HEAT TREATMENTHARDENING TREATMENTThe steel is heated to 1500 to 16000 F (8150 C) and then quenched in oil to harden the working edge.Not more than 1 - 2mm of the tip is heated for hardening purpose, otherwise the instrument will lose its balance after sharpening. MANUFACTURINGPROCESSBlank steel is bent to the degree of angulation needed in the shank and blade.The edges are milled to produce the cutting edge and structural design.Martensitic type of stainless steel is used for manufacturing cutting instruments (high strength and hardness). Other alloys:Alloys of nickel, cobalt or chromium are used in the manufacture of hand instruments. Adv.:- High resistance to acid - Hardness Use: Manufacture of mixing and inserting instruments. Stellite Cobalt 65 – 90% Chromium 35% Trace amounts : tungsten, molybdenum and iron. Mainly used for working points and cement instruments.Carbon steel Carbon 1 – 1.2% Manganese 0.2% Silicon 0.2% Iron 98.4 – 98.6%Adv.:- Harder than stainless steel.Disadv:- When unprotected, it will corrode. Remains bright under most conditions.Disadv:- Maintaining the sharpness of the blade is a problem. Stainless steel Chromium 18% Carbon 1% Iron 81- 81.4%Adv.:- Chromium in the alloy reduces the corrosion tendency by depositing an oxide layer on the surface of the metal. Hard and wear resistant but is brittle too. MATERIALSUSEDHand cutting instruments are manufactured from two main materials:Stainless steelCarbon steelSome instruments are made with carbide inserts to provide more durable cutting edge. George Hollenback – Invented pneumaticcondenser. Ferrier – Developed a new set of instruments called ferrier set which were more refined and had uniform thickness on the cutting edge.Dr. Wedelstaedt- Developed Wedelstaedt chisel now referred to as “Curved Chisel”.Dr. Wood Bury - First to modify blacks instrumentation.ĝesigned 39 sets of Hand instruments for Class III cavity preparations & condensing points for building gold foil restorations. Black - Developed many of the instruments and techniques. Black - Credited with the first acceptable nomenclature for and classification of hand instruments. Instrument with large, straight blades modified to smaller, angled blades.ĭr. Many dentists made their own hand instruments in an effort to find a suitable instrument for specific need.Įarly hand instruments were grasped in the palm of the hand.Īs cavity preparations refined and the access to various surfaces of teeth desired:- Grasp changed to pen grasp. There was no uniformity of manufacture and nomenclature. These instruments had bone or ivory handles (effective sterilization was not possible). The application of the instrument.HISTORYMost hand instruments of the mid 19th century(1860’s) with large, heavy handles and inferior metal alloys in the blade, were cumbersome, awkward to use and ineffective. INTRODUCTIONThe term “instrument” refers to a tool, device or implement used for specific purpose or type of work and is preferred in professional or scientific fields as precision items are generally required to perform specific procedures.In order to perform, the intricate or detailed procedures associated with operative dentistry, the dentist must have a complete knowledge of the purpose and application of the many instruments required. HAND INSTRUMENTS IN OPERATIVE DENTISTRYBy:- Dr Abhijeet D KhadeNair Hospital Dental College,MumbaiĬontents:-Introduction HistoryMaterials usedHeat treatmentClassificationNomenclatureInstrument formulaInstrument partsMeasuring gauzesTypes of hand cutting instrumentsHand instrument techniqueSharpening hand instrumentsSterilization and disinfectionSummary and conclusionReferences
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