Manoeuvring Bioactive Materials in Dentistry- A Review

Bioactivity refers to bio-inductive activity. The materials which induce such activity are bioactive materials. These materials induce a reaction from living tissue. Bioactive materials have a role in the promotion of the healing process, repair, maintaining the vitality of pulp, etc. The material should be sterile, bacteriostatic and bactericidal in nature. Bioactive materials are used in dentin remineralization, maintaining long-term restorations bonded with cement, and repairing intra-bony lesions. A biomaterial is a substance, external layer or assembly that interconnect with an organic system. Biognosisan analysis of, structure or uses of biologically generated materials, their mechanisms and processes for the formation of likely products by arti icial mechanisms that mimics natural structures. A biomaterial is a substance, external layer or assembly that interconnect with an organic system. These materials differ in their form and function and composition. Bioactive substances function works due to the inauguration of growth initiators and multiple cells. It aids in “growth, immigration, and distinction of odontoblast-like cells producing tissue matrix. Bioactive matrix form an outer layer of an apatite-like substance in association with inorganic phosphate solution. Bioactive materials like calcium hydroxide, mineral trioxide aggregate, biodentin, etc., are commonly used in routine practice. As these materials have multiple purposes, this review focuses to highlight newer materials in the category of bioactivity and their implications in dentistry particularly.


Bioactivity, Bioactive materials, MTA, Biodentin
A Bioactivity refers to bio-inductive activity. The materials which induce such activity are bioactive materials. These materials induce a reaction from living tissue. Bioactive materials have a role in the promotion of the healing process, repair, maintaining the vitality of pulp, etc. The material should be sterile, bacteriostatic and bactericidal in nature. Bioactive materials are used in dentin remineralization, maintaining long-term restorations bonded with cement, and repairing intra-bony lesions. A biomaterial is a substance, external layer or assembly that interconnect with an organic system. Biognosis-an analysis of, structure or uses of biologically generated materials, their mechanisms and processes for the formation of likely products by arti icial mechanisms that mimics natural structures. A biomaterial is a substance, external layer or assembly that interconnect with an organic system. These materials differ in their form and function and composition. Bioactive substances function works due to the inauguration of growth initiators and multiple cells. It aids in "growth, immigration, and distinction of odontoblast-like cells producing tissue matrix. Bioactive matrix form an outer layer of an apatite-like substance in association with inorganic phosphate solution. Bioactive materials like calcium hydroxide, mineral trioxide aggregate, biodentin, etc., are commonly used in routine practice. As these materials have multiple purposes, this review focuses to highlight newer materials in the category of bioactivity and their implications in dentistry particularly.

INTRODUCTION
Bioactivity of the materials used in dentistry mainly refers to its bio-inductive activity. Terms like "bioactive", "bio-inductive", "biomaterials", and "biomimetic" refers to this activity. The bioactive material is a material that induces a reaction from living tissue, like the formation of hydroxyapatite. It acts on vital tissue, promoting healing, repair. It also has a role in the maintainance of pulp vitality. In dentistry, it has a role in regeneration, repair and reconstruction. Ideally, the material should be sterile. It should be bacteriostatic and bactericidal. Bio-inductivity refers to the ability of a material to produce a biological response. "Biomaterial is a substance, external layer or an assembly that interconnect with an organic system." "Biognosisan analysis of, structure or uses of biologically generated materials, its mechanisms and processes for the formation of likely products by arti icial mechanisms that mimics natural structures (Bhushan et al., 2015)." Bioactive matter acts due to inau-guration of different development initiators and cells. Such materials may produce an apatite-like product with inorganic phosphate solution. They help in remineralization, long-term bonded restorations, and intra-bony defects. Bioactive materials act by producing hydroxyapetite as it contacts with "phosphate-containing" physiological liguid. Apatite production is initiated with an interaction of Ca 2 + released from the material with phosphates. These materials induce cellular changes in pulpal tissue and result in the production of reparative dentin at the surface of exposed pulp in vital pulp therapy. It aids in "growth, immigration, and distinction of odontoblast-like cells producing tissue matrix." This non mineralized ground substance is mineralized by osteo-dentin at irst and later by the formation of tertiary dentin (Hegde et al., 2017). These bioactive materials also have a role in endodontic therapies. They lead to periodontal and periapical healing and thus improves the outcome of the endodontic treatment. The main purpose of this review is to appraise various "bioactive materials" and their implications in dentistry.

CALCIUM HYDROXIDE [Ca(OH)2]
Ca(OH) 2 is snowy, odourless dust. It was developed by Hermann in 1930. It has good biological properties like antibacterial effects and the ability to decrease osteoclastic activity and induce mineral tissue formation (O'brien, 2009). Apexi ication, the treatment for non vital teeth with open apex, is commonly treated with Ca(OH) 2 . It dissolves organic tissues and passivates bacterial endotoxins (Mahalaxmi, 2013). It breaks into "ca ions and OH ions". The Ca 2 + reduces " penetrability " and decreases " low of serum" and thus decreases the level of "repressive pyrophosphatases", causing calci ication. OH − ions neutralizes acidity by "osteoclasts". The basic pH of the material, i.e. 11, is due to the release of hydroxyl ions. It causes an increase in levels of "calcium-pyrophosphatase", decreasing the levels of "repressive pyrophosphate", and thereby promotes calci ication (Hegde et al., 2017 3. Pediatric dentistry-as pediatric obturating material (Anusavice et al., 2013;O'brien, 2009).

Mineral Trioxide Aggregate
Discovered by "Mahmoud Torabinejad" (1993) "Loma Linda University" (Sonarkar and Purba, 2015). It mainly constitutes "calcium and silicate". It mainly comprises "di-calcium silicate, tri-calcium silicate, tri-calcium aluminate, gypsum, and tetracalcium-alumino-ferrite". Initially, only Grey MTA was introduced (Hegde et al., 2017). White MTA was introduced in 2000 to eliminate discoloration and esthetic problems (Anusavice et al., 2013). It has been observed histologically that MTA leads to the formation of new cementum in periradicular tissue area and a low in lammatory response with bridge formation in the pulp space (Peter et al., 2015). It forms an "apatite-like" sheath on its uppermost layer when it contacts with physiologic liquid or with activated tissue luids. MTA dissolve in tissue luids releasing "Ca, Si, Bi, Al, and Mg". Calcium is the most dominantly released. It leads to the precipitation of hydroxyapatite (HA). This reaction continues beside the dentinal wall. As MTA is placed in root canals, it gradually dissolves and HA seals the space of MTA and dentin. This reaction results in the formation of a chemical bond that seals between the MTA dentin interface (Peter et al., 2015).

Uses
In primary teeth a. Pulp covering. h. Coronal barrier for regenerative endodontics.

Calcium Enriched Mixture Cement
It was introduced by "Asgary in 2006". It is a "new root canal cement", which was further named as a "Calcium-empowered mixture". It is a "water dependant cement" mainly comprising of " Cao, Capo 4 , CaCo 3 Ca-si, Caso 4 , Cacl 2 ". The cement leaches both "calcium and phosphorous" and leads to the formation of appetite crystals. CEM has pH and increased low, similar to MTA. In the contrary, it has reduced manipulating time, ilm size, and lower cast than MTA. "Asgary et al." stated that this cement initiate dentinogenesis after direct pulp capping and pulpotomy and in apexogenesis. It also induces cementogenesis after perforation repair or surgery.

Biodentin
Biodentin was introduced by Septodont in the year 2011. It is a rapidly-setting calcium silicate based material (Hegde et al., 2017). It was introduced as a "bioactive dentin replacement material" with properties likely that of dentin. The material stimulates tertiary dentine formation by activation of pulpal cells. It is composed of a " combination of calcium and zirconium dioxide as a radiopacifer". In contact with dentine, biodentin leads to the formation of the tag-like structures, namely the "Mineral In iltration Zone," which may contribute to adhesive properties. Calci ication is in the form of" osteodentine" (Asgary et al., 2009 11. Retrograde surgery (Anusavice et al., 2013;Sonarkar and Purba, 2015).

Bioaggregate
First nanoparticular mineral cement introduced. Bio-Aggregate is a ine white hydraulic cement-like powder. It is composed of contamination-free bioceramic nanoparticles. It is similar to MTA in its composition. It is an insoluble, radiopaque, and aluminium-free material mainly formed of calcium.
As an aluminium-free formulation, it stimulates the proliferation of PDL ibroblasts and helps in periodontal regeneration (Hegde et al., 2017).

Formation of the calci ic barrier at the apex in cases with an open apex.
3. Resorption of root.

Endosequence Root Repair Material
It is ca-si material. It is mainly available in paste or putty form.
It comprises "calciumphosphate monobasic, Ca silicates, zirconium-oxide and tantalum-oxide". It is a hydrophilic bioceramic, insoluble, radiopaque material. It is an aluminium free material with high pH. It sets and hardens in the presence of moisture. It initiates tissue luid results in the precipitation of apatite crystals (Hegde et al., 2017).
It forms a tight seal in gutta-percha (GP), sealer, and dentin. These sealers have antibacterial property because of its high pH (Hegde et al., 2017).

Bio Root Rcs
It is a "Mineral-based material". It has a tricalcium, silicate setting system. The powder is mainly composed of "zirconium oxide as radiopaci ier and a watersobtion polymer for adhesion enhancement". The liquid consists of "water, calcium chloride as a setting modi ier and a water reducing agent". It stimulates physiological mineralization. It creates a nidus for the repair of periapical tissues. It has bioactive properties, including safety, oxyapatite formation, mineralization, high pH and sealing properties (Hegde et al., 2017).

Bioactive Luting Agents
Modi ication of bioactive chemically bonded cement of which Ceramic has been used most commonly in restorative dentistry. It is a "calcium-aluminate" based material. It is used for cementation. It acts on the mechanism of calcium-aluminate and GIC. Glass ionomer component has advantages like Low pH, modi ied low and setting method, initial adhesiveness to the tooth structure, early strength. Calcium aluminate help to; increased strength and retention time, biocompatibility, blocking of tooth material gap, apatite formation, lack of degradation, stable basic cement pH (Hegde et al., 2017).

Uses
1. Cementation of the prosthesis.

Cementation of gold intracoronal and extra coronal restoration.
3. Luting of the secondary retentive matrix.

Doxadent
It is "calcium-aluminate cement". It is marketed as a powder and liquid system. It is mainly composed of "alumina, calcium-oxide, H 2 O, zirconium-dioxide, and the alkali-oxides". On mixing powder and liquid, calcium-aluminate gets dissolved in water and form "calcium, aluminium and hydroxyl ions", which leads to the formation of "katoite and gibbsite" (Bhushan et al., 2015).

Resin Impregnation with Titanium Oxide
The titanium oxide nanoparticles are incorporated in dental monomers and dentin bonding adhesives. This promotes hydroxyapatite formation and enhances the strength and bactericidal property of the restoration. The nanoparticles incorporated seals the marginal gaps and re-mineralizes both enamel and dentin. Thus, it reduces the chances of secondary caries formation (Bhushan et al., 2015).

Uses
As a direct pulp capping agent.

Uses
As a direct pulp capping agent.

Calcium Phosphate
Available in the form of paste, cement, ceramics and scaffold. It consists of " tetra calcium phosphate and dicalcium phosphate'. It helps in "biological and pathological mineralization". It induces dentin barrier generation with no necrosis of super icial tissue. This eliminates pulpal in lammation. Also known as hydroxyapatite cement. It is composed of one acidic and one basic calcium phosphate compound. It was introduced by ADA Paffenbarger Research Center (Bhushan et al., 2015;Rudagi and Rudagi, 2012).

Uses
1. As coatings on various materials to enhance its bioactivity.
2. Used to ill and heal bone defects.
3. Used in combination with scaffolds in regenerative procedures.