| Abstract|| |
Background: Mineral trioxide aggregate (MTA) fulfills many of the ideal properties of the root-end filling material. However, its low cohesive property often makes it difficult to handle. Biodentine, new calcium-silicate-based cement has been developed to improve some MTA drawbacks such as its difficult handling property and long-setting time.
Aim: The objective of this study was to compare at different times the microleakage of roots filled with Biodentine and white MTA (WMTA)-Angelus and to investigate their setting time, handling properties and compressive strength.
Materials and Methods: Root canals of single-rooted teeth were instrumented, filled with either Biodentine or WMTA-Angelus (n = 15 each) with two positive and two negative control roots and stored at 37°C. Sealing was assessed at 4, 24 h, 1, 2, 4, 8, and 12 weeks by a fluid filtration method. The initial setting time, handling properties, and compressive strength of the test groups were investigated by a vicat needle, questionnaire of operational hand feel, and universal instron machine, respectively.
Results: Significant differences in microleakage were found between two groups at 4-h and 24 h (P < 0.05) and no difference at 1, 2, 4, 8, and 12 weeks. No significant difference was seen in the setting time of MTA-Angelus and Biodentine, though latter was found to have better handling consistency. Compressive strength of Biodentine was significantly higher than MTA-Angelus.
Conclusions: The results suggest that the new calcium-silicate-based endodontic cement provides improvement in sealing ability as well as clinical manageability of dental filling materials.
Keywords: Biodentine, fluid filtration, mineral trioxide aggregate, root-end filling material
|How to cite this article:|
Butt N, Talwar S, Chaudhry S, Nawal RR, Yadav S, Bali A. Comparison of physical and mechanical properties of mineral trioxide aggregate and Biodentine. Indian J Dent Res 2014;25:692-7
The placement of a root-end filling material during periapical surgery is a procedure of paramount importance to seal the root canal.  Several materials have been tested as root-end filling materials, but none of them has been demonstrated to be free from limitations.  Mineral trioxide aggregate (MTA), a calcium silicate-based endodontic material possesses excellent biocompatibility and sealing ability;  thus, it is considered a promising material for various endodontic applications such as pulp capping, pulpotomy, apexogenesis, apical barrier formation in teeth with open apexes, repair of root perforations, and as a root canal filling material, besides a root-end filling material. , Despite its good physical and biologic properties, some clinicians still claim to have difficulties in handling this material after its preparation to fill a retroprepared root cavity. A commonly encountered problem is the difficulty to condense the cement inside the root as it easily tends to be washed out from its seat. 
|How to cite this URL:|
Butt N, Talwar S, Chaudhry S, Nawal RR, Yadav S, Bali A. Comparison of physical and mechanical properties of mineral trioxide aggregate and Biodentine. Indian J Dent Res [serial online] 2014 [cited 2019 Oct 23];25:692-7. Available from: http://www.ijdr.in/text.asp?2014/25/6/692/152163
Several new calcium silicate-based materials have recently been developed, , aiming to improve some MTA drawbacks such as its difficult handling property and long-setting time (ProRoot MTA).  Biodentine ™ (Septodont, Saint Maur des Fosse's, France) is among these materials and is claimed to be used as a dentine restorative material in addition to endodontic indications similar to those of MTA. It is available in powder-liquid formulation where the powder is composed of tricalcium silicate, dicalcium silicate, calcium carbonate, calcium oxide, iron oxide, and zirconium oxide and the liquid constitutes of calcium chloride as an accelerator and hydrosoluble polymer as a water reducing agent.  Biodentine shows apatite formation after immersion in phosphate solution,  indicative of its bioactivity.
The aim of this study was to compare in vitro at different times, the sealing ability, calculated as a fluid filtration rate, of roots filled with two commercially available calcium silicate cements: Biodentine and white MTA (WMTA) (Angelus, Londrina, PR, Brazil) and evaluation of their initial setting time, handling properties and compressive strength. The null hypothesis was tested as no difference in the sealing property, setting time, handling consistency, and compressive strength between the cements.
| Materials and methods|| |
Thirty-four single-rooted human teeth with mature apices were used. Teeth extracted for periodontal reasons were chosen and stored in distilled water and thymol (0.1%) until use. Roots were inspected with an optical endodontic microscope (OMPI Pico; Carl Zeiss Meditec Inc., Germany) to detect crack formation or resorption areas. Teeth with such defects were excluded from the study.
The coronal portion of each tooth was removed at the cemento-enamel junction using a size 701 high-speed fissure bur (SS White, Lakewood, NJ) under water spray to obtain a working length of 14 ± 1 mm.  The coronal part of each canal was preflared using gates glidden drills (Dentsply Maillefer, Ballaigues, Switzerland). All root canals were instrumented up to a master apical size 40 in crown-down fashion using protaper rotary NiTi instruments (Dentsply Maillefer, Ballaigues, Switzerland).
At each instrument change, all canals were irrigated with 1 mL of 5.25% NaOCl followed by 0.5 mL of 17% ethylenediaminetetraacetic acid (Prime Dental Product Pvt Ltd., Mumbai, India). A final irrigation of 2.0 mL 5.25% NaOCl left in place for 3 min was performed at the end of canal instrumentation. The canals were dried with paper points size 40 (Dentsply, Ballaigues, Switzerland) and obturated with laterally condensed Gutta-percha (Mynol; Ada Products Company, Inc., Milwaukee, WI) without sealer as a stop for placement of the root-end fillings.
The apical 3 mm was resected at 90° to the long axis of the tooth by using a high-speed carbide fissure bur with water. Then each tooth received root-end preparation, 3 mm in depth using a no. 245 bur (SS White, Lakewood, NJ) in a high speed handpiece with water spray. A single periodontal probe served as the measuring device for preparation depth. All the preparations were washed with distilled water for 5 s and then lightly dried with 2 paper points size 80 (Diadent Group International, Korea). Four teeth were used as positive and negative controls. For negative controls, two roots were filled with wax and completely covered by two layers of nail varnish to test the reliability of the isolation method. For positive control, no varnish on root-end filling was applied to other two roots. The prepared root sections were placed back into the distilled water and thymol (0.1%) until further use.
The remaining 30 teeth were then randomly divided into two equal groups (n = 15). Teeth in group 1 were filled with Biodentine prepared as suggested by the manufacturer. Teeth in group 2 were filled with WMTA-Angelus cement. The restorative materials were placed with an MTA carrier (Dentsply Maillefer) in increments, and their condensation was accomplished with a stainless steel condenser to simulate the clinical situation. After root-end filling procedures, a wet cotton pellet was applied to the MTA-Angelus for 30 s, the excess material removed and the fillings lightly burnished to simulate the clinical application. Gutta-percha was later removed after retrograde filling placement to ensure that the fluid movement was a function of the apical filling material alone.
Finally, the external surface of all these teeth was double coated with nail varnish, except for the canal orifice and the apical foramen (2-mm apical surface free from varnish) and allowed to dry. Samples were then placed in sterile saline 0.9% and stored at 37°C.
All the steps were executed by the same operator.
Fluid filtration system
The method used to measure fluid transport through the root canal as an index of coronal-apex micromovements has been previously described. , A fluid flow meter for fluid movement measurements was built in the Department of Biochemistry, Maulana Azad Institute of Dental Sciences, New Delhi [Figure 1]. The root section was connected to polyethylene tubing. The polyethylene tubing on either side of the specimen was filled with deionized water. A 25 μL micropipette was connected at the outlet side of the specimen. Using a Gilmont microsyringe, water was sucked back into the open end of the micropipette to create an air bubble. The whole set-up was then placed in a water bath (20°C) and using a syringe, the air bubble was adjusted to a suitable position within the capillary. Finally, water reservoir supplied the hydrostatic pressure of 70 cm H 2 O (6.895 kPa)  from the inlet side to force the water through the voids along the filling, thus displacing the air bubble in the micropipette.
The linear movement of 1.0-mm air bubble in the micropipette was measured with a 0.5-mm graduated scale [Figure 2]. Telescopic magnification and a digital electronic timing device (Fisher Scientific Co., Pittsburgh, PA) were used for all readings. The order of sample measurements was completely randomized by a computer software package (Statgraphics Plus, version 6, Manugistics, Inc., 1992).
|Figure 2: The linear movement of 1.0-mm air bubble in the micropipette (a); root segment attached to connecting tubes (b)|
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Fluid filtration measurements of each specimen were obtained at the following time intervals: 4 h, 24 h, 1, 2, 4, 8, and 12 weeks after placement of the root-end fillings. The fluid movement of each sample was measured for 3 min, 3 times in succession at each test period. Between measurements, the specimens were kept in 0.9% sterile saline at 37°C. Positive and negative control samples were examined at the beginning of each experimental session. Linear measurements were converted to μl/min/70 cm H 2 O.
Time to initial set
After mixing, the test materials were placed in 10 cylindrical stainless steel mold each with a diameter = 4 mm and height = 6 mm. A custom-made device with a stainless steel piston was used to apply a pressure of 3.22 MPa for 1 min for adequate condensation. The initial setting times of Biodentine and WMTA-Angelus were tested every 3 min with a vicat needle (Jin-Ching-Her, Taiwan) (a movable rod weighing 300 g with a 1-mm removable needle). The setting time was recorded when the needle failed to create an indentation of 1 mm in depth in three separate areas. 
Handling property rating
In the handling test, a rating from excellent to very poor was given for the mixing samples. Three operators mixed the samples for 3 times in a blind-blind test and rated the samples each one mixed. Excellent means the sample's handling property was just as IRM (Dentsply, Konstanz, Germany), and the practitioner can make the mixture as a block that can be applied by a dental filling instrument. Besides, very poor means the sample mixed was just as a sand felling with no cohesiveness.
After initial test, all molds (n = 40) were then stored for 15 min in 100% relative humidity at 37°C ± 2°C and then removed from the mold and stored in distilled water at 37°C ± 2°C, until the time of compressive strength testing to simulate the clinical condition. Specimens were divided randomly into four groups (n = 10) for each time interval. Testing was then performed at a set time of 1 h, 1 day, 7 days, and 28 days on the Universal Instron Testing Machine (Instron, India) at a cross-head speed of 0.5 mm/min [Figure 3]. The maximum load required to fracture each specimen under compressive loading was recorded using Series 9 computer software, and compressive strength was calculated in megapascals according to the formula.
|Figure 3: Universal instron testing machine for evaluation of compressive strength|
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C = 4P⁄ᴫD 2
where P is the maximum load applied in Newton and D is the mean diameter of the specimens in millimeters.
A log 10-transformation of the data was performed to normalize the data before statistical evaluation. The data were analyzed using repeated measures ANOVA and Tukey multiple comparison test at α =0.05. Results were processed with an SPSS 12.0 statistics program (SPSS Inc., Chicago, IL, USA).
| Results|| |
Statistical analysis of the fluid filtration [Table 1] results revealed significant differences amongst the two root-end filling materials examined at 4 and 24 h storage periods (P < 0.001). The power of the analysis with α = 0.05 was 0.964. Of the pairwise comparisons (Tukey test), significant differences were found between group 1 and group 2 at 4 and 24 h (P < 0.001) and no difference at 1, 2, 4, 8, and 12 weeks storage periods (P > 0.05). No fluid movement was seen in the negative control group. Fluid movement in the positive control group was higher than that exhibited by the two test groups ranging from 8.87 to 25.08 μl/min/70 cm H 2 O.
|Table 1: Mean microleakage value±SD for experimental groups after different storage periods|
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The initial setting times and handling properties of the groups are shown in [Table 2]. The setting times of Biodentine and WMTA-Angelus were 6.5 ± 1.7 and 8.5 ± 2.4 min; with no significant difference (P > 0.05). The handling property of WMTA-Angelus was grainy and sandy, making delivery to the root-end cavity and compacting difficult. The working properties of Biodentine were better and similar to typical IRM.
|Table 2: Means of initial setting and handling properties of two experimental groups|
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The results of the compressive strength measurements are summarized in [Table 3]. The results are also graphically depicted in [Figure 4]. Significant differences were observed between both groups at all 4 times intervals (ANOVA). The setting of Biodentine is illustrated by a sharp increase in the compressive strength reaching 304 MPa after 1-month that is more than MTA-Angelus. The compressive strength of the latter developed after 1-week reaching up to 90 MPa that is comparably lower than Biodentine.
|Figure 4: The compressive strength (in MPa) of mineral trioxide aggregate-Angelus and Biodentine versus time measured after 1-h, 1-day, 7 days, and 28 days|
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|Table 3: Mean values (MPa) and SD for compressive strength at 1‑h, 1‑day, 7 days, 28 days; for each test material|
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| Discussion|| |
The quality and durability of any dental material are a key component for the survival of a restoration in clinical conditions; the marginal adaptation and the intimate contact at the interface with the surrounding tissues (dentine and enamel) are determinative features. Both Biodentine and MTA-Angelus provided a valid and stable apical seal during the entire 12-week period. Neither showed evidence of deterioration in the ability to restrict fluid movement along the walls of the canal preparation.
The fluid filtration system, originally designed by Pashley et al.,  has been demonstrated as a valid technique to measure fluid movements. It is widely used to test the sealing capacity of different restorative materials and endodontic sealers , over time (longitudinal period) without specimen destruction. A pressure of 6.895 kPa was used in this study instead of the physiological pressure through dentine of 1.3 kPa  to force the apical leakage and to obtain detectable fluid movement values.
In the present study, the seal produced by WMTA-Angelus, leaked at 4 and 24 h that was significantly higher as compared with Biodentine. The seal, however, greatly improved with time and maintained until the end of the experiment. This warrants that the fluid movements among the two calcium silicate-based cements do not differ and the hypothesis tested was proven. The relatively severe leakage observed during the initial 24-h period can be caused by longer setting reaction seen with WMTA-Angelus.  Various hydration products form in the hydration reaction between calcium silicate cements and water, such as porous calcium silicate hydrate (CSH) colloidal gel, portlandite (calcium hydroxide), ettringite (hexacalcium aluminate trisulfate hydrate), calcium monosulphoaluminate or calcium monocarboaluminate. Porous CSH hardens to form a solid network within 4-6 h and with complete setting after several days.  The sealing ability of a material is determined by different phenomenon such as porosity, marginal adaptation, and hydrophilicity. When calcium silicate cements are mixed with water, several porosities and micro-channels are created and play a crucial role in the hydration reaction, but may also affect the early sealing ability of the cements.
Biodentine, a fast-setting calcium silicate-based endodontic material exhibits the same excellent biological properties as MTA-Angelus.  After mixing, the calcium silicate particles of Biodentine, as all calcium silicate materials, react with water to form a high-pH solution containing Ca 2+ , OH− , and silicate ions. In the saturated layer, the CSH gel precipitates on the cement particles, whereas calcium hydroxide nucleates.  The CSH gel polymerizes over time to form a solid network and the release of calcium hydroxide increases the alkalinity of the surrounding medium. Saliva, as other body fluids, contains phosphate ions;  an interaction between the phosphate ions of the storage solution and the calcium silicate-based cements leads to the formation of apatite deposits that can increase the sealing efficiency of the material as reported previously.  A study conducted by Han and Okiji  demonstrated that Biodentine has more prominent biomineralization ability than MTA, with wider calcium and silicon rich layer at material-dentine interface.
The setting time is one of the most clinically relevant factors. A long-setting duration may cause clinical problems because of the cement's inability to maintain shape and support stresses during this period.  The setting time of MTA-Angelus mixed with water was 8.5 min. In contrast, Biodentine exhibited shorter setting time (6.5 min) though not statistically significant. Accelerated setting reduces the risk of dislodgement and contamination of MTA-like cements when used as root-end filling material.  An important feature of a root-end filling material is its handling property. IRM besides being a retro-filling material has the benefit of being cost-effective, easy to mix, and handle.  Hence, it was used for determining handling characteristic. MTA-Angelus is grainy and has a poor consistency, making it difficult to manipulate in clinical situations. In contrast, Biodentine was relatively easier to handle and on thorough amalgamation it rolled into a dough-like consistency that could be easily condensed.
Compressive strength is an indicator of the setting process and strength of the material.  According to the results of this study, the compressive strength of MTA-Angelus was 41 MPa at 24 h that increased to 76.8 MPa at 28 days. These results are similar to those reported by Torabinejad et al.  (40 MPa at 24 h and 67.3 MPa after 21 days). Several studies have reported modifications of MTA to overcome its shortcomings and improve its physical properties. , Biodentine exhibited compressive strength of 170 MPa at 24 h that increased substantially to 304 MPa after the material was placed in moisture for 28 days. This value of compressive strength is close to that reported for human dentine (297 ± 24 MPa).  The compressive strength of Biodentine was significantly higher than that of MTA at all time intervals. The smooth structure of the set cement comprised of fine particle agglomerates that are comprised of hydration product of CSH gel that may be responsible for causing the particles to adhere to one another. The set WMTA-Angelus cement possessed coarser structure in comparison with that of Biodentine. This may explain why each exhibited lower strength than latter. The formation of CSH gel also reduces the porosity with time. The crystallization of the latter continues up to 4 weeks, therefore, improving the strength as well as other mechanical properties (sealing ability). This may explain decrease in compressive strength with MTA-Angelus after a week interval as compared with Biodentine. Thus, the null hypothesis tested was rejected in this case. The high mechanical strength of Biodentine may be attributed to the elimination of aluminates that leads to weakening and fragility of the set material as reported by manufacturer. With physical properties superior to those of MTA, especially in terms of setting time and compressive strength, it exhibits the same characteristics of sealing ability, with controlled (size and spatial organization) formation of calcium salts.
The differences in properties between Biodentine and MTA-Angelus may potentially be caused by the processing parameters such as sintering temperature, oxide amounts, and raw materials. The former cement displays advantageous shortened setting time and better handling properties and may have potential for dentin repair applications in dentistry. The previous statements, however, should be addressed in future experiments before any conclusive statements can be made.
| Conclusions|| |
Within the limits of this study, it may be concluded the sealing quality of Biodentine and commercially available MTA cement (MTA-Angelus) is comparable. The enhancement in handling properties of Biodentine may make it more convenient for use in various clinical applications. The present results suggest that Biodentine is a potential material for use as a dentin repair and root-end filling material. However, more studies are necessary before warranting unlimited clinical use.
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Department of Conservative Dentistry and Endodontics, Maulana Azad Institute of Dental Sciences, MAMC Complex, Bahadur Shah Zafar Marg, New Delhi
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2], [Table 3]