INTRODUCTION:

Biodentine is a calcium-silicate based material that has drawn attention in recent years and has been advocated to be used in various clinical applications, such as root perforations, apexification, resorptions, retrograde fillings, pulp capping procedures, and dentine replacement. There has been considerable research performed on this material since its launching; however, there is scarce number of review articles that collates information and data obtained from these studies. Therefore, this review article was prepared toprovidethereaderwithageneralpictureregardingthefindingsaboutvariouscharacteristics of the material. The review initially focuses on various physical properties of the material with sub-headings and continues with biocompatibility. Another section includes the review of studies on Biodentine as a vital pulp treatment material and the article is finalized with the summary of some case reports where the material has been used.

Physical properties of bio-dentin:-

Composition:-

The product file of Bio-dentin states that the powder component of the material consists of tricalcium silicate, dicalcium silicate, calcium carbonate and oxide filler, iron oxide shade, and zirconium oxide. Tricalcium silicate and dicalcium silicate are indicated as main and second core materials, respectively, whereas zirconium oxide serves as a radio pacifier. The liquid, on the other hand, contains calcium chloride as an accelerator and a hydrosoluble polymer that serves as a water reducing agent. It has also been stated that fast setting time, one unique characteristics of the product, is achieved by increasing particle size, adding calcium chloride to the liquid component, and decreasing the liquid content. The setting period of the material is as short as 9–12 minutes. T his shorter setting time is an improvement compared to other calcium silicate materials ^[1]. Some authors have indicated that there are few studies on the properties of newly developed materials such as Bio-dentin^[2]. The material is characterized by the release of calcium when insolution ^[3,4]Tricalcium silicate based materials are also defined as a source of hydroxyapatite when they are in contact with synthetictissue fluid^[5–7]. An important feature of the calcium carbonate additive was to act as a nucleation site for C–S–H, thereby reducing the duration of the induction period, leading to a faster setting time. The tricalcium silicate grains in Bio-dentin were also reported to be finer and calcium chloride and a water soluble polymer were included in the liquid portion ^[8].

Setting time:-

The setting time of Biodentine was determined as 45 minutes. This short setting time was attributed to the addition of calcium chloride to the mixing liquid^[9]. Calcium-chloride has also been shown to result in accelerated setting time for mineral trioxide aggregate ^[10]. An interesting finding of the study by Grechetal^[9] was that the highest setting period was determined for Bioaggregate, another tricalcium silicate based material. However, 9–12 minutes indicated in the product sheet is the initial setting time, whereas Grech et al. ^[9] evaluated the final setting time. Therefore, both papers are not comparable. Villat et al. ^[11] preferred a different methodology for the assessment of the setting time, the impedance spectroscopy that assesses the changes in electrical resistivity. Interestingly, impedance values were stabilized after 5 days for the glass ionomer cement while at least 14 days were necessary for the calcium silicate based cement. The authors speculated that this result was due to the higher porosity for Biodentine cement, characterizing higher capacity of ion exchanges between the material and its environment ^[11].

Compressive strength:-

Compressive strength is considered as one of the main physical characteristics of hydraulic cements. Considering that a significant area of usage of products such as Biodentine is vital pulp therapies, it is essential that the cement has the capacity to withstand masticatory forces, in other words, sufficient compressive strength to resist external impacts. The product sheet of Biodentine states that a specific feature of Biodentine is its capacity to continue improving in terms of compressive strength with time until reaching a similar range with natural dentin^[12].

Biodentine showed the highest compressive strength compared to the other tested materials. The authors attributed this result to the enhanced strength due to the low water/cement ratio used in Biodentine. They stated that this mode of the material is permissible as a water soluble polymer is added to the mixing liquid.^[13] Kayahan et al. evaluated the compressive strength from another perspective and drew conclusions specifically pertaining to clinical usage. Considering that acid etching is one of the steps following the application of Biodentine for the provision of mechanical adhesion, the authors aimed to assess whether any alterations exist in terms of compressive strength following the etching procedure.

Porosity and Material-Dentine Interface Analysis:-

Tricalcium silicate based materials are especially indicated in cases such as perforation repair, vital pulp treatments, and retrograde fillings where a hermetic sealing is mandatory. Therefore, the degree of porosity plays a very important role in the overall success of treatments performed using these materials, because it is critical factor that determines the amount to fleakage. Porosity has been shown to have an impact upon numerous other factors including adsorption, permeability, strength, and density. It has further been stated that the maximum pore diameter, which corresponds to the largest leak in the sample, along with bacterial size and their metabolites, will be indicative of the leakage that occurs along the root-end filling materials.

Bond Strength:-

Considering that Biodentine is recommended for use as a dentine substitute under permanent restorations, studies were performed that assess the bond strength of the material with different bonding systems. When different time intervals were compared, the lowest bonding value was obtained for the etch-and rinse adhesive at a 12-minute period, whereas the highest was obtained for the 2-step self-etch adhesive at the 24-hour period^[14]. Another area of use of Biodentine, specifically from an endodontic point of view, is the repair of perforations, which is likely to be encountered in clinical practice. It is essential that a perforation repair material should have sufficient amount of push-out bond strength with dentinal walls for the prevention of dislodgement from the repair site. Aggarwal et al.^[15] studied the push-out bond strengths of Biodentine, Pro Root MTA, and MTA Plus in furcal perforation repairs. Push-out bond strength increased with time. Their results showed that the 24 h push-out strength of MTA was less than that of Biodentine and blood contamination affected the push-out bond strength of MTA Plus irrespective of the setting time. A favorable feature of Biodentine determined by the authors was that blood contamination had no effect on the push-out bond strength, irrespective of the duration of setting time^[15]. El-Ma’aita et al. ^[16]aimed to assess the effect of smear layer on the push-out bond strength of calcium silicate cements and whether the removal of this layer would have any overall influence on the bonding characteristics of these materials. The authors used Biodentine, Pro Root MTA, and Harvard MTA as root fillings. The results showed that the removal of the smear layer significantly reduced the push out bond strengths of calcium silicate cements and the smear layer was a critical issue that determines the bond strength between dentine and calcium silicate cements such as Biodentine. The authors attributed this result to the inability of calcium silicate cement particles to penetrate the dentinal tubules due to their particle size. They speculated that the smear layer is important in the formation of the interfacial layer and may be involved in the mineral interaction between the CSC and radicular dentin. It is appropriate to mention that it is not customary to use calcium-silicate based materials for the obturation of the entire root canal system and such an approach might not be preferable especially in narrow and curved root canals. On the other hand, the study by El-Ma’aita et al. ^[16] is significant because it successfully demonstrated the bonding characteristics of these popular materials which are unique in contemporary dental applications.

Radiopacity:-

Radiopacity is an important property expected from a retrograde or repair material as these materials are generally applied in low thicknesses and they need to be easily discerned from surrounding tissues. Mean while, according to ANSI/ADA specification number 57, all endodontic sealers should be at least 2mm Al more radiopaque than dentin or bone^[17]. For the determination of the radio pacities of filling materials, the method developed by Tagger and Katz ^[18]is generally used where radiographic images of the material are taken along side an aluminium step-wedge. Zirconium oxide is used as a radiopacifier in Biodentine contrary to other materials where bismuth oxide is preferred as a radiopacifier. The reason for such a preference might be due to some study results which show that zirconium oxide possesses biocompatible characteristics and is indicated as a bioinert material with favorable mechanical properties and resistance to corrosion ^[19].Another consideration should be made based on the clinical scenarios where Biodentine is intended to be used. In cases where there is direct contact with the surrounding connective tissue, biocompatibility is of primary significance. Though the confirmation of adequate placement of the material is important in such cases by relying on the radiopacity value, one can prefer to make a judgement by clinical observation in case the usage of additives to obtain high radiopacity value is likely to compromise the overall biocompatibility.

Effectonthe Flexural Properties of Dentin:-

An important issue related to the usage of calcium silicate based materials is their release of calcium hydroxide on surface hydrolysis of their calcium silicate components^[3]. On the other hand, it has also been indicated that prolonged contact of root dentine with calcium hydroxide as well as MTA has detrimental and weakening effects on the resistance of root dentine ^[20,21]. Therefore, it is critical to consider the effects of released calcium hydroxide on dentine collagen, specifically in procedures where there is a permanent contact of dentine with calcium silicate based materials. Sawyer et al. ^[22]evaluated whether prolonged contact of dentine with calcium silicate based sealers would have any influence on its mechanical properties. According to the results of their study where they compared Biodentine with MTA Plus, they determined that both materials altered the strength and stiffness of the dentine tissue after ageing in 100% humidity.

Microleakage:-

When specifically used as a liner or base material, leakage of Biodentine should especially be considered as leakage may result in postoperative sensitivity and secondary caries, leading to the failure of the treatment. Koubi et al^[23] were the first to assess the in vitro marginal integrity of open-sandwich restorations based on aged calcium silicate cement and resin-modified glass ionomer cement. Results of glucose filtration analysis after one-year ageing showed that both materials displayed similar leakage patterns and Biodentine performed as well as the resin modified glass ionomer cement. Another significant property of Biodentine was that it did not require specific preparation of the dentin walls. They explained the good marginal integrity of Biodentine with the ability of calcium silicate materials to form hydroxyapatite crystals at the surface. These crystals might have the potential to increase the sealing ability, especially when formed at the interface of the material with dentinal walls. Furthermore, the interaction between the phosphate ions of saliva and the calcium silicate based cements might lead to the formation of apatite deposits, thereby increasing the sealing potential of the material. The authors additionally expressed the nanostructure and small size of the forming gel of the calcium silicate cement as one of the factors that influenced the sealability as this texture allowed the material to better spread onto the surface of the dentine. Slight expansion was also noted for these materials which contributed to their better adaptation ^[23]. Another study comparing the leakage of Biodentine with a resin modified glass ionomer (FujiIILC) was one by Raskin et al. ^[24] where silver penetration was evaluated in cervical lining restorations. Similar results were reported to those by Koubietal.^[23] and Biodentine as a dentine substitute in cervical lining restorations or as a restorative material in approximal cavities, when cervical extent was under CEJ, appeared to perform well without any conditioning. The only disadvantage was related to the operating time that was determined to be longer than the resin modified glass ionomer^[23].

Discoloration:-

One study evaluated Biodentine from this perspective where Biodentine, along with 4 different materials, was exposed to different oxygen and light conditions and spectrophotometric analysis was performed at different periods until 5 days ^[24]. Favorable results were obtained for Portland Cement (PC) and Biodentine and these 2 materials demonstrated color stability over a period of 5 days. Based on their results, the authors suggested that Biodentine could serve as an alternative for use under light-cured restorative materials in areas that are esthetically sensitive^[25]. 2.12. Wash-Out Resistance. Washout of a material is defined as the tendency of freshly prepared cement paste to disintegrate upon early contact with fluids such as blood or other fluids. The results of the available study on these characteristics of Biodentine did not reveal favorable results as the material demonstrated a high washout with every drop used in the methodology^[9]. The authors attributed this result to the surfactant effect water soluble polymer added to them aterial to reduce the water/cementratio^[9].

Biocompatibility of Biodentine:

Biocompatibility of a dental material is a major factor that should be taken into consideration specifically when it is used in pulp capping, perforation repair or as a retrograde filling. During the aforementioned procedures, the material is in direct contact with the connective tissue and has the potential to affect the viability of periradicular and pulpal cells. Cell death under these circumstances occurs due toapoptosis or necrosis ^[26]. Therefore, it is essential that toxic materials are avoided and materials promoting repair or that are biologically neutral are preferred during procedures in which the material is directly in contact with the surrounding tissue. Though the information accumulated so far regarding the biocompatibility of Biodentine is rather limited, the available data generally is in favor of the material in terms of its lack of cytotoxicity and tissue acceptability. Han and Okiji ^[27]compared Biodentine and white ProRoot MTA in terms of Ca and Si uptake by adjacent root canal dentine and observed that both materials formed tag-like structures. They observed that dentine element uptake was more prominent for Biodentine than MTA. The same authors^[28]in another study also showed the formation of tag-like structures composed of Ca and P-rich and Si-poor materials. They also determined a high Ca release for Biodentine. Laurent et al. ^[29] were the first to show the promising biological properties of Biodentine on human fibro blast cultures. Biodentine favorably affected healing when placed directly in contact with the pulp by enhancing the proliferation, migration, and adhesion of human dental pulp stem cells, confirming the bioactive and biocompatible characteristics of the material .

Biodentine as a Vital Pulp Treatment Material When materials’ influences are to be evaluated in terms of pulpal response during vital procedures, in vivo study designs are helpful and animal and human teeth are generally preferred to demonstrate the effects of pulp capping agents. These should further be supported by clinical trials to establish a clear picture regarding the general characteristics of the materials. MTA, which is generally considered a gold standard, has been investigated in various human and animal experimental models. On the other hand, studies comparing MTA with Biodentine in terms of vital pulp treatment behavior are rather limited. The first study to demonstrate the induction of effective dentinal repair was the one by Tran et al.^[31] where the material was applied directly on mechanically exposed rat pulps. In their study where Biodentine was compared to MTA and calcium hydroxide in terms of reparative dentine bridge formation, they noted that the structure induced by Ca(OH)2 contained several cell inclusions, also called tunnel defects as previously reported by Cox et al. in 1996 ^[32]. These defective regions were regarded as undesirable areas facilitating the migration of the microorganisms towards the pulp and predisposing the tooth to an endodontic infection. On the contrary, the dentine bridge formation induced by Biodentine showed a pattern well-localized at the injury site unlike that caused by calcium hydroxide that exhibited an expanding structure in the pulp chamber. The quality of the formed dentine was also much more favorable compared to calcium hydroxide and an orthodentin organization was noted in which dentine tubules could be clearly visualized. Moreover, cells secreting the structure well exhibited DSP expression as well as osteopontin expression, which are critical regulators of reparative dentine formation ^[32]. An interesting clinical and histological study performed on molars to be extracted for orthodontic reasons showed that Biodentine had a similar efficacy to MTA in clinical setting and may well be regarded as an alternative for pulp capping procedures. Complete dentinal bridge formation and absence of an inflammatory response were observed as major findings^[33]. Pulpotomy is another vital pulp treatment method in which Biodentine is advocated to be used. This method is widely used in pediatric dentistry and involves the amputation of pulp chamber and the placement of a material for the preservation of the radicular pulp tissue’s vitality. This methodology is specifically useful and preferred when the coronal pulp tissue is inflamed and a direct pulp capping is not a suitable option.

CONCLUSION:

Biodentine, a popular and contemporary tricalcium silicate based dentine replacement and repair material, has been evaluated in quite a number of aspects ever since its launching in 2009. The studies are generally in favor of this product in terms of physical and clinical aspects despite a few contradictory reports. Though accumulation of further data is necessary, Biodentine holds promise for clinical dental procedures as a biocompatible and easily handled product with short setting time. As more research is performed regarding this interesting alternative to MTA, we will be provided with more reliable data and more confidently implement Biodentine into routine clinical applications.

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Received on 17.06.2016 Modified on 24.06.2016

Research J. Pharm. and Tech 2016; 9(9):1524-1528.

DOI: 10.5958/0974-360X.2016.00298.5