Project: Research project

Project Details


The overall goal of this research is to improve the performance of
composite resins as posterior restorative materials. Specifically, this
goal is addressed by the systematic study of the effects of polymer cross-
linking upon model restorative resin systems of controlled composition. By
controlling cross-link density, it may be possible to manipulate physical
properties and to design polymers for specific applications. Four specific
aims are directed toward testing these hypotheses: 1. to develop a linear
polymer model for the determination of cross-link determination. This
preliminary step will use mono-functional molecules that are very similar
to the difunctional molecules of BIS-GMA and TEGDMA to make homopolymers
and blends (80/20, 70/30, and 50/50 wt/wt). The glass transition (Tg) will
be determined by dynamic mechanical analysis (DMA) and differential
scanning calorimetry (DSC) for these linear systems. The relationship
between Tg and the physical properties of surface hardness, elastic
modulus, and fracture toughness will be studied. 2. to develop a model
resin system to study the cross-linking potential of BIS-GM and TEGDMA and
the resultant chemical and physical properties. Using the monofunctional
monomer of BIS-GMA used in Specific Aim #1, co-monomers will be made of
BIS-GMA and also of TEGDMA in ratios of 80/20, 70/30, and 50/50 wt/wt. A
test will be developed to distinguish between the extent of cross-linking
among the various formulations. A comparison of Tg values and monomer
conversion of the linear system to the cross-linked model will be made. A
measure of the extractable monomer remaining after cure will be correlated
with cross-link density. Comparison of the effects on physical properties
(hardness, elastic modulus, and fracture toughness) of changing cross-link
density will be made. 3. to determine the extent of cross-linking
occurring in model resin systems of BIS-GMA and TEGDMA. Co-monomer blends
using only these two molecules will be made in ratios similar to those in
the first two Specific Aims. Comparison of the results of cross-link
density, monomer conversion, glass transition temperature, hardness,
elastic modulus, and fracture toughness, will be made to those of the model
system in Specific Aim #2. 4. to determine the factors affecting cross-
linking and the impact that these factors have on physical properties. The
following factors will be varied to study their influence on cross-link
density and the resultant chemical and physical properties: main monomer
type; monomer/co-monomer ratio; curing method (heat or light-cured); level
of heat cure (high or low); treatment with light-curing (light-cured only
or light-cured plus cost-cure heated with or without a heat-induced free
radical generator); and the effect of concentration on free radical
generator. Chemical property evaluation will consist of cross-link
density, Tg, and monomer conversion. Physical property evaluation will
consist of hardness, and fracture toughness. Correlation of the different
test variables will be made to the different chemical and physical tests to
determine the influence of formulation and cure mode on these parameters.
Effective start/end date9/30/919/29/97


  • Medicine(all)
  • Dentistry(all)