONS

For restoring extensively damaged anterior teeth, multiple unidirectional FRC posts are recommended.

CLINICAL RELEVANCE

Although different FRC post/core systems are available for the restoration of damaged root canal treated anterior teeth, multiple unidirectional FRC posts tend to be a good option when the ferrule is missing.

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.

Biomechanical behavior of endocrowns vs fiber post-core-crown vs cast post-core-crown for the restoration of maxillary central incisors with 1 mm and 2 mm ferrule height: A 3D static linear finite element analysis

To analyze the stress distribution of the maxillary central incisor with oblique fracture, repaired by different methods, using 3-dimensional finite element analysis. From the biomechanical point of view, it is expected to provide a reference for clinical selection of restoration method which is more conducive to stress distribution and preservation of dental tissue as much as possible.Use cone beam CT and finite element software to establish the finite element models of the maxillary central incisor with oblique fracture, and then create models according to 5 repairing methods(A. fiber post-core-crown group; B. cast post-core-crown group; C.3 mm deep endocrown; D.4 mm deep endocrown; E.5 mm deep endocrown)after root canal treatment, and analyze the Von Mises equivalent stress and maximum principal stress distribution and peak value of each model.When the height of dentin ferrule was fixed, the value of the Von Mises equivalent stress and the maximum principal stress in residual tooth tissue: group A was the highest, and there was no significant difference in group B, C, D and E. And the stress distribution area of 5 groups were the same. In prosthodontic layer: group B was the highest, while group A was the lowest, and the stress peak slightly increased with the increase of depth in group C, D and E. And the 5 groups were with the same stress distribution area as well. In adhesive layer: group A was the highest, while group B was the lowest, and there was little difference among group C, D and E. Group A was concentrated in 1/3 of the post tip, while group B,C,D and E were concentrated in 1/3 of the post and the post tips.Complete and high enough dentin ferrule is a requirement for repairing heavily defected maxillary central incisor with fiber post-core crown and cast post-core crown. When the dentin ferrule is incomplete, the stress distribution of the endocrown is more excellent than post-core-crown. And the endocrown with a depth of 3 mm retainer may be the best repair method. As for post-core crown restoration, the cast post-core crown is more favorable for the uniform distribution of residual tooth tissue than the fiber post-core crown.

In vitro fracture resistance of zirconia, glass-fiber, and cast metal posts with different lengths

Aim:

Post-and-core restorations require sufficient length of the post for retention of the prosthesis and root strength. The effect of different lengths of prefabricated zirconia posts (ZPs) on the fracture strength of endodontically treated teeth needs evaluation. Hence, the aim of this study was to evaluate the in vitro fracture resistance of endodontically treated incisors restored with ZP, glass-fiber (GFP), and cast posts (CP) of different lengths.

Settings and Design:

Comparative in-vitro study.

Materials and Methods:

Sixty extracted incisors were endodontically treated, tooth preparations were carried out, and the impression of the coronal portion of each prepared tooth was made using polyvinyl siloxane impression material loaded in copper tubes. The coronal portion of each tooth was removed, maintaining a 2 mm ferrule. The teeth were restored with one of the three posts: CPs, GFP, or ZPs, with intraradicular lengths of either 6 or 8 mm (n = 10). The CP and core patterns were fabricated using post space impressions and core buildup and cast using Nickel–Chromium alloy. After composite resin core buildup of GFP and ZPs treated teeth using the previously made copper tube impressions, the teeth were loaded to fracture in an oblique direction in the universal testing machine.

Statistical Analysis Used:

Data were analyzed using two-way ANOVA and Tukey–Kramer tests (α = 0.05).

Results:

The highest and lowest values of fracture resistance were reported with ZP8 and GFP6 groups, respectively. There was no significant difference in fracture resistance between the posts of length 6 mm and 8 mm in CP, GFP, and ZP groups. There was no significant difference (P = 0.953) in fracture resistance between CP (284.8 N) and ZP (258.31 N) groups, while the GFP group (160.61 N) had a significantly lower value of fracture resistance than the CP and ZP groups. Two-way ANOVA test for fracture resistance of the post systems and post lengths showed that there was no significant correlation between the post systems and post length on the fracture resistance. There was a greater percentage of favorable fractures in GFP and ZP groups (65% each), than the CP group (20%).

Conclusion:

For the post systems tested, extending the post length does not significantly increase the fracture resistance of the restored teeth. The ZP represents a viable alternative to the cast metal post during the esthetic restoration of endodontically treated anterior teeth.

Microtomographic Analysis of Resin Composite Core Material Porosity

PURPOSE

To nondestructively evaluate the porosity of ten contemporary resin composite core materials using microtomographic (microCT) analysis.

MATERIAL AND METHODS

Resin composite core material samples (n = 12) including dual-cure, visible light cure only, and a self-cure material were fabricated using a standardized mold following manufacturer's recommendations. After storage in phosphate buffered saline for one week, specimens were analyzed using a microCT unit at 5.3-µm resolution over a rotational range of 360°. Image 3D recombination and analysis was accomplished using microCT software. Evaluated parameters included material volume investigated, closed pore number and volume, as well as closed pore percentage. Parameter mean values were evaluated with Kruskal-Wallis/Dunn at a 95% confidence level (α = 0.05).

RESULTS

Mean percent total porosity with standard deviation identified significant differences in decreasing order as Ti-Core: 2.2 (0.4) > Ti-Core Auto E: 1.3 (0.3) = Ti-Core Flow Plus: 1.1 (0.02) > Clearfil Photo Core: 0.94 (0.5) = Clearfil DC Core Plus: 0.6 (0.18) = MultiCore Flow: 0.58 (0.1) > Fluorocore 2+: 0.14 (0.2) = Build-It FR: 0.068 (0.02) = Gradia Core: 0.03 (0.02) = Rebilda DC: 0.02 (0.01). A pilot microCT evaluation evaluating a mixing tip revealed incomplete mixture between the two resins with porosity introduced from turbulence as the materials are forced through the tip during preparation.

CONCLUSIONS

A wide range of porosity was identified between the ten materials evaluated. These preliminary results warrant more investigation evaluating additional resin composite core materials, the preparation capabilities of automix tips, and porosity presence in the unmixed materials.

Influence of endodontic sealers with different chemical compositions on bond strength of the resin cement/glass fiber post junction to root dentin

OBJECTIVE

This study evaluated the influence of endodontic sealers with different chemical compositions on bond strength of resin cement/glass fiber post junction to root dentin.

MATERIALS AND METHODS

Seventy-two maxillary canines roots were instrumented with Reciproc (#R50) and distributed in 6 groups (n = 12) according to endodontic sealers: G1-control (no sealer); G2-Endofill; G3-Sealapex; G4-AH Plus; G5-Sealer Plus; G6-EndoSequence BC. The glass fiber post was cemented with Panavia F in 10 of the specimens. Two specimens from each group did not receive post and were analyzed by SEM to verify presence of filling material. Three slices were obtained from each third. The first slice was subjected to push-out test and type of failure. The second slice was imaged using laser confocal microscopy for evaluation of dentin/resin cement adhesive interface. Bond strength (BS) data were analyzed using two-way ANOVA and Tukey's post hoc tests; for LCM data, we used Kruskal-Wallis and Dunn's tests.

RESULTS

Endofill yielded the lowest BS values (p < 0.05). The control and AH Plus groups differed from all others (p < 0.05). In all groups, adhesive to dentin failure predominated. Most specimens of control and AH Plus groups had acceptable interfaces, while those of EndoSequence BC, Sealapex, and Sealer Plus groups ranged between acceptable and poor interfaces. Overall, few filling material remnants were observed on the dentin.

CONCLUSION

EndoSequence BC, Sealapex, Sealer Plus, and Endofill negatively interfere with BS of glass fiber post/resin cement junction to root dentin.

CLINICAL RELEVANCE

In cases whose restoration planning includes a post cemented with resin cement, it is recommended that endodontic sealer be based on epoxy resin.

Surface characterization and bonding properties of milled polyetheretherketone dental posts

PEEK has been used in many dental applications except intra-radicular post. The aim of this study is to test polyetheretherketone (PEEK) as a dental post material through tensile bond strength (TBS) and surface roughness (SR), and to compare it with glass-fiber and cast-metal posts. Thus, 60 human maxillary central incisors with a single root were endodontically treated and divided into three groups (n = 20) according to the type of post (Group P: PEEK, Group F: Glass-fiber, Group M: Cast-metal). Appropriate surface treatment was employed for each group and SR was determined by a three-dimensional non-contact profilometer before cementation. All posts were luted to the canal dentin using self-etch resin cement (Panavia F2.0). Pull-out test was performed on a universal testing machine at a speed of 0.5 mm/min crosshead speed until failure, and TBS were calculated. One-way ANOVA, Tukey's HSD, and Pearson chi-squared tests were performed for statistical analyses (α = 0.05). According to the results, group F demonstrated the highest SR (2.93 ± 0.18 µm) and lowest TBS values (10.05 ± 0.53 MPa), while group P exhibited lowest SR (1.37 ± 0.11 µm) and highest TBS values (14.33 ± 0.58 MPa) (p < 0.001). No significant differences in failure modes were identified among groups, mostly adhesive (p = 0.243). As conclusion, PEEK may be a reliable and contemporary option for dental post systems when used with appropriate surface treatment and luting agent. This high-performance polymer may be a novel candidate as a contemporary dental post system due to its superior mechanical, chemical, thermal, and esthetical properties with low risk of fracture.

Effects of the Ferrule Design on Fracture Resistance to Endodontically-Treated Teeth Restored with Fiber Posts: A Systematic Review

Aim:

The aim of this review is to determine the influence of the ferrule design in endodontically-treated teeth using fiber posts on their fracture resistance.

Materials and Methods:

The electronic databases examined were Medline, Scopus, and PubMed from April 2019 to October 2019. The studies were selected using well-established inclusion criteria.

Results:

In total, 79 articles were identified, 16 of which were selected after considering the titles and abstracts. After reading the full-text articles, the total number of articles included in this review was 7 with a low risk of bias.

Conclusion:

A full ferrule with a maximum height is the best design for resistance to fractures in all groups of teeth, but if it is impossible to provide this condition, the ferrule height from the palatal/lingual wall of the tooth should be increased.

The PROSPERO ID: 153543.

The effect of individualization of fiberglass posts using bulk-fill resin-based composites on cementation: an in vitro study

Objectives

This study evaluated the bond strength of various fiberglass post cementation techniques using different resin-based composites.

Materials and Methods

The roots from a total of 100 bovine incisors were randomly assigned to 5 treatment groups: G1, post + Scotchbond Multi-Purpose (SBMP) + RelyX ARC luting agent; G2, relined post (Filtek Z250) + SBMP + RelyX ARC; G3, individualized post (Filtek Z250) + SBMP; G4, individualized post (Filtek Bulk-Fill) + SBMP; G5, individualized post (Filtek Bulk-Fill Flow) + SBMP. The samples were subjected to the push-out (n = 10) and pull-out (n = 10) bond strength tests. Data from the push-out bond strength test were analyzed using 2-way analysis of variance (ANOVA) with the Bonferroni post hoc test, and data from the pull-out bond strength test were analyzed using 1-way ANOVA.

Results

The data for push-out bond strength presented higher values for G2 and G5, mainly in the cervical and middle thirds, and the data from the apical third showed a lower mean push-out bond strength in all groups. No significant difference was noted for pull-out bond strength among all groups. The most frequent failure modes observed were adhesive failure between dentine and resin and mixed failure.

Conclusions

Fiberglass post cementation using restorative and flowable bulk-fill composites with the individualization technique may be a promising alternative to existing methods of post cementation.

Ferrule Design Does Not Affect the Biomechanical Behavior of Anterior Teeth Under Mechanical Fatigue: An In Vitro Evaluation

Objectives:

To investigate the survival and failure mode of fiber-post resin restorations over preparations with different ferrule designs when submitted to a fatigue load test.

Methods and Materials:

Fifty bovine incisors were selected and divided into five groups (n=10) according to ferrule design: a no-ferrule group, a 2-mm circumferential ferrule group, a 2-mm buccal ferrule group, a 2-mm lingual ferrule group, and a 2-mm buccal and lingual ferrule group. The fiberglass post was cemented and the composite core was built up and prepared, followed by cementation of a full composite crown. The samples were subjected to a cyclic fatigue test with loading applicator at 135°; a staircase approach was used until fracture. Survival (cycles to fracture) and failure modes were recorded. Survival data were analyzed with the log-rank test, while Kruskal-Wallis and Fisher exact tests were used to analyze failure mode data (α=0.05).

Results:

The median number of cycles to fracture ranged from 215,000 to 236,153. The log-rank test showed no statistically significant difference in survival rates among the groups (p=0.82). Regarding failure mode, three types were observed: I, post and/or core fracture; II, root fracture in the cervical third; and III, root fracture in the middle third. No statistical difference was observed among the groups (Kruskal-Wallis test, p=0.147).

Conclusion:

The ferrule design had no effect on fatigue resistance or failure mode of endodontically treated incisor teeth restored with a fiber post, composite core buildup, and composite crown.

Fracture Strength and Stress Distribution in Premolars Restored with Cast Post-and-Cores or Glass-Fiber Posts Considering the Influence of Ferule

Objectives

The aim of this study was to evaluate the influence of ferule and the post type on the fracture strength and stress distribution in premolars.

Materials and Methods

Forty human mandibular premolars were decoronated, allocated in four groups, and restored as follows: CPC-NF: cast post-and-core and absence of ferule; CPC-F: cast post-and-core and presence of ferule; FPC-NF: glass-fiber posts and absence of ferule; FPC-F: glass-fiber posts and presence of ferule. The fracture strength (FS) and failure patterns were evaluated. Finite element analysis (FEA) evaluated the stress distribution.

Results

FS did not differ between CPCs and FPC either in presence or in absence of ferule. The presence of ferule increased FS with both post types. Mean values of FS for ferule groups were higher than functional or parafunctional loads reported in literature, which was not the case for FPC-NF when compared to parafunctional loads. FEA with a functional load showed slightly higher compressive stresses in dentin in the group CPC-NF, which was much lower than the compressive strength of dentin. Lower percentage of catastrophic failures was observed in nonferule groups irrespective of post type, which was explained by the stress concentration in the cervical root region when FEA with the FS load was simulated.

Conclusion

Ferule effect was shown to be more important than post type in the analysis. Both posts showed potential to withstand functional loads irrespective of presence of ferule. However, the mean FS was lower than parafunctional loads for FPC in the absence of ferule.

In Vitro Fracture Strength of Teeth Restored with Lithium Disilicate Onlays with and without Fiber Post Build-Up

To our knowledge there is no data about the mechanical performance of indirect restoration adhesively cemented on teeth without an adequate build-up to provide the correct geometrical configuration. The aim of this study was to compare the fracture strength of human teeth restored with lithium disilicate onlays, with and without fiber post build-up.

METHODS

Twenty human mandibular molars were horizontally sectioned and divided into two groups (n = 10). No treatment was applied in group A. Teeth in group B were endodontically treated, built-up using fiber post and composite core and prepared with a circumferential chamfer providing a 1 mm circumferential ferrule. Lithium disilicate onlays were pressed and luted on teeth using dual-curing luting composite. Teeth were tested under static load. Failures were classified as restorable or not restorable. Failure loads were analyzed with one-way analysis of variance. Failure modes were compared using Pearson's Chi-square tests.

RESULTS

The mean fracture loads were 1383.5 N for group A and 1286.3 N for group B. No difference was found (p = 0.6). Ninety per cent of fractures were classified as not restorable in both groups, with no difference (p = 0.8).

CONCLUSIONS

For teeth restored with adhesive procedures and lithium disilicate onlays, the presence of build-up with fiber post to provide retention and resistance form does not influence the fracture strength.

Influence of restorative procedures on endodontically treated premolars: Finite element analysis of a CT-scan based three-dimensional model

An endodontically treated tooth with mesial-occlusal-distal (MOD) cavity is often restored with composite resin. Palatal and buccal cusp reduction (MODP, MODPB), and/or fiber-reinforced composite posts (P), are used in an attempt to improve the longevity of the restoration. The aim of this study was to determine the effects of these procedures on von Mises stress values and distribution in dental tissues and restorative materials using finite element analysis. Based on CT scans of an extracted second upper premolar, six 3D endodontically treated tooth models (MOD, MODP, MODPB, MOD+P, MODP+P, MODPB+P) were created. Each model was subjected to a summary force of 150 N on the occlusal surface simulating the normal biting pattern and maximal von Mises stresses were calculated. MODP seems to reduce von Mises stress values in dental tissues and P seems to transfer some of the stresses from dental tissues to the composite filling.

Multi-Fiber-Reinforced Composites for the Coronoradicular Reconstruction of Premolar Teeth: A Finite Element Analysis

A coronoradicular reconstruction (CRR) has conventionally used a metallic inlay core (MIC) or a single-fiber-reinforced composite (sFRC) but extensive dentin removal can lead to root fracture. We propose herein a multi-fiber-reinforced composite (mFRC) based on a bundle of thin flexible fibers that can be adapted to the root anatomy without removing additional dentin. The aim of this study was to compare the mechanical behavior of the root reconstructed with mFRC, MIC, or sFRC using a finite element analysis (FEA). Models with or without a ferrule effect were created using Autodesk© software and divided into four parts: root, post, bonding composite or cement, and zirconia crown. For both models, extreme stress values (ESV), stress distribution, and risk of fracture were calculated for an oblique force (45°) of 100 N applied to the top of the buccal cusp. Results indicated that mFRC and mFRCG present a lower risk of fracture of the root and of the CRR without ferrule and thus could be valuable alternatives for premolar CRR. Further studies are necessary to evaluate the clinical success of these CRR.

Longevity of bond strength of resin cements to root dentine after radiation therapy

AIM

To evaluate the bond strength and adhesive interface between several resin cements and root dentine immediately and 6 months after radiotherapy.

METHODOLOGY

Sixty maxillary canines were selected and randomly assigned to two groups (n = 30): one group was not irradiated and the other one was subjected to a cumulative radiation dose of 60 Gy. The teeth were sectioned to obtain roots 16 mm long and the canals were prepared with the Reciproc system (R50) and filled using a lateral condensation technique with an epoxy resin sealer. Each group was divided into three subgroups (n = 10) according to the resin cement used for fibreglass fibre post cementation: RelyX-U200, Panavia-F2.0 and RelyX ARC. The posts were cemented in accordance with the manufacturer's recommendations. Three 1-mm-thick dentine slices were then obtained from each root third. The first two slices in the crown-apex direction of each third were selected for the push-out test. The failure mode after debonding was determined with a stereo microscope. The third slice from each root third was selected for scanning electron microscopy (SEM) analyses to examine the resin cement-dentine interface with 100, 1000, 2000 and 4000× magnification. Bond strength data were analysed by anova and Tukey's test (α = 0.05).

RESULTS

Significantly lower bond strength (P < 0.0001) was obtained after irradiation compared to nonirradiated teeth. RelyX-U200 cemented fibre posts had the higher bond strength (15.17 ± 5.89) compared with RelyX ARC (P < 0.001) and Panavia-F2.0 (P < 0.001). The evaluation after 6 months revealed lower bond strength values compared to the immediate values (P < 0.001) for irradiated and nonirradiated teeth. Cohesive failures occurred in the irradiated dentine. SEM revealed fractures, microfractures and fewer collagen fibres in irradiated root dentine. RelyX-U200 and Panavia-F2.0 were associated with a juxtaposed interface of the cement with the radicular dentine in irradiated and nonirradiated teeth, and for RelyX ARC, hybrid layer formation and tags were observed in both irradiated and nonirradiated teeth.

CONCLUSION

Radiation was associated with a decrease in the push-out bond strength and with lower resin cement/root dentine interface adaptation. Self-adhesive resin cement was a better alternative for fibre post cementation in teeth subjected to radiation therapy. The bond strength decreased after 6 months.

The Influence of Post System Design and Material on the Biomechanical Behavior of Teeth with Little Remaining Coronal Structure

PURPOSE

To evaluate the influence of different post systems on the biomechanical behavior of teeth with a severe loss of remaining coronal structure.

MATERIALS AND METHODS

Fifty standardized bovine teeth (n = 10 per group) were restored with: cast post-and-core (CPC), prefabricated metallic post (PFM), parallel glass-fiber post (P-FP), conical glass-fiber post (C-FP), or composite core (no post, CC). The survival rate during thermomechanical challenging (TC), the fracture strength (FS), and failure patterns (FP) were evaluated. Finite element models evaluated the stress distribution after the application of 100 N.

RESULTS

All specimens survived TC. Similar FS was observed among post-containing groups. Groups P-FP and CC presented 100% repairable fractures. The von Mises analysis showed the maximum stresses into the root canal in groups restored with metallic posts. Glass-fiber posts and CC presented the maximum stresses at the load contact point. Glass-fiber groups showed lower stresses in the analysis of maximal contact pressure; CPC led to the highest values of contact pressure. The modified von Mises (mvM) stress in dentin did not show differences among groups. Moreover, mvM values did not reach the dentin fracture limit for any group.

CONCLUSIONS

The type of intracanal post had a relevant influence on the biomechanical behavior of teeth with little remaining coronal structure.

Influence of remaining coronal thickness and height on biomechanical behavior of endodontically treated teeth: survival rates, load to fracture and finite element analysis

Objective

To evaluate the effect of restorative strategy (fiber post vs cast post and core), coronal height (0 mm vs 2 mm) and thickness (higher than 1 mm vs lower than 1 mm) on survival rate, fracture resistance and stress distribution.

Material and Methods

Seventy-two bovine teeth were cleaned and allocated in six groups (n = 12). Twenty-four teeth were sectioned at 13 mm length (no remaining coronal structure) and forty-eight were sectioned at 15 mm (2 mm remaining coronal structure). Half of the forty-eight had remaining coronal thickness lower than 1 mm and the other half had thickness higher than 1 mm. All root canals were prepared at 10 mm (luting length), fiber posts were cemented in thirty-six specimens and cast post and core in other thirty-six. All teeth were restored with metallic crowns. Specimens were submitted to 1.5 million cycles (100 N, 45°, 10 Hz at 2 mm below incisal edge) and evaluated at each 500,000 cycles to detect failures. Specimens that survived were submitted to load to fracture test. Bidimensional (Rhinoceros^® 4.0) models were obteined survival data submitted to Kaplan-Meier (α=0.05) analysis and load to fracture values submitted to ANOVA and Tukey tests (α=0.05).

Results

Groups without remaining coronal structure showed survival rates lower than other groups (p=0.001). ANOVA showed higher values of load to fracture for groups with coronal thickness higher than 1 mm (p=0.0043). Finite element analysis showed better stress distribution in groups with remaining coronal structure and restored with fiber post.

Conclusion

Specimens without remaining coronal structure have lower survival rates. Specimens with remaining structure lower than 1 mm and without coronal structure support the same load to fracture value independently of the restorative strategy.