The wall-to-wall polymerization contraction and hygroscopic expansion of Durafill, Heliosit, Silux and Visio-Dispers were examined in dentin cavities in extracted human teeth. The linear shrinkage varied from 0.24% to 0.63% and only two of the tested materials were able to close the marginal gap owing to water absorption. The gaps were nearly always broadest in the apical part of the filings. Measurements of the marginal gaps were made at different levels between 100 and 1200 microns below the free surface of the fillings and the wall-to-wall polymerization contraction was found to increase markedly from the level of 100 microns down to 800 microns. The contraction pattern of the four light-cured resins differed significantly from the one found in a chemically-cured material.
Absorption Chemical Phenomena