[Marginal adaptation of posterior resins: effect of hygroscopic expansion and layer placement technique on Class II...

Human teeth were filled with two posterior resins, Heliomolar and P-50, using Gluma as dentin adhesive. After this the teeth were extracted and the author studied the microleakage. The composite filling of the cavities was done following two techniques, one by layers and other with the bulk technique. The teeth were kept in saline solution at 37 degrees C and after 30 days the teeth were studied. The Heliomolar composite was able to avoid the microleakage in almost 100% of the samples independently of the inserting technique used. The P-50 composite was not able to avoid the microleakage unless in a very small number of teeth and this happened only when the layer technique was used. The difference between both is due to the greater amount of organic component in the microfilled resins producing thus a greater higroscopic expansion.