In modern dentistry, cleaning and shaping of the root canal system can be efficiently performed. Due to improvements on instruments and techniques, it is now possible to obtain a success rate of nearly 90% with conventional root canal therapy. However, several factors inherent to the endodontic procedures, such as perforations, instrument breakage, calcifications and anatomic anomalies can lead to treatment failure. In some cases, conventional endodontic treatment is not sufficient to solve the problem and a surgical endodontic intervention is required (1, 2).
Endodontic obturation comprises complete three-dimensional filling of the root canal system with materials that exhibit satisfactory physical and biological properties (3, 4). Ideally, the filling material should adequately seal the root canal and simultaneously prevent fluid percolation into the root canal space, stimulate the resolution of periapical pathologies, and encourage deposition of cementum to achieve biological seal (5-7).
Filling materials should meet several requirements, such as biocompatibility, antibacterial properties, dimensional stability, radiopacity, ease of manipulation, insolubility in oral fluids, and adaptability to the root canal walls (8) as well as the ability to produce a hermetical seal. However, none of the currently available materials feature all the characteristics of the ideal sealer (9, 10).
Every year, a great number of new endodontic filling materials are developed (11) but none of these materials have presented better results than the association of gutta-percha with conventional sealers (12, 13).
In dentistry, calcium silicates have been tested for treatment of dentin hypersensitivity and gave promising results in endodontics (13). However, the most famous calcium silicate cement remains the mineral trioxide aggregate. MTA was introduced in 1993 (14) and is designed for root-perforation treatment, retrograde filling, and open-apex closure on immature teeth. Three excellent reviews have described the physical and bacteriological properties, (15) the leakage and biocompatibility investigations (12) and the mechanisms of action (16) of MTA. In 2001, the company Angelus Soluções Odontológicas introduced the MTA developed in Brazil, which is apparently identical to the MTA developed by Torabinejad (17, 18). More recently, in an effort to incorporate the desirable biological properties of MTA into an easy to manipulate and to insert material, the manufacturer has added specific components to MTA-based cements. (3)
Biodentine TM powder is mainly composed of tricalcium-silicate, calcium carbonate and zirconium oxide as the radio-pacifier, whilst its liquid contains calcium chloride as the setting accelerator and water reducing agent (19). BiodentineTM shows apatite formation after immersion in phosphate solution, indicative of its bioactivity (20).
This material exhibits the same excellent biological properties as MTA and can be placed in direct contact with dental pulp (19) although its sensitivity to abrasion makes it a poor enamel substitute (20-23).
Presently, the literature is scarce on studies evaluating the physical and chemical properties of BiodentineTM as well as on the sealing ability of this cement (24-26). Therefore, the objective of the present study was to analyse the sealing ability of BiodentineTM, while simultaneously comparing the performance of this material with conventional MTA AngelusTM by the fluid filtration method at observation periods of 48 hours.
MATERIAL AND METHODS
Specimen selection and preparation
The study sample comprised 21 extracted maxillary anterior teeth. The teeth were procured from tooth bank at the Department of Oral Surgery Department. Teeth with multiple canals, resorptions, cracks, fractures, canal calcification, external root resorption and/or incomplete apex formation were excluded from the sample.
For disinfection, the specimens were stored in 10% formalin and then placed in normal saline kept moist before the experiment.
The clinical crowns were removed by sectioning at the cementum-enamel junction using a low-speed diamond saw (Buehler isometTM 1000, Germany) attached to laboratorial handpiece under continuous air/water spray to create a standardized root length of 16 mm.
Each root was submitted to radiographic examination to evaluate anatomy and apical morphology.
The canals were initially explored using #15 hand-held K-files (Dentsply, Dentsply/Maillefer, Ballaigues, Switzerland). Subsequently, teeth were numbered and their real canal lengths were determined by manually inserting #15 K-files into the canals, until the instrument tips were visible at the apical foramen.
At each file change, canals were irrigated with 1.0 mL of 2.5% NaOCl (Hyposol, Sodium Hypochloride, India). Afterwards, a final flush with 1.0 mL of NaOCl followed by 5.0 mL of saline (Isotonic sodium chloride, Eczacıbası, Turkey) was performed. Specimens were instrumented up to stainless steel files size of #40 (Dentsply, Dentsply/Maillefer, Ballaigues, Switzerland) following the stepback technique, and after that the canals were irrigated with 20 mL of 0.5% NaOCl solution (Hyposol, Sodium Hypochloride, India).
Before obturating the canals, apical ends were cut 2 mm from the dental apex at angles of 90º using a #4138 diamond-coated bur (Dentsply, Dentsply/Maillefer, Ballaigues, Switzerland) under continuous air/ water spray. Working root canal length was established 16± 1 mm in order to standardize all specimens.
The root canals were dried with paper points (Absorbent, Paper Point, Korea) and filled using the lateral condensation technique.
At that point, the samples were stored at 37 º C for 15 days for inhibition of liquid infiltration and dehydration. Samples were randomly placed into two study experimental groups (n=14) and control group (n=7).The groups were further divided into subgroups of 7 teeth each, according to the materials.
Root-end filling procedures
In the group White MTA AngelusTM (Angelus, Angelus Odontológica, Londrina, PR, Brazil), the material was prepared following the manufacturer’s instructions, mixed at a 1:1 ratio (powder: sterile water) and applied with a Lentulo spiral (Dentsply-Maillefer Instruments SA, Ballaigues, Switzerland) at low speed up to 3 mm short of the apical foramen. The MTA was condensed up to the apical end with an ISO K file #90 wrapped in cotton. Another K file wrapped in moistened cotton was used to remove the excess MTA from the dentin walls. The MTA was condensed up to the apical end with aid of an ISO 90 K-file wrapped in cotton. Another K-file wrapped with moistened cotton was used to remove the excess MTA from the dentinal walls. In case of overfilling, the excess material was also removed.
In group BiodentineTM (Septodont, Septodont Specialités, Saint-Maur des Fosses, France), the material was also prepared according to the manufacturer’s instructions, mixed at three portions of powder and one drop of saline solution, and applied with a Lentulo spiral (Dentsply-Maillefer Instruments SA, Ballaigues, Switzerland) in low speed as described for MTA AngelusTM. The condensation and excess removal was performed as described for the MTA.
In the control group, samples were not obturated with any material.
Three radiographs were taken at different stages of specimen preparation: on sample selection; during endodontic treatment and after treatment.
Fluid Infiltration Technique
The coronal access of the specimens was sealed with sticky wax (Cavex, modelling wax, Netherlands). After this period, the external root surfaces of the specimens in the experimental and the control groups were completely covered by two coats of nail varnish (Flormar, Turkey), except for an area of 1.0 mm around the root apex. The specimens in the control group had their root surfaces completely covered, but without root end.
Leakage was evaluated by the fluid infiltration technique as described by Vasconcelos et al. (3).
The specimens from all groups were placed in basic fuchsine for 48 hours at room temperature. Vertical grooves were cut on the buccal and palatal aspects of all the specimens, and the teeth were longitudinally sectioned by 12.7 mm diamond water in blade (Buchler, Germany). The length of dye penetration between the filling material and tooth structure was measured separately in millimetres, using a calibrated stereomicroscope (Leica MZ75, Germany) at 20 × magnification under same conditions. Linear dye penetration was measured independently by three observers at three different times under the same conditions; the mean value of the recorded measurements was chosen as the extent of dye penetration into each specimen.
Statistical analysis was performed by SPSS software package, Version 16.0 for Windows (SPSS Inc., Chicago, IL, USA). Quantitative values are presented as mean ± standard deviation (SD). One-way Analysis of Variance (ANOVA) was used to indicate differences between the experimental groups and the control. In addition, Tukey Multiple Comparisons Test was used to indicate differences within each group.
All samples in the experimental groups demonstrated variable amounts of apical leakage. Based on dye penetration results, they were not completely sealed in any of the groups.
Regarding the comparisons between each group, significant differences were observed (P=0.0193). Teeth filled with MTA AngelusTM showed lower leakage values than BiodentineTM. A statistically significant difference (P < 0.05) was observed between the various amounts of microleakage in teeth with both biomaterials.
Achieving a hermetic seal by entirely filling the root canal space decreases the risk that microorganisms left in the canal might come in contact with oral or periapical fluids, a potential source of nutrition. This could lead to failure of endodontic therapy, even years after the treatment is completed (20). Based on these facts, leakage studies are of crucial importance to evaluate the different factors involved in the process of root canal obturation.
Several methodologies have been proposed to establish the sealing ability of filling materials, including evaluation of leakage of bacteria, human saliva, protein complex, fluid filtration and dye leakage (27, 28).
Dye penetration and bacterial leakage are more widely used (29). The dye penetration method is qualitative in nature and also destructive, therefore a longitudinal evaluation of microleakage is impossible. In addition, it was shown that alkaline materials cause methylene blue discoloration, which may lead to unreliable conclusions in dye penetration tests (30).
Currently, the most widely accepted method is fluid filtration, proposed by Derkson et al. (31). The main advantage of the fluid filtration technique is the possibility of preserving the specimens after each assay, allowing analysis at different study periods. Moreover, this method has proven to be sensitive and reproducible (3).
Among the dyes, use of methylene blue at different concentrations has been outstanding (28). However, Wu et al. (32) conducted an interesting study and stated that methylene blue suffers discoloration when in contact with some alkaline filling materials, which may cause unrealistic results of such materials in leakage studies. Methylene blue discoloration occurs because it is unstable when in contact with alkaline materials. Such materials cause hydrolysis of methylene blue, resulting in formation of a clear compound named thionine. This would explain why methylene blue is discoloured by calcium hydroxide.
Therefore, when performing the leakage test to assess the sealing ability of MTA AngelusTM, in this study, basic fuchsine was selected instead of methylene blue, based on the previously mentioned studies (35).
The limitation of dye leakage studies is that they measure the degree of leakage in only one plane, making it impossible to evaluate the total amount of leakage (36).
This study evaluated the sealing ability of Biodentine TM and the biomaterials commonly used in clinical practice. However, not many studies have demonstrated this empirically.
The present study compared the sealing ability of two root canal filling materials. The findings show that white MTA had less leakage than BiodentineTM regardless of thickness, apical foramen diameters, or the passage of time.
There are a few studies that have assessed the leakage of two experimental root-filling cements using fluid filtration method. Several studies have indicated that MTA exhibits significantly lesser leakage than other materials (36, 37).
MTA yields better results because it produces less leakage than other materials used in root-end filling (17, 36), however MTA has other beneficial properties, such as easy handling, biocompatibility and lack of technical sensitivity (3).
Sealing ability studies are still important in endodontics, especially as an initial screening for newly developed filling materials. Because MTA is ranked with good sealing ability results in several studies, (39-42) it is important that new endodontic materials display at least similar or better ability to prevent leakage as MTA. The mechanism that provides MTA with superior sealing ability results is not completely understood. Analysing the contact of MTA with a synthetic tissue fluid and root dentine, Sarkar et al. (43) suggested that MTA initially produced a mechanical seal and further dissolved leading to the formation of hydroxyapatite crystals, which reacted with dentine to create a chemical adhesion (43). However, Tay et al. (44) were unable to verify similar root-end filling leakage results with White MTA. Still, it is possible that a significant difference could not be detected by the statistical model owing to the elevated standard deviation displayed by the white MTA group (45).
Regarding BiodentineTM, according to the manufacturer, this material has similar or better physical, chemical and biological characteristics compared to MTA, with the same clinical indications. Since this material is also a mineral trioxide aggregate, this study evaluated the possibility of using it as apical plug, as well as its sealing ability and marginal adaptation, because no previous information was found in the literature regarding the sealing ability of BiodentineTM. The lapse of time also improves sealability of endodontic biomaterials.
Just after mixing, the calcium silicate particles of Biodentine, like all calcium silicate materials, react with water to form a high-pH solution containing Ca2+, OH−, and silicate ions. In the saturated layer, the calcium silicate hydrate gel precipitates on the cement particles, whereas calcium hydroxide nucleates (46). The calcium silicate hydrate gel polymerizes over time to form a solid network, while the release of calcium hydroxide increases the alkalinity of the surrounding medium. Saliva, like other body fluids, contains phosphate ions; (47) an interaction between the phosphate ions of the storage solution and the calcium silicate-based cements leads to the formation of apatite deposits that may increase the sealing efficiency of the material (48).
Since the introduction of Biodentine™ the literature has been scarce apart from manufacturers’ scientific files on its use as endondontic material. Within the limitations of this in vitro study, it can be concluded that MTA exhibited less microleakage when compared to BiodentineTM but BiodentineTM could be used as an alternative material for endodontic treatments. However, further in vitro and in vivo studies should be conducted to determine the sealing ability of BiodentineTM and also establish these results.