Dental Medicine Nanosystems : Nanoparticles and their use in Dentistry and Oral Health Care

The major goal in dentistry and oral health care is maintaining the health of oral tissues. Thus, to achieve this goal, the advances in nanosciences and nanotechnology have paved the way to approach this goal. The application of these nanotechnologies to dental medicine have given rise to nanodentistry, whitch is an innovative branch of science. Many studies indicate extensive application of the medical nanosystems in numerous fields of nanodentistry such as prevention, diagnosis, therapeutic, restoration and tissue regeneration. The lattery, cover all dentistry specialties such as restorative dentistry, periodontics, endodontic, orthodontics, prosthodontics, oral implantology and regenerative dental Medicine. These dental Medicine nanosystems as nanostructred materials constitute new innovative nanoproducts that make possible the maintenance of oral health care in a very precise, safe and effective way. The objective of this review is to expose briefly, the recent advances in these dental Medicine nanosystems, especially in nanoparticles and nanoparticles-based nanomaterials. In addition, the article sets out to describe the various potential applications of this type of nanostructured materials and the challenges they present in clinical, cosmetic and esthetic dental and oral health care.

Nanotechnology is the engineering of functional systems by controlling atoms and molecules to achieve effective, complete control of the structure of matter with new functions. The nanotechnology tools and ideas allow to create a new nanosystem with novel, physico-chemicals, mechanicals, and biological properties. However, the applications of these nanotechnologies has rapidly expanded into all areas of health care science including that of odonatological science [1] . Nanotechnology aided in processing a variety Dental Medecine Nanosystems (DMN) with innovative applications. Nanosystems means the assembly of nanoscale components for the purpose of performing a function. In the literature, nanosystems are described as manufactured nanostructured particles (nanoparticles) and nanostructured materials (nanomaterials) or their combination.The nanomaterials may have intrinsic properties related to their structures and their components or develop new properties related to the simple structuring caused by the incorporation of the nanoparticles. In the recent years, various advances in engineering of nanoparticles and nanomaterials or their combination, have allowed the development of a new innovative DMN. The advances in the applications of these DMN cover all dentistry specialities namely restorative dentistry [2] , periodontics [3] , endodontic [4] , orthodontics [5][6] , prosthodontics [7] , oral implantology [8][9] , regenerative dentistry [10] . They also cover dental fields such as prevention, diagnosis, therapeutic, restoration and tissue regeneration [11] . DMN are numerous, varied and have greatly extended. This field has been the subject of potential in a wide spectrum of dental industry and oral health care. The present review, focuses on the following DMN: nanoparticles [12-13-14] , nanoparticles-based nanomaterials [15-16-17-18] . Nanoparticles are divided into, organic nanoparticles [19] , inorganic [20] and hybrids [21] . In this regard, they are often used in dentistry and oral health care in free or incorporated form. Dental materials (metals, composites / resin-composites and polymers) are used as restorative systems, adhesives and bonding systems, cement and sealant systems and tissue regenera-Hassan Lboutounne (2017), Dental Medicine Nanosystems: Nanoparticles and their use in Dentistry and Oral Health Care. Int J Dent & Oral Heal. 3:10, 145-157. DOI: 10.25141/2471-657X-2017-10.0150 tive systems. The incorporation of nanoparticles in dental materials proves to be very promising as it makes it possible to obtain new DMN systems. Hence, it will improve the functional and structural properties of dental materials, while optimize clinical, cosmetic and esthetic dental and oral health care performances [22] . On the other hand, recently, the nanosafty of the inorganic nanoparticles for use in diverse biomedical applications including dentistry was investigated. The results of which are encouraging and emphasise the need for more precise and more detailed studies [23] . The aim of this review is to demonstrate and to describe the recent advances in the nanoparticles and their incorporation into dental nanomaterials. In addition, view their potential applications for prevention, therapeutic, restoration, tissues regeneration and diagnosis.

Dental Prevention and Prophylaxis Applications
Tooth wear is a dental disease and includes tooth erosion and toothloss. The comprehension of the main oral problems and the challenges related to DMN in the oral environment and this constitutes the basis for developing innovative and new nanoproduct that can provide an improved oral tissue protection. This could be beneficial especially for improving the effectiveness of preventive therapy for dental pathologies and oral diseases. Currently, estab-lished prevention of dental plaque relies heavily on tooth-brushing and the strengthening of tooth enamel by fluoride. Therefore, the development of enhanced dental medicine nanosystems for oral hygiene is of paramount importance in increasing the protection of the teeth and of the oral cavity from detrimental processes [24] . These developments concern nanoparticles and nanoparticles-based materials, in particular, aspects related to preventing the formation of dental plaque, biofilm and primary, secondary infections. However, the organic and inorganic nanoparticles were used in free or incorporated forms, and several strategies are used to design these dental prevention nanostructured materials such as dental medicine nanosystems as show as in Figure 1. On the other hand, the prevention of the biofilm development concernes dental equipment and this is the case in dental unit water lines (DUWL) [25] . It was reported that the problem of the susceptibility of biofilm development and bacterial growth in DUWL, leads to water contamination, which causes health and ecological effects. Overall, recent advances in the design and use of these DMN for dental prevention and prophylaxis are described in Table 1

Dental Therapeutic Applications
Dental therapeutic treatments can have a triple purpose, preventive therapy, curative therapy and tissues regenerative therapy. The innovative therapeutic nanostructured materials, as nanoparticles or nanoparticles based nanomaterials was recently reviewed [22] . However, their use for dental applications have undergone extensive investigations due to their potential antimicrobial effect. In this regard, the exploitation of their toxic properties to bacteria, fungi and viruses as well as their incorporation into dental materials in order to control oral infections was reported [19-26-27-28-29-30-31-32-33] . Accordingly, all these studies, have reviewed the importance of this antimicrobial effect of these nanoparticles whether in free form or incorporated form. Thus, the therapeutic nanostructured materials are a real therapeutic alternative in dentistry. Several strategies are used to design and to formulate this nanostructured materials for the treatment of dental and oral diseases. Regardingly, Figure 1 illustrates the design of the therapeutic dental nanostructured materials. In addition, the recent studies reflect recent advances in DMN for dental therapeutics applications (combination of preventive therapy and curative therapy) are described in Table 3  advances in regenerative dentistry, by using stem cells, signaling molecules, growth factors molecules, nanomaterials and nanoparticles are reported [10-37-38-39] . Thus, the overall, recent advances in the use of nanoparticles for dental tissues regenerative applications are described in Table 5.

Dental Restoration Applications
The nanoparticles are promissing for incorporation in dental materials-related restorative materials systems, adhesives-bonding systems, cements and sealants systems and prothesis bases systems. Therefore, these nanoparticles have potential to significantly improve the biological, mechanical, optical, thermal and the physico-chemical properties of dental medicine nanosystems (nanostructured materials). Thus, the production of nanostructured and functionnalized dental materials with more efficient biological properties must take into consideration the non-sacrifice of the other properties of these dental materials. Concerning restorative nanomaterials, in the dental implantology, infection is the most common factor that leads to dental implant failure. Antibacterial implant surfaces based on nano-scale modifications appear as an attractive strategy for control of peri-implantitis.The summary of the application of nanoparticles as dental implant coating nanomaterials that control and improve the implant success rate, with focus on enhanced osseointegration and antimicrobial effect was overviewed [34] . The investigation of the addition of an antibacterial agent to dental implants may provide the opportunity to decrease the percentage of implant. However, the use of nanoparticles to coat implants could provide osteoconductive and antimicrobial functionalities to prevent failure. But, the current research in dental adhesives and bonding naomaterials, aims at increasing the durability of resin-dentin bonds. Thus, the fundamental processes responsible for the aging mechanisms involved in the degradation of resin-bonded interfaces and the potential approaches to prevent and counteract this degradation by creating stable resin-dentin bonds that are able to resist the collagenolytic hydrolysis are also reviewed [35] . In the case of dental cements and sealants nanomaterials, glass ionomer cement (GICs) are usualy used as restorative materials have still lots of challenges due to their secondary caries and low mechanical properties. Therefore, many efforts have been proposed to modify the antibacterial and the mechanical features of GICs in order to prevent the secondary caries. Particularly, to achieve this goal, the nanoparticles were incorporated into GICs and their effectiveness has been proven [36] . Finaly, in the case of dental prothesis nanomaterials, the incorporation of nanoparticles was used in order to have a high biocompatibility with the oral tissues, excellent esthetics, superior mechanical properties. Clinical failures of complete or partial dental prothesis are most likely in the form of fracture either due to fatigue or impact forces of mastication. Several strategies are used to improve and to ameliorate the structure and the functions of these dental restoration materials as well as all the problems related to their contact with the various dental tissues and especially the interfaces. Thus, Figure 1 illustrates the design of the restorate dental nanostructured materials. In addition, the latest studies and in DMN for dental restoration applications (combination of restoration, prevention and therapy) are described in Table 6

Dental Diagnosis Applications
The cancer diagnosis which involves the design, characterization, production, and application of dental nanosystems was reviewed [40] . Recently, an increased amount of efforts have been made to develop less invasive early diagnostic modalities for oral cancer, of which the in vivo high resolution imaging of oral epithelial tissues using novel optical systems and the chemical analysis of saliva show great promise as valuable tools. The metalic nanoparticles as iron nanoparticles (Fe-NPs) single or conjugated with polysaccarides, and gold nanoparticles (Au-NPs) single or conjugated with antibodies or peptides for specific cellular biomarkers were used in dental diagnostic. They have recently been investigated as optical or magnetical contrasting agents in medical imaging techniques for early detection of oral cancer, and for identifying and differentiating infectious pathogens [41] .

Conclusion
The applications of nanostructured materials (nanoparticles and nanomaterials or their combination) such as dental medicine nanosystems (DMN) generally imply products that may bring prevention, diagnosis and therapy diseases and / or restoration of disorders and / or tissues regenerative of oral cavity benefits. The advances in surface and interface processing and engineering of nanoparticles, nanomaterials and their combination, allowed the design of a new nanostructured materials with innovative properties which can be a real support for the improvement of dental treatments. Currently, there is a wide range of this DMN develop-ments and applications in different fields and specialties of dentistry and made dental procedures fast, reliable, effective, safe and less painful. The development of the DMN have raised substantial interest thanks to their use nowdays either in pre-clinical investigation they have already been approved and are in clinical practice of dentistry and oral health care. Currently, the challenge is to detail the cytotoxicity studies in vitro and especially in vivo, with the aim of taking numerous research outcomes and convert them into strategies for the development of clinical, cosmetical, esthetic dental practice and oral health care marketable nanoproducts. In addition, the development of new functional nanostructured materials and their design in the form of nanosystems, including "nanomachines" or "nanorobots" more effective and more suitable for dental treatment and oral health are in full evolution.