Produkt Katalog - Langer-Küretten - Hu-Friedy

50I2REFERENCE GUIDE I ALLGEMEINE INFORMATIONBLACK’S FORMULABlack’s Formula is a system ofuniversally accepted numbers designedby Dr. G. V. Black that describe theshape, size and angle of cavitypreparation instruments. Both dentistsand manufacturers use Black’s Formulato communicate about instrumentdesign.Black’s Formula is based on theconcept of instrument balance.Balance is established by keeping theblade of the instrument within 2 mm ofthe long axis of the handle line.Proper balance is necessary to achieveoptimal cutting with minimal effort.Black’s InstrumentNumbering Formula15812;The first number (15) represents thewidth of the blade in tenths of amillimeter.AngleLengthWidthThe second number (8) representsthe length of the blade in wholemillimeters.8070900102030The third number (12) represents theangle the blade forms with the longaxis of the handle expressed indegrees centigrade.6040Black’s Formula uses a centigradescale to measure instrument angles.Out of balance instrumentABalanced instrumentB;About the Fourth NumberSome instruments, such as margintrimmers, are constructed with a cuttingedge at an angle other than a rightangle. In these cases, a fourth number(in degrees centigrade) is placed in theformula that indicates the degree ofangle of the cutting edge to the longaxis of the handle.Example: Margin Trimmer15-95-8-129515 8 1215 95 8 12The fourth number is placed betweenthe first and second numbers.