Surface permeability and degradation of dental composites resulting from oral temperature changes

The surface changes in dental composites caused by thermal cycling and different temperatures were evaluated by use of silver nitrate to stain the surface layers. Rapid temperature change resulted in the formation of layers within the surface which may have resulted from microcracking. Slow rates of change increased the depth and rate of diffusion of silver nitrate. Determination of the temperature changes at the surface of a restoration in the mouth indicated that in vivo temperature change is more likely to increase the depth of diffusion of oral fluids than to cause microcracking of the surface.