|Year : 2021 | Volume
| Issue : 1 | Page : 36-41
Comparative evaluation of fracture resistance of endodontically treated premolars with one remaining cavity wall restored using different techniques and materials: An in vitro study
Aun Taherali Taheri1, Anuja Ikhar1, Pradnya Prashant Nikhade1, Gopal Tawani1, Aditya Patel2, Zahra Ali3
1 Department of Conservative Dentistry and Endodontics, Sharad Pawar Dental College (DMIMS), Wardha, Maharashtra, India
2 Department of Conservative Dentistry, College of Dentistry, Jazan Unviersity, Jazan, Saudi Arabia
3 Sri Sai Dental College, Vikarabad, Hyderabad, Telangana, India
|Date of Submission||11-Jan-2020|
|Date of Decision||11-Apr-2020|
|Date of Acceptance||22-Apr-2020|
|Date of Web Publication||09-Jan-2021|
Dr. Aun Taherali Taheri
Department of Conservative Dentistry and Endodontics, Sharad Pawar Dental College, Wardha, Maharashtra
Source of Support: None, Conflict of Interest: None
Introduction: This study was aimed to evaluate and compare the effectiveness of conventional posterior composites, and short fiber-reinforced composites with and without the use of glass fiber post (GFP) and polyethylene fiber post on fracture strength of endodontically treated maxillary premolar teeth.
Materials and Methods: Root canal treatment was performed on the sixty extracted maxillary premolars followed by mesio-occluso-distal cavity preparation and removal of the lingual wall. The teeth were randomized into six groups (A1, A2, A3; B1, B2, and B3). In Group A, a conventional posterior composite was used as a core material, and in Group B, short fiber-reinforced composite was used. Groups A and B were divided according to the post systems used. In Groups A1 and B1, 3 mm deep cavities were prepared in the palatal canal and restored with respective core materials. In Groups A2 and B2 GFP were placed in 10 mm post space prepared in the palatal canal and restored with respective core material. While in Groups A3 and B3 polyethylene, fiber post was placed, followed by core build-up with respective core materials. Samples were subjected to fracture resistance testing in the Universal testing machine, and the fractured samples were inspected in stereomicroscope under 20× for identifying fracture patterns. The data were analyzed using one-way ANOVA, followed by post hoc Tukey's test. The failure pattern was analyzed using the Chi-square test.
Results: Higher fracture resistance values were seen with groups restored with the post as compared to groups restored without post, but the difference was not statistically significant (P > 0.05). The short fiber-reinforced composite showed higher resistance values than the conventional composite (P < 0.05). No significant difference in fracture resistance was observed when the samples were restored with either of the post (P > 0.05). The use of post resulted in a significantly higher number of favorable fracture of the teeth (P < 0.05).
Conclusion: The use of post did not have a profound effect on the fracture resistance but had a positive effect on failure patterns in teeth with one remaining wall. In root canal treated teeth with one wall remaining, the use of either post with short fiber reinforced composite is recommended.
Keywords: Fracture resistance, glass fiber post, polyethylene fiber post, short fiber-reinforced composite
|How to cite this article:|
Taheri AT, Ikhar A, Nikhade PP, Tawani G, Patel A, Ali Z. Comparative evaluation of fracture resistance of endodontically treated premolars with one remaining cavity wall restored using different techniques and materials: An in vitro study. Saudi Endod J 2021;11:36-41
|How to cite this URL:|
Taheri AT, Ikhar A, Nikhade PP, Tawani G, Patel A, Ali Z. Comparative evaluation of fracture resistance of endodontically treated premolars with one remaining cavity wall restored using different techniques and materials: An in vitro study. Saudi Endod J [serial online] 2021 [cited 2021 Jan 19];11:36-41. Available from: https://www.saudiendodj.com/text.asp?2021/11/1/36/306614
| Introduction|| |
Endodontic procedures result in a significant decrease in the strength of the teeth. According to Larson et al. and Mondelli et al. reduction of the coronal tooth structure due to caries, preexisting restorations, access cavity preparation, and biomechanical preparation results in the weakening of the teeth. According to Reeh et al., access cavity preparation affects the stiffness of premolar by 5%, whereas MOD cavity preparations reduce tooth stiffness by approximately 14%–44%. Resistance to fracture decreased as more and more tooth structure is lost. Root canal-treated teeth with one remaining wall are more susceptible to fracture.,
The purpose of restoration is not only to seal the canal system but also to repair and strengthen the remaining tooth structure. To strengthen the tooth after root canal treatment, various treatment modalities have been used, such as complex amalgam restoration, indirect cast restoration, crown coverage, metal posts, and nanocomposites.
In 1980, Nayyar et al. introduced a technique for corono-radicular stabilization, in which 2–4 mm cavity is prepared in the canal; amalgam is then first condensed into this cavity followed by condensing the rest of the cavity. Later on, Hürmüzlü et al. replaced amalgam with composite, which resulted in improved fracture resistance of the teeth.
According to Peroz et al., the use of a post is necessary in root canal treated teeth if either one wall or no cavity wall is present. According to many studies, restoration done with post and core in teeth with minimal cavity walls remaining can have a significantly good fracture strength, increases the core retention and also decreases the risk of failure., The two types of posts recently used are prefabricated fiber post and custom-made fiber post. Angelus Reforpost is a type of prefabricated fiber post which has longitudinally arranged glass fibers, they are parallel in shape with grooves and a conical tip. A type of customized fiber post is Polyethylene Fibres (Ribbond-THM), which consists of plasma-treated, unidirectional, and braided high strength polyethylene fibers. They have a patented leno weave design with a lock-stitch pattern, i.e., a lace-like, which efficiently transfers the force all over the leno weave structure without transferring stress back to the matrix, thus creating a change in stress dynamics.
Composite resin has shown higher fracture resistance values compared to glass ionomer cement and cention N when used as a core material. Fiber-reinforced composites are resin-based materials that have been recently introduced that contain fibers which help in increasing the physical properties of the composite. GC Ever X posterior is one of the glass fiber-reinforced composites, used as a dentin replacement that contains short glass fibers made of barium glass and silanated E-glass fibers. These fibers are randomly oriented in the composite, which provides the isotropic reinforcement in multiple directions rather than single or two directions.
Despite various studies, controversies still exist as to which material and which technique gives a promising result in the restoration of extensively damaged endodontically treated teeth. Therefore, this in vitro study was carried out with the aim to compare the effectiveness of conventional posterior composites (CPC) and short fiber-reinforced composites (SFRC) with and without the use of glass fiber post (GFP) and polyethylene fiber post (PEP) on fracture strength of endodontically treated maxillary premolar teeth.
| Materials and Methods|| |
The observational study was carried out in the Department of Conservative Dentistry and Endodontics.
Institutional Ethical Clearance was granted with Ref. No. DMIMS (DU)/IEC/2017-18/6735.
Sixty freshly extracted human permanent maxillary premolars teeth having two root canals with approximately 15 mm root length were selected for the study. Teeth with root resorption, fracture lines, carious, or root canal treated teeth were excluded from the study. Teeth were stored in 0.1% thymol solution (Alpha Chemika, Mumbai, India).
Access cavities were made with #2 round diamond points (Mani, Utsunomiya, Japan). Biomechanical preparation was done with rotary Protaper Universal files (Dentsply Maillefer, Switzerland) from SX to F2. Irrigation was done using saline and 3 ml of 2.5% sodium hypochlorite (Vishal Dentocare, Ahmedabad, India) in between each instrument. Obturation was done using Gutta Percha (DiaDent, Seoul, Korea) and AH Plus sealer (Dentsply Maillefer, Switzerland).
First, MOD cavities were made with #557 straight bur (Mani, Utsunomiya, Japan). The palatal cusp was then removed using a diamond disc such that buccal wall thickness was 1.5 mm at the occlusal surface and 2 mm at cementoenamel junction (CEJ) in buccolingual direction and 4 mm mesiodistally [Figure 1]. All the measurements were done using Vernier caliper (Prism Pharmatech solution).
|Figure 1: The schematic presentation of cavity preparation in premolar. (a) Proximal view. (b) Occlusal view|
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The samples were randomly divided into six groups, with ten teeth in each group [Figure 2].
In Groups A1 and B1, Nayyar's Technique was used for restoration, in which GP was removed and cavities of 3 mm deep and 1.5 mm diameter were prepared using no. 6 Gates Glidden Bur (Mani, Utsunomiya, Japan) in the palatal canal orifice [Figure 3]. The Groups A1 and B1 were used as a control group in this study.
|Figure 3: Schematic presentation of 3 mm cavity preparation in the palatal canal. Proximal view|
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In group A2, A3, B2, and B3, 10 mm of post space were made in the palatal canal using No. 3 Peeso Reamer bur, such that apical 4–5 mm of GP remains in the canal.
- In Group A1 Etching of the cavity was done with 37% phosphoric acid (Prime Dental, Mumbai) for 15 s, followed by rinsing and air drying for 15 s. 5th Generation bonding agent (Adper Single Bond2, USA) was coated on the cavity surface using an applicator tip and was cured for 20 s at an intensity of 600 mW/cm2. CPC (Filtek P60, 3M, USA) was first placed in deep cavities and light-cured for 40 s. Then, the remaining core portion was filled with the same composite and light-cured from all sides for 40 s
- In Group B1 etching and bonding agent was applied as in Group A1. While restoring, the missing walls and the occlusal 1–2 mm were restored with CPC (Filtek P60, 3M). The cavity in the canal and the remaining cavity was filled with SFRC (GC Ever X Posterior, Turku, Finland)
- In Group A2 etching of the canal was done with 37% phosphoric acid (Prime Dental) for 15 s. followed by rinsing with water and air drying. Prime and Bond NT and self-cure activator (Calibra, Dentsply, USA) were mixed in equal quantity, and the mix was applied in the canal using applicator tip and cured for 20 s. Angelus Reforpost (No. 1) was cleaned with alcohol, and Silane (Angelus, Londrina PR, Brazil) was applied to the post and kept for 1 min. Dual cure resin cement (Calibra, Dentsply Sirona, USA) was mixed, and the mix was coated in the canal using lentulo spiral and also on Reforpost. The Reforpost was then inserted in the canal and cured for 40 s. Core portion was then restored by CPC (Filtek P60, 3M) and cured for 40 s from all sides
- In Group B2 Angelus post was placed as in Group A2. Core build-up was done using SFRC as in Group B1
- In Group A3 Etching and bonding agent application of the canal was done as in group A2. Polyethylene Fibre (Ribbond, THM, Inc; Seattle, WA USA.) having 2-mm thickness was cut to the specified length, i.e., double the length of post space and core. The fiber was soaked in resin (Prime and Bond NT). Resin cement (Calibra, Dentsply Sirona, USA) was coated in the canal using lentulo spiral, and the fiber was compacted in the canal with the help of endodontic plugger. The core portion of the fiber was twisted and then cured for 40 s. The remaining core portion was build using CPC (Filtek P60, 3M)
- In Group B3, Ribbond post was placed as in Group A3. Core build-up was done using SFRC as in Group B1.
After finishing and polishing restorations using Super Snap Shofu finishing kit, the root portion of the samples was coated with 0.2–0.5-mm thickness of light body impression material (Photosil, DPI, Mumbai). Samples were fixed in cold-cure acrylic (DPI, Mumbai) up to 2 mm below the CEJ. Samples were then kept in saline solution at 37°C for 1 week.
Fracture resistance of the samples was tested in a universal testing machine at an angle of 30° to the long axis of the direction of load. The load was applied with a 4 mm diameter stainless-steel ball in the central fissure area at a crosshead speed of 1 mm/min until the fracture occurred. Values were recorded in Newton.
Fractured samples were then seen under a stereomicroscope at 20× to identify the pattern of failure, “Favourable fracture” was considered when the fracture was coronal to CEJ, and “Non-favourable fracture” was considered when the fracture occurred below the CEJ. Statistical analysis of the fracture resistance was performed using the One-way ANOVA test, followed by the post-hoc Tukey test. The difference between fracture modes was analyzed using the Chi-Square test. P =0.05 was considered as the level of significance.
| Results|| |
The mean fracture resistance value in descending order were B2 > B1 > A2 > B3 > A3 > A1 [Table 1]. When the inter-group comparison was made using post hoc Tukey test, a statistically significant difference in fracture resistance value was seen when Group A1 was compared with Group B1and B2 (P < 0.05), no significant difference was seen when all other groups were compared with each other (P > 0.05).
|Table 1: Comparison of fractures resistance values of the groups using One-way ANOVA|
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The failure pattern distribution in all the groups is shown in [Table 2]. A significantly higher number of teeth with fracture pattern below the CEJ level was seen in groups restored without post that is Groups (A1 + B1) when compared to groups restored with the post that is groups (A2 + A3 + B1 + B2 + B3) P < 0.01.
| Discussion|| |
Endodontic procedures result in a significant decrease in strength of the teeth as the sound tooth structure is removed due to access cavity preparation and use of GG burs to enlarge the canal orifice, which decreases the pericervical area. The selection of best technique along with material depends on the functional demands of teeth and on the quantity of remaining coronal tooth structure to be restored.
Maxillary premolars were selected for the study as they have a tendency for separation of the cusps due to its position and its anatomic shape. According to the studies by Sorrentino et al. Salameh et al. Hou et al. Zicari et al. and Krejci et al. fracture resistance is associated with the remaining cavity walls and the amount of ferrule present. Hence, as the number of cavity walls, decreases fracture resistance of teeth decreases. Hence, in the present study, premolars with one cavity wall, i.e., buccal wall remaining was used to evaluate the efficacy of post in terms of fracture resistance.
PDL simulation was done according to Soares et al. PDL simulation might have an impact on the fracture behavior and can also modify the failure pattern in the samples. The simulation of periodontal ligament is essential to determine the stress distributions as similar as possible to the clinical situation. The mechanical response of soft tissue to external stress is nonlinear and viscous, which is similar to the characteristics of elastomeric impression materials.
In this study, to evaluate fracture strength of teeth restored with different techniques, the subgroups restored without the post was compared to subgroup restored with the post, that is Group A1 was compared to group A2 and A3; while Group B1 was compared to Group B2 and B3; no significant difference was seen; however, values obtained were higher with groups restored with the post (P > 0.05) [Table 1]. This showed that when the core material is kept the same, restoration done using either of the posts showed higher resistance values compared to the restoration done without post without any significant difference. The result was in accordance with the study of Krejci et al. and Fokkinga et al. The better results in groups restored using Nayyar's core technique could be due to the increase in strength when thicker bulk of composite is placed in 2-3 mm of the cavity below the CEJ in the canal.
Furthermore, to evaluate the fracture strength of teeth restored using different core materials, the subgroups of A (A1, A2, and A3) were compared with respective subgroups of B (B1, B2, B3). Higher resistance values were seen with subgroups of B, and a significant difference was present only between A1 and B1 (P < 0.05) [Table 1]. Thus, when the restoration method is kept the same, and different core materials are compared, higher values are obtained when restored using SFRC. This was in accordance with the results of Barreto et al. and Frater et al. Garoushi et al. and Kemaloglu et al. The reason why SFRC showed better values in all the subgroups could be due to the reinforcement effect of glass fibers when used as a substructure under the conventional composite which transfers stresses from the matrix to the glass fibers and helps in stopping the crack propagation and thus increasing the fracture resistance.
When Group A2 was compared with Group A3 and GROUP B2 was compared to Group B3, i.e., when the core material was kept the same, and different post systems were compared, higher values were seen with GFP though the values were not significant (P > 0.05) [Table 1]. This was in accordance with results obtained by Torabi et al. and Bagdagul et al. Costa et al. reported higher fracture resistance values for the Ribbond fiber post. Lower values for PEP in the present study could be due to the post space preparation, which is generally not recommended for this customizable post system. Removal of Gutta Percha only is indicated, which maintains the normal shape and strength of the root and provides extra mechanical retention by the small undercuts present. In our study to standardize the procedure post space was prepared.
In the present study when the failure pattern was compared between the groups that were restored with the post (A2, A3, B2, B3) and the groups restored without the post (A1, B1), it was seen that in the groups restored without post showed a significantly higher number of unfavorable fracture [Table 2]. Unfavorable fractures are the fractures that occur below the CEJ and shows poor restorability of the tooth. This finding was similar to the results found in the study by Memarpour et al. Hou et al. and Sorrentino et al. where the teeth with no or one cavity wall remaining, postrestoration showed a greater number of favorable fractures. Favorable fractures with fiber post might have occurred due to adhesive fracture between post and the core material, as the adhesion of composite to already polymerized post surface is very little, and no chemical reaction occurs between the methacrylate matrix of composite and the highly polymerized epoxy matrix. When the groups restored with post were compared with one another, no significant difference was seen in the failure pattern (P > 0.05), which showed that the use of either of the post resulted in favorable fracture pattern.
Thus, teeth restored with GFP and SFRC showed the best outcome in terms of fracture strength in endodontically treated premolars with one wall, followed by teeth restored using SFRC with Nayyar's core technique.
The results of this study could help to establish a more effective technique to improve the fracture strength of grossly destructed endodontically treated teeth, overcoming the drawbacks of the conventional technique. Cyclic loading of the samples, which simulates the intraoral functional loading, was not done in our study, which could have affected the results. Further studies can measure fracture resistance after the cyclic loading of the samples.
| Conclusion|| |
Based on the results following conclusions were drawn from the study:
- No significant difference in fracture resistance was seen whether the teeth were restored with post or without post
- A significant difference was seen in the failure pattern, though. Teeth restored with post showed favorable failure pattern
- The use of polyethylene post or GFP did not affect the fracture strength of the teeth significantly
- SFRC used as a core material showed higher values than the conventional composite.
Thus, the use of either of the two posts along with reinforced composite can be recommended for restoring endodontically treated teeth with one remaining cavity wall as it showed good results both in terms of fracture resistance and fracture pattern.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2]