Polymerization stress of experimental composites containing random short glass fibers.

•Polymerization stress increased when 3% of particles were replaced by short fibers.•Polymerization stress was not affected by replacing 6% of particles with fibers.•Fiber orientation imposed by specimen height did not affect polymerization stress.•Flexural modulus was reduced by the replacement of particles with 3% and 6% fibers.•Volumetric shrinkage was reduced only in the composite with 6% of fibers.