Effect of nano-sized prepolymers to resin matrix of dental composite

Objectives: The knowledge on the efficiency of the organic prepolymers in the dental composites is limited. In this study the influence of reactive polymeric nanoparticles (RPNPs) as nano-sized organic prepolymers on the mechanical properties of different composite was examined. The aim of this study is to examine how the organofillers influence the mechanical and rheological properties as volumetric shrinkage, compression strengths and viscosity of the dental resin matrices. Methods: Organofillers were polymerized in two types of mole ratios (3/7 and 7/3). Two series of nanocomposites were formed by mixing two types of organofillers and Bis-GMA based dental resin in the range of 5 and 25 w/w%. The nanoparticles were analyzed by TEM, DLS and 1H-NMR methods. The characterization of reinforced resins was performed by compression strength (Instron 4302), volumetric shrinkage (buoyancy method) and rheology (AR 550) methods. Results: The mean hydrodynamic diameter of organofillers was in the range of 150 and 350 nm. The Mann-Whitney statistical analysis of contraction data showed that the shrinkage was significantly decreased by increasing the volume of filler compared to the reference resin. As a result it was found that the compression strength values (223.72±36.10 MPa) for the nanocomposites modified with reactive polymeric nanoparticles separated significantly from reference unfilled resin (167.59±26.99 MPa). Conclusion: The prepolymerized nanoparticles have remarkable effect on the rheological properties, polymerization shrinkage and compression strength. The photopolymerization shrinkage and compression strengths were improved significantly by adding prepolymers due to the specific structure of nanoparticles. The work/publication is supported by the TÁMOP 4.2.1/B-09/1/KONV-2010-0007 project. The project is co-financed by the European Union and the European Social Fund.