HARDNESS AND STRESS-CORROSION OF RUBBER DAM CLAMPS

Rubber dam clamps fracture infrequently during use. There are no Ameri can National Standards Institute or International Standards Organizati on standards for their manufacture. The purpose of this study was to m easure the hardness of the clamps and test their resistance to a stres s-corrosion test. Upper molar, lower molar, and premolar clamps were o btained from two manufacturers (A, B). The Rockwell C hardness at four sites on the bow of each clamp was then determined. Fresh clamps were placed on blocks corresponding to the average buccal-lingual dimensio n of the tooth on which they would be used. These blocks were then sub merged in room temperature 5.25% sodium hypochlorite for 20 min and th en allowed to air dry for 30 min. This was repeated 10 times. Rockwell C hardness values ranged from C30 to 38, with the clamps of manufactu rer B being significantly harder. None of the clamps from manufacturer B cracked or corroded. When a third batch received from manufacturer A was tested in the same manner, none of the clamps fractured or corro ded either.