Influence of the colloidal crystal-like arrangement of polymethylmethacrylate bonded aerosil particles on the polymerization shrinkage of composite resins.
OBJECTIVE
Determination of the roles on the polymerization shrinkage during light-curing of composite resins of (i) the filler structuring effect of methylmethacrylate polymer adsorbed on fractal silica particles and (ii) of the crystal-like arrangement of the filler within the matrix.


METHODS
Firstly, the domain of major efficiency of polymer in the aerosil agglomeration was determined. Secondly, the monomer system was changed in order to implement the spontaneous concentration of the filler within in a crystal-like arrangement. Finally, the rate of the polymerization shrinkage during light-curing of the resin was determined on the sediment recovered after centrifugation and on the colloidal crystal. Micro-modifications to the size of the samples were determined with the aid of the CCD Line Scan Sensor (H.-D. Rudolph GmbH, Germany).


RESULTS
The composite micro-structure and the rate of polymerization shrinkage during light-curing of the resin are correlated with the amount of polymer initially supplied to the system that controls the degree of filler agglomeration. Different types of matrix/filler systems with typical shrinkage characteristics were sampled from the sediment containing amorphous and organized phases. The colloidal crystal-like system was determined to concentrate the filler within the matrix, and to give rise to the smallest shrinkage.


CONCLUSIONS
This study suggests that the silica particles embedded in a micro-structured polymer network (the filler scaffold) slowly develop spontaneously towards a colloidal crystal-like arrangement, and opens up new processes to reduce polymerization shrinkage.
Pefferkorn
A
A
Institut Charles Sadron, CNRS, UPR 022, 6 rue Boussingault, 67083 Strasbourg Cedex, France. peffer@cerbere.u-strasbg.fr
Pefferkorn
E
E
Haïkel
Y
Y
D003102:Colloids; D003188:Composite Resins / Q000138:chemical synthesis / Q000737:chemistry / Q000528:radiation effects; D003460:Crystallization; D003799:Dental Stress Analysis; D006244:Hardness; D008027:Light; D008422:Materials Testing; D010316:Particle Size; D044367:Phase Transition; D019904:Polymethyl Methacrylate; D016062:Porosity; D012822:Silicon Dioxide
D003102:Colloids; D003188:Composite Resins; D012822:Silicon Dioxide; D019904:Polymethyl Methacrylate