Influence of Fillers & Fluorinated Divinyl Urethane Monomers on Resin Composite Physical Properties

 Lagowski, Michael 1 ; Shiguetomi, Kenyiro 2 ; Finer, Yoav 1, 2 ; Santerre, J Paul 1, 2;

 1.  Institute of Biomaterials and Biomedical Engineering, University of Toronto; 2.  Faculty of Dentistry, University of Toronto

Background: The interfacial reaction of salivary enzymes with resin composites contribute to the loss of material integrity, increased surface roughness, and release of degradation products that affect cariogenic bacterial virulence, suggesting that improving the composite's physical and chemical stability is paramount to restorative success.

Objectives: To incorporate fluorine and urethane chemistries into resin composites in order to reduce enzyme-mediated hydrolysis of susceptible ester linkages while maintaining mechanical strength.

Methods: Fluorinated divinyl urethane monomers and silanated barium borosilicate filler (BBS) were prepared, where monomers were characterized by 1H-NMR and fillers by thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). Different composite formulations were assessed for mechanical strength (flexural, compressive) and hydrophobicity (contact angle, water uptake). Candidate materials with adequate performance relative to a control analog will be assessed for biodegradation resistance in on-going studies, under simulated salivary esterase incubation conditions.

Results: Eight fluoromonomers were successfully synthesized and assessed for their effects on mechanical strength and hydrophobicity after being incorporated into resin formulations at 35wt% (polymeric matrix). Best candidates were selected and assessments repeated but with increasing fluoro-monomer concentration from 35 to 55wt%.  A novel monomer, 'F3LHB', was shown to perform best (i.e. comparable strength modulus commercial controls and greatest hydrophobicity) at 35wt% and 45wt%. BBS was silanated with methacrylated silane and compared to a commercial equivalent via flexural testing, and showed no statistical difference between groups. Fluoro-silane was incorporated alongside methacrylated silane to produce a multi-functional BBS filler. TGA yielded a loss of 0.4-0.8wt% silane, indicating near-monolayer coverage of the fillers.

Conclusion: The feasibility of formulating composites with fluorinated monomers and fillers with practical physical properties was shown, and subsequent work will look at biochemical stability.

Impact: This work will yield new materials for resisting enzyme-related biodegradation by introducing fluorine chemistry into composites

Acknowledgement: NSERC Discovery Grant.