|Year : 2016 | Volume
| Issue : 4 | Page : 377-382
Comparison of fracture resistance of simulated immature teeth with an open apex using Biodentine and composite resin: An in vitro study
Murtuza Saifuddin Zhabuawala, Roopa R Nadig, Veena S Pai, Yashwanth Gowda
Department of Conservative Dentistry and Endodontics, Dayananda Sagar College of Dental Sciences, Bengaluru, Karnataka, India
|Date of Web Publication||29-Sep-2016|
Murtuza Saifuddin Zhabuawala
Department of Conservative Dentistry and Endodontics, Dayananda Sagar College of Dental Sciences, Bengaluru, Karnataka
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Aim: To evaluate the fracture resistance in simulated immature teeth that had been backfilled using composite resin and Biodentine after using Biodentine as an apical plug material immediately and after 3 months of aging. Materials and Methods: Sixty extracted human maxillary central incisors were simulated in an immature open apex. The roots of all the specimens were then standardized to a length of 10 mm and canals were instrumented to obtain the radicular dentin thickness around 1.5 mm. All the specimens were then randomly divided into three groups of twenty teeth each. Group I (control) - 4 mm apical plug of Biodentine backfilled with thermoplasticized gutta-percha. Group II - 4 mm apical plug of Biodentine and then backfilled with ParaCore. Group III - completely filled with Biodentine. Ten samples from each group were randomly divided into two subgroups. In subgroup A: Specimens were stored for 1 week. In subgroup B: Specimens were stored in phosphate-buffered saline solution for 3 months and were subjected to universal testing machine. Statistical analysis was done using one-way analysis. Results: No significant difference in fracture resistance between the groups was observed when tested immediately. After 3 months of aging, only Biodentine group showed a significant reduction in fracture resistance without significant reduction with other two groups. Conclusion: Biodentine group has shown a drastic reduction in fracture resistance after 3 months of aging, and hence cannot be recommended as a reinforcement material in immature teeth with thin dentin walls.
Keywords: Biodentine, composite resin, fracture resistance, immature teeth, thermoplasticized gutta-percha
|How to cite this article:|
Zhabuawala MS, Nadig RR, Pai VS, Gowda Y. Comparison of fracture resistance of simulated immature teeth with an open apex using Biodentine and composite resin: An in vitro study. J Indian Soc Pedod Prev Dent 2016;34:377-82
|How to cite this URL:|
Zhabuawala MS, Nadig RR, Pai VS, Gowda Y. Comparison of fracture resistance of simulated immature teeth with an open apex using Biodentine and composite resin: An in vitro study. J Indian Soc Pedod Prev Dent [serial online] 2016 [cited 2019 Nov 19];34:377-82. Available from: http://www.jisppd.com/text.asp?2016/34/4/377/191424
| Introduction|| |
Dental impact injuries involve young adults and mainly children between 8 and 12 years old. , The most common site is maxillary anterior teeth.  These injuries often lead to pulpal necrosis leaving an incomplete root with an open apex and thin dentinal walls with wide funnel-shaped canal.  Endodontic restoration of such teeth is a challenge due to lack of apical constriction and thin walls.  Calcium hydroxide (CH) is used to induce apexification with Cvek ,,, reporting increase in cervical fracture by 28%-77% if left for a long time.
Mineral trioxide aggregate (MTA) has gained popularity in single visit apexification as it has a good sealing ability, high degree of biocompatibility, low cytotoxicity, antimicrobial properties, ability to set in the presence of moisture, shorter treatment time, and induction of hard tissue deposition periradicularly. ,,, However, Shabahang et al.  and White et al.  reported that MTA promotes apical closure equal to that seen with CH and tooth strength is weakened after exposure to MTA for more than 5 weeks.
Recently, a new calcium silicate-based cement Biodentine has been introduced and advocated to be used as dentin substitute. Similar to MTA, Biodentine is biocompatible and biologically active. The compressive strength and elasticity modulus are closer to dentin with superior handling characteristics than MTA. 
The fragility of roots in immature teeth due to thin dentinal walls can compromise tooth strength, and therefore reinforcement of radicular dentin is of utmost importance in such cases and several materials and techniques have been examined in this regard. ,,,, Composite resin has the ability to bond to root dentin walls, increasing the strength of the roots. However, it has certain disadvantages such as polymerization shrinkage stresses, difficulty in complete curing, and increased c-factor in the root canal system.  An alternative is the use of fiber post with an elastic modulus similar to dentin shown to have "Monoblock" effect. , A mismatch between the diameter of postspace and the fiber post could pose a problem, particularly in immature teeth with large root canals. 
Placing an apical plug of MTA or Biodentine followed by placement of composite resin for radicular reinforcement has certain practical difficulties such as many interfaces between the materials used, multiple treatment visits, removal of extra MTA/Biodentine that has adhered to the root dentine may interfere with bonding, and an attempt to remove the adhered material might result in unnecessary removal of already weakened radicular dentin. To overcome the above practical difficulties, there have been attempts to fill the entire canal with these materials. A study conducted to evaluate the fracture resistance of simulated immature teeth with Biodentine apical plug and backfilling with various materials concluded that backfilling with gutta-percha, fiber post, or Biodentine does increase the force required to fracture immature teeth.  However, in all of these above studies, testing was done immediately after obturation and these studies involved teeth specimens with canal wall thickness of >2.5 mm. Stuart et al.  suggested that the canal wall reinforcement of teeth with a wall thickness of 2 mm or more may not be necessary. Therefore, evaluation of fracture resistance of rehabilitated teeth with canal wall thickness of <1.5 mm is crucial and more relevant. Hence, this study was undertaken to evaluate the reinforcing ability of dual cure composite resin and Biodentine on immature root dentin immediately and after 3 months of aging.
| Materials and Methods|| |
Sixty extracted human maxillary central incisors were selected for the study, disinfected with 5.2% sodium hypochlorite for 2 h and stored in distilled water until the beginning of the experiment. The roots of teeth were standardized to a length of 10 mm as measured from the apex to the facial cementoenamel junction (CEJ) by cutting the root tip to simulate incomplete root formation. Endodontic access cavities were made using round bur and Endo Z-bur in a high-speed handpiece and root canals were prepared using ProTaper rotary instruments. To achieve a simulation of teeth with immature apices, Peeso Reamers between #1 and #6 were introduced into the root canal until #6 pass freely out of the apex. After instrumenting with Peeso reamers, the radicular dentin thickness was 2.5 mm. Further 703 carbide bur was used to obtain the remaining dentin thickness around 1 to 1.5 mm. The samples were then subjected to CBCT analysis to confirm the dentin thickness. The root canals were irrigated using 3 ml of 3% sodium hypochlorite and final flush with 5 ml of 17% ethylenediaminetetraacetic acid was carried out to remove the smear layer. Biodentine mixed according to manufacturer's instruction was placed with a carrier and adapted using hand plugger in the 4 mm apical portion of the canal. The teeth were radiographed to verify correct position of the Biodentine. Samples were wrapped in wet gauze, placed in an incubator, and allowed to set for 12 min at 37°C with 100% humidity. Specimens were randomly divided into 3 groups with twenty specimens in each group.
Group 1 (n = 20): AH Plus sealer was applied to the canal walls, backfilled with gutta-percha using Obtura II. Excess sealer was removed from the chamber with a dry cotton pellet.
Group 2 (n = 20): Dual cured composite resin (ParaCore/Coltene Whaledent) was inserted into the canal, and the excess resin was removed, and light activation was performed for 40 s.
Group 3 (n = 20): Biodentine (Septodont/France) was mixed and placed to a level just below the facial CEJ.
In all the groups after obturation, the access openings 2 mm below CEJ were filled with nanocomposite (Filtek Z350xT; 3M ESPE, USA). Immediately after filling, ten samples from each group were randomly divided into two subgroups. In subgroup A: Specimens were stored for 1 week in phosphate-buffered saline. In subgroup B: Specimens were stored in phosphate-buffered solution for 3 months until fracture resistance testing. [Figure 1] shows radiographs of representative samples of the groups.
|Figure 1: 1. Simulation, 2.Gutta percha( group 1), 3.Paracore( group 2), 4.Biodentine( group 3)|
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To simulate periodontal membrane, the root surfaces were coated with 0.2-0.3 mm thick layer of polyvinyl siloxane impression material and then embedded in the acrylic resin leaving the gap of 2 mm between the top of acrylic and to the CEJ. A custom-made jig was used to fix the cylinders at an angle of 45° and a compressive load was applied from the palatal surface at crosshead speed of 1 mm/min until fracture using universal testing machine. The maximum force required to fracture each specimen was recorded. The data were statistically analyzed using one-way analysis of variance. The level of significance was set at P = 0.05.
| Results|| |
The mean values with standard deviations are presented in [Table 1], [Table 2] and [Graph 1 [Additional file 1]], [Graph 2 [Additional file 2]]. In immediate tested samples, higher mean fracture resistance was recorded in ParaCore Group followed by Biodentine and gutta-percha group, respectively. There was no statistically significant difference in mean fracture resistance between the groups. In delayed tested samples, higher mean fracture resistance was recorded in ParaCore group followed by gutta-percha and Biodentine group, respectively. The difference in mean fracture resistance was found to be significantly different between the groups (P < 0.01). On comparing immediate and delayed testing of Biodentine samples, the difference between them was found to be statistically significant (P < 0.001). However, there was no significant difference in the bond strength values between immediate and delayed specimens of gutta-percha and ParaCore groups.
|Table 1: Mean fracture values for all groups measured in Newtons along with their standard deviations mmediate|
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|Table 2: Mean fracture values for all groups measured in Newtons along with their standard deviations elayed|
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| Discussion|| |
Reinforcement of endodontically treated immature teeth is crucial for the long-term survival of these teeth as they are more susceptible to external and masticatory forces. Prerequisites for selection of such a material for reinforcement are that it should be applied easily in clinical practice, bond successfully to dentin and serve as a good barrier against microleakage.  Reinforcing capability of Biodentine was evaluated in this study because in addition to being bioactive and biocompatible material, it has improved handling characteristics and less time consuming than MTA. Han and Okiji  suggested that BD may have a remarkable biomineralization capability than MTA.
In most of the studies, found in the literature, to simulate immature teeth, the canals were instrumented with Peeso reamers (1-6) until a size 6 Peeso can be passed 1 mm beyond the apex to simulate open apex, this would only result in dentin thickness of 2-2.5 mm. Investigations have revealed that the reinforcement of a canal with a diameter <1.5 mm is not necessary while wall thickness of 2.63 mm is insufficient to weaken tooth structure.  Therefore, preparation of the canal was further enlarged with 702 carbide burs to approximate Cvek's stage 3 root development. Cvek's stage 3 root development was selected for the present model; because at this stage, the root-to-canal ratio in a mesiodistal dimension at the CEJ is nearly 1:1. , In the present study, after the simulation of all the samples, cone-beam computed tomography was used to find out the accurate thickness of the remaining radicular dentin.
While testing for fracture resistance, average angle of Class I occlusal contact between upper and lower incisors were considered, and load was applied at 45°. , On evaluating the results, in immediate tested specimens, teeth restored with ParaCore group showed the highest fracture resistance followed by Biodentine and then gutta-percha. However, there was no statistically significant difference between the groups tested in the study. A preliminary study by Yasir  reported that there was no significant difference between Biodentine and gutta-percha on fracture resistance of immature teeth. A similar study by Topçuoglu et al.  suggested that there is no difference between Biodentine and gutta-percha group on fracture resistance when Biodentine apical plug was backfilled with Biodentine, gutta-percha, or fiberpost in immature teeth.
In the present study, access composite is extended 2 mm apical to CEJ to provide an additional root strength necessary to minimize cervical root fracture. Seto et al.  reported that composite resin to a depth of 3 mm would significantly strengthen the roots in immature teeth. Hence, this could be one possible reason, why there was no statistically significant difference in the fracture strength between the control group and the experimental groups in the current study.
After 3 months of storage, teeth restored with ParaCore have shown the highest fracture resistance followed by gutta-percha. Biodentine showed the least fracture resistance. On comparing the bond strength values of immediate and delayed ParaCore groups although there was a reduction in fracture resistance in the delayed group, it was not statistically significant. Tay et al.  reported that self-etch adhesives imbibed water and induced collagenolytic activity leading to degradation of resin-dentin interface affecting the longevity of adhesively bonded post. Tay et al.  concluded that etch and rinse had better bond durability over time than self-etch as self-etch is hydrophilic and degrade over time making Monoblock questionable. However, our study was of 3 months duration and the longevity of the bond with extended time periods needs further evaluation.
On comparing the bond strength of immediate and delayed Biodentine samples, there seems to be a drastic reduction in the tooth strength after 3 months of storage. It has been shown that CH due to its alkalinity induces caustic degradation on exposed collagen due to breakage of intermolecular bonds between collagen fibrils making them susceptible to water absorption and swelling. , A recent study by Sawyer et al.  reported that flexural strength for dentin exposed to Biodentine and MTA decreased significantly after 2 and 3 months. Atmeh et al.  examined the dentin cement interfacial interaction with Biodentine and reported altered intertubular microstructure in the mineral infiltration zone changing its optical properties. Under scanning electron microscopy micrographs altered dentin due to caustic denaturing and increased permeability by the alkaline, Biodentine was observed. Therefore, it is possible that the above reaction might have led to decreased tooth strength of the Biodentine samples after 3 months. Another possible reason for the reduction in the tooth strength with Biodentine after 3 months of aging could be on account of poor solubility of Biodentine. Singh et al.  have reported that the solubility of Biodentine after 30 days and 60 days immersion period was significantly higher as compared to MTA. Vivan et al.  theorized that a material releasing calcium ions to exert biologic effect to some extent solubilize and dissociate from fully hardened cement thus resulting in disintegration. In the present study, radiographic examination of the samples observed, showed a reduction in the radiopacity of Biodentine after 3 months of aging which could suggest the disintegration of this material over a period of time. Hence, further evaluation is required for Biodentine to be used in apexification procedure. It is interesting to note that Hatibovic-Kofman et al.  compared the influence of MTA and CH on fracture resistance in sheep teeth and stated that over 1-year period, MTA and CH have shown a 2% and 26% decrease in fracture resistance. Authors reported that after initial decrease in the fracture resistance of MTA treated teeth, the process is reversed, and fracture resistance increases for a period between 2 months and 1 year. It can be explained by the fact that MTA induces the expression of tissue inhibitor of metalloproteinase-2 in dentin matrix and suppress the degenerative activities of MMP-2 and-14. Whether similar phenomenon can be observed in Biodentine needs further evaluation.
| Conclusion|| |
The fracture resistance of immature teeth with an apical plug of Biodentine followed by obturation with gutta-percha, ParaCore, or Biodentine was similar when tested immediately. After 3 months of aging, teeth obturated completely with Biodentine has shown a drastic reduction in the fracture resistance whereas there was no significant reduction in fracture strength in teeth with an apical plug of Biodentine backfilled with gutta-percha and composite resin. Within the constraints of the present study, it can be inferred that Biodentine cannot be recommended as a reinforcement material in immature teeth with thin dentinal walls. Further in vitro and in vivo investigations are necessary to validate the above findings.
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Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2]