The purpose of this investigation was to evaluate the differences in the mechanical properties of 3 composite materials in relationship to the intraoral and extraoral curing techniques of direct and indirect (inlay) restorations, and how the mechanical properties are affected by water sorption. Creep characteristics in compression as well as the stress-strain relationship at a constant loading rate both in compression and flexure, were determined. A secondary aim was to investigate the influence of filler content and monomer composition on the mechanical properties. The results are presented as creep curves and as values for elastic moduli, ultimate strength, and ultimate strain. The materials were cured with 2 curing methods. Method A was light curing with a handheld curing unit, and method B was curing in light curing ovens. Water sorption increased the creep values for all types of specimens. Curing in light ovens (method B) gave significantly lower creep values at high stresses than curing with a handheld curing unit (method A). Water sorption decreased the modulus and ultimate strength values for specimens cured with method A. The ultimate strength values also differed for dry and wet specimens cured with method B. There were no general differences in compressive and flexural stress-strain properties between specimens cured according to the methods A and B.’

How different curing methods affect mechanical properties of composites for inlays when tested in dry and wet conditions.
Kildal KK, Ruyter IE.
Eur J Oral Sci. 1997 Aug; 105(4): 353-361.