Monomer selectivity by dentin collagen in different mobile phases and strategies to preserve the hybrid layer

• Grant number: 16/05916-1
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Start date: November 01, 2016
• End date: July 31, 2019
• Field of knowledge: Health Sciences - Dentistry - Dental Materials
• Principal Investigator: Josimeri Hebling Costa
• Grantee: Giovana Anovazzi Medeiros
• Host Institution: Faculdade de Odontologia (FOAr). Universidade Estadual Paulista (UNESP). Campus de Araraquara. Araraquara , SP, Brazil

Abstract

Two main challenges to establish more efficient and stable resin-dentin bonds are: (1) infiltrating the etched dentin with more hydrophobic monomers and (2) making the collagen resistant to degradation. Current researches on adhesion are designed to better understanding how to overcome those challenges. By developing the experiments included in the present project, we aim to investigate the selectivity imposed by both mineralized and demineralized dentin (collagen matrix) on monomers found in adhesive systems and to contribute to the understanding of how different mobile phases could influence such selectivity and could allow the infiltration of hydrophobic monomers. Also, it will be an objective of this project to determine the minimum amount of water necessary to allow dentin proteolytic enzymes (MMPs) to break down collagen. In order to accomplish that, we will first have to demonstrate if the rate of collagen degradation is comparable between human and bovine dentin matrices. That is important because bovine teeth will be used in the second experiment of this project. In the third experiment, we want to investigate if the dentin collagen biomodification using a cross-linker (proanthocyanidin, PA) can improve the mechanical properties of collagen to withstand air drying (physical dehydration) without shrinking. Additionally, in the experiment, it will be evaluated the effect of this collagen biomodification on the immediate and long-term bond strength to dentin. In order to respond to these objectives, several methodologies will be used such as total MMPs activity, dry mass determination, ICTP and CTX fragments release, exclusion chromatography (collagen column), immediate and 12- month microtensile and nanoleakage. Finally, in the last experiment, it will be investigated the effect of the physical dehydration of PA-biomodified dentin on the MMP-2 and MMP-9 gene expression by odontoblast-like cells. All collected data will be analyzed as to distribution and homoscedasticity of the groups to be compared. Based on the results of these initial tests, parametric or non-parametric tests will be selected considering the number of groups and type of the response variable. All statistical inferences will be taken considering the 5% level of significance.