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ROTARY CUTTING INSTRUMENTS OR DENTAL BURS

Dr. ROTARY CUTTING INSTRUMENTS OR DENTAL BURS. Set Induction: Discussing the definition, classification and types of r otary cutting instruments or dental burs used in dentistry. SERIES OF PROCEDURAL STEPS.

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ROTARY CUTTING INSTRUMENTS OR DENTAL BURS

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  1. Dr. ROTARY CUTTING INSTRUMENTS OR DENTAL BURS

  2. Set Induction: Discussing the definition, classification and types of rotary cutting instruments or dental burs used in dentistry.

  3. SERIES OF PROCEDURAL STEPS • Following steps are involved in the finishing & polishing process in dentistry – • Bulk reduction • Cutting • Grinding • Finishing • Polishing

  4. What is bulk reduction • Is the removal of unwanted large portion or material of the tooth or appliances quickly. • Done by cutting & grinding instruments like – diamond points (and discs), carbide burs (& stones), steel burs & bonded abrasives.

  5. Bulk reduction by cutting • CUTTING is a removal of unwanted material for shaping, is done by using regularly shaped instruments with sharp edged blades • Instruments used are – tungsten carbide bur, steel bur or instrument in a blade like fashion • Cutting is done by • Hand cutting instruments • Rotary cutting instruments

  6. Hand cutting instruments • These instruments are used to cut hard or soft tissue of the mouth. • These have one, two or more regular shaped sharp cutting edges or points at one or both ends of stainless steel shafts • Cutting blades have different shapes, sizes & fixed at different angles at the neck of the shafts (denoted by instrument numbering)

  7. Hand cutting instruments are composed of three parts: handle, shank and blade

  8. Instruments , E. g – • Excavators, chisels, hoe, enamel hatches, gingival marginal trimmers, scalars to remove calculus deposits, Spoon excavator etc. • These instruments are to be maintained , sterilized & properly sharpened conditions before use

  9. Chisel: • Chisels are used for cutting enamel and dentin • A- Straight

  10. Hoe: It has the same uses of the chisel.

  11. Hatchet: • Also called enamel hatchet. • Used for cutting enamel and dentin and comes as right or left types for using on opposite sides of the cavity.

  12. Gingival margin trimmer:

  13. Spoon excavator: Spoon excavators (withcorresponding instrument formulas) • A-Binanglespoon (13-7-14) • B- Triple-anglespoon (13-7-14) • C- Spoon (15-7-14)

  14. Uses of Hand cutting instruments • For removing carious debris, damaged enamel, cutting & leveling enamel surfaces, producing cavosurfaces bevels etc during cavity preparations

  15. Rotary cutting instruments • These are known as dental burs , have small regular shaped sharp multiple cutting edges at the bur – head • This is connected to through neck (shank) to the steel shaft of the bur • The other end (shaft) is connected through latch or friction grip to air-rotar

  16. Air –rotar handpiece

  17. Definition • Bur is defined as a rotary cutting instrument, with cutting heads of various shapes & having two or more sharp edge blades, used as a rotary grinder. • E.G- Steel , carbide bur , diamond bur • ADA Specification No. 23 for dental excavating burs.

  18. Parts of Rotary Cutting Instruments • Three basic parts are • Head: is the cutting, polishing, or finishing portion. • Neck (shank) : Portion of the rotary instrument that connects the shaft to the head. • Shaft: Portion that fits into the air rotar hand piece. • Straight shaft • Latch type shaft • Friction grip shaft

  19. Shank Neck Head

  20. Burs classifications

  21. Burs - classified according to • Bur head material – diamond, tungsten carbide, silicon carbide, alumina, hardened steel. • Bur –head designs –number of teeth ,rake angle (+Ve, -ve, zero) • Rotation speed – low, medium, high, ultra high according to the cutting material

  22. Burs - classified according to • Mode of attachment to the hand piece, - straight, latch type or friction grip type. • Rotating mechanism - electrical motor, compressed air –turbine system , with or without cooling water stream or air jets • According to the length of their head - long, short or regular. • According to their shapes,- round, inverted cone, pear shaped, wheel shaped, tapering fissure, straight fissure, end cutting etc.

  23. Burs - classified according to • Clinical use – • Finishing of restorations • Surgical removal of bone • Cavity preparation. • Excavation of decay. • Trimming & finishing acrylic dentures. • Taking out old fillings (amalgam). • Tooth preparation for crown & bridges. • Separating crowns and bridges. • Implant procedures

  24. Dental burs • Dental steel burs • Tungsten Carbide burs • Diamond bur

  25. 1.Dental steel burs

  26. 1. Dental steel burs • Prepared by shaping & cutting a steel blank using fine diamond points • Three basic parts – head , neck , & shank • Bur head is small & has 6,8,10,12 sharp blades (teeth) • Bur head shapes,- round, fissure & inverted cone, flame , pear , wheel tapering fissure, straight fissure, cross cut fissure, end cutting etc.

  27. 2.Tungsten Carbide burs

  28. 2. Tungsten Carbides bur :- • Prepared by heating tungsten with carbon at high pressure & temp.1500*C , the abrasive powders are sintered & hot pressed on the metal shaft, the head is cut & shaped

  29. Uses of tungsten carbide bur • Commonly used for cutting, & finishing • Used for hard base metals & other alloy casting, reducing silver amalgam & composites restorations.

  30. 3.Diamond bur

  31. Diamond burs - Resinoid bonding • Abrasive particles like synthetic diamond chips are bonded through heat resistant polyamide resinoids, then cold pressed & cured . • For better retention , the matrix are electroplated with nickel & titanium nitride . Diamond burs

  32. Diamond bur uses • Cut excellently & are used for brittle & hard material like enamel, base metal alloy , cutting & forming tungsten carbide bur , steel burs • Diamond burs easily get clogged while cutting dentin

  33. Assignment :- • Definition of dental bur. • Classifications of dental burs. • Discriminate hand cutting instruments and rotary cutting instruments used in dentistry. • Types of dental burs used in dentistry.

  34. Mcq The hardest cutting tool is of :- • (a) Martensified carbon steel, • (b) Tungsten carbide, • (c) Silicon carbide • (d) Diamond points and discs…… • Ans- (d) Diamond points and discs.

  35. Mcq Bulk reduction of appliances is done by • (a) Hand cutting or mechanical rotary instruments, • (b) Abrasions, • (c) Glazing, • (d) Polishing. • Ans-(a) Hand cutting or mechanical rotary instruments.

  36. References: • Phillips Science of Dental Materials - Kenneth J. Anusavice. 12thedition.2013.p-231-253. • Science of Dental Materials –V Shama Bhat, B.T Nandish. 2nd edition.2013.p-325-327

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