Challenges facing restoration of endodontically treated teeth

 

The restoration of endodontically treated teeth is significant practical part that involves a different treatment choice of variable qualities. The challenge could also be sophisticated by substantial loss of coronal part of tooth structure and also the ability to predict restorative success.[1] Procedures were distributed after completion of the endodontic treatment and their impact on the prognosis of devitalized teeth have been given increasing attention. These procedures could enable the passage of microorganisms and their by-products to the apical part of the root and into the alveolar bone, which is considered potential reason for delayed failures. The results of those “events” could also be necessary to determine the success on long-term of the endodontic treatment.[2] The clinical decision on whether endodontically treated (ET) teeth require crown and post poses a challenge to dental practitioners.

Do posts strengthen ET teeth? It's been urged that ET teeth dry out over time and the dentin in ET teeth undergoes changes in collagen cross-linking. Therefore, it's been urged that ET teeth are more brittle and will fracture simply than teeth which have not been endodontically treated.[3] It's believed that it's the loss of tooth structure from tooth decay, trauma or both of them that makes ET teeth more vulnerable to fracture.[4] Some clinicians believe that a post should be placed into the root following Endodontic treatment to strengthen or reinforce it. Some studies, however, indicate that posts don't strengthen teeth, instead, the preparation of a post space and the placement of a post will weaken the root and will result in root fracture.[5] These studies more counsel that a post should to be used only if there's not sufficient tooth structure remaining to support the ultimate restoration. So, the principle function of a post is that the retention of a core to support the coronal restoration.

When to use a post: Since a post does not reinforce an ET tooth and preparing a post space may increase the risk of root fracture and failure of treatment, it is necessary to make a judicious decision whether to use a post in any clinical situation. Most teeth require trauma, extensive caries or endodontic treatment with restoration. The assessment of the need for a post is based on how much natural tooth substance endures to maintain a core buildup and to support final restoration after caries removal and endodontic treatment. Many ET molars don't need a post because they have more dent material and a wider pulp chamber to maintain a core buildup. To retain a core buildup after endodontic treatment, premolars have less tooth substance and smaller pulp chambers than molars do, and posts are required more often in premolars. Also, a few studies have found that an anterior tooth with limited loss of tooth structure does not need a post in an ET. Tooth decoloration is a problem, whitening and veneer placement can be considered as a study by Baratieri and colleagues concluded that the use of posts did not increase the fracture resistance of ET maxillary incisors receiving direct composite veneers.[6]

 

Discussion

Potential complications associated with post and core preparation

A study included 95 patients who were randomly selected from the Oral Diagnostic Departments of Hamdard University Dental Hospital (HUDH), Karachi, and Nishtar Dental Institute (NID), Multan.  Sixty-two women and thirty-three men were included in this study. The age range was 18-47. Patients were assessed using self-designed proforma after six months of postal delivery and core restorations. Gingivitis was the most common complaint reported in 21 patients 22.1% followed by loss of retention / re-cementation requirement found in 15 patients 15.7% respectively.[7] Microleakage can also occur during Post Space Preparation: A small amount of obturation material persists in the root canal after post space preparation. At the apical area, this residual filling acts as the last barrier against microbial invasion along the root canal, which may cause periapical inflammation in time. The results of these events are canal degradation and bacterial species invasion at the walls of the apical part of the root canal.[8]

Principles of core buildup

Core materials that most commonly used are cast gold, amalgam, resin-based composite and glass ionomer cement. Both cast gold and amalgam have been used successfully for several years, as they show perfect strength and bad solubility, and their coefficient of thermal expansion is similar to that of tooth substance. The placement of cast gold post and core, however, is an indirect procedure requiring two visits. Placing an amalgam core requires a prolonged setting time, making it difficult to prepare immediately after placement if a crown is the final restoration. Placing amalgam can be challenging in badly brokendown teeth, and many patients are concerned about the presence of mercury in amalgam, regardless of whether there is scientific evidence to support the claim of toxicity. Both gold and amalgam are not esthetically pleasing, especially under the newer all-porcelain restorations.[9]

Principles in the use of a post

There are two major posts categories: Custom-made and prefabricated. For decades, custom-made cast gold post and center has been used as a base restore to enable final restauration of ET teeth.[6]

Impression for the indirect pattern fabrication of ETT.

The preference for the use of a cast post and prefabricated post depends on various factors, such as the configuration of the canal and the remaining structure of the tooth. It has been said that if a canal requires extensive preparation, a well-adapted cast post and core will be more retentive than a prefabricated post that does not correspond to the canal configuration. The cast post and core are fitted to the prepared space of the root canal and designed to withstand torsional forces. One drawback of cast post though is its tedious and time-consuming technique of wax pattern. The custom cast post and center have a long track record of performance. They provide excellent service with moderate-to-severe damage to root canal treated tooth. The performance of modified indirect cast post and core fabrication technique depends on the accuracy of the impression replicating the internal surface of the prepared root canal. The benefit of indirect methodology is that by delegating the template for the post and center to the dental laboratory, it conserves chair side time.[10]

 

Optical impressions

Optical impressions eliminate patient discomfort; Intra Oral Scanners IOS are time-efficient and improve surgical practices for the dentist, removing plaster models and allowing easier contact with the dental technician and patients; however, with IOS, deep margin lines in prepared teeth and/or in the case of bleeding can be difficult to spot, there is a learning curve, and there is a training curve. The new IOS is sufficiently precise to catch impressions of all natural teeth and implants for the manufacture of a whole range of prosthetic restorations (inlays / onlays, copings and frames, single crowns and fixed partial dentures); in addition, they can be used for smile modeling and for the manufacture of posts and bases, flexible partial prostheses and obturators. To date, the literature does not advocate the use of IOS with natural teeth or replacements in long-term restorations. Finally, IOS can be used for guided surgery in implant dentistry and in orthodontics for the manufacturing of aligners and custom-made instruments.[11]

Technique of fabrication custom made posts

Usually custom posts are used in canals that have a non-circular cross section or an extreme taper. Extending canals to a pre-formed post may result in weakening and perforation of the root. The goal of fied prosthodontic clinicians is to rapidly produce and accurately fit custom-made posts. Manufacturing the resin pattern in vivo using the bead-brush technique may lose the dentist's time and effort.

The resin injection technique helps and facilitates manufacturing of custom posts. It is done by using a special distribution tip and piston as developed for restorative content 3M ESPE Vitremer glass ionomer (3 M ESPE dental goods, D-82229 Seefeld, Germany) (Figure 1).

Resin is mixed into the delivery tip and the piston is used to incorporate the resin material into the post space.[12]

ferrule effect in ETT

The stiffness of the core material did not influence the fracture resistance or teeth loss mode restored to the core by cast crowns with margins of 2 mm apical. The prevailing form of loss was root fractures which were unrepairable. Only those composite cores showed repairable fractures.[9] A study revealed the following findings under the limits of the experiments:

1. Significantly increasing ferrule length (P,.05) improved the fracturing tolerance of preserved endodontically treated teeth with prefabricated posts and cores.

2. Compared with the 0-mm and 1-mm ferrule classes, the 3-mm ferrule group displayed considerably greater fracture resistance (P,.05).

3. The presence of 2 mm of ferrule length increased significantly (P,05) the resistance of endodontically treated teeth restored with a prefabricated post and core compared to non-ferrule teeth. [13]

A study involving randomized and prospective clinical trials comparing post-supported and post-free ETT restoration highlights the importance of the remaining coronary tooth structure as a predictive factor for both restoration and survival of the dentures. For most writers, counting the number of remaining cavity walls from 4 (i.e. access cavity only) to no wall seems simple, as mentioned above, possibly derived from the configuration factor (C-factor) (Fig. 2,3). [14]

 

Fiber reinforced posts

During the last years, a major progress within the development of bondable fiber reinforced composite (FRC) posts for reinforcing the endodontically treated teeth were discovered. Plenty of benefits like high fatigue resistance, low modulus of elasticity, that is analogous to it of dentine, glorious light-weight physical phenomenon etc. are attributed to the FRC posts.

There are different kinds of FRC:

Carbon fiber posts: Because of their dark color and complicated covering under both ceramic or plastic restorations, carbon fiber posts cannot be categorized as traditional aesthetic posts. There's coated post available to overcome this complication. Many drawbacks are a lack of radiopacificity and low adhesion to plastic resin cores. [15]

Prefabricated glass and quartz-fiber posts: Fibers bounded by a methacrylate or epoxy-polymer matrix with a high conversion degree and a highly cross-linking structure binding the fibers.[16] The fibers have energy and rigidity, while the chemical compound matrix passes stresses to the fibers and thus protects them from the oral accompanying wetness. [17]

Individual fibre posts: Since the benefits of the prefabricated fiber posts are well known, a new concept for individually formed composite reinforced fiber (FRC) posts has been introduced.[18] It is based on reducing the need for preparation to the deeper sections of the root canal, thereby facilitating the application of higher amounts of FRC content to the opening of the tooth by the coronal root canal.

Polyethylene fiber posts: Polyethylene-reinforced resin provides sufficient durability that is necessary for post and core therapeutic performance, and reasonable fracture tolerance with increased occurrence of repairable fractures in structurally damaged canals.

Hollow fiber posts: Because of filling shortage and polymerization shrinkage, gaps, defects, and cavities may occur at the interface between dentin and restorative material, or at the interface between post and restorative material. [19]

Recent advances and ethics posts of ETT

Endo crowns

Endo crowns are such restorations that show the benefit of both the crown and the core being built as a single unit that achieves more stability and retention. Material interfaces with various elasticity modules are the weak point of a restorative device, because the discrepancy between hardness and stiffness affects the stress delivery. Furthermore, the endo crown also offers the advantage of reducing the effect of multiple interfaces with a thicker ceramic occlusal portion in the restorative system compared to the classic crown. These reasons give endo-crown restoration the lowest stress values on the dentin and luting cement. [20]

CAD / CAM (Ceramic post) post

A study on cases has revealed that one-piece post and cores made of zirconia and glass ceramic were manufactured to support all-ceramic fixed partial dentures. This article is about the manufacture of one-piece milled ceramic post and core for endodontically treated teeth that support fixed partial dentures. Post-core structures made out of high-strength ceramic materials, zirconia and lithium disilicate supported all ceramic fixed partial dentures without compromising the esthetics using CAD-CAM technology. Additionally, it was possible to fabricate the post and core preciously fitted into a prepared post space and anatomically correct core. Further work will be performed on the survival rate of these restorations.[21]

Postless build-ups with crowns

The inner walls of the pulp chamber were used in recent studies on posterior crowns to bond the core build-ups, without using additional intra root canals retention. It was deduced that the post did not affect the fatigue resistance of the molars being treated endodontically, but instead, caused further root fractures. Because of the larger ratio of catastrophic failures, therefore the use of a post can be debated.[22]

Recent esthetic posts.

Different posts solutions have been launched to the market, and evidence suggests that they can be successfully integrated into clinical practice. The selected post and core technique must be conservative, morphological, retentive, aesthetic and resistant to radicular failure. The available laboratory and clinical evidence validates the use of fiber posts in post-retained restorations as an alternative to metal posts and preferably to other tooth-colored posts, such as zirconia dowels. Newer post systems are incessantly being introduced into the market some examples are [23]:

Luscent Anchor Post System

The Luscent Anchor Post (Dentatus) is a fibre-glass, clear resin post designed to refract and transmit natural colors of the tooth for post-and-core esthetic foundations. It is composed of glass fibers embedded in a matrix of resin. They attach to the complex of composite core crowns and deliver advantages in light transillumination, radiolucency, preservation and superb aesthetics. [fig. 4].

Cosmopost

Conclusion

Conclusion

It is a ceramic post system and is indicated principally in esthetically necessary anterior region of upper jawbone and jaw [Fig. 5].

The number of endodontic procedures with highly predictable results has steadily increased in the last decade. Consequently, teeth restoration after endodontic treatment is becoming an integral part of dental restorative practice. Proper restoration of ET teeth begins with a good understanding of their physical and biomechanical properties, anatomy, and a sound knowledge of the endodontic, parodontal, restorative and occlusal principles. Although many new restorative materials have become available over the past several years, some basic concepts remain the same in restoring ET teeth. The explanation there are so many kinds of posts available with different styles and materials is that they do have such strengths and weaknesses. Suitable strength, elasticity modulus, durability, biocompatibility, esthetics and retrievability should be used in selection criteria. The new fiber-reinforced posts deliver impressive results, but longer-term clinical evaluation is required. While there are several exciting new materials available and there are clear reasons for their use, long-term clinical evaluations are important.

References

 

 References 

References
[1] Baba NZ, Goodacre CJ. Restoration of endodontically treated teeth: contemporary concepts and future perspectives. Endodontic Topics. 2014 Nov;31(1):68-83.

[2] Heling I, Gorfil C, Slutzky H, Kopolovic K, Zalkind M, Slutzky-Goldberg I. Endodontic failure caused by inadequate restorative procedures: review and treatment recommendations. The Journal of prosthetic dentistry. 2002 Jun 1;87(6):674-8.

[3]. Carter JM, Sorensen SE, Johnson RR, Teitelbaum RL, Levine MS. Punch shear testing of extracted vital and endodontically treated teeth. Journal of biomechanics. 1983 Jan;16(10):841-8.

[4]. Reeh ES, Douglas WH, Messer HH. Stiffness of endodonticallytreated teeth related to restoration technique. J Dent Res 1989;68:1540-4.

[5]. Trope M, Maltz DO, Tronstad L. Resistance to fracture of restored endodontically treated teeth. Endod Dent Traumatol1985;1:108-11

[6]. Cheung W. A review of the management of endodontically treated teeth: Post, core and the final restoration. The Journal of the American Dental Association. 2005 May 1;136(5):611-9.

[7]. Imran M, Shahid R, Hussain M, Jawaid M, Khan M. Complications after post and core treatment. Pakistan Oral and Dental Journal. 2015 Sep 30;35(3).

[8]Slutzky-Goldberg I, Slutzky H, Gorfil C, Smidt A. Restoration of endodontically treated teeth review and treatment recommendations. International journal of dentistry. 2009;2009.

[9]. Pilo R, Cardash HS, Levin E, Assif D. Effect of core stiffness on the in vitro fracture of crowned, endodontically treated teeth. J Prosthet Dent 2002;88:302-6

[10]. Shaikh A, Mandke L, Padhye L. Fabrication of cast post and core by a modified indirect procedure and postcementation using a novel technique. Indian J Oral Health Res 2017;3:91-5

[11]. Mangano F, Gandolfi A, Luongo G, Logozzo S. Intraoral scanners in dentistry: a review of the current literature. BMC oral health. 2017 Dec 1;17(1):149.

[12]. Awad MA, Abdulghaffar HS. Custom-made post and core-part I: technique to fabricate direct custom-made post with resin pattern. J Dent Health Oral DisordTher. 2014;1(3):00013.

[13].Pereira JR, De Ornelas F, Conti PC, Do Valle AL. Effect of a crown ferrule on the fracture resistance of endodontically treated teeth restored with prefabricated posts. The Journal of prosthetic dentistry. 2006 Jan 1;95(1):50-4.

[14]. Naumann, M., Schmitter, M., Frankenberger, R., &Krastl, G. (2018). “Ferrule Comes First. Post Is Second!” Fake News and Alternative Facts? A Systematic Review. Journal of Endodontics, 44(2), 212–219.

[15]. Quintas AF, Dinato JC, Bottino MA. Aesthetic posts and cores for metal-free restoration of endodontically treated teeth. Practical periodontics and aesthetic dentistry: PPAD. 2000;12(9):875-4.

[16]. Kallio TT, Lastumäki TM, Vallittu PK. Bonding of restorative and veneering composite resin to somepolymeric composites. Dental Materials. 2001 Jan 1;17(1):80-6.

[17]. Vallittu  PK.A  review  of  fiber-reinforced  denture  base resins. J Prosthodont. 1996. Dec;5(4):270–6.

 [18] Lassila  LVJ,  Tanner  J,  Le  Bell  A-M,  Narva  K,  Vallittu PK.  Flexural  properties  of  fiber  reinforced  root  canal posts. Dent Mater. 2004. Jan;20(1):29–36. 

[19]. Bonchev A, Radeva E, Tsvetanova N. Fiber Reinforced Composite Posts–A Review of Literature. Int J Sci Res. 2017;6(10):1887-93.

[20]. Papalexopoulos D, Filippatos G. Restoring Endodontically Treated Teeth: From Immediate Restorations to the. Reverse” Preparation Approach”. EC Dental Science. 2019;18:2159-68. 

[21].  BankoğluGüngör M, KarakocaNemli S, Doğan A, Tamam E, Turhan Bal B. Cad-Cam Fabricated One-Piece Ceramic Post and Core for Teeth Supporting Fixed Partial Dentures: Report of Two Cases. J Dent App. 2015;2(8):278-81.

[22]. de CARVALHO MA, Lazari PC, Gresnigt M, DEL BEL CU, Antoninha A, MAGNE P. Current options concerning the endodontically-treated teeth restoration with the adhesive approach. Brazilian Oral Research. 2018 Jan 2;32.

[23]. Jhavar N, Bhondwe S, Mahajan V, Dhoot R. Recent Advances in Post Systems: A Review. Journal Of Applied Dental and Medical Sciences. 2015 Oct;1:3.