To bevel the gingival margin of a tooth during cavity preparation.Margin Trimmer N. 79/80 (Black’s Formula: 15-80-8-12), Mesial Cavity preparation margin trimmers are used with a lateral scraping motion to bevel the enamel at the cervical seat of the cavity preparation.The blade of the instrument must be always kept parallel to the cavity wall to remove unsupported enamel rods or roughness. RUBBER DAM FRAME mm110 RUBBER DAM FRAME mm110