Title: 2480 - Monomer Conversions and Shelf Life of Novel Composites
Yousef Eshmawi (Presenter)
Umm Al-Qura University, Faculty of Dentistry
Paul Ashley, UCL Eastman Dental Institute
Anne Young, UCL Eastman Dental Institute
Objectives: The aim was to assess polymerisation kinetics versus composition, depth and high temperature aging for new composite pastes.
Methods: Four resin-composite pastes were prepared by combining urethane dimethacrylate (UDMA) and poly(propylene glycol) dimethacrylate (PPGDMA) monomers with filler. The dental glass filler had high or low levels of Polylysine and Monocalcium Phosphate Monohydrate included to promote novel dentine sealing and self-repair features. Pastes were stored at room temperature or aged for 18 days at 60°C. FTIR spectra of lower surfaces of samples of 1, 2 or 4mm depth were obtained using a diamond ATR system before, during and after 20 or 40s exposure of the top surfaces to a blue light emitting diode curing unit (Demi Plus, Kerr) (1100-1200 mW/cm2). Reaction delay time, time of light exposure required for 50% conversion and final monomer conversions were determined. Vertise Flow (Kerr) and ACTIVA kids (PULPDENT) were used as commercial controls.
Results: Experimental composite monomer polymerisation profiles were only mildly affected by additive addition or high temperature aging and similar to those of commercial controls. Delay times were a consequence of photobleaching being required to enable sufficient light penetration into deeper specimens. Average experimental composite delay times were 5, 8 and 28s whilst 50% reaction times were 12, 18 and 45s at 1, 2 and 4mm depth respectively. At 1 and 2 mm depth, final conversions of 73 and 70% could be achieved with 20s light exposure. 40s light was required to gain 60% conversion at 4 mm depth.
Conclusions: Experimental formulations were stable upon high temperature aging suggesting good shelf life and had competitive rates and levels of conversion to commercial materials. 20s light exposure is sufficient for good monomer conversion up to 2mm depth but longer times or composite layering methods would be required for deeper cavities.
This abstract is based on research that was funded entirely or partially by an outside source:
Umm Al-Qura University, Makkah, Saudi Arabia
The submitter must disclose the names of the organizations with which any author have a relationship, the nature of the relationship, and the clinical or research area involved. The following is submitted: This work is part of the PhD project for Dr. Yousef Eshmawi (Presenter) at UCL Eastman Dental Institute, Department of Biomaterials and Tissue Engineering, London, UK and the scholarship support from Umm Al-Qura University Faculty of Dentistry, Makkah, Saudi Arabia is acknowledged. Co-authors affiliations: Dr Paul Ashley Paediatric Dentistry UCL Eastman Dental Institute London, UK Anne Young Professor of Biomaterials UCL Eastman Dental Institute London, UK