Methacrylate-modified riboflavin as a collagen crosslinking agent for biomedical applications

• Grant number: 12/17679-3
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate
• Start date: January 20, 2013
• End date: September 19, 2013
• Field of knowledge: Health Sciences - Dentistry - Dental Clinics
• Principal Investigator: Giselle Maria Marchi
• Grantee: Lívia Aguilera Gaglianone
• Supervisor: Carmem Silvia Costa Pfeifer
• Host Institution: Faculdade de Odontologia de Piracicaba (FOP). Universidade Estadual de Campinas (UNICAMP). Piracicaba , SP, Brazil
• Institution abroad: Oregon Health & Science University, United States
• Associated to the scholarship: 11/22114-2 - Effect of low viscosity resins composition and pre-heating on degree of conversion, mechanical properties and influence on penetration in inicial enamel caries lesions., BP.DR

Abstract

The aims of the present proposal are: a) Design and characterize a bifunctional, polymerizable Riboflavin (RF) molecule, with the added capacities of establishing interactions with collagen in the substrate and with the resin in the adhesive; b) Test the microtensile bond strength of resin composites to tooth structure with the use of Riboflavin-modified adhesives, both short- and long-term (six months). For synthesis of modified molecule, RF will be functionalized through the condensation reaction of one of the primary alcohols in its backbone with the isocyanate functionality in 2-isocyanatoethyl methacrylate or butyl isocyanate. Once the synthesis of new RF molecule was completed, its collagen crosslinking potential will be evaluated through tests with collagen type I and II, by the amide peak identification and stiffness of dentin collagen through nano-DMA and tensile test (universal testing machine, 0.5 mm/min, a 10 N load cell), respectively. Potential interactions of RF as an initiator will be tested by following the kinetics of polymerization of its modified versions (nearIR spectroscopy) that will be added in an experimental adhesive which formulation will be 60 BisGMA/ 40 HEMA mol ration and a commercial adhesive will be used as a control, also evaluating phase-separation during polymerization through light transmission test. After all these information, micro-tensile bond strength will be tested. For specimen preparation, three surface protocols will be evaluated: no treatment, conventional acid etching (phosphoric acid at 37%) or less aggressive acid etching (less time/lower concentration), as well as different adhesive systems (experimental adhesive formulation, one commercial multi-step and one commercial self-etching adhesive formulation), with or without the addition of RF. Midcoronal dentin of twelve human mandibular molars (n=3) will be exposed and they will be treated according to the groups previously described. After resin composite restoration, the teeth will be sectioned and the specimens will be stored in 37°C in water for either 24 h or six months, which will be subjected to thermal cycling. After 24 h or six months aging, the beam specimens will be glued to a jig and micro-tensile bond strength will be measured with a universal testing machine at a cross-head speed of 1 mm/min. After ¼TBS testing, the debonded dentin specimens will be imaged with scanning electron microscopy to evaluate the failure modes. Data will be analyzed with adequate statistical analysis. (AU)