THE SURFACE OF INVESTMENTS POURED AGAINST DIFFERENT DUPLICATING MEDIA

Two phosphate-bonded investments that were poured into molds of a dupl icating gel and a poly(vinyl siloxane) duplicating medium were examine d for surface hardness. Untreated surfaces were also examined by the c onfocal microscope and the scanning electron microscope. The Brinell h ardness of samples poured in poly(vinyl siloxane) was greater than tha t of the same investment poured in duplicating gel. Investments were h ardest as set and were significantly softened by drying. Cast hardener s achieved some rehardening of the dried investment samples. Microscop ic examination of the investment surfaces revealed greater surface irr egularity of samples poured in duplicating gel than in poly(vinyl silo xane), particularly in one investment.