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Table of Contents
ORIGINAL ARTICLE
Year : 2019  |  Volume : 6  |  Issue : 3  |  Page : 62-65

Comparative analysis of fracture resistance of two different glass-fiber postsystems: An in vitro study


1 Lecturer, Department of Conservative Dentistry and Endodontics, AMC Dental College and Hospital, Ahmedabad, Gujarat, India
2 Assistant Professor, Department of Dental and Implant Surgery, Shree Krishna Medical College and Hospital, Karamsad, Gujara, India
3 Reader, Department of Conservative Dentistry and Endodontics, Narsinhbhai Patel Dental College and Hospital, Visnagar, Gujarat, India
4 Senior Lecturer, Department of Pedodontics and Preventive Dentistry, Bapuji Dental College and Hospital, Davangere, Karnataka, India
5 Senior Lecturer, Department of Prosthodontics and Crown and Bridge, College of Dental Sciences and Research Centre, Ahmedabad, Gujarat, India

Date of Submission09-Sep-2019
Date of Acceptance13-Sep-2019
Date of Web Publication22-Oct-2019

Correspondence Address:
Dr. Rajendra Bharatiya
Department of Conservative Dentistry and Endodontics, AMC Dental College and Hospital, Ahmedabad, Gujarat
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/INPC.INPC_34_19xs

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  Abstract 


Aim: The aim of this study was to evaluate the incidence of root fracture of endodontically treated teeth restored with two different types of glass-fiber posts luted with glass-ionomer cement (GIC).
Materials and Methods: Forty maxillary central incisors were sectioned at 1 mm of the cementoenamel junction and endodontically treated. The teeth were divided into two groups (n = 20) where Group I included teeth restored with Reforpost (No. 1, Angelus, Brazil) and Group II with Selfpost (Size 1, Medicept, UK). The posts were luted with GIC, and core built up was done using composite resin. The fracture strength was evaluated using a universal testing machine. The data obtained were tabulated and subjected to statistical analysis.
Results: The comparison of the mean strength required (in Newtons) to fracture the teeth was higher in Group I that is Reforpost than Group II (Selfpost) implicating highly significant differences in their fracture resistance (P ≤ 0.001).
Conclusion: The conclusion drawn was that Group I (Reforpost post) exhibited better resistance to fracture than that of Group II (Selfpost post).

Keywords: Fracture resistance, glass-fiber post, Reforpost, selfpost


How to cite this article:
Bharatiya R, Prajapati U, Gupta A, Patel NA, Khan MM, Sutaria BS. Comparative analysis of fracture resistance of two different glass-fiber postsystems: An in vitro study. Int J Prev Clin Dent Res 2019;6:62-5

How to cite this URL:
Bharatiya R, Prajapati U, Gupta A, Patel NA, Khan MM, Sutaria BS. Comparative analysis of fracture resistance of two different glass-fiber postsystems: An in vitro study. Int J Prev Clin Dent Res [serial online] 2019 [cited 2019 Dec 10];6:62-5. Available from: http://www.ijpcdr.org/text.asp?2019/6/3/62/269708




  Introduction Top


Endodontic treatment is an attempt to save and preserve the tooth with damaged pulp in function.[1] An endodontically treated tooth can resume full function; however, special techniques are needed to restore such a tooth that are coronally deficient teeth with sound root.[2]

Coronal tooth structure loss requires utilization of the radicular dentin for the support of core. The primary purpose of a post is to retain a core in a tooth with extensive loss of coronal tooth structure.[3],[4] Post and core equally distributes torquing forces to supporting tissues through radicular dentin and thus protect and strengthen the tooth. It disperse forces along the root and provide retention for the core which has replaced the lost coronal tooth structure.[5] However, preparation of a postspace adds a certain degree of risk to a restorative procedure. The placement of posts also may increase the chances of root fracture and treatment failure.[6],[7] Posts are categorized a number of different ways such as active or passive, parallel or tapered, and by material composition.

Based on the material used, endodontically treated anterior teeth were traditionally restored with cast metal post and cores. These metallic posts have a much higher modulus of elasticity than the supporting dentin, leading to stress concentration and failure and inferior esthetics as they do not allow light transmission.[8] They are very rigid and strong. As they are round, they offer little resistance to rotational forces. This is not a problem if adequate tooth structure remains, but if minimal tooth structure remains, antirotation features must be incorporated into the postpreparation with slots or pins.[9] This disadvantages of the metal post have led to search for a plastic based material that has modulus closer to that of dentin.[10]

Carbon fiber or the tooth-colored posts gained popularity in the 1990s. Their main proposed advantage was that they were more flexible than metal posts and had approximately the same modulus of elasticity (stiffness) as dentin. Hence, when bonded in place, it was thought that forces would be distributed more evenly in the root, resulting in fewer root fractures.[11]

Hence, the aim of this study was to evaluate the incidence of root fracture of endodontically treated teeth restored with two different types of glass-fiber posts luted with glass-ionomer cement (GIC).


  Materials and Methods Top


Forty freshly extracted maxillary central incisors were selected for the purpose of the study with their lengths ranging from 14 to 16 mm and buccolingual diameters ranging from 6 to 8 mm. This was done to eliminate the dimension variation factor as shown in [Table 1] that represents the significance value (based on the ANOVA test) of lengths and buccolingual diameters of all the specimens belonging to different groups.
Table 1: Buccolingual diameter and length of specimens

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The selection criteria included tooth with mature root apex, extracted for periodontal and orthodontic reasons, no caries, no restorations, no previous endodontic treatment, and no cracks that might affect fracture resistance to experimental compressive loading. All teeth were thoroughly cleaned with an ultrasonic scaler and stored in 10% neutral buffered formalin solution for <1 week at room temperature that disinfections them and does not alter their cutting characteristics.[12],[13] They were then decoronated 1 mm above the cementoenamel junction, flattened and smoothened with 2-mm grit abrasive paper. The roots were mounted individually in modeling wax, such that the apex of the root was retained on the hard surface. The roots were then endodontically instrumented 1 mm short of the apex with the step-back technique using K-files (Dentsply, Maillefer), irrigated with a 2.5% sodium hypochlorite solution, rinsed with saline and dried with paper points (Dentsply). They were then obturated with thermoplasticized gutta-percha (E and Q master, Meta Biomed, Korea) and a resin sealer (AH26; Dentsply DeTrey, Konstanz, Germany).

After the completion of endodontic treatment, the coronal root canal openings were restored with a temporary restorative material (GC Fuji II, GC Dental Products Corp., Tokyo, Japan) and kept in saline-soaked gauze to maintain moistness.

Specimen preparation

After 24 h, postspace preparation was done with Peeso reamer No. 3 (Mani, Japan) leaving 5-mm gutta-percha in the apices, to preserve the apical seal. The teeth were then assigned to two experimental groups (n = 20) [Table 2].
Table 2: Groups

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Fiber posts were cleaned with alcohol and dried with air. Salinization was done with silane agent (Monobond-S, Ivoclar Vivadent, US). Root canals for each group were etched with 37% phosphoric acid for 15 s. Core buildup was completed to the final core height of 6 mm. Buccolingual and mesiodistal dimensions were also restored to their original dimensions as that of the tooth, with the help of composite finishing kit (Soflex, Japan). The teeth were then removed from modeling wax and mounted individually in addition silicone putty (EliteP & P Zhermack). Each root was mounted vertically, such that the apex of the root was retained on the hard surface.

Load application

All the specimens were placed individually on the testing platform of an instron universal testing machine (Model 4206, Instron Corp., Canton, MA, USA). Direct vertical load was applied to the long axis of the tooth, at a crosshead speed of 1 mm/min until failure occurred. Reading for an individual tooth was recorded.


  Results Top


The present study was conducted to evaluate the incidence of root fracture of endodontically treated teeth restored with two different types of glass-fiber posts luted with GIC cement. The comparison of the mean strength required (in Newtons) to fracture the teeth was higher in Group I that is Reforpost than Group II (Selfpost) implicating highly significant differences in their fracture resistance (P ≤ 0.001) with Group I exhibiting higher resistance to fracture than that of Group II [Table 3].
Table 3: Statistical analysis

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  Discussion Top


Preservation of tooth structure is important when restoring the coronal portion of the tooth. Coronal tooth structure should be preserved to provide resistance and retention form for the crown.[11] The loss of tooth structure makes retention of subsequent restorations more problematic and increases the likelihood of fracture during functional loading. Different clinical techniques have been proposed to solve these problems, and opinions vary about the most appropriate one.[14] Today, both endodontic and prosthodontic aspects of treatment have advanced significantly; new materials and techniques have been developed, and a substantial body of scientific knowledge is available on which clinical treatment decisions are based.[15]

The most commonly used technique for restoring a coronally deficit tooth is by the use of a post and core. An ideal post system should have fracture strength more than that of physiologic masticatory forces, but it should not be very high to cause catastrophic root fracture. If the postmaterial is having the modulus of elasticity same as that of the root dentin, applied forces are evenly distributed along the length of the post and the root.[16] If the modulus of elasticity is significantly greater than dentin, it will create stresses at the tooth cement-postinterface, increasing the chances of postseparation and failure.[17] Postdiameter, postdesign, postlength, remaining dentin, cement, cementation technique, core material, and biocompatibility of postmaterial are several factors which may affect fracture-treated teeth.[18]

Glass-fiber post has a modulus of elasticity that approximates (9–50 GPa) the dentin which may allow postflexion to mimic tooth flexion. Hence, the glass-fiber post will absorb and distribute the stresses and thus reduced stress transmission to the root.[19] In contrast, the modulus of elasticity of the metal post is 8–9 times than that of dentin. Hence, the metal posts are stiffer and do not absorb stresses. It also concentrates the stresses produced by occlusal and lateral forces on the root causing unfavorable root fractures.[20]

Some researchers adopted the idea that stiffer the post the more even the stress distribution.[21] Others have opposed this idea.[22] Hence, the aim of this study was to evaluate the fracture strength of two different prefabricated glass posts when luted with GIC and resin cement in endodontically treated teeth. Results showed a statistically significant difference between teeth restored with different prefabricated glass posts luted with GIC. The teeth restored with Reforpost glass posts showed better resistance to fracture than the one restored with Selfpost glass posts.

The highest fracture resistance of the Group I could be mainly due to its design. The numerous taper present in the post simulates serrations. Moreover, the taper of the post exists only for 3 mm from the apex and it restarts again. This feature makes this post act almost like a parallel post in the presence of resin cement in the serrations. It had been already reported that parallel posts with serration would have more retention.[23] The parallel-sided shape of Reforpost favors its mechanical interlocking with the root canal walls. Its conical tip allows less tooth preparation at the apical third, saving dentin in this area. The inner metal framework further reinforces the strength of the post.

This study simulates a realistic condition with a reduced amount of tooth structure which has 1 mm of remaining coronal dentin. Hence, the post and core bears the compressive load.[24] Cylindrical posts with parallel sides were selected for this study as tapered post increases the fracture strength but can result in unrestorable complicated fracture on loading.[25]

Universal testing machine (4206, Instron Corp., Canton, MA, USA) was used to check the fracture strength. Clinically, the velocity of mandibular movement varies considerably; the compressive load at a crosshead speed of 1 mm/min was maintained because it is considered as an acceptable value.[26]

The teeth were mounted in material for load testing that did not simulate the resiliency of the periodontal ligament and alveolar bone. Furthermore, the universal testing machine applies a single unidirectional load that does not duplicate multidirectional characteristics of masticatory forces.[18] Hence, from these two points, it is clear that although this type of in vitro study does not represent the complete in vivo situation, it gives us a glimpse about how the system of post and core might work.


  Conclusion Top


The present study was conducted to evaluate the incidence of root fracture of endodontically treated teeth restored with two different types of glass-fiber posts luted with GIC cement.

Forty maxillary central incisors were sectioned at 1 mm of the cementoenamel junction and endodontically treated. The teeth were divided into two groups (n = 20) and restored with prefabricated glass-fiber post luted with GIC. Core built up was done using composite resin. The fracture strength was evaluated using an instron universal testing machine (Model 4206, Instron Corp., Canton, MA, USA), and the results were recorded. The comparison of the mean strength required (in Newtons) to fracture the teeth was higher in Group I that is Reforpost than Group II (Selfpost) implicating highly significant differences in their fracture resistance (P ≤ 0.001) with Group I exhibiting higher resistance to fracture than that of Group II. Hence, in conclusion, although Group I exhibited better resistance to fracture, more studies should be encouraged to be done for a better understanding of the subject in toto.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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Purton DG, Love RM. Rigidity and retention of carbon fibre versus stainless steel root canal posts. Int Endod J 1996;29:262-5.  Back to cited text no. 16
    
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Maccari PC, Conceição EN, Nunes MF. Fracture resistance of endodontically treated teeth restored with three different prefabricated esthetic posts. J Esthet Restor Dent 2003;15:25-30.  Back to cited text no. 17
    
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Fernandes AS, Dessai GS. Factors affecting the fracture resistance of post-core reconstructed teeth: A review. Int J Prosthodont 2001;14:355-63.  Back to cited text no. 18
    
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    Tables

  [Table 1], [Table 2], [Table 3]



 

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