Comparación entre dentina bovina y humana sometidas a proceso de desmineralización/remineralización y efectos de la aplicación de nanohidroxiapatita funcionalizada con proantocianidina sobre dentina humana

Abstract

The first step in the development of research for novel preventive and therapeutic dental strategies is to simulate carious lesions in laboratory. Although in vitro methods have limitations, the pH-cycling model can mimic the dynamics of mineral loss and gain similar to caries-affected dentin. On the other hand, with the progress of conservative dentistry methods, it is a great challenge to obtain an adequate amount of sound human teeth for use in in vitro research. An alternative is the use of the bovine tooth as a substitute for the human one. However, the behavior of bovine dentin by the artificial caries production method has not yet been analyzed, nor have the possible differences compared to human dentin been examined. Therefore, it is important to investigate the chemical and structural properties and mechanical response of bovine dentin to evaluate its suitability as an alternative to human teeth in in vitro investigations. In addition to the importance of finding an ideal substrate for in vitro dental research, current studies are still looking for a treatment that ensures the longevity of dental restorations and the strengthening of caries-affected dentin. Given the increasing attention towards more sustainable approaches, the use of proanthocyanidinfunctionalized nanohydroxyapatite is presented as a promising alternative for dentin treatment, as it could act on both organic and inorganic components of dentin due to its dual mechanism of action as a remineralizing agent and as a collagen cross-linking agent. Although the stability of this nanomaterial had already been confirmed, its efficacy as a dentin treatment had not yet been evaluated. Based on the aforementioned issues, the present doctoral thesis is divided into 3 chapters. In the first chapter, the chemical composition, microstructural and mechanical properties of human and bovine dentin subjected to a demineralization/remineralization process by the pH-cycling method were compared. As the results of this first part showed that human and bovine dentin are different in terms of microstructure, chemical composition, mechanical strength and in their response to the demineralization/remineralization process, we have decided to use the human tooth as a substrate for the following phases of the work. In the second chapter of this doctoral thesis, hydroxyapatite nanoparticles functionalized or not with proanthocyanidin were synthesized and characterized and their possible effects on demineralized human dentin were evaluated by the pH-cycling method. Since the results obtained showed that proanthocyanidin-functionalized nanohydroxyapatite can promote remineralization while improving collagen stability in demineralized dentin, we decided to use these nanoparticles in the third phase of the work. In the third chapter of this doctoral thesis, the effect of proanthocyanidinfunctionalized nanohydroxyapatite used as a primer in different concentrations on microtensile strength and endogenous enzyme activity in human dentin subjected to pHcycling after 24 h and 6 months of laboratory aging was evaluated. For this purpose, a two-step self-etch adhesive system was used. The results showed that pretreatment of dentin with proanthocyanidin-functionalized nanohydroxyapatite increased the bond strength and reduced MMP-2 and MMP-9 activities after 6 months. This doctoral thesis ends with a conclusion section where the objectives are answered.