EFFECT OF MICRO- AND NANO-FILLERS ON THE COEFFICIENT OF THERMAL EXPANSION OF COMPOSITE SYSTEMS WITH POTENTIAL APPLICATIONS IN STOMATOLOGY

This experimental study aims to assess the effect of selected filler types on the longitudinal thermal expansion of composite systems. The studied issue concerns the dimensional stability or durability of white dental fillings, composite systems of photo polymerizing polymer with particulate fillers of micrometer and nanometer dimensions, mainly based on silica and zirconia. ChS Epoxy 455 epoxy resin cured with P11 hardener was used as the matrix of the composite systems on which the effect of selected filler types was evaluated. The fillers were particulate and fibrous materials of different chemical compositions, sizes, and combinations. Synthetic silica nanoparticles, cellulose particles, hybrid fillers derived from modified rice husk, and cellulose nanocrystals were used as fillers. The longitudinal thermal expansion of the prepared composite systems was evaluated in the temperature range of 20 degrees to 40 degrees C, which corresponds to the temperatures to which dental fillings are usually exposed. The selected fillers fracture surfaces of samples were analyzed on a scanning electron microscope, and the longitudinal thermal expansion was measured on a thermomechanical analyzer. Based on the dimensions and chemical compositions of fillers used, the quality of the interphase, and the arrangement of the fillers in the polymer matrix, the contribution of these reinforcing elements to the potential influence of the thermal expansion coefficient was evaluated. In view of results obtained, the following experiments will focus on the study of material combinations of particulate and fibrous fillers, the evaluation of the influence of the environment on materials, and machinability.