Efectos químicos y mecánicos del fluoruro diamínico de plata en la dentina

Résumé

Dental caries is the most prevalent chronic disease worldwide. This disease is characterized by a multifactorial etiology and a slow progression leading to the destruction of dental hard tissues. The current understanding of the pathophysiology of dental caries and the development of new therapeutic resources has contributed to the acceptance of minimally invasive dentistry in the operative approach for caries lesions and even non-invasive dentistry in early and moderate stages. From this point of view, the evolution of the caries lesion can be arrested or reversed by remineralization procedures of the affected tissues. Silver diamine fluoride (SDF) is an inexpensive, safe and easily accessible option for the treatment of caries lesions. Moreover, SDF treatment requires minimal instrumentation and does not require complex facilities for its application. In particular, the most remarkable characteristic of this material is its ability to arrested caries lesions with a non-invasive approach. Specifically, when SDF is applied to carious tooth tissue, a series of chemical reactions occur that promote caries arrest, as well as the desensitization of the tooth by occluding the dentinal tubules. Additionally, this product has antimicrobial and remineralising action and inhibits dentin collagen degradation. However, despite multiples investigations on the mechanism of action of SDF, there is no established protocol for the application of this material in dentine tissue. On the other hand, considering the characteristics of SDF, it is also essential to evaluate the properties of this material in different oral environments. pH cycling is an appropriate procedure to evaluate several dental materials under different periods of demineralization and remineralization that simulated a caries process in vitro. In this context, this methodology allows us to determine certain fundamental aspects of SDF under particular conditions, such as its remineralizing capacity, which is essential for a minimally invasive dental practice. Besides its many advantages, SDF has a major aesthetic inconvenience. This material produces black staining on the tooth surface due to the oxidation of the free silver ions in its formulation, and this black staining is the main reason for the patients rejection of SDF treatment. To overcome this aesthetic problem, different commercial brands have added potassium iodide (KI) during application. However, using this compound has been shown to compromise the antimicrobial activity of SDF. In this context, the use and implementation of nanotechnology have emerged as an alternative during the last decades to try to solve this problem. This method consists of developing AgNPs to avoid surface staining without compromising the properties of the SDF for these treatments. However, the properties of these AgNPs in their application and the possible interactions of these AgNPs with tooth structures are still unknown. Based on the above considerations, it is evident that there is no consensus on the rehabilitation of cavities treated with SDF, nor is it unclear how to address the aesthetic problem associated with the use of this material. Therefore, the main objective of this Ph.D. thesis is to evaluate the physicochemical, morphological, and mechanical effects of silver composites on demineralized dentin. This doctoral thesis is structured in six chapters. Firstly, Chapter 1 presents a theoretical background based on an extensive literature review on different topics and issues related to this doctoral research. For this purpose, some basic concepts are introduced by describing the mineralized structures of the tooth. Then, different techniques for treating dental caries lesions and their remineralization process are presented. Subsequently, the use of SDF, its mechanisms of action, and its clinical implications are discussed. Finally, this chapter introduces some fundamental concepts in the field of nanotechnology in dentistry. In Chapter 2, the principal and specific objectives of this Doctoral Thesis are presented. Chapter 3 evaluates the immediate physicochemical effects of the use of different commercial brands of SDF and their relationship with the immediate adhesive response of etch and rise and self-etch adhesive systems. Chapter 4 analyses the remineralizing capacity of SDF and NaF under pH cycling conditions. Furthermore, Chapter 5 discusses the synthesis of silver nanoparticles by green chemistry, using plant extract (Camellia sinensis), and functionalized with chitosan and NaF as an alternative material to SDF. In addition, this chapter evaluates the application of these AgNPs on the physicochemical and mechanical properties of demineralised dentin. Chapter 6 presents the conclusions from the research carried out in each of the studies described above.