EFFECT OF PLASMA TREATMENT ON THE WETTABILITY OF ELASTOMERIC IMPRESSION MATERIALS

This study investigated the effect of ''plasma treatment'' on the wett ability of impression materials and void formation in die stone casts. Four addition reaction silicones, one condensation reaction silicone, and one polyether impression material were used. Wettability was dete rmined before and after plasma treatment by contact angle registration of a saturated aqueous solution of calcium sulfate (CaSO4) on flat su rfaces made from the tested impression materials. Two groups of surfac es were used for each material. The surfaces in one of the groups were exposed to saliva for 5 minutes. The same impression materials were u sed to produce four groups of die stone casts from a master die. Two g roups were produced from impressions that had been exposed to milk. On e group from the exposed and one from the bare surfaces were plasma-tr eated before pouring. Voids in the stone casts were counted under a st ereoscopic microscope. The results indicated that after plasma treatme nt, the drop of CaSO4 solution completely spread over the addition typ e silicone surfaces. The corresponding die stone casts were found to b e void free. It was concluded that plasma treatment produced high-ener gy impression surfaces that result in void-free die stone casts from t he addition type silicone materials.