The Open Dentistry Journal




ISSN: 1874-2106 ― Volume 14, 2020
REVIEW ARTICLE

State of the Art Contemporary Prefabricated Fiber-Reinforced Posts



Emad S. Elsubeihi1, *, Tareq Aljafarawi1, Heba E. Elsubeihi1
1 Department of Restorative Dentistry, College of Dentistry, Ajman University, Ajman, UAE

Abstract

Background:

There is an increased interest in investigating and use of prefabricated fiber-reinforced posts by scientists and clinicians in the restoration of endodontically treated teeth.

Objective:

The objective of this narrative review was to summarize the composition of contemporary prefabricated fiber-reinforced posts and elucidate its effect on the different properties of these posts.

Methods:

PubMed/Medline, Scopus, and Google Scholar were searched from January 1990 to December 2019 for English Language articles describing the composition and properties of prefabricated fiber-reinforced posts. First, the search strategy was established for Medline / PubMed using the following terms ((Fiber post[All Fields] OR (fiber reinforced post[All Fields] AND composition[All Fields] AND (“matrix”[MeSH Terms] OR (“fiber”[All Fields] AND “properties”[All Fields] AND “epoxy”[All Fields]) OR “dimethacrylate”[All Fields]) AND NOT (CAD CAM[All Fields])). The search strategy was then adapted for Scopus and Google Scholar databases to identify eligible studies.

Results:

The current state of the art of prefabricated fiber-reinforced posts revealed a myriad of products with different formulations which are reflected on the mechanical and handling characteristics of the different posts available in the market. More recent research and development efforts attempted to address issues related to the improved transmission of polymerization light through the post to the most apical end of the restoration inside the root canal. Others focused on the development of new matrix materials for fiber-reinforced posts.

Conclusion:

A review of the literature revealed that currently available prefabricated fiber-reinforced posts consist of a heterogeneous group of materials which can have a significant effect on the behavior of posts. Understanding different formulations will help clinicians in scrutinizing the vast literature available on prefabricated fiber-reinforced posts. This, in turn, will help them make an informed decision when selecting materials for the restoration of endodontically treated teeth.

Keywords: Fiber-reinforced post, Glass fibers, Composition, Review, Prefabricated fiber posts, Post matrix.


Article Information


Identifiers and Pagination:

Year: 2020
Volume: 14
First Page: 313
Last Page: 323
Publisher Id: TODENTJ-14-313
DOI: 10.2174/1874210602014010313

Article History:

Received Date: 24/03/2020
Revision Received Date: 13/04/2020
Acceptance Date: 20/04/2020
Electronic publication date: 26/06/2020
Collection year: 2020

© 2020 Elsubeihi et al.

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: https://creativecommons.org/licenses/by/4.0/legalcode. This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.


* Address correspondence to this author at the Department of Restorative Dentistry, College of Dentistry, Ajman University, P.O. Box 346, Ajman, UAE; Tel: +971-6-748 2222; Fax: +971-6-743 8888; E-mail: e.elsubeihi@ajman.ac.ae





1. INTRODUCTION

Although restoration of endodontically treated teeth is a daily clinical decision in restorative dentistry practice, there appears to be disagreement in recommendations regarding the selection of materials and techniques for their restorations [1Faria AC, Rodrigues RC, de Almeida Antunes RP, de Mattos MdaG, Ribeiro RF. Endodontically treated teeth: characteristics and considerations to restore them. J Prosthodont Res 2011; 55(2): 69-74.
[http://dx.doi.org/10.1016/j.jpor.2010.07.003] [PMID: 20709618]
, 2Türp JC, Heydecke G, Krastl G, Pontius O, Antes G, Zitzmann NU. Restoring the fractured root-canal-treated maxillary lateral incisor: in search of an evidence-based approach. Quintessence Int 2007; 38(3): 179-91.
[PMID: 17333995]
]. Loss of a large proportion of coronal tooth structure due to caries, previous restorations, and endodontic access cavity preparation, results in an increased need for the placement of intra-radicular posts during the restoration of endodontically treated teeth. Until the early 1990s, accepted methods to fabricate intra-radicular posts included custom-made cast metal posts and cores or prefabricated metal posts, made of stainless steel or titanium alloys, in combination with different core materials.

Originally clinicians believed that posts could reinforce the root canal treated teeth [3Cheung W. A review of the management of endodontically treated teeth. Post, core and the final restoration. J Am Dent Assoc 2005; 136(5): 611-9.
[http://dx.doi.org/10.14219/jada.archive.2005.0232] [PMID: 15966648]
]. However, later studies have pointed out that posts do not strengthen teeth. In fact, these studies demonstrated that the preparation of a post space and the placement of a metal post can weaken the root and may lead to root fracture [4Lovdahl PE, Nicholls JI. Pin-retained amalgam cores vs. cast-gold dowel-cores. J Prosthet Dent 1977; 38(5): 507-14.
[http://dx.doi.org/10.1016/0022-3913(77)90025-7] [PMID: 335051]
-7Trope M, Maltz DO, Tronstad L. Resistance to fracture of restored endodontically treated teeth. Endod Dent Traumatol 1985; 1(3): 108-11.
[http://dx.doi.org/10.1111/j.1600-9657.1985.tb00571.x] [PMID: 3893998]
]. These and other studies have, therefore, suggested that a post should be used only when the remaining coronal tooth tissue can no longer provide adequate support and retention for the coronal restoration [8Morgano SM. Restoration of pulpless teeth: Application of traditional principles in present and future contexts. J Prosthet Dent 1996; 75(4): 375-80.
[http://dx.doi.org/10.1016/S0022-3913(96)90028-1] [PMID: 8642522]
, 9Torbjörner A, Fransson B. A literature review on the prosthetic treatment of structurally compromised teeth. Int J Prosthodont 2004; 17(3): 369-76.
[PMID: 15237888]
].

Disadvantages of metallic posts such as the risk of corrosion, root fractures, loss of retention, coupled with increased demand for aesthetic restorations that necessitates placement of aesthetic posts underneath all ceramic crowns led to the development of posts made of aesthetic materials such as ceramic zirconia [10Bittner N, Hill T, Randi A. Evaluation of a one-piece milled zirconia post and core with different post-and-core systems: An in vitro study. J Prosthet Dent 2010; 103(6): 369-79.
[http://dx.doi.org/10.1016/S0022-3913(10)60080-7] [PMID: 20493326]
], fiber-reinforced composites [11Alnaqbi IOM, Elbishari H, Elsubeihi ES. Effect of fiber post-resin matrix composition on bond strength of post-cement interface. Int J Dent 2018; 2;2018: 4751627. eCollection
[http://dx.doi.org/10.1155/2018/4751627]
], and polyetherketoneketone (PEKK) [12Song CH, Choi JW, Jeon YC, et al. Comparison of the microtensilebond strength of a polyetherketoneketone (PEKK) tooth post cemented with various surface treatments and various resin cements. Materials (Basel) 2018; 11(6): E916.
[http://dx.doi.org/10.3390/ma11060916] [PMID: 29844270]
]. Among these, fiber-reinforced posts attracted the attention of researchers and clinicians alike, resulting in increased use of these posts in clinical situations. The increased demand for fiber-reinforced posts resulted in the development of an enormous variety of fiber-reinforced posts with different compositions. Studies have shown that different prefabricated fiber-reinforced posts exhibited variations with regard to mechanical properties [13Alonso de la Peña V, Darriba IL, Caserío Valea M, Guitián Rivera F. Mechanical properties related to the microstructure of seven different fiber reinforced composite posts. J Adv Prosthodont 2016; 8(6): 433-8.
[http://dx.doi.org/10.4047/jap.2016.8.6.433] [PMID: 28018560]
, 14Chieruzzi M, Pagano S, Pennacchi M, Lombardo G, D’Errico P, Kenny JM. Compressive and flexural behaviour of fibre reinforced endodontic posts. J Dent 2012; 40(11): 968-78.
[http://dx.doi.org/10.1016/j.jdent.2012.08.003] [PMID: 22917560]
], ability to transmit polymerization light [15Goracci C, Corciolani G, Vichi A, Ferrari M. Light-transmitting ability of marketed fiber posts. J Dent Res 2008; 87(12): 1122-6.
[http://dx.doi.org/10.1177/154405910808701208] [PMID: 19029079]
, 16Galhano GA, de Melo RM, Barbosa SH, Zamboni SC, Bottino MA, Scotti R. Evaluation of light transmission through translucent and opaque posts. Oper Dent 2008; 33(3): 321-4.
[http://dx.doi.org/10.2341/07-93] [PMID: 18505223]
], radiopacity [17Erik AA, Erik CE, Yıldırım D. Experimental study of influence of composition on radiopacity of fiber post materials. Microsc Res Tech 2019; 82(9): 1448-54.
[http://dx.doi.org/10.1002/jemt.23298] [PMID: 31119821]
], as well as interactions with different materials such as luting cements and composite core materials [11Alnaqbi IOM, Elbishari H, Elsubeihi ES. Effect of fiber post-resin matrix composition on bond strength of post-cement interface. Int J Dent 2018; 2;2018: 4751627. eCollection
[http://dx.doi.org/10.1155/2018/4751627]
, 18Zicari F, De Munck J, Scotti R, Naert I, Van Meerbeek B. Factors affecting the cement-post interface. Dent Mater 2012; 28(3): 287-97.
[http://dx.doi.org/10.1016/j.dental.2011.11.003] [PMID: 22169674]
].

Therefore, understanding the differences in the composition of the various prefabricated fiber-reinforced posts is essential for clinicians to be able to select appropriate materials for the restoration of endodontically treated teeth. Hence, the aim of this narrative review is to summarize the current knowledge on the composition of contemporary prefabricated fiber-reinforced posts.

2. MATERIALS AND METHODS

It is well accepted that systematic reviews follow a predetermined method to methodically search, select, appraise, synthesize, and analyze the literature [19Greenhalgh T, Thorne S, Malterud K. Time to challenge the spurious hierarchy of systematic over narrative reviews? Eur J Clin Invest 2018; 48(6)e12931
[http://dx.doi.org/10.1111/eci.12931] [PMID: 29578574]
]. As systematic reviews are designed to answer focused questions, they do not allow for a comprehensive insight of some topics particularly those tracing the development of a clinical concept [19Greenhalgh T, Thorne S, Malterud K. Time to challenge the spurious hierarchy of systematic over narrative reviews? Eur J Clin Invest 2018; 48(6)e12931
[http://dx.doi.org/10.1111/eci.12931] [PMID: 29578574]
-21Collins JA, Fauser BC. Balancing the strengths of systematic and narrative reviews. Hum Reprod Update 2005; 11(2): 103-4.
[http://dx.doi.org/10.1093/humupd/dmh058] [PMID: 15618290]
], such as that of the current review on the different compositions of prefabricated contemporary fiber-reinforced posts. The question to be answered in this review was “what are the different formulations/compositions of prefabricated fiber-reinforced posts?”. To answer this, a narrative review was used to avoid losing valuable information that may occur as a result of the strict inclusion/exclusion criteria used in systematic reviews, thus allowing for the selection of relevant literature to the question.

For this review, the literature search was carried out using the electronic databases PubMed/Medline, Scopus, and Google Scholar from January 1990 to December 2019. The search strategy was first established for Medline via PubMed using the following terms: ((Fiber post[All Fields] OR (fiber reinforced post[All Fields] AND composition[All Fields] AND (“matrix”[MeSH Terms] OR (“fiber”[All Fields] AND “properties”[All Fields] AND “epoxy”[All Fields]) OR “dimethacrylate”[All Fields]) AND NOT (CAD CAM[All Fields])). The search strategy was then adapted for Scopus and Google Scholar databases to identify eligible studies. Additionally, hand searching of retrieved articles was also performed for further relevant publications. The search was limited to English language literature.

The articles screened were divided into relevant or nonrelevant for the present review based on the following inclusion criteria; 1) articles describing the composition of prefabricated fiber-reinforced posts, and 2) properties as related to the composition of prefabricated fiber-reinforced posts. Articles describing custom-made fiber posts and CAD-CAM made posts were excluded.

3. RESULTS

A total of 2640 articles were identified from the three electronic databases (Fig. 1). First, the identified articles were uploaded into a reference manager software library (Zotero, Corporation for Digital Scholarship, NY) and duplicate articles were excluded. The titles and abstracts of the remaining articles were then screened by two independent reviewers (T.A and H.E.E). Three hundred and twenty-seven articles satisfied the inclusion criteria and were selected for full-text reading. Following readings of full-text articles, 53 articles were selected. The inclusion of articles was based on discussions between the two reviewers. To assess consistency among the reviewers, the inter-reviewer reliability was calculated (Cohen’s Kappa Index Value 0.886 [95% CI 0.950; 0.82]; p = 0.001). Disagreements between the two reviewers were resolved through discussion with the third reviewer (E.S.E.). A hand search of the selected articles yielded further 4 articles that were considered pertinent to the topic. Ultimately, 57 articles [1Faria AC, Rodrigues RC, de Almeida Antunes RP, de Mattos MdaG, Ribeiro RF. Endodontically treated teeth: characteristics and considerations to restore them. J Prosthodont Res 2011; 55(2): 69-74.
[http://dx.doi.org/10.1016/j.jpor.2010.07.003] [PMID: 20709618]
-3Cheung W. A review of the management of endodontically treated teeth. Post, core and the final restoration. J Am Dent Assoc 2005; 136(5): 611-9.
[http://dx.doi.org/10.14219/jada.archive.2005.0232] [PMID: 15966648]
, 5Guzy GE, Nicholls JI. In vitro comparison of intact endodontically treated teeth with and without endo-post reinforcement. J Prosthet Dent 1979; 42(1): 39-44.
[http://dx.doi.org/10.1016/0022-3913(79)90328-7] [PMID: 379307]
-18Zicari F, De Munck J, Scotti R, Naert I, Van Meerbeek B. Factors affecting the cement-post interface. Dent Mater 2012; 28(3): 287-97.
[http://dx.doi.org/10.1016/j.dental.2011.11.003] [PMID: 22169674]
, 22Duret B, Duret F, Reynaud M. Long-life physical property preservation and prosthodontic rehabilitation with the Composipost. Compend Contin Educ Dent 1996; 17(Suppl. 20): S50-6.-61Stylianou A, Burgess JO, Liu PR, Givan DA, Lawson NC. Light-transmitting fiber optic posts: An in vitro evaluation. J Prosthet Dent 2017; 117(1): 116-23.
[http://dx.doi.org/10.1016/j.prosdent.2016.06.020] [PMID: 27646793]
] were included in this review.

Information from the selected articles was synthesized in this narrative review under the following headings; i) historical background, ii) advantages of fiber-reinforced posts, iii) composition of fiber-reinforced posts, and iv) conclusions, as described in the following sections.

4. HISTORICAL BACKGROUND

Fiber-reinforced posts introduced in the early 1990s [22Duret B, Duret F, Reynaud M. Long-life physical property preservation and prosthodontic rehabilitation with the Composipost. Compend Contin Educ Dent 1996; 17(Suppl. 20): S50-6.]as an alternative to cast post-and-core metal posts [1Faria AC, Rodrigues RC, de Almeida Antunes RP, de Mattos MdaG, Ribeiro RF. Endodontically treated teeth: characteristics and considerations to restore them. J Prosthodont Res 2011; 55(2): 69-74.
[http://dx.doi.org/10.1016/j.jpor.2010.07.003] [PMID: 20709618]
, 23Theodosopoulou JN, Chochlidakis KM. A systematic review of dowel (post) and core materials and systems. J Prosthodont 2009; 18(6): 464-72.
[http://dx.doi.org/10.1111/j.1532-849X.2009.00472.x] [PMID: 19500237]
, 24Bateman G, Ricketts DNJ, Saunders WP. Fibre-based post systems: A review. Br Dent J 2003; 195(1): 43-8.
[http://dx.doi.org/10.1038/sj.bdj.4810278] [PMID: 12856030]
]. The technology of fiber-reinforced posts development was based on the principles of fiber-reinforced acrylic and composites. The dental use of this technology started in the 1960s to strengthen acrylic base materials for removable partial dentures [25Narva KK, Vallittu PK, Helenius H, Yli-Urpo A. Clinical survey of acrylic resin removable denture repairs with glass-fiber reinforcement. Int J Prosthodont 2001; 14(3): 219-24.
[PMID: 11484568]
]. This was followed by the attempts to combine reinforcing fibers with dimethacrylate composite resin to be used for the fabrication of fixed partial dentures [26Vallittu PK. An overview of development and status of fiber-reinforced composites as dental and medical biomaterials. Acta BiomaterOdontol Scand 2018; 12;4(1): 44-55.
[http://dx.doi.org/10.1080/23337931.2018.1457445]
, 27Freilich MA, Karmaker AC, Burstone CJ, Goldberg AJ. Development and clinical applications of a light-polymerized fiber-reinforced composite. J Prosthet Dent 1998; 80(3): 311-8.
[http://dx.doi.org/10.1016/S0022-3913(98)70131-3] [PMID: 9760363]
].

The first introduced fiber-reinforced post, namely Composipost®, consisted of carbon/graphite fibers embedded in an epoxy resin matrix [22Duret B, Duret F, Reynaud M. Long-life physical property preservation and prosthodontic rehabilitation with the Composipost. Compend Contin Educ Dent 1996; 17(Suppl. 20): S50-6.]. They were characterized by good mechanical properties, such as high stiffness and tensile strength, in addition to electrical conductivity and comparatively low toxicity [28Soares CJ, Santana FR, Pereira JC, Araujo TS, Menezes MS. Influence of airborne-particle abrasion on mechanical properties and bond strength of carbon/epoxy and glass/bis-GMA fiber-reinforced resin posts. J Prosthet Dent 2008; 99(6): 444-54.
[http://dx.doi.org/10.1016/S0022-3913(08)60106-7] [PMID: 18514666]
, 29Lassila LV, Tanner J, Le Bell AM, Narva K, Vallittu PK. Flexural properties of fiber reinforced root canal posts. Dent Mater 2004; 20(1): 29-36.
[http://dx.doi.org/10.1016/S0109-5641(03)00065-4] [PMID: 14698771]
].

Fig. (1)
Flowchart of the screening and selection process.


The main drawbacks of carbon fiber-reinforced posts were their black color limiting their use under all-ceramic and composite restorations in areas of high aesthetic demand, and their radiolucency, which made it difficult to identify these posts on radiographs due to the carbon content [30Vichi A, Ferrari M, Davidson CL. Influence of ceramic and cement thickness on the masking of various types of opaque posts. J Prosthet Dent 2000; 83(4): 412-7.
[http://dx.doi.org/10.1016/S0022-3913(00)70035-7] [PMID: 10756290]
, 31Asmussen E, Peutzfeldt A, Heitmann T. Stiffness, elastic limit, and strength of newer types of endodontic posts. J Dent 1999; 27(4): 275-8.
[http://dx.doi.org/10.1016/S0300-5712(98)00066-9] [PMID: 10193104]
]. These limitations of carbon fiber-reinforced posts led to the development of fiber-reinforced posts with more esthetic and radiopaque properties using silica fibers in the form of quartz or glass fibers embedded in a polymer matrix [30Vichi A, Ferrari M, Davidson CL. Influence of ceramic and cement thickness on the masking of various types of opaque posts. J Prosthet Dent 2000; 83(4): 412-7.
[http://dx.doi.org/10.1016/S0022-3913(00)70035-7] [PMID: 10756290]
, 31Asmussen E, Peutzfeldt A, Heitmann T. Stiffness, elastic limit, and strength of newer types of endodontic posts. J Dent 1999; 27(4): 275-8.
[http://dx.doi.org/10.1016/S0300-5712(98)00066-9] [PMID: 10193104]
].

5. ADVANTAGES OF FIBER-REINFORCED POSTS

It has been suggested that the most significant advantage of fiber-reinforced posts as compared to other metallic, or ceramic posts is their modulus of elasticity. Several authors believe that the similarity between the elastic moduli of fiber-reinforced posts and dentine will distribute the stress and less likely to cause root fracture in endodontically treated teeth as compared to metal posts [22Duret B, Duret F, Reynaud M. Long-life physical property preservation and prosthodontic rehabilitation with the Composipost. Compend Contin Educ Dent 1996; 17(Suppl. 20): S50-6., 32Wolff D, Geiger S, Ding P, Staehle HJ, Frese C. Analysis of the interdiffusion of resin monomers into pre-polymerized fiber-reinforced composites. Dent Mater 2012; 28(5): 541-7.
[http://dx.doi.org/10.1016/j.dental.2011.12.001] [PMID: 22230106]
, 33Dietschi D, Ardu S, Rossier-Gerber A, Krejci I. Adaptation of adhesive post and cores to dentin after in vitro occlusal loading: Evaluation of post material influence. J Adhes Dent 2006; 8(6): 409-19.
[PMID: 17243599]
]. The modulus of elasticity of glass fiber posts, however, has been shown to range from 20- 56 GPa [34Stewardson DA, Shortall AC, Marquis PM, Lumley PJ. The flexural properties of endodontic post materials. Dent Mater 2010; 26(8): 730-6.
[http://dx.doi.org/10.1016/j.dental.2010.03.017] [PMID: 20413150]
, 35Novais VR, Rodrigues RB, Simamoto Júnior PC, Lourenço CS, Soares CJ. Correlation between the mechanical properties and structural characteristics of different fiber posts systems. Braz Dent J 2016; 27(1): 46-51.
[http://dx.doi.org/10.1590/0103-6440201600377] [PMID: 27007345]
], which is relatively close to that of dentin (range between 18 - 20 GPa) as compared to that of cast metal alloy and prefabricated metal posts which range from 86 - 200 GPa [34Stewardson DA, Shortall AC, Marquis PM, Lumley PJ. The flexural properties of endodontic post materials. Dent Mater 2010; 26(8): 730-6.
[http://dx.doi.org/10.1016/j.dental.2010.03.017] [PMID: 20413150]
]. Therefore, the elastic moduli of some prefabricated fiber-reinforced posts is about 2-3 times, whereas that of metal posts is about 4-10 times that of dentine [34Stewardson DA, Shortall AC, Marquis PM, Lumley PJ. The flexural properties of endodontic post materials. Dent Mater 2010; 26(8): 730-6.
[http://dx.doi.org/10.1016/j.dental.2010.03.017] [PMID: 20413150]
].

The other advantage of fiber-reinforced posts is their ability to bond with most resin cements and resin-based composite core materials. Luting of the fiber-reinforced post to the dentinal wall with resin cement gives advantages like reducing the wedging effect of the post in root canal thus reducing the incidence of root fracture [36Santos AF, Meira JB, Tanaka CB, et al. Can fiber posts increase root stresses and reduce fracture? J Dent Res 2010; 89(6): 587-91.
[http://dx.doi.org/10.1177/0022034510363382] [PMID: 20348486]
-38Naumann M, Sterzenbach G, Rosentritt M, Beuer F, Frankenberger R. Is adhesive cementation of endodontic posts necessary? J Endod 2008; 34(8): 1006-10.
[http://dx.doi.org/10.1016/j.joen.2008.05.010] [PMID: 18634936]
].

Fiber-reinforced posts also overcome limitations of metal posts like the possibility of corrosion and associated possible biocompatibility concerns that may trigger allergic reactions [39de Moraes AP, Cenci MS, de Moraes RR, Pereira-Cenci T. Current concepts on the use and adhesive bonding of glass-fiber posts in dentistry: a review. Appl Adhes Sci 2013; 1: 4.
[http://dx.doi.org/10.1186/2196-4351-1-4]
]. Furthermore, improved aesthetics of fiber-reinforced posts with glass or quartz fibers offered the most satisfactory visual properties which allowed the use of all ceramic crowns with improved aesthetics of the restored endodontically treated teeth [39de Moraes AP, Cenci MS, de Moraes RR, Pereira-Cenci T. Current concepts on the use and adhesive bonding of glass-fiber posts in dentistry: a review. Appl Adhes Sci 2013; 1: 4.
[http://dx.doi.org/10.1186/2196-4351-1-4]
]. Moreover, the use of fiber-reinforced posts simplified clinical procedures by eliminating the need for laboratory steps and facilitated re-treatment in cases of endodontic failure as a result of their easier removal techniques [39de Moraes AP, Cenci MS, de Moraes RR, Pereira-Cenci T. Current concepts on the use and adhesive bonding of glass-fiber posts in dentistry: a review. Appl Adhes Sci 2013; 1: 4.
[http://dx.doi.org/10.1186/2196-4351-1-4]
-41de Rijk WG. Removal of fiber posts from endodontically treated teeth. Am J Dent 2000; 13(Spec No): 19B-21B.
[PMID: 11763867]
].

6. COMPOSITION OF FIBER-REINFORCED POSTS

There is a myriad of commercially available fiber-reinforced posts on the market to choose from (Table 1). They are essentially composed of pre-stretched fibers bounded by a polymer resin matrix [11Alnaqbi IOM, Elbishari H, Elsubeihi ES. Effect of fiber post-resin matrix composition on bond strength of post-cement interface. Int J Dent 2018; 2;2018: 4751627. eCollection
[http://dx.doi.org/10.1155/2018/4751627]
]. The different components of the fiber-reinforced post are shown in Figs. (2 and 3).

Fig. (2)
Fig. (2-A) shows a scanning electron microscope image of a cross-section of prefabricated fiber-reinforced post surrounded by a composite core (X 100). Fig. (2-B) Magnified image (X700)in the middle of the post demonstrating glass fibers surrounded by the polymer matrix. C: Composite core. P: Prefabricated fiber-reinforced post. M: Polymer matrix. F: Glass fiber.


Table 1
Commonly used/investigated prefabricated fiber-reinforced posts.


Fig. (3)
Different components of prefabricated fiber-reinforced posts. * Some manufacturers add fillers such as zirconia, barium, and silicate dioxide to improve radiopacity. Polyimide matrix is still experimental, and no known commercial prefabricated fiber-reinforced post has Polyimide matrix.


6.1. Matrices used in Fiber-reinforced Posts

The functions of the matrix in fiber-reinforced posts are to hold the fibers together in the post, as well as interact with functional monomers contained in the adhesive cements for successful bonding of post to root dentine and to composite core materials [31Asmussen E, Peutzfeldt A, Heitmann T. Stiffness, elastic limit, and strength of newer types of endodontic posts. J Dent 1999; 27(4): 275-8.
[http://dx.doi.org/10.1016/S0300-5712(98)00066-9] [PMID: 10193104]
]. Furthermore, the matrix transfers stresses between fibers and protects fibers from the outside environment such as chemicals, moisture, and mechanical shocks [42Zhang M, Matinlinna JP. E-glass fiber reinforced composites in dental applications. Silicon 2012; 4: 73-8.
[http://dx.doi.org/10.1007/s12633-011-9075-x]
]. Thus, the matrix may influence the compressive strength of the post, as well as interlaminar shear properties between the matrix and the fiber [42Zhang M, Matinlinna JP. E-glass fiber reinforced composites in dental applications. Silicon 2012; 4: 73-8.
[http://dx.doi.org/10.1007/s12633-011-9075-x]
].

During the manufacturing of fiber-reinforced posts, glass or quartz fibers are pre-stretched and treated with silane coupling agent before they are impregnated in the resin matrix [43Grandini S, Goracci C, Monticelli F, Tay FR, Ferrari M. Fatigue resistance and structural characteristics of fiber posts: three-point bending test and SEM evaluation. Dent Mater 2005; 21(2): 75-82.
[http://dx.doi.org/10.1016/j.dental.2004.02.012] [PMID: 15681005]
]. The resin-impregnated fibers are then heat cured to form blocks of different shapes and diameters. Finally, the blocks are shaped into posts with different geometries and diameters through a milling process [44Manhart J. Fibreglass-reinforced composite endodontic posts. EndodPract 2009; 16: 54-8.]. As a result of the milling process, some of the fibers are exposed onto the surface of the prefabricated posts (Fig. 4).

Two major types of matrices are used in prefabricated fiber-reinforced posts. The first type consists of a highly cross-linked polymer matrix polymerized by the manufacturers, while the second type consists of unpolymerized, the so-called interpenetrating polymer matrix where the dentist can polymerize it during the fabrication of the post-core restoration [11Alnaqbi IOM, Elbishari H, Elsubeihi ES. Effect of fiber post-resin matrix composition on bond strength of post-cement interface. Int J Dent 2018; 2;2018: 4751627. eCollection
[http://dx.doi.org/10.1155/2018/4751627]
].

The most common types of matrices used in the polymerized cross-linked fiber-reinforced posts are epoxy-based or diamethacrylate-based cross-linked matrix. Less commonly, some manufacturers use polymethylmethacrylate-based resin matrix for their posts. Additionally, some investigators have suggested the use of aromatic polyimides as a matrix for fiber-reinforced posts [45Gao H, Zhang ZT, Fan L, Wang DS, Zuo HJ, Sheng Y. Development of a novel polyimide composite core materials reinforced with carbon fiber. Chinese J Prosthodont 2007; 3: 210-2.].

Fig. (4)
Scanning electron microscope image (500X) of the surface of the prefabricated fiber-reinforced post. Note matrix and exposed glass fibers as a result of the manufacturing process.


Epoxy resin are thermosetting polymers, also known as polyepoxide, that are formed by the reaction of the base epoxide with the reactor polyamine [46Lamichhane A, Xu C, Zhang FQ. Dental fiber-post resin base material: a review. J Adv Prosthodont 2014; 6(1): 60-5.
[http://dx.doi.org/10.4047/jap.2014.6.1.60] [PMID: 24605208]
]. On the other hand, the aromatic monomer Bis-GMA (bisphenol A glycidyl methacrylate) used widely as a matrix in dental composite resin materials have also been used as a matrix in fiber-reinforced posts. Bis-GMA matrix is known to be stiffer than the epoxy matrix [47Drummond JL, Bapna MS. Static and cyclic loading of fiber-reinforced dental resin. Dent Mater 2003; 19(3): 226-31.
[http://dx.doi.org/10.1016/S0109-5641(02)00034-9] [PMID: 12628435]
]. As a result, flexural strength tests have shown that Bis-GMA-based matrix to experience greater stresses than epoxy-based matrix in fiber-reinforced posts [47Drummond JL, Bapna MS. Static and cyclic loading of fiber-reinforced dental resin. Dent Mater 2003; 19(3): 226-31.
[http://dx.doi.org/10.1016/S0109-5641(02)00034-9] [PMID: 12628435]
]. Only a few manufacturers use polymethylmethacrylate of high molecular weight (> 220 KDa) as a matrix for fiber-reinforced posts [48Seefeld F, Wenz HJ, Ludwig K, Kern M. Resistance to fracture and structural characteristics of different fiber reinforced post systems. Dent Mater 2007; 23(3): 265-71.
[http://dx.doi.org/10.1016/j.dental.2006.01.018] [PMID: 16519929]
].

The wide use of carbon-reinforced polyimide composite materials in aerospace and automobile industries has triggered researchers to investigate the possible use of these materials in fiber-reinforced posts [49Liaw DJ, Wang KL, Huang YC, Lee KR, Lai JY, Ha CS. Advanced polyimide materials: Syntheses, physical properties and applications. Prog Polym Sci 2012; 37(7): 907-74.
[http://dx.doi.org/10.1016/j.progpolymsci.2012.02.005]
]. Fiber-reinforced aromatic polyimides have been shown to have high strength and stiffness, lower density, high fatigue endurance, low thermal coefficient, and the ability to withstand extreme temperature changes [49Liaw DJ, Wang KL, Huang YC, Lee KR, Lai JY, Ha CS. Advanced polyimide materials: Syntheses, physical properties and applications. Prog Polym Sci 2012; 37(7): 907-74.
[http://dx.doi.org/10.1016/j.progpolymsci.2012.02.005]
, 50Li J. The effect of surface modification with nitric acid on the mechanical and tribological properties of carbon fiber-reinforced thermoplastic polyimide composite. Surf Interface Anal 2009; 41(9): 759-63.
[http://dx.doi.org/10.1002/sia.3089]
].

Gao and colleagues demonstrated that polyimide-based resin reinforced by high strength carbon fibers have good mechanical and biological properties and suggested its use in clinical situations [45Gao H, Zhang ZT, Fan L, Wang DS, Zuo HJ, Sheng Y. Development of a novel polyimide composite core materials reinforced with carbon fiber. Chinese J Prosthodont 2007; 3: 210-2.]. Recently, Yang and Xu [51Yang A, Xu C. Synthesis and characterization of a polyimide-epoxy composite for dental applications. Mech Compos Mater 2018; 54(1): 71-8.
[http://dx.doi.org/10.1007/s11029-018-9719-7]
] found that blending polyimide and epoxy polymers have favorable mechanical properties and suggested its use as a matrix for fiber-reinforced posts. However, no fiber-reinforced post with polyimide matrix has been marketed.

6.2. Fibers used in Fiber-reinforced Posts

As it has been already alluded to, original fibers used in fiber-reinforced posts were made of carbon [22Duret B, Duret F, Reynaud M. Long-life physical property preservation and prosthodontic rehabilitation with the Composipost. Compend Contin Educ Dent 1996; 17(Suppl. 20): S50-6., 28Soares CJ, Santana FR, Pereira JC, Araujo TS, Menezes MS. Influence of airborne-particle abrasion on mechanical properties and bond strength of carbon/epoxy and glass/bis-GMA fiber-reinforced resin posts. J Prosthet Dent 2008; 99(6): 444-54.
[http://dx.doi.org/10.1016/S0022-3913(08)60106-7] [PMID: 18514666]
]. As these carbon fibers did not fulfill aesthetic requirements under all-ceramic restorations, manufacturers developed more aesthetic fibers made of silica. Silica-based fibers can be either glass or quartz [30Vichi A, Ferrari M, Davidson CL. Influence of ceramic and cement thickness on the masking of various types of opaque posts. J Prosthet Dent 2000; 83(4): 412-7.
[http://dx.doi.org/10.1016/S0022-3913(00)70035-7] [PMID: 10756290]
, 31Asmussen E, Peutzfeldt A, Heitmann T. Stiffness, elastic limit, and strength of newer types of endodontic posts. J Dent 1999; 27(4): 275-8.
[http://dx.doi.org/10.1016/S0300-5712(98)00066-9] [PMID: 10193104]
]. The incorporated glass or quartz fibers imparted similar biomechanical properties, as carbon-fiber-reinforced posts, including elasticity, high tensile strength, low electrical conductivity, resistance to solubility and biochemical degradation [31Asmussen E, Peutzfeldt A, Heitmann T. Stiffness, elastic limit, and strength of newer types of endodontic posts. J Dent 1999; 27(4): 275-8.
[http://dx.doi.org/10.1016/S0300-5712(98)00066-9] [PMID: 10193104]
,39de Moraes AP, Cenci MS, de Moraes RR, Pereira-Cenci T. Current concepts on the use and adhesive bonding of glass-fiber posts in dentistry: a review. Appl Adhes Sci 2013; 1: 4.
[http://dx.doi.org/10.1186/2196-4351-1-4]
,52Giachetti L, Grandini S, Calamai P, Fantini G, Scaminaci Russo D. Translucent fiber post cementation using light- and dual-curing adhesive techniques and a self-adhesive material: push-out test. J Dent 2009; 37(8): 638-42.
[http://dx.doi.org/10.1016/j.jdent.2009.04.007] [PMID: 19477571]
]. On the other hand, some manufacturers used zirconia enriched glass fibers [15Goracci C, Corciolani G, Vichi A, Ferrari M. Light-transmitting ability of marketed fiber posts. J Dent Res 2008; 87(12): 1122-6.
[http://dx.doi.org/10.1177/154405910808701208] [PMID: 19029079]
].

Due to their favorable mechanical properties and transparent appearance, glass fibers had become the most commonly used fibers in fiber-reinforced posts [46Lamichhane A, Xu C, Zhang FQ. Dental fiber-post resin base material: a review. J Adv Prosthodont 2014; 6(1): 60-5.
[http://dx.doi.org/10.4047/jap.2014.6.1.60] [PMID: 24605208]
]. Based on their chemical composition there are several types of glass fibers available including A-glass (Alkali glass), C-glass (chemically resistant glass), D-glass (dielectric glass), R-glass (resistant glass), S-glass (high strength glass), and E-glass (electric glass) among others [42Zhang M, Matinlinna JP. E-glass fiber reinforced composites in dental applications. Silicon 2012; 4: 73-8.
[http://dx.doi.org/10.1007/s12633-011-9075-x]
]. However, the most common types used in fiber-reinforced posts are the S-glass and E-glass fibers [46Lamichhane A, Xu C, Zhang FQ. Dental fiber-post resin base material: a review. J Adv Prosthodont 2014; 6(1): 60-5.
[http://dx.doi.org/10.4047/jap.2014.6.1.60] [PMID: 24605208]
]. S-glass is known to have higher tensile strength and is rather expensive to produce, whereas E-glass has good tensile and compressive strength, as well as electrical properties and lower production cost [42Zhang M, Matinlinna JP. E-glass fiber reinforced composites in dental applications. Silicon 2012; 4: 73-8.
[http://dx.doi.org/10.1007/s12633-011-9075-x]
]. However, E-glass has lower tensile modulus and lower fatigue resistance resulting in relatively poor impact resistance as compared to S-glass [42Zhang M, Matinlinna JP. E-glass fiber reinforced composites in dental applications. Silicon 2012; 4: 73-8.
[http://dx.doi.org/10.1007/s12633-011-9075-x]
]. On the other hand, quartz fibers made out of pure silica in crystallized form, which is an inert material with a low coefficient of thermal expansion, has been used in several commercial fiber-reinforced posts [29Lassila LV, Tanner J, Le Bell AM, Narva K, Vallittu PK. Flexural properties of fiber reinforced root canal posts. Dent Mater 2004; 20(1): 29-36.
[http://dx.doi.org/10.1016/S0109-5641(03)00065-4] [PMID: 14698771]
] as seen in Table 1.

In addition to the types and properties of individual fibers, other fiber-related factors can affect the mechanical properties that may affect the clinical success of fiber-reinforced posts [42Zhang M, Matinlinna JP. E-glass fiber reinforced composites in dental applications. Silicon 2012; 4: 73-8.
[http://dx.doi.org/10.1007/s12633-011-9075-x]
]. These include fiber orientation, fiber density, impregnation of fibers with the matrix polymer, and adequate adhesion of fibers to the matrix polymer [53Le Bell-Rönnlöf AM. Fibre-reinforced composites as root canal posts.Department of Prosthetic Dentistry and Biomaterials Science 2007; 3428-7., 42Zhang M, Matinlinna JP. E-glass fiber reinforced composites in dental applications. Silicon 2012; 4: 73-8.
[http://dx.doi.org/10.1007/s12633-011-9075-x]
].

In fiber-reinforced posts, continuous unidirectional fibers are used [53Le Bell-Rönnlöf AM. Fibre-reinforced composites as root canal posts.Department of Prosthetic Dentistry and Biomaterials Science 2007; 3428-7.]. Fibers direction influences the mechanical properties of fiber-reinforced posts [54Dyer SR, Lassila LV, Jokinen M, Vallittu PK. Effect of fiber position and orientation on fracture load of fiber-reinforced composite. Dent Mater 2004; 20(10): 947-55.
[http://dx.doi.org/10.1016/j.dental.2003.12.003] [PMID: 15501323]
]. The fibers are continuous and oriented parallel to the post longitudinal axis Fig. (5) with different diameters ranging from 6.0 to 21.0 microns [42Zhang M, Matinlinna JP. E-glass fiber reinforced composites in dental applications. Silicon 2012; 4: 73-8.
[http://dx.doi.org/10.1007/s12633-011-9075-x]
, 48Seefeld F, Wenz HJ, Ludwig K, Kern M. Resistance to fracture and structural characteristics of different fiber reinforced post systems. Dent Mater 2007; 23(3): 265-71.
[http://dx.doi.org/10.1016/j.dental.2006.01.018] [PMID: 16519929]
]. Fibers density (i.e. the number of fibers per mm2 of the post-cross-sectional surface) usually provided by the manufacturers’ and is expressed by weight or volume and varies from one brand to the other. Increased fiber density improves the strength and load-bearing capacity of fiber-reinforced posts [53Le Bell-Rönnlöf AM. Fibre-reinforced composites as root canal posts.Department of Prosthetic Dentistry and Biomaterials Science 2007; 3428-7.]. In a transverse section of the post 30-50% of the area is occupied by fibers [30Vichi A, Ferrari M, Davidson CL. Influence of ceramic and cement thickness on the masking of various types of opaque posts. J Prosthet Dent 2000; 83(4): 412-7.
[http://dx.doi.org/10.1016/S0022-3913(00)70035-7] [PMID: 10756290]
, 55Goracci C, Ferrari M. Current perspectives on post systems: A literature review. Aust Dent J 2011; 56(Suppl. 1): 77-83.
[http://dx.doi.org/10.1111/j.1834-7819.2010.01298.x] [PMID: 21564118]
] with fibers of smaller diameter allowing higher packing density of up to 70%.

The fibers should be well impregnated, meaning that resin should come in contact with the surface of every fiber, in order to achieve adequate adhesion of the fibers to the polymer matrix [53Le Bell-Rönnlöf AM. Fibre-reinforced composites as root canal posts.Department of Prosthetic Dentistry and Biomaterials Science 2007; 3428-7.]. With good impregnation, optimal reinforcement and transfer of stresses from the polymer matrix to the reinforcing fibers are achieved [42Zhang M, Matinlinna JP. E-glass fiber reinforced composites in dental applications. Silicon 2012; 4: 73-8.
[http://dx.doi.org/10.1007/s12633-011-9075-x]
]. During the fabrication of posts, fibers are pre-stressed, and resin injected under pressure to fill the spaces between the fibers, giving them solid cohesion [56Perdigão J, Gomes G, Lee IK. The effect of silane on the bond strengths of fiber posts. Dent Mater 2006; 22(8): 752-8.
[http://dx.doi.org/10.1016/j.dental.2005.11.002] [PMID: 16427122]
]. The smaller the diameter of the fiber filaments the better the matrix ability to spread between the fibers leading to an increase in interlaminar tightness [48Seefeld F, Wenz HJ, Ludwig K, Kern M. Resistance to fracture and structural characteristics of different fiber reinforced post systems. Dent Mater 2007; 23(3): 265-71.
[http://dx.doi.org/10.1016/j.dental.2006.01.018] [PMID: 16519929]
]. In addition, fibers are pre-coated with silane in order to improve the adhesion at the fiber-resin matrix interface [42Zhang M, Matinlinna JP. E-glass fiber reinforced composites in dental applications. Silicon 2012; 4: 73-8.
[http://dx.doi.org/10.1007/s12633-011-9075-x]
, 56Perdigão J, Gomes G, Lee IK. The effect of silane on the bond strengths of fiber posts. Dent Mater 2006; 22(8): 752-8.
[http://dx.doi.org/10.1016/j.dental.2005.11.002] [PMID: 16427122]
]. This also protects the fibers from damage during handling, modifying the catalytic and wettability properties of fiber surfaces so that their chemical resistance increased [57Goracci C, Raffaelli O, Monticelli F, Balleri B, Bertelli E, Ferrari M. The adhesion between prefabricated FRC posts and composite resin cores: Microtensile bond strength with and without post-silanization. Dent Mater 2005; 21(5): 437-44.
[http://dx.doi.org/10.1016/j.dental.2004.07.012] [PMID: 15826700]
].

A durable adhesion between fibers and matrix of posts ensures that the load is transferred to the stronger fibers, thus optimizing the function of fibers as the reinforcing component of fiber-reinforced posts. On the other hand, if adhesion is not so durable and if any voids appear between the fiber and the matrix, these voids may act as initial fracture sites that encourage the breakdown of the material [42Zhang M, Matinlinna JP. E-glass fiber reinforced composites in dental applications. Silicon 2012; 4: 73-8.
[http://dx.doi.org/10.1007/s12633-011-9075-x]
]. Differences in the coefficient of thermal expansion between fibers and resin matrix may affect the structural integrity of the post following thermal fluctuations in the mouth. There are large variations in the coefficient of thermal expansion between the polymer matrix (40-80 X10-6/°C) and that of E-glass (8 X10-6/°C), quartz (0.2 X10-6/°C), and carbon (0.4 X10-6/°C) fibers [29Lassila LV, Tanner J, Le Bell AM, Narva K, Vallittu PK. Flexural properties of fiber reinforced root canal posts. Dent Mater 2004; 20(1): 29-36.
[http://dx.doi.org/10.1016/S0109-5641(03)00065-4] [PMID: 14698771]
]. It has been shown that thermocycling decreased the flexural modulus of different fiber posts by approximately 10% [29Lassila LV, Tanner J, Le Bell AM, Narva K, Vallittu PK. Flexural properties of fiber reinforced root canal posts. Dent Mater 2004; 20(1): 29-36.
[http://dx.doi.org/10.1016/S0109-5641(03)00065-4] [PMID: 14698771]
]. This suggests that the mismatch in the coefficient of thermal expansion between fibers and matrix polymers might affect the long-term integrity of fiber posts.

Studies reported that post debonding is the most common type of failure seen in teeth restored with prefabricated fiber-reinforced posts [58Parisi C, Valandro LF, Ciocca L, Gatto MR, Baldissara P. Clinical outcomes and success rates of quartz fiber post restorations: A retrospective study. J Prosthet Dent 2015; 114(3): 367-72.
[http://dx.doi.org/10.1016/j.prosdent.2015.03.011] [PMID: 26013066]
]. In vitro studies have shown that the bond strength of luted fiber-reinforced posts was significantly lower in the apical third of canals followed by the middle third as compared to a coronal third of root canals [28Soares CJ, Santana FR, Pereira JC, Araujo TS, Menezes MS. Influence of airborne-particle abrasion on mechanical properties and bond strength of carbon/epoxy and glass/bis-GMA fiber-reinforced resin posts. J Prosthet Dent 2008; 99(6): 444-54.
[http://dx.doi.org/10.1016/S0022-3913(08)60106-7] [PMID: 18514666]
, 59Amižić IP, Baraba A, Ionescu AC, Brambilla E, Van Ende A, Miletić I. Bond strength of individually formed and prefabricated fiber-reinforced composite posts. J Adhes Dent 2019; 21(6): 557-65.
[http://dx.doi.org/10.3290/j.jad.a43649] [PMID: 31802072]
]. In fact, various fiber-reinforced posts have been shown to reduce the transmission of polymerization light intensity differently as light travels from the coronal toward the apical third of root canals [15Goracci C, Corciolani G, Vichi A, Ferrari M. Light-transmitting ability of marketed fiber posts. J Dent Res 2008; 87(12): 1122-6.
[http://dx.doi.org/10.1177/154405910808701208] [PMID: 19029079]
].

Fig. (5)
Scanning electron microscope image (X 500) of prefabricated fiber-reinforced post that sustained a cohesive fracture within the post. Note the unidirectional arrangement of glass fibers.


Fig. (6)
Schematic drawing of a cross-section of iLumi glass fiber post (A) and conventional prefabricated fiber-reinforced post (B). Note the monolayer of optical glass cladding material around each glass fiber of the iLumi post. F: glass fiber. M: polymer matrix.


The difference in light transmission between different fiber-reinforced posts can be attributed to differences in type and number of fibers, as well as the diameter and orientation of fibers [15Goracci C, Corciolani G, Vichi A, Ferrari M. Light-transmitting ability of marketed fiber posts. J Dent Res 2008; 87(12): 1122-6.
[http://dx.doi.org/10.1177/154405910808701208] [PMID: 19029079]
]. In addition, the refractive index of the matrix used which can be influenced by factors such as the type of monomer, pigments, and fillers used can also affect absorption and scattering of light transferred to various depths of posts in the root canals [60Chen YC, Ferracane JL, Prahl SA. A pilot study of a simple photon migration model for predicting depth of cure in dental composite. Dent Mater 2005; 21(11): 1075-86.
[http://dx.doi.org/10.1016/j.dental.2005.05.002] [PMID: 16085305]
]. Recently a novel fiber-reinforced post (iLumi fiber optic post; iLumi Sciences), was introduced into the market with the premise that it is able to transmit light to the most apical parts of the canal, thus improving the retention of the post and reducing the debonding rate [61Stylianou A, Burgess JO, Liu PR, Givan DA, Lawson NC. Light-transmitting fiber optic posts: An in vitro evaluation. J Prosthet Dent 2017; 117(1): 116-23.
[http://dx.doi.org/10.1016/j.prosdent.2016.06.020] [PMID: 27646793]
]. In the iLumi fiber optic post, each fiber is thermally coated with optical glass cladding made of a non-corrosive, biocompatible material, the exact nature of which is kept confidential by the manufacturer (Fig. 6). This monolayer around each fiber is believed to force the light to be internally reflected and transmits to the apical end of the post. Studies have shown that this results in complete polymerization of resin cement as compared to other types of translucent fiber-reinforced posts [61Stylianou A, Burgess JO, Liu PR, Givan DA, Lawson NC. Light-transmitting fiber optic posts: An in vitro evaluation. J Prosthet Dent 2017; 117(1): 116-23.
[http://dx.doi.org/10.1016/j.prosdent.2016.06.020] [PMID: 27646793]
]. While manufacturers claim that this resulted in increased bond strength of the apical third of luted iLumi fiber optic post, this has not been independently demonstrated.

It is highly desirable that posts cemented in root canals be visible on radiographs for evaluation and follow up. Therefore, prefabricated posts should have radiopacity similar to or close to that of root dentine. Studies have shown that different types of prefabricated fiber-reinforced posts exhibited different radiopacity levels. The composition of the post appears to be the most significant factor affecting the radiopacity of prefabricated fiber-reinforced posts [17Erik AA, Erik CE, Yıldırım D. Experimental study of influence of composition on radiopacity of fiber post materials. Microsc Res Tech 2019; 82(9): 1448-54.
[http://dx.doi.org/10.1002/jemt.23298] [PMID: 31119821]
]. Elements that appear to affect the radiopacity of the prefabricated fiber-reinforced post include silicon (Si), which may present in the form of silica, as well as zirconia (Zr), barium (Ba), and aluminum (Al) [17Erik AA, Erik CE, Yıldırım D. Experimental study of influence of composition on radiopacity of fiber post materials. Microsc Res Tech 2019; 82(9): 1448-54.
[http://dx.doi.org/10.1002/jemt.23298] [PMID: 31119821]
]. Differences in percentages of the various radiopaque elements, their atomic number, and crystallization forms seem to affect the radiopacity from one type of fiber-reinforced to the other [17Erik AA, Erik CE, Yıldırım D. Experimental study of influence of composition on radiopacity of fiber post materials. Microsc Res Tech 2019; 82(9): 1448-54.
[http://dx.doi.org/10.1002/jemt.23298] [PMID: 31119821]
]. These elements can be present in the fibers, matrix and/or added as fillers in some commercially available prefabricated fiber-reinforced posts.

CONCLUSION

Increased interest in the use of prefabricated fiber-reinforced posts resulted in the development of an enormous number of prefabricated cross-linked fiber-reinforced posts with different compositions, geometries, and properties. Understanding the composition of the different prefabricated fiber-reinforced posts available will aid clinicians in understanding the vast literature on the topic and help in their selection for clinical use. While the exact composition of the different prefabricated fiber-reinforced post is kept confidential by the manufacturers, the basic composition consists of pre-stretched fibers embedded in a resin polymer matrix. The functions of the different components and how they influence each other was discussed.

CONSENT FOR PUBLICATION

Not applicable.

FUNDING

This work was supported by research grant [No. 2018-A-DN-03] from Ajman University, Ajman, United Arab Emirates.

CONFLICT OF INTEREST

The author declares no conflict of interest, financial or otherwise.

ACKNOWLEDGEMENTS

Declared none.

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