I he adaptation of a complete crown to the gingival margin is an important factor for the sound prognosis of teeth. Ill-fitting margins contribute to the accumulation of bacterial plaque and thus predispose the tooth to caries and periodontal disease.’ Therefore, an exact reproduction of the abutment at the finishing line of the preparation is of particular importance among the several factors’ governing the proper seating of complete crowns. Since the impressions must also include a narrow zone of unprepared tooth hurface immediately apical to the finishing line, they are usually removed over more or less pronounced undercuts. Consequently, the impressions are highly liable to deformation in this critical area. This clinical problem has been greatly reduced in recent years by the introduction of the tray impression technique combined with highly elastic impression materials. However, individual impressions of each abutmc’tlt using relatively tight-fitting impression bands are still preferred in SOIII~ c,lirricnl instances. Both thermoplastic and elastic compounds are commonly used with this technique. A description of their physical properties will give a clue to the range of indication for each material, but little seems to have been done to stud) thfair suitability specifically for the copper-band technique. The present investigation studied the applicability of one thermoplastic material and different types of elastic materials for the copper-band technique. The impressiol t technique simulated the clinical method, often resorting to relatively tightfitting bands when the application ‘of impression material subgingivally is difficult. Impressions were taken of abutments with varying degrees of taper belobv the finish ing line. The impressions were inspected for rupture of the materials, and the exactIIC~ of intact impressions \vas measured indirectly on stone dies. Finally, a siniplt% rntxthod to avoid deformation of elastic impressions in soft copper bands evolved.