"Never doubt that a small group of thoughtful, committed citizens can change the world. Indeed, it is the only thing that ever has."
Cureus is on a mission to change the long-standing paradigm of medical publishing, where submitting research can be costly, complex and time-consuming.
The SIQ for this article will be revealed
systematic review, fiber post, finite element analysis, stress distribution, post materials
Vijetha Badami , Hemabhanu Ketineni, Sabiha PB, Sneha Akarapu, Satya Priya Mittapalli, Ayesha Khan
Cite this article as: Badami V, Ketineni H, PB S, et al. (September 29, 2022) Comparative Evaluation of Different Post Materials on Stress Distribution in Endodontically Treated Teeth Using the Finite Element Analysis Method: A Systematic Review. Cureus 14(9): e29753. doi:10.7759/cureus.29753
The aim of this systematic review is to summarize and conclude findings to reveal the stress ranges developed by various post materials by finite element analysis. This, in turn, aids in the selection of better post material clinically. The electronic databases PubMed and Google Scholar were searched in this review by using specific inclusion and exclusion criteria. Among 14586 articles, 22 articles were included in this systematic review, as they satisfied the eligibility criteria. The search covered all articles published from 1997 to December 2021. All records identified were retrieved and imported into the Rayyan bibliographic software, which is a systematic review screening software. Later, data extraction and analysis of 22 articles were done. Twenty-two articles, which were all finite element analysis studies, were included. Among these, 18 studies used maxillary central incisor scanned models, two studies used a maxillary canine model, and the remaining two used the mandibular premolar model for finite element analysis. All these tooth models are restored with post models made of different materials. This systematic review revealed a difference in stress distribution in endodontically treated teeth when using different post materials. Among 22 studies, 15 studies evaluated glass fiber posts and the results showed that they induce less stress on restored endodontically treated teeth when compared to other posts, with maximum stress concentration at the cervical third of the root. Prefabricated posts like stainless steel and Titanium showed more stress on the restored tooth structure with stress concentration at the cervical and apical third of the root. Prefabricated zirconia also showed more stress on the restored tooth with maximum stress concentration at the middle third of the root.
An endodontically treated tooth is significantly weaker than a vital tooth and presents challenges in restoring it to form and function. Often, because of the minimal remaining tooth structure, posts are inserted to aid in the retention of the core. There are a number of options available in terms of materials for both the post and core, posts can be prefabricated or custom-made. The characteristics of the post include material elastic modulus, diameter, and height, which contribute greatly to the resistance to fracture of the restored tooth [1].
The selection of specific materials and techniques for the restoration of endodontically treated teeth is influenced by the changes that accompany root canal therapy, which include the amount of remaining tooth structure, physical changes in tooth structure, the anatomic position of the tooth, the occlusal forces on the tooth, the restorative requirements of the tooth, and the aesthetic requirements of the tooth [2].
Previously custom-cast posts and cores made of metals like gold, silver, palladium, and base metal alloys have been used. In recent times, non-metal posts like fiber-reinforced composites, glass fiber-reinforced posts, carbon fiber posts, and zirconia posts have been introduced [3]. Recently, they have been using PEEK (polyether ether ketone), which includes carbon fiber-reinforced (CFR)-PEEK, glass fiber reinforced (GFR)-PEEK, and PEKK (polyether ketone-ketone [1]. These metal-free posts have advantages like biocompatibility, corrosion resistance, and similar mechanical properties to a natural tooth, less expensive, less time-consuming, and in some situations less invasive than customized posts and cores [4]. The modulus of elasticity is directly proportional to stiffness. During transverse loading, stiffer posts undergo less deformation since they have high resistance to bending but they have a marked wedging effect, which increases the risk of fracture due to longitudinal loading [5].
Despite the availability of numerous in-vitro studies, it still remains undetermined as to which is the best post system, especially in terms of choice of materials. Some authors advise posts with a high modulus of elasticity and some recommend close to that of dentin and some say no significant difference between these two [4]. A lot of studies are published using finite element analysis (FEA) trying to show the stress distribution on the endodontically treated teeth by different post materials under defined conditions. Although intense research is conducted in this field, a consistent conclusion has not yet been established. The aim of this systematic review is to give an understanding of finite element analysis studies conducted in this field. This helps summarize and conclude findings to reveal the stress ranges developed by various post materials and in turn helps in best post material selection clinically.
This systematic review followed Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. The use of checklists in the PRISMA is likely to improve the reporting quality of a systematic review and provides substantial transparency in the selection process of papers in a systematic review.
A PICOS question was formulated based on the population, intervention, comparison, outcomes, and study design. The PICOS question was which post material had developed high stresses and low stress in endodontically treated teeth when tested through finite element analysis. The population considered here were scanned models of extracted teeth, the intervention was a post while the comparison was done between different post materials, the outcome assessed was stress distribution on the models, and the study design considered was those including finite element analysis.
An extensive search was carried out using electronic databases PubMed and Google Scholar along with a manual search to identify all articles related to stress distribution of different post and core materials using FEA. The electronic databases PubMed and Google Scholar were consulted by using the keywords “post and core materials, finite element analysis, stress distribution, and endodontically treated teeth.” The search included articles published in the English language from 1997 to December 2021. Identified articles were transferred into the Rayyan bibliographic software, which is systematic review screening software. The references of the selected articles were screened to identify other potentially relevant articles that have been missed during the initial search. Initial screening of identified articles was done by an assessment of title and abstract, and irrelevant articles were eliminated based on inclusion and exclusion criteria as mentioned below. The entire search process is depicted in Figure 1.
To be included, a study must be in vitro, evaluating stress distribution on human permanent teeth scanned models restored with different post materials using finite element analysis, and publications with full-text availability. Exclusion criteria included in vivo studies, reviews, studies not testing stress distribution by finite element analysis, studies using Bovine teeth models, and studies not including comparative evaluation of different post materials' stress distribution on restored teeth.
Two reviewers separately assessed all titles and abstracts based on inclusion and exclusion criteria. Initially, a combined assessment of 25 articles was done; later, the assessment of the articles was done separately. In case there was a difference of opinion, they would resolve it collectively. After that, data extraction and analysis of included articles were done. The data that were extracted included the journal, year of publishing, author, and tooth, which is tested, post materials, core materials, crown material, software of FEA, amount of force used, and area of its focus and results, as depicted in Tables 1-3.
The search of the electronic databases yielded 14586 articles; removing duplicates and unrelated articles resulted in a total of 210 articles. After reading their titles and abstracts, 185 studies were regarded as irrelevant or did not fulfill the inclusion criteria. Finally, the full texts of 22 articles that remained were studied in detail, as the full text of three articles full text was not available.
Among these, 18 studies pertained to the maxillary central incisor scanned model, two studies used the maxillary canine model, and the remaining two used the mandibular premolar model for finite element analysis. All these tooth models are restored with posts made of different materials. For the development of various post models, they used properties like modulus of elasticity and Poisson's ratio of these materials. In the case of prefabricated post models, they are restored with a composite core, and in the case of custom casting and computer-aided design and computer-aided manufacturing (CAD-CAM), the core is made of a similar material as the post. All these models are restored with crowns. To evaluate stress distribution in various different tooth models restored with different post materials force was generated on the model at a predetermined area by finite element analysis software and results were noted (Table 4).
The survival of endodontically treated and restored teeth depends on the amount of remaining coronal structure, restorative procedures, and material selection [26,27]. In particular, the preservation of at least one residual coronal wall or a circumferential 2-mm ferrule effect may contribute to overall tooth mechanical resistance [28]. Posts can be classified based on the elastic modulus, with metallic posts (prefabricated or cast metal posts), ceramic posts, and carbon fiber posts presenting high values and glass fiber posts presenting low elastic modulus [29]. The time needed for preparation, application, and esthetic performance have become important issues in daily practice, however, the strength and reliability of the system used are even more important [7]. During post and core treatment to restore a compromised endodontically treated tooth, the space is filled with a material that has a definite stiffness, unlike the pulp tissue and this creates an unnatural stress distribution within the tooth [1]. Posts that are stiff materials, unlike pulp tissue, create unnatural stresses on restored teeth [1]. Different post materials produce different stresses on restored teeth. FEA is the most widely used numerical method, allowing the reproduction of mechanical behavior under a mechanical load based on the properties of the materials [30]. To evaluate the stress distribution of these different post materials, many in vitro studies were conducted by using finite element analysis but a consistent conclusion has not been established. So in order to know which post material has better stress distribution in endodontically treated teeth, this systematic review was conducted.
After a detailed literature search, 22 articles were taken into consideration. Glass fiber posts have been used in 15 studies, of which they showed the least stress in 11 studies, prefabricated stainless steel used in five studies has been shown to produce more stresses on tooth structure in four studies, and prefabricated titanium used in seven studies showed high stresses in five studies. The modulus of elasticity (MOE) of enamel is around 80 GPa and that of dentin is 18.6GPa. Materials having MOE values close to enamel or dentin will have a better distribution of stress on restored teeth. The MOE value of glass fiber posts is around 40 Gpa, stainless steel, nickel-chromium (Ni-Cr), and zirconium are around 200, and that of titanium is 115 Gpa [1,11]. The forces generated to act on scanned models ranged from 100N-400N. A 100N force was frequently used in these studies, and the direction of these forces was mostly palatal. CAD-CAM posts made of various materials, such as fiber-reinforced composite (FRC), high-density polymer, polymer-infiltrated ceramic network, nanoceramic, composite resin, hybrid ceramic, lithium disilicate, titanium, Yttria-stabilized zirconia (Y-TZP) material, and zirconia, and tested in studies showed that there is no statistical difference in the stress distribution of these posts [21,24]. CAD-CAM/cast zirconia have better stress distribution than prefabricated zirconia [16]. Similarly, cast titanium has better stress distribution than prefabricated titanium. Cast metal post-and-core systems caused lower levels of stress compared to prefabricated metallic posts. When compared between carbon posts and fiber posts, the latter showed better stress distribution. Polyether ether ketone (PEEK) posts showed better stress distribution than polyether ketone-ketone (PEKK) posts [1]. Carbon fiber-reinforced-polyether ether ketone (CRF-PEEK), glass fiber reinforced-polyether ether ketone (GFR-PEEK), and PEKK materials can be used as materials of choice since they have similar stress distribution when compared to fiber-reinforced composite (FRC) post [1].
The stress distribution of glass fiber posts, even though homogenous, is mostly concentrated in the cervical region, whereas stainless steel, titanium, zirconia, and cast posts showed stress within the post, cervical, and apical regions of tooth structure. So fiber post fractures are less likely to occur in the root since its core and post failure indices were higher. Materials like fiber posts that show a homogenous stress distribution, have a modulus of elasticity similar or close to that of dentin. One study concluded that cast posts, stainless steel, titanium, and ceramic posts induced a more favorable stress distribution pattern in comparison with FRC posts [3].
The limitations of this systematic review are: all the post and core restorations were given crowns made of different materials, which could influence their stress distribution. The forces used in most of the studies are static forces, whereas in the oral cavity, there are masticatory forces that should be taken into consideration. Studies involving fiber posts are more when compared to other posts, which may have an influence on the outcome.
Glass fiber posts induce a more homogeneous stress distribution with the least stresses on restored teeth as compared to all other posts. The maximum stress concentration is at the cervical third of the tooth. Prefabricated posts, in general, cause greater stress than custom posts. Prefabricated posts made of stainless steel and titanium exhibit more stresses on the restored tooth structure, with maximum stress concentration at the cervical and apical thirds of the root, whereas prefabricated zirconia posts manifest maximum stress concentration at the middle third.
Department of Conservative Dentistry and Endodontics, MNR Dental College and Hospital, Hyderabad, IND
Department of Conservative Dentistry and Endodontics, MNR Dental College and Hospital, Hyderabad, IND
Department of Conservative Dentistry and Endodontics, MNR Dental College and Hospital, Hyderabad, IND
Department of Conservative Dentistry and Endodontics, MNR Dental College and Hospital, Hyderabad, IND
Department of Conservative Dentistry and Endodontics, MNR Dental College and Hospital, Hyderabad, IND
Department of Conservative Dentistry and Endodontics, MNR Dental College and Hospital, Hyderabad, IND
Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work.
Badami V, Ketineni H, PB S, et al. (September 29, 2022) Comparative Evaluation of Different Post Materials on Stress Distribution in Endodontically Treated Teeth Using the Finite Element Analysis Method: A Systematic Review. Cureus 14(9): e29753. doi:10.7759/cureus.29753
Peer review began: September 19, 2022 Peer review concluded: September 25, 2022 Published: September 29, 2022
© Copyright 2022 Badami et al. This is an open access article distributed under the terms of the Creative Commons Attribution License CC-BY 4.0., which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Scholarly Impact Quotient™ (SIQ™) is our unique post-publication peer review rating process. Learn more here.
This link will take you to a third party website that is not affiliated with Cureus, Inc. Please note that Cureus is not responsible for any content or activities contained within our partner or affiliate websites.
Scholarly Impact Quotient™ (SIQ™) is our unique post-publication peer review rating process. SIQ™ assesses article importance and quality by embracing the collective intelligence of the Cureus community-at-large. All registered users are invited to contribute to the SIQ™ of any published article. (Authors cannot rate their own articles.)
High ratings should be reserved for work that is truly groundbreaking in its respective field. Anything above 5 should be considered above average. While all registered Cureus users can rate any published article, the opinion of domain experts is weighted appreciably more than that of non-specialists. An article’s SIQ™ will appear alongside the article after being rated twice and is recalculated with each additional rating.
Visit our SIQ™ page to find out more.
Scholarly Impact Quotient™ (SIQ™) is our unique post-publication peer review rating process. SIQ™ assesses article importance and quality by embracing the collective intelligence of the Cureus community-at-large. All registered users are invited to contribute to the SIQ™ of any published article. (Authors cannot rate their own articles.)
Already have an account? Sign in.
Please note that by doing so you agree to be added to our monthly email newsletter distribution list.
By joining Cureus, you agree to our Privacy Policy and Terms of Use.