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References

Schwartz RS, Robbins JW Post placement and restoration of endodontically treated teeth: a literature review. J Endodont. 2004; 30:289-301
Theodosopoulou JN, Chochlidakis KM A systematic review of dowel (post) and core materials and systems. J Prosthodont. 2009; 18:464-472
Maccari PC, Cosme DC, Oshima HM Fracture strength of endodontically treated teeth with flared root canals and restored with different post systems. J Esthet Rest Dent. 2007; 19:30-36
Verissimo C, Simamoto Junior PC Effect of the crown, post, and remaining coronal dentin on the biomechanical behavior of endodontically treated maxillary central incisors. J Prosthet Dent. 2014; 111:234-246
Baba NZ, Golden G, Goodacre CJ Nonmetallic prefabricated dowels: a review of compositions, properties, laboratory, and clinical test results. J Prosthodont. 2009; 18:527-536
Nakamura T, Ohyama T, Waki T Stress analysis of endodontically treated anterior teeth restored with different types of post material. Dent Mater J. 2006; 25:145-150
Stankiewicz N, Wilson P The ferrule effect. Dent Update. 2008; 35:222-228
Ahmed SN, Donovan TE, Ghuman T Survey of dentists to determine contemporary use of endodontic posts. J Prosthet Dent. 2017; 117:642-645
Mattison GD, Delivanis PD, Thacker RW, Hassell KJ Effect of post preparation on the apical seal. Prosthet Dent. 1984; 51:785-789
Mannocci F, Machmouridou E, Watson TF Microtensile bond strength of resin–post interfaces created with interpenetrating polymer network posts or cross-linked posts. Med Oral Patol Oral Cir Bucal. 2008; 13:E745-752
Fernandes AS, Dessai GS Factors affecting the fracture resistance of post-core reconstructed teeth: a review. Int J Prosthodont. 2001; 14:355-363
Peroz I, Blankenstein F, Lange K-P, Naumann M Restoring endodontically treated teeth with posts and cores – a review. Quintessence Int. 2005; 36
Sorensen JA, Martinoff JT Clinically significant factors in dowel design. J Prosthet Dent. 1984; 52:28-35
Jotkowitz A, Samet N Rethinking ferrule – a new approach to an old dilemma. Br Dent J. 2010; 209:25-33
Makarewicz D, Le Bell-Rönnlöf A-MB, Lassila LVJ, Vallittu PK Effect of cementation technique of individually formed fiber-reinforced composite post on bond strength and microleakage. Open Dent J. 2013; 7:68-75
Muttlib NAA, Azman ANP, Seng YT Intracanal adaptation of a fiber reinforced post system as compared to a cast post-and-core. Acta Stomatol Croat. 2016; 50:329-336
Fox K, Gutteridge DL An in vitro study of coronal microleakage in root-canal-treated teeth restored by the post and core technique. Int Endod J. 1997; 30:361-368
Qualtrough AJ, Mannocci F Tooth-colored post systems: a review. Oper Dent. 2003; 28:86-91
Beltagy T Fracture resistance of rehabilitated flared root canals with anatomically adjustable fiber post. Tanta Dent J. 2017; 14:96-103
Qian YM, Zhong Q, Chen S [Comparison of clinical effects of Co–Cr alloy cast post-core and everStick fiber post in restoration of labially or lingually inclined maxillary central incisor]. Shanghai J Stomatol. 2017; 26:89-93
Lassila LV, Tanner J, Le Bell AM Flexural properties of fiber reinforced root canal posts. Dent Mater. 2004; 20:29-36
Bolay Ş, Öztürk E, Tuncel B, Ertan A Fracture resistance of endodontically treated teeth restored with or without post systems. J Dent Sci. 2012; 7:148-153
Xie Q, Wu W, Liu P, Vallittu PK Fatigue resistance of resin-bonded post–core–crown treated teeth with flared root canal. J Adhes Sci Technol. 2009; 23:1113-1124
Kremeier K, Fasen L, Klaiber B, Hofmann N Influence of endodontic post type (glass fiber, quartz fiber or gold) and luting material on push-out bond strength to dentin in vitro. Dent Mater. 2008; 24:660-666
Bell A-ML, Lassila LVJ, Kangasniemi I, Vallittu PK Bonding of fibre-reinforced composite post to root canal dentin. J Dent. 2005; 33:533-539
Lastumaki TM, Lassila LV, Vallittu PK The semi-interpenetrating polymer network matrix of fiber-reinforced composite and its effect on the surface adhesive properties. J Mater Sci. 2003; 14:803-809
Goracci C, Juloski J, Schiavetti R The influence of cement filler load on the radiopacity of various fibre posts ex vivo. Int Endodont J. 2015; 48:60-67
Cagidiaco MC, Garcia-Godoy F, Vichi A Placement of fiber prefabricated or custom made posts affects the 3-year survival of endodontically treated premolars. Am J Dent. 2008; 21:179-184
Ferrari M, Vichi A, Fadda GM A randomized controlled trial of endodontically treated and restored premolars. J Dent Res. 2012; 91:(7 Suppl)72s-78s

Individually Formed Glass Fibre Reinforced Composite Posts for Compromised Teeth with Oval and Flared Endodontic Canals

From Volume 48, Issue 1, January 2021 | Pages 62-67

Authors

Ayman AL-Oulabi

BDS, MResDent (Prosthodontics), MFDS RCSEd, FRACDS

BDS, MFDS RCSEd, FRACDS, Postgraduate Trainee

Articles by Ayman AL-Oulabi

Email Ayman AL-Oulabi

Yew Hin Beh

DDS, MFDS RCSEd, Postgraduate Trainee

Articles by Yew Hin Beh

Zaihan Ariffin

BDS, Grad DipClinDent, DClinDent, FRACDS, Associate Professor

Articles by Zaihan Ariffin

Email Zaihan Ariffin

Yanti Johari

BDSc, GradDipClinDent, DClinDent (Prosthodontics)

BDSc, Grad DipClinDent, DClinDent, FRACDS, Senior Lecturer, Prosthodontics Unit, School of Dental Sciences, Universiti Sains Malaysia, Kelantan, Malaysia.

Articles by Yanti Johari

Abstract

Potential excessive removal of tooth structure during retreatment, and canal preparation for a post will weaken the tooth substantially. An alternative to prefabricated or cast metal and fibre posts, is a soft and flexible fibre-reinforced composite post that can be used to aid a good adaptation and preserve the tooth structure. These two case reports highlight the use of fibre-reinforced composite posts in teeth with severe loss of tooth structure with wide flared and oval canals.

CPD/Clinical Relevance: Case selection and proper treatment planning are important before considering and selecting any type of post placement.

Article

The primary purpose of a post is to retain the core and coronal restoration in teeth that have suffered substantial loss of tooth structure.1 Various materials and techniques have been proposed for the restoration of endodontically treated teeth.2 Traditionally, prefabricated and cast (custom) metal posts have been used. Cast metal posts and cores offer the best canal adaptation and overall fit compared to prefabricated fibre posts.3 However, these posts have many associated disadvantages, such as discolouration, corrosion and a high modulus of elasticity, greater than that of dentine, which can concentrate stresses on the dentine and may lead to an increased risk of catastrophic root fracture.4 With the increased demand for tooth-coloured posts, several non-metallic posts, such as fibre-reinforced posts, have been marketed to improve aesthetics and the adhesion of the post to the dental structure. Different examples of fibre-reinforced posts are epoxy resin posts reinforced with carbon fibres, epoxy or methacrylate resin posts reinforced with quartz or glass fibres, zirconia posts, and ultra-high polyethene fibre-reinforced posts.5In vitro and in vivo studies have found that glass-fibre posts and resin cores are an excellent alternative to metal and other non-metallic posts because of their modulus of elasticity, which is closer to that of dentine, decreasing the risk of root fracture.2,6Table 1 shows the modulus of elasticity of dentine and various post materials.7


Dentine 15–19
Quartz fibre 20
Glass fibre 30
Cast gold 75–100
Titanium 100
Carbon fibre 120
Zirconia 200
Stainless steel 200

The use of prefabricated fibre post systems have become more popular than cast metal posts among the dentists because they provide a reliable outcome, aesthetics and function, and shorten clinical time and provide cost effective treatment.8

The problems with over-flared and oval canals in an aesthetic zone can be overcome by using a direct, anatomically and adjustable individually formed glass-fibre reinforced composite (FRC) posts, such as everStick Post (GC, Japan). This post is minimally invasive, soft and flexible. It is made of continuous silanized glass fibres impregnated with resin consisting of bisphenol A-glycidyl methacrylate (Bis-GMA) and polymethyl methacrylate (PMMA), which, during polymerization form a semi-interpenetrating polymer network matrix. It can be customized and closely adapted to the morphology of the root canal giving a good fit. In the following two case reports, we present two indications for using a customized chairside fibre post (everStick Post).

Case report 1

A 24-year-old male was referred from the Oral and Maxillofacial Department to the Prosthodontics Unit to replace his missing UL1 to enhance the aesthetic appearance. The patient's records revealed that he had a motor vehicle accident 2 months previously that resulted in an oblique crown root fracture of UR1, crown fracture of teeth UR2, UL2 and a middle root fracture of UL1. He was medically fit. Clinical examination and special investigations revealed UL1 was extracted earlier because of a horizontal root fracture, while UR1 and UL2 were heavily restored with composite resin. UR1 and UL2 were not responsive to cold or heat and were tender to percussion. A periapical radiograph revealed periapical radiolucency involving UR1 and UL2 (Figure 1). The diagnosis was necrotic pulp with symptomatic apical periodontitis for both teeth.

Figure 1. Pre-operative photographs. (a) Intraoral view of the clinical case on patient presentation. (b) Periapical radiograph reveals periapical radiolucency associated with teeth UR1 and UL2 and missing UL1.

After assessing the restorability of the teeth with consideration of ferrule effect and root canal anatomy, the treatment plan was set to include root canal treatment on UR1 and UL2, crown lengthening palatally on UR1, post and core construction using glass-fibre reinforced composite (FRC) post, on UR1 and UL2. The final definitive restorations for UR1, UR2 and UL2 were single, full coverage crowns and an implant-retained crown to replace UL1.

The clinical step-by-step procedure for construction and placement of the everStick Post involved was as follows:

  • Placement of the rubber dam and opening of the access cavity.
  • Approximately half to two-thirds of the length of the gutta percha (GP) from root canal filling was removed using Gates Glidden burs. A heated endodontic plugger was used to seal the minimum of 5 mm GP left at the apices of the roots to prevent apical microleakage.9
  • The canals were rinsed and cleansed with a copious amount of 2.5% sodium hypochlorite followed by saline to remove debris and then dried with paper points.
  • The depth of the canal preparation was measured using an endodontic file instrument. Approximately 2 mm was added to the length to support the coronal part.
  • The 1.5-mm everStick Post was selected. Two posts were cut together within the silicone packaging material, using normal sharp scissors. To avoid the posts sticking to the tweezers, the beaks of the tweezers can be coated with Stick Resin (GC Japan) when the posts are removed from the silicone packaging material.
  • The posts were inserted into the prepared canals and minimal adjustments were made to taper them apically using scissors. Additional fibre posts were added after creating space with an endo-probe next to the main posts to fill the voids caused by the oval and flared anatomy of the canals. (Posts can be cut lengthwise with scissors to create thinner ‘sections’ of posts for filling voids – the different ‘sections’ stick to one another). The posts were removed and reinserted several times to ensure proper adaptation of the fibres to the root canal anatomy (Figure 2).
  • A periapical radiograph was taken to confirm the fitting of the posts within the canal, although the posts are not clearly visible on the radiograph (Figure 3).
  • The posts were finally inserted into the canals and light-cured for 20 seconds inside the canals. They were then removed for light-curing for 40 seconds outside the canals. As the posts are anatomical, they will only go back into the canal the way they came out. Before final cementation, the posts were coated with Stick Resin, which was ‘thinned out’ with compressed air and light-cured before cementation. This step ensures the interpenetrating network patented for the everStick fibres.10 (This technique of post curing is the indirect technique; in the direct technique, the post and the self-adhesive cement are cured simultaneously).
  • A self-adhesive resin cement (Rely X Unicem, 3M ESPE, Germany) was inserted into the canal, using the RelyX Unicem Aplicap Elongation Tip attached the nozzle. This enables the operator to insert the cement apically and gradually back fill the whole post space as the applicator tip is removed. The constructed post was then inserted into the uncured cement in the canal and light-cured.
  • The core build-up was completed and properly cured from all directions. The Rely X unicem cement is a self-cure resin cement and will continue to be chemically cured even in the absence of light.
  • The final preparation for full porcelain fused-metal crowns was completed and a temporary bridge was constructed using bis-acryl resin (Protemp 4, 3M, ESPE, Germany) to replace UL1 during the osteointegration period of the implant UL1 (Figure 5).
  • The final definitive restoration was to be single crowns for UR2, UR1 and UL2. The missing UL1 was to be replaced with an implant-retained crown.

    • Figure 2. The everStick Post after moulding to the canal shape and curing. (a) everStick post for UR1 (b) everStick Post for UL2.
    Figure 3. Periapical radiograph shows the fitting of everStick post inside the canal.
    Figure 4. Clinical steps after post cementation. (a) The post cemented under rubber dam isolation after removing all the composite (minor finish line was done earlier when the tooth was assessed to estimate the ferrule height and width after crown preparation. (b) The teeth after buildup by composite.
    Figure 5. The bis-acryl temporization using Protemp. (a) Frontal view. (b) Palatal view. Note the palatal margin of the Protemp after performing crown lengthening.

    Case report 2

    A 62-year-old female patient was referred to the Prosthodontics Unit regarding treatment of a heavily restored UL5 with post, core and crown, and also replacement of other missing teeth. The patient's main complaint was to improve the chewing ability and to restore the missing teeth. Her medical history revealed hypertension controlled by medication with regular follow-ups.

    Clinical examination revealed an asymptomatic UL5, which had been endodontically treated and restored with an extensive composite resin (Figure 6). A periapical radiograph revealed that the UL5 was successfully root canal-treated with no periapical radiolucency. The restoration was removed for further investigation and a single wide oval canal was found (Figure 7). The treatment plan was to perform a post and core restoration using an everStick Post, followed by the construction of a full coverage porcelain fused to metal crown.

    Figure 6. Pre-operative intraoral view of the clinical case on patient presentation.
    Figure 7. UL5 after removal of root canal filling.

    The clinical step-by-step procedure for the construction and placement of glass FRC post involved:

  • Under rubber dam isolation, a two-thirds length of GP was removed using Gates Glidden drills, and a heated endodontic plugger was used to seal the minimum of 5 mm GP left at the apex of the root.
  • The canal was rinsed and cleansed with a copious amount of 2.5% sodium hypochlorite, followed by saline to remove the debris, and dried with paper points.
  • A 1.2-mm everStick Post was chosen, cut to the desired length and adapted as the main post for the flared canal. Additional fibre posts were added after creating space with an endo-probe (Figure 8).
  • The post was removed and reinserted several times to allow proper adaptation of the fibres to the root canal anatomy and a periapical radiograph was taken to confirm the fit of the post.
  • The adapted post was light-cured for 20 seconds inside the canal, with further light-curing for 40 seconds outside the canal (Figure 9).
  • The same bonding protocol as in case 1 was followed.
  • A nanofilled composite, Filtek Z350XT (3M, ESPE, USA) was used to build up the core (Figure 10).
  • The tooth was restored by full coverage porcelain fused to metal crown and a cast partial cobalt– chromium removable denture was planned to replace other missing teeth (Figure 11).

    • Figure 8. Occlusal view of the adapted everStick Post.
    Figure 9. The moulded everStick Post for UL5 during curing.
    Figure 10. Clinical buccal view of the completed post placement and coronal core build-up.
    Figure 11. The tooth UL5 restored by full coverage metal–ceramic crown.

    Discussion

    Clinically, it is well established that the longevity of a post-retained crown, used to restore an endodontically treated tooth, is affected by many factors: remaining tooth structure (number of walls remaining), ferrule, post-selection (length, diameter, design, material, cementation), definitive restoration, tooth morphology and position, functional demands, periodontal status and aesthetics.11,12,13

    In the first case, there were no remaining walls present on the UR1 and UL2. The UR1 had an oval canal with a compromised palatal ferrule. A crown lengthening procedure was planned to establish a good palatal ferrule to resist the functional forces applied to the palatal surface of the UR1 since this tooth is non-axially loaded.14 UL2 had a wide flared canal with a complete ferrule. In the second case, the UL5 had two remaining walls (buccal and lingual) with a complete ferrule and a wide flared canal.

    The individually formed glass FRC posts were selected over prefabricated fibre posts because of the oval and flared anatomy of the canals. Furthermore, these FRC posts offered a minimally invasive approach15 and the likelihood of iatrogenic damage to the tooth, such as perforations and the unnecessary destruction of existing tooth tissue, would be avoided.16

    The individually formed glass FRC posts were selected over cast metal posts due to the aesthetic advantage, cost-effective chairside technique and a modulus of elasticity similar to that of dentine, which reduces the risk of a catastrophic root fracture. Moreover, there is a risk of microleakage and reinfection when a temporary post crown is used while waiting for the indirect cast post and core to be made in the laboratory.17 Ceramic posts were avoided as the preparation for these posts would have resulted in undesired tooth tissue loss. Furthermore, the rigidity of the ceramic material, as with cast metal, can increase the risk of root factures as discussed.18

    The use of the anatomically adjustable everStick Post in the restoration of compromised teeth with flared canals in these cases showed to be effective, by improving fracture resistance and, therefore, reducing the chances of unfavourable root fractures.19 Comparison of the clinical effects of the everStick Post and chrome–cobalt alloy cast posts and core shows the everStick Post to be better in terms of preventing root fracture. In the case of a root fracture with the everStick Post, the fracture pattern is usually more favourable and allows repair. Furthermore, there is an aesthetic advantage because the gingival margin will show less discolouration.20

    The everStick Post has a flexural strength of 1145 MPa and a Young modulus of elasticity of 15 MPa, which appear to be superior to other commercially available FRC posts. These properties allow reduction in stress formation on the fibre– matrix interface during deflection.21 However, despite these properties, some incidences of root fracture have occurred with the everStick Post.22

    An in vitro study showed that individually formed FRC posts in flared canals provided good resistance against cyclic loading, and sustained cyclic loading with no failures when compared with prefabricated FRC posts, which showed failure of all posts through fracture or dislodgement due to debonding at the cement–post interface.23 Adaptation of formed FRC posts (everStick Post) has been studied and it was found that there is no significant difference between them and cast post core and that both can adapt well to canal walls.16

    Proper adaptation of formed FRC posts to the post space can reduce the stress concentration at the cement–post interface due to the thinness of the cement used. A thin layer of luting cement reduces the risk of the shrinkage strain, which can reduce bond strength, by minimizing stress during polymerization, which, in turn, reduces the incidence of post displacement.24

    No adhesive (post–cement) failure was found with individually formed glass FRC posts compared with prefabricated carbon or titanium posts, suggesting better interfacial adhesion of cement to the formed FRC posts.25 The low incidence of adhesive failures with the everStick Post can be explained by the presence of a semi-interpenetrating polymer network (semi-IPN) in its polymer matrix. This polymer network allows monomers of adhesive resin cements to diffuse better, producing interdiffusion bonding.26

    There are two techniques for handling the everStick Post: the indirect and direct techniques. With the indirect technique, the post is pre-polymerized completely prior to bonding. While in direct technique, the uncured post is inserted to the post space filled with the luting cement and light-polymerized in situ at the same time. In the two reported cases, an indirect technique for curing the posts was followed according to the manufacturer's instructions. However, an in vitro study showed that the direct technique offers a higher bond strength and less microleakage when a push-out test is conducted. This involves applying forces on root specimens restored with posts and different luting cements to evaluate the first interfacial failure between the dentine, cement and post, which indicates a debond. The pre-polymerized post in the indirect technique is easier to push out from the post space.15

    In terms of fracture resistance, an in vitro study showed that maxillary anterior teeth restored with an everStick Post recorded the highest mean of fracture load up to 1825.7N compared with other FRC posts.26 All in vitro study results should be interpreted with caution because they do not take into account all the other variables in the oral environment, such as moisture, temperature, salivary pH and fluctuations in the oral cavity pH, presence of bacteria and their byproducts, and masticatory loading.

    From a clinical standpoint, the everStick Post has the disadvantage of being radiolucent. A study of various posts showed that the everStick Post is among several with low radiopacity.27 Hence, it is recommended to use low filler content resin luting cements (eg Rely X Unicem, 3M, ESPE, Germany) to distinguish the post from the surrounding root structure. These cements also have a favourable elastic behaviour during curing.

    On clinical performance, there are two randomized clinical trials (RCT) performed on premolars. The first study concluded that teeth restored with prefabricated fibre posts had a higher survival rate (90.9%) than those restored with a custom-made everStick Post (76.7%) in a 3-year follow-up.28 In another RCT on premolars with a 6-year follow-up, the failure risk was lower in teeth restored with prefabricated posts than in those restored with customized fibre posts.29 Unfortunately, there are no RCTs on the performance of the everStick Post in maxillary anterior teeth owing to anterior teeth and their occlusion behaving in a different way to posterior teeth.14

    Conclusion

    The use of individually formed glass FRC aids in restoring endodontically treated teeth with flared and oval canals with a minimally invasive approach, allowing good adaptation to canal post wall as well as offering better aesthetic outcomes. However, further studies are needed in relation to the longevity of the everStick Post, especially in the anterior teeth.