Temperature-dependent properties of resin-composites before and during the setting process

UoM administered thesis: Phd

  • Authors:
  • Ahmad Alnazzawi

Abstract

Dental Resin-Composites contain inorganic particles, coated with organic coupling agent, dispersed in an organic resin-matrix. In their precured state they are viscous pastes that change rapidly to a hardened mass after photo-activation. Temperature change is expected to modify several physical properties.The aims were to determine the extent to which increasing temperature from ambient (23 oC) to body temperature (37 oC) may affect properties before and during the setting process. Six representative resin-composites were selected [GRO, GCK, VDD, FXE, GDP, and GDA].Temperature-dependence of handling properties (packing stress and viscosity) of pre-cured resin composites was examined using a penetrometer instrument at 23 oC, 30 oC, and 37 oC. Viscosity was reduced significantly by up to 93 % at 37 oC compared to 23 oC. Temperature-dependence of degree-of-conversion (DC) was measured by FTIR spectroscopy at 23 oC and 37 oC. DC was also time-dependent after photo-activation at both temperatures, with all examined materials having higher DC at 1 h than 0 h.A modified bonded-disk instrument was used for simultaneous measurement of: shrinkage-strain, exotherm, and Coefficient of Thermal Expansion (CTE) at 23 oC. Shrinkage-strain, exotherm, and CTE were all found to correlate negatively with filler-load. Positive correlation was found also between shrinkage-strain and CTE.Temperature-dependence of shrinkage-strain kinetics, at 23 oC and 37 oC, was examined with the bonded-disk instrument. Mean 1h shrinkage-strains at 37 oC were numerically and significantly greater (p

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Original languageEnglish
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Award date31 Dec 2012