Dental composite restorative materials are based on photoinitiated methacrylate comonomer systems. The rate of initiation is currently being altered by the use of light sources of different intensities. There are theories as to the potential effects of varying the initiation rates. A fundamental understanding of the impact of initiation rates on the conversion and networking of various resin systems will help in the development of better restorative materials. The principle goal of this investigation is to identify the effects on conversion and the resulting properties as a result of varying the rate of initiation. Initially, the total energy fluxed will be matched for the various light intensities (integrated to the photoinitiator absorbtion spectra) by altering the exposure times. A dimethacrylate comonomer resin will be investigated initially using a visible light photosensitizer. The conversion can be monitored using near IR. The following properties will be investigated in the resulting polymer: flexural strength, flexural modulus, Tg, and polymerization shrinkage. The comonomer system primarily tested will be BisGMA/TEGDMA as the baseline for varying light intensity. Other comonomers using ethoxybisGMA and urethane dimethacrylate will also be evaluated to ascertain the effects of varying viscosity and monomer flexibility. The career development planned with this work includes the completion of graduate course work that will enable the completion of a PhD in materials sciences at the Colorado School of Mines. The experience will provide the background to move from a primarily teaching position to a contributing researcher in fundamental polymer development. The University of Colorado Health Sciences Center is developing a new biomaterials research center and establishing relations with the Colorado School of Mines Metallurgical and Materials Engineering Department in its new specialty area of biomaterials. Intercampus research is also growing with the polymer chemistry group in the Chemical Engineering Department at the University of Colorado, Boulder.
