Monomer Modification to Improve the Conversion in a Novel Composite

Objectives: The aim of this research is to develop a composite dental material that has higher monomer conversion by replacing the commonly used bulk monomer (BisGMA) with (UDMA) and by replacing (TEGDMA) with a more biocompatible and larger diluent monomer (PPGDMA)
The study assesses the effect of including an adhesion promoting monomer (4META), and different levels of initiator (CQ) and polymerisable activator (DMAEMA) on conversion, colour and clarity of composite monomers.
Methods: Monomers were prepared by mixing UDMA and either PPGDMA or TEGDMA at a 3:1 ratio. (CQ & DMAEMA) were added at 0.5, 0.75 or 1 wt%. All monomers contained the adhesion promoting monomer (4META at 5 wt%). A standard 7-μm glass was used at a powder/monomer ratio of 4 to make composites.
UV-spectrometry was used to check the colour and clarity of the monomers. FTIR (infrared) was used to determine monomer conversion (MC) with 40s light exposure at 1 mm depth in composites
Results: (DMAEMA) resulted in increased clarity of the monomers by enhancing dissolution of (4META). (CQ) concentration enhanced monomer light absorption and colour.
Maximum composite conversion was obtained with 0.75 wt% CQ. Composites prepared with (PPGDMA) had approximately 20% higher conversion. The addition of (DMAEMA) had no significant effect on MC of composites containing (PPGDMA) but increased MC in those containing (TEGDMA).
Conclusions: Increasing the solubility of 4 META through DMAEMA addition should enable it to polymerise more readily with the other monomers. Gaining maximum conversion at intermediate CQ levels suggests too much of this initiator may reduce light penetration and conversion at lower sample depths. Enhanced conversion with use of PPGDMA may result in a reduction of leaching of unreacted monomers into the oral cavity and thereby improve cell compatibility.