Current Bioactive Dental Materials

INTRODUCTION

In this highly competitive market of dental materials, researchers are always looking for the next best material to improve the prognosis of restorative dentistry. Many dental restorations fail due to secondary caries, pulpal sensitivity or inflammation, marginal gaps and discoloration1. Researchers have been testing new dental restorative materials to combat these issues. Bioactive dental materials are one way to decrease the failure rate of restorative dentistry. There are many types of bioactive dental materials out there in the market. The discussion of the varies type of bioactive dental materials will be discussed.

As well as the definition of bioactive dental material and what makes a dental material to be considered as a bioactive dental material. A review of commercially available bioactive dental materials composition and their clinically application will also be discussed.

BIOACTIVITY

There are multiple definitions to describe what a bioactive material in dentistry is. A general way to define a bioactive material is; any material that interacts and is able to form a bond between the tissues and the material is consider a bioactive material.

In dentistry, a bioactive material could be considered as a material that is bactericidal, bacteriostatic, stimulates reparative dentin formation, and maintain pulp vitality when applied in the oral cavity by releasing ions such as calcium, phosphate, and fluoride to strengthen the tooth3. A more specific definition and accurate definition of a bioactive material used in dentistry would include both definitions stated above, as well as the definition that the material has the potential to induce mineral attachment to the dentin substrate by promoting hydroxyapatite interaction with dentin and tooth surfaces3.

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Bioactive dental materials has the compatibility to develop a natural bond between the living tissues and non-living materials12. Thus, when discussion bioactive materials, the definition of bioactive materials with hydroxyapatite formation and interaction with the dentin and tooth surfaces will be referred to.

COMMERCIALLY-AVAILABLE BIOACTIVE DENTAL MATERIALS

Calcium Hydroxide

Calcium hydroxide is used for endodontic treatments such as partial pulpotomy, direct and indirect pulp capping14. Calcium hydroxide dissociates into calcium and hydroxyl ions. The calcium ions reduce permeability in the capillaries. Reduced permeability will lessening the serum flow and decreases the amount of inhibitory pyrophosphates that causes mineralization. The antibacterial effects of calcium hydroxide are due to the release of the highly reactive hydroxyl ions13. The hydroxyl ions that are released, will buffer out the acid that are produced by osteoclasts. The hydroxyl ions interaction with the acids will create a pH level that is favorable for pyrophosphatase activity, which can lead to an increase level of calcium dependent pyrophosphatase. Once in contact with the tissue, calcium hydroxide triggers a necrosis and inflammatory response which makes the tissues to repair itself and calcifies13. The calcification of the orifice of the pulp during a pulpotomy can encourage the healing of the pulp. The effect of calcium hydroxide is due to the injury caused by the hydroxyl ions. Calcium hydroxide stimulates the pulp to repair the dentin and form a reparative dentin bridge. The dentin bridge forms a seal that fights against bacterial infection of area13.

Theracal LC

Theracal LC is another calcium silicate based material used for deep caries lesions and indirect and direct pulp capping5. Theracal LC is also used as a protective liner when used with restorative materials. Theracal LC is a light curable material indicated to be use as a base or a liner under composite and amalgam restorations5. Theracal LC is used to a create a bond between the different layers within the restoration. By creating the bond between the layers in the restoration, Theracal LC helps to minimize microleakage in the restoration5. Theracal LC also has antimicrobial activity. The polymerization of Theracal LC produces very low heat, low heat will have a less adverse effect on the pulpal tissue making Theracal LC a suitable material for pulp capping procedures5. Theracal LC sets faster and is easier to handle when compared to MTA. Theracal LC has the ability to form hydroxyapatite. The ability to form hydroxyapatite, allows Theracal LC to create a biological seal to the dentin. The ability of Theracal LC to create this biological seal is what makes Theracal LC a bioactive material5.

Bioglass (BG)

Bioglass is a bioactive glass (BG) material. It is mainly composed calcium oxide, silicon oxide, sodium oxide, and silicon oxide6. BG is used for procedures such as pulp capping. BG can be incorporated in to bone grafting procedures and also coating of metal implants to help with osseointegration. BG can also be used as a treatment for hypersensitivity, and remineralization of enamel and dentin. BG has antibacterial properties, and it can also induce proliferation, differentiation and mineralization of dental pulp cells6. Hypersensitivity in teeth is originated from exposed dental tubules7. Changes in the environment of the teeth causes the dental tubules to move, causing sensitivity. BG is able to promote crystallization on the surface of the dental tubules by the precipitation of calcium phosphate. The crystallization will coving the dental tubules, which will then relieve the pain due to dental hypersensitivity7. BG demineralizes the tooth by releasing ions such as calcium and phosphate which are antibacterial. When BG is incorporated into composite materials, BG can prolong the life of the composite restoration. BG remineralization and antibacterial effects can reduce the development of secondary caries. BG also has the ability to be used as a coating agent on titanium dental implants. Coating the metal implants can improve osseointegration of the implant.

Calcium Phosphate

Calcium phosphate can be used as a coating agent to coat the titanium dental implants. Coating the titanium dental implants with calcium phosphate can increase the osseointegration of the dental implant to the bone in the jaw8. Calcium phosphate can be applied on to the implant in several ways. Plasma spraying the calcium phosphate on to the titanium implant is the most frequently used technique when applying commercial calcium phosphate coating8. Plasma sprayed surfaces are consisted of a mixture of crystalline and amorphous calcium phosphate phases8. Another technique is called the sputtering technique, the sputtering technique allows for a more thing and stable homogenous coating of the calcium phosphate to the titanium dental implant8. The thin coating to the implant improves the osseointegration when compared to thick coating. The thick coating prevents the implant from adhering to the tissue which can potentially fracture and lead to implant failure11. Coating the implant with calcium oxide can increase the resistance of the implant to shear forces during the placement of the implant11.

Titanium Oxide (TiO2)

Titanium oxide nanoparticles can be incorporated into dental resins such as dental monomers and dentin bonding adhesives9. TiO2 reacts with water to form hydroxyl groups that will increase surface area and promote cellular attachment15.TiO2 increases the strength of the resin material as well as bactericidal properties. Titanium oxide has the ability to create a thin titanium oxide layer, creating a corrosion resistant layer. TiO2 nanoparticles has bioactive properties by forming a layer of hydroxyapatite. TiO2 upregulates osteoblast differentiation. Increasing osteoblast differentiation helps with the formation of hydroxyapatite. The formation of hydroxyapatite helps with remineralization of dentin and enamel. Hydroxyapatite also increases marginal integrity and increases potential bond strength over time9. With the benefits of Titanium oxide in resin materials, the reduction in secondary caries in composite restoration is also another benefit with Resin impregnation with titanium oxide9. Titanium oxide can also be incorporated on to titanium based implants. A coating around the titanium implants with TiO2 can increase the healing process of the implant surgery by increasing osteoblast differentiation. TiO2 has been shown to improve osseointegration by increasing protein signaling, apatite formation, and upregulating collagen synthesis15.

CM Crown & Bridge Cement:

CM Crown & Bridge Cement is a calcium aluminate-glass ionomer luting cement2. CM Crown & Bridge is used for permanently cementing crowns, inlays, fixed partial dentures, onlays, gold inlays, and all zirconia and all alumina crowns2. CM Crown & Bridge Cement is considered a bioactive material due to its ability to form hydroxyapatite2. When comparing microleakage, retentiveness, and cytotoxicity, researchers found that the values were equivalent when compared to other cements like Rely X Luting Plus2.

BIOACTIVE MATERIAL IN DENTISTRY

Mineral Trioxide Aggregate (MTA):

MTA is a calcium silicate-base cement use in endodontic treatment. MTA is made of Portland cement, bismuth oxide, gypsum, silicon dioxide, calcium oxide, magnesium oxide, potassium sulfate, and sodium sulfate. MTA is generally used as a root replacement filler material1. MTA was the first bioactive cement that was adopted for the use for endodontic and restorative treatment1. MTA has antibacterial properties and reparative features. MTA has the ability to form dental bridges or tertiary dentin when it comes into contact with dentin. The hydraulic properties of MTA allow the material to be bioactive when placed in contact with tissues and fluids in the oral cavity. MTA also has the ability to form calcium hydroxide as well as hydroxyapatite, making MTA a bioactive material which repairs dentin.1. Bismuth oxide is also added as a radio pacifier, making the cement visible on radiographs1. MTA is used for endodontic treatments such as root canals, pulpotomy, repair of root perforations, apexification, and also pulp capping1. MTA is considered the material of choice when sealing root canals in apical surgery and management of perforations 14. Although MTA has an excellent biocompatibility, MTA has a long setting time. MTA setting time can be about to two hour and forty-five minutes15. MTA can also lead to tooth discoloration. The tooth discoloration is due to the bismuth oxide and sodium hypochlorite or collagen in the dentin15. The tooth discoloration can lead to clinical challenges when using MTA.

Biodentine

Biodentine is a bioactive material made of tricalcium silicate, zirconium oxide, dicalcium silicate, calcium oxide, and calcium carbonate. Biodentine is mainly used as a dentin replacement in deep large coronal restorations in direct restorations4. Biodentine can also be used for pulp capping, pulpotomy, and root canal filling and apex closure. Biodentine can also be used as a temporary restoration. The advantage of using Biodetine as a dentin replacement, is that the calcium silicate based material replaces the dent in bulk4. The tricalcium silicate in Biodentine stimulates the transforming growth factor 1 which helps with differentiation of progenitor cells and dentin tissue formation10. Biodentine has the ability to induce pulp cell differentiation into odontoblast cells that can facilitate tertiary dentine formation10. Biodetine contains chloride, which increases the setting time making Biodetine set faster than Mineral Trioxide Aggregate (MTA) Biodentine has a setting time of ten to twelve minutes15. Biodentine has a lesser grey tooth discoloration when compared to MTA. Biodentine has a higher level of calcium ion release when compared to MTA. Biodentine also has a better sealing ability. Therefore, Biodentine can be a more suitable dental material for clinical use when compared to MTA5.

CONCLUSION:

In conclusion, the definition of a bioactive dental material is the ability of the material to create a hydroxyapatite seal between the tooth surface and the material. There are a lot of bioactive materials available in the market. Being a smart consumer and knowing all the pros and cons of each material can be very beneficially when running a dental practice. Some bioactive materials can lead to pulpal irritation which can lead to a restoration failure. Carefully selecting the right material can increase the longevity of the dental restoration significantly. Researchers are always looking for new ways to incorporate these bioactive materials into different restorative materials. An ongoing research right now is to figure out how to incorporate the benefits of the bioactive material effects into resin composite materials. Bioactive dental materials can help reduce recurrent decay microleakage, and pulpal sensitivity in restoration. Bioactive dental materials can also prolong the longevity of a restoration by remineralization of the tooth. Although there are still a lot of uncertainties when it comes to using bioactive materials in dentistry. The increase use of bioactive materials in the dental practice will definitely increase in the near future. The increase usage and development of bioactive material is definitely bright in the field of dentistry.