Bioactive Materials Opportunity and Challenges in Dentistry

The global dental materials market is projected to be close to $10 billion by 2025 [1]. Advances in dentistry are closely...


Introduction
The global dental materials market is projected to be close to $10 billion by 2025 [1]. Advances in dentistry are closely related to this scenario, and the primary impetus is to facilitate the workflow of dentists and increase the comfort of the patients. Therefore, notable research projects have been carried out which are currently underway, to develop new elements with improved properties, or which can be processed using advanced technologies [2][3][4].
The ideal material to restore or replace lost oral tissues may be difficult to achieve, but the effort persists at a determined rate. The literature is profuse with new biocompatible approaches, aimed at clinical efficiency and effectiveness; the examples in regenerative medicine, which stimulate biomimetic processes, are of great interest, but with difficulties of predictability in the clinical setting [5]. This knowledge has provided guidance for the development of biomaterials that are bioactive rather than simply biocompatible, containing additives at the nano-scale, essential components, or additional molecules and ions that have antimicrobial, tissue anabolic, or demineralizing potential [6][7].
Efforts were then directed to reduce polymerization shrinkage as a strategy to reduce postoperative sensitivity, cusp deflection, and microleakage [8]. In the current decade, bulk-fill materials are becoming increasingly popular due to the clinical appeal of depth of cure and reducing the time required to insert composite into cavity preparation [9,10]. In general, these current composite resins have a longer longevity, better preservation of the dental structure, adhesion to enamel and dentin surfaces, aesthetics, and proper handling. However, recurrent caries remains a predominant reason for failure, and replacement of these restorations by bacterial micro leakage throughout the composite resin/tooth reconstruction, contributes to postoperative sensitivity, inflammation, and pulp Furthermore, it has been stated that there is a potential impact of composite resins on the ecology of microorganisms in the dental bio film, due to the greater accumulation, in these restorative materials [12]. Also, the effect of the biodegradation by-products derived from them; on the important physiological functions of S. mutans indicate its potential influence on bio film formation and microbial survival on the surfaces of the oral cavity [13,14].
Therefore, there is strong in vitro evidence of the synergistic effect of cyclic loading and exposure to bacteria, which aids in the penetration of the bacterial bio film at the margin of these restorations and dentin, possibly leading to development fastest secondary caries in vivo. To overcome these problems, efforts have been devoted to the development of a new generation of dental materials called by some "bioactive" that contain additives that have remineralizing and antimicrobial capabilities [15][16][17][18][19][20][21][22][23][24].

Bioactive Materials in The Current Dental Market and Its Mechanism of Action [25]
1.

2.
Materials that deposit hydroxyapatite and also remineralize.

3.
Materials that stimulate pulp regeneration remineralize and deposit hydroxyapatite.

Materials that Remineralize
Fluoride is retained intraorally after treatments such as fluoridated toothpaste and the application of fluoride varnish and is then released into saliva over time. It can remain on teeth, mucosa, dental plaque or within a bioactive restorative.
Its retention is clinically beneficial as it can be released during cariogenic challenges to decrease demineralization and improve remineralization. Materials that deposit hydroxyapatite and also remineralize. Ionomeric glasses create a new ion-enriched layer at the glass/tooth ionomer interface. This layer contains phosphate and calcium ions from dental tissues, and calcium (or strontium), phosphate and aluminum from glass ionomer cement.
The remineralization process creates a harder dentin surface. The filler (Isofiller) that acts as a shrinkage stress reducer leading to less microleakage [27,28]. Among the non-resin based hydroxyapatite depositing materials, they bind with an acid-base reaction and produce an alkaline pH after setting. High pH levels (7.5 or more) seem to stimulate a more active and complete bioactivity. Ceramir

Conclusion
The recent research studies on the physical, chemical, and biological properties of some bioactive materials are discussed in this short review. Calcium silicate cements properties have led to a growing series of innovative clinical applications. The capacity to promote calcium-phosphate deposit suggests their use for dentin remineralization and tissue regeneration. They can induce the chemical formation of a calcium phosphate/apatite coating when immersed in biological fluids. Studies of the next generation of bioactive dental materials for "Regenerative Dentistry" will guide their clinical evolution.