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Hand instruments in operative dentistry

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Hand instruments in operative dentistry

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Hand instruments in operative dentistry

  1. 1.  Introduction  History  Materials used  Classification  Parts of a hand cutting instrument  Instrument nomenclature  Instrument formula  Instrument design  Instrument applications  Techniques  Rests and guards  Sharpening hand instruments  Sterilization and disinfection  References
  2. 2. • The term ‘instrument’ refers to a tool, device or implement used for a specific purpose or type of work and is preferred in professional or scientific fields as precision items 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. The instruments available The purpose of the instrument The position or manner of use The application of the instrument.
  3. 3.  Most hand instruments used earlier were with large, heavy handles and inferior metal alloys in the blade, were cumbersome, awkward to use and ineffective.  These instruments had bone or ivory handles.  No uniformity of manufacturer and nomenclature.  Many dentists made their own hand instruments.  Early hand instruments were grasped in the palm of the hand.
  4. 4.  Dr.G.V.Black- credited with the first acceptable nomenclature for and classification of hand instruments  Dr.Arthur.D.Black- developed many of the instruments and techniques  Dr.Charles E.Woodbury- first to modify blacks instrumentation.Designed 39 sets of hand instruments for class III cavity preparations and condensing points for gold foil restorations  Dr.Wedelstaedt- developed Wedelstaedt chisel now referred to as curved chisel  Dr.Waldon I Ferrier- developed a new set of instruments called ferrier set which were more refined and had uniform thickness on the cutting edge  Dr.George Hollenback- invented pneumatic condenser.
  5. 5.  Hand instruments are manufactured from two main materials: 1. Stainless Steel 2. Carbon Steel  Some instruments are made with carbide inserts to provide more durable cutting edge.
  6. 6.  Stainless steel 1. Chromium- 18% 2. Carbon-1% 3. Iron-81.4%  Advantages- 1. Chromium in the alloy Reduces corrosion tendency by depositing an oxide layer on the surface of the metal. 2. Remains bright under most conditions.  Disadvantages- 1. Maintaining the sharpness of the blade is a problem 2. Loses a keen edge during much use  Mainly used for working points and cement instruments.
  7. 7.  Carbon steel- 1. Carbon-1% 2. Manganeese-0.2% 3. Silicon-0.2% 4. Iron- 98.4-98.6%  Advantages-  Harder than stainless steel  Disadvantages-  When unprotected, it will corrode.
  8. 8.  Stellite 1. Cobalt - 65- 90% 2. Chromium - 35% 3. Trace amounts: tungsten, molybdenum , iron  Advantages: 1. High resistance to acid 2. Hardness  Use-  Manufacture of mixing and inserting instruments
  9. 9.  G.V.BLACK- first acceptable nomenclature for and classification of hand instruments 1 ) CUTTING A. Excavators  ordinary hatchet  hoes  angle formers  spoons B. Chisels  straight  curved  bin angle  enamel hatchet  GMT C. Other cutting insruments:  Knives,  carvers  files,  Scalers 2 ) NON-CUTTING: Amalgam condensors Mirrors Explorers Probes
  10. 10.  HAND HELD A ) Examining mouth & teeth:  Mouth mirrors  Probes B ) Scaling- scalers C) Cutting teeth & removing caries -  excavators chisels,  hatchets, hoes D ) Placing & condensing restorative materials:  plastic instruments  condensors/  pluggers E ) Carving & finishing o ROTARY o AUXILLARY a. Fibre optic lights for illumination b. Lights used for polymerization c. Ultrasonic scalers
  11. 11. 1. Cutting instruments  Hand  Hatchets  Chisel  Hoe  Excavator  Others  ROTARY  Burs  Stones  Disk  Others 2. Condensing instruments Pluggers  Hand  Mechanical 3. Plastic instruments  Spatulas  Burnishers  Carvers  Packing instruments.
  12. 12. 4. Finishing & polishing instruments:  Hand  Orange wood sticks  Polishing Points  Finishing strips  Rotary  Finishing burs  Mounted brushes  Mounted stones  Rubber cups  Impregnated disk & wheels. 5. Isolation instruments  Rubber dam frame Clamps Forceps Punch  Saliva ejectors  Cotton roll holders  Evacuating tips & equipment 6. Miscellaneous:  Mouth mirrors  Probes  Scissors  Pliers  Others.
  13. 13. 1. Exploring or diagnostic instruments:  Mouth mirror  Explorer or Probe  Straight proble  Right angled probe  Arch shaped ( shepherd’s hook )  Interproximal ( back action)  Tweezers  Seperators  Cheek retractors  Air syringe 2. Isolating instruments:  Cotton roll holder  Rubber dam  Saliva ejector  Suction apparatus. 3. Hand cutting instruments  Excavators  Spoon  Cleoid  Discoid  Hatchet  Hoe  Chisels  Straight  Mono angle  Bin angle  Triple angle  Modified chisel  Wedelsteadt  Enamel hatchet  Gingival marginal trimmer  Angle former.
  14. 14. 4 ) Restoring instrument:  Mixing instruments:  Cement spatula  Agate spatula  Plastic carrying/ filling instrument  Packing instruments:  Amalgam carrier.  Condensing instrument:  Round condenser  Parallelogram  Burnishing instrument:  Ball shaped  Egg shaped  Conical shaped  Carving instruments:  Hollenbeck carver  Diamond carver  Ward’s carver 5 ) Miscellaneous instruments:  Matrices  Retainers  Scissors
  15. 15.  Handle/Shaft  Shank  Blade with cutting edge or nib with face.
  16. 16.  Straight and is usually without variations in size. It maybe serrated to increase friction for hand gripping.  Length-5.5 inches  Diameter-5.5 mm  Available in various sizes and shapes- small, medium, large diameter  Hexagonal or octagonal  Smooth, serrated or knurled  Knurled to facilitate control and to increase the friction for hand gripping  Instrument formula incorporated on it  Manufacturing kit number incorporated on it  Handle is either continuous with shank or separable.
  17. 17.  Connects the shaft with the blade or working point or nib.  It usually extends from its connection with the shaft to where the blade begins.  It is here where any angulation of the instrument can be placed.  Smooth, round, tapered and contrangled  Have one or more bends to avoid the instrument from having tendency to twist in use where force is applied  G.V.Black classified instruments depending on the number of angles in the shank as- 1. Mon angle 2. Bin angle 3. Triple angle 4. Quaternary angle
  18. 18.  Balance is accomplished by designing the angles of the shank so that the cutting edge of the blade lies within the projected diameter of the handle and nearly coincides with the projected axis of the handle .  For optimal antirotational design, the blade edge must not be off axis by more than 1 to 2 mm.  All dental instruments and equipment need to satisfy this principle of balance.
  19. 19.  Functional end of the instrument bearing the cutting edge.  It begins at the angle if one angle is present at the shank, or at the last angle, if more than one angle is present in the shank or at the point which terminates in the shank.  The blade ends in the cutting edge.  For non cutting instruments the part corresponding to the blade is termed as “nib”  Working surface or the end of the nib is known as the “face”
  20. 20.  It is the working part of the instrument. It is usually in the form of a bevel in different shapes.  Beveled- 1. single beveled 2. Bibeveled 3. Triple beveled 4. Circumferentially beveled  Regular bevel - distal to shaft  Reverse bevel- mesial to shaft eg:- binangle chisel
  21. 21.  Blade angle- defined as the angle between the long axis of the blade and the long axis of the shaft.  Cutting edge angle- defined as an angle between the margins of the cutting edge and the long axis of the shaft.  Some instruments have a blade on both ends of the handle and are known as double-ended instruments.
  22. 22.  Enamel and dentin are difficult substances to cut and require the generation of substantial forces at the tip of the instrument.  Hand instruments must be balanced and sharp.  Balance allows for the concentration of force onto the blade without causing rotation of the instrument in the grasp.  Sharpness concentrates the force onto a small area of the edge, producing a high stress
  23. 23. 1. Order- denotes the purpose of the instrument. Eg:- excavator, scaler 2. Sub order- denotes the position or manner of use of the instrument Eg:- push, pull 3. Class- form of the blade. Eg:- hatchet, chisel 4. Angle/ Subclass- denotes the number of angles in the shank/ shape of the shank Eg:- 1- mon angle, 2- bin angle  NAMING GOES FROM 4-1 Eg:- ‘bin angle’ ‘hatchet’ ‘push’ ‘excavator’
  24. 24.  To describe the parts of an instrument accurately.  3 unit instrument formula:  First unit : Width of the blade in 1/10 of a mm.  Second unit : length of the blade in mm  Third unit : Angle the blade forms with the axis of handle in centigrade.
  25. 25.  4 Unit instrument formula:cutting edge of the instrument is at an angle other than right angle to the blade.  First unit : Width of the blade in 1/10 of a mm.  Second unit : Angle the cutting edge forms with the axis of the handle in centigrade.  Third unit : length of the blade in mm  Fourth unit : Angle the blade forms with the axis of handle in centigrade.  Eg- GMT and Angle former.
  26. 26. • Most hand instruments- single bevel, end of blade forms primary cutting edge • Two additional edges- secondary cutting edges , extend from primary edge for length of blade • Bi beveled instruments- e g:- ordinary hatchets- 2 bevels that form cutting edge.
  27. 27. • Spoon excavators and gingival margin trimmers : scraping or lateral cutting motion. • Enamel hatchets- planing or direct cutting motion, as well as a lateral cutting motion. • For such single-beveled designs, the instruments must be made in pairs, having the bevels on opposite sides of the blade.
  28. 28.  Such instruments are designated as right or left beveled and are indicated by appending the letter R or L to the instrument formula.  To determine whether the instrument has a right or left bevel, the primary cutting edge is held down and pointing away, and if the bevel appears on the right side of the blade, it is the right instrument of the pair.  This instrument, when used in a scraping motion, ismoved from right to left. The opposite holds true for the left instrument of the pair.
  29. 29.  Most instruments are available with blades and shanks on both ends of the handle- double-ended.  In many cases the right instrument of the pair is on one end of the handle, and the left instrument is on the other end.  Sometimes similar blades of different widths are placed on double-ended instruments.  Single-ended instruments may be safer to use, but double-ended instruments are more efficient because they reduce instrument exchange.
  30. 30.  Instruments having the cutting edge perpendicular to the axis of the handle such as bin-angle chisels, those with a slight blade curvature (Wedelstaedt chisels), and hoes are single-beveled and not designated as rights or lefts, but as having a mesial bevel or a distal bevel.  If when one observes the inside of the blade curvature (or the inside of the angle at the junction of the blade and shank) the primary bevel is not visible, the instrument has a distal bevel . Conversely, if the primary bevel can be seen (from the same viewpoint) the instrument has a mesial or reverse bevel.
  31. 31. • Hand instruments- made of either stainless steel, carbon steel or blades of tungsten carbide soldered to a steel handle. • Carbon steel (better cutting edge)> stainless steel, however, carbide blades are most efficient in cutting, even though they are brittle.  Main principle- of cutting with hand instruments- to concentrate force on a very thin cross section of the instrument at the cutting edge. • Thinner the cross section, more the pressure that is Concentrated, more efficient the instrument will be.
  32. 32.  A direct cutting instrument is one in which the force is applied in the same plane as that of the blade & handle -> single planed instrument ( used in direct and lateral cutting )  Lateral cutting instruments are those in which the force is applied at a right angle to the plane of the blade and handle, usually have curved blade -> double planed instrument (used only in lateral cutting).
  33. 33. • In order to gain access, many instruments have shank, bent at one or more points to angle the blade relative to the handle. • Depends on - length of blade - degree of angulation in shank • The working point is moved out of line with the angle of handle. • If this occurs more than 3 mm, from the handle axis, the instrument will be out of balance in lateral cutting motion and force will be required to keep the instrument from rotating in one hand. • To solve this problem, modern instruments are designed to have one or more angles in the shank placing the working point within 3mm from the axis of the handle this known as CONTRANGLING
  34. 34. • Short blade and small blade angle requires only bin angle contrangling,while longer blades and greater blade angles require triple contrangling. • Length of the blade required is determined by depth of the cavity and the blade angle is determined by the accessibility requirements. • Hence, greater angles are required for more posterior teeth and incisal portions of proximal cavities in anterior teeth. • So, in addition to balance, contrangling will provide better access and a clearer view for the field of operation.
  35. 35.  Chisels:- - Cutting edge of the instrument is at a right angle to the axis of the instrument. - Used for planing or cleaving enamel. 1) Straight chisel:- - No bend in shank - Single beveled/ Triple beveled. - Minimal accessibility. - Used with push stroke or lateral scraping action.
  36. 36. 2) Mono angle chisel:- - Blade is shorter as compared to straight chisel. - Single angle in the shank to enhance the convenience form. - Used with push stroke or lateral scraping action. Hoe:- Difference between mono angle chisel and hoe:- - If the angle of the blade is less than 12.5 centigrade, it is mono angle chisel and if it is more than 12.5 centigrade, it is hoe. - Used with pull stroke. Use:- To define line and point angles. - Class III and V preparations for direct filling gold restorations.
  37. 37. 3) Binangle chisel:- - Two angles in the shank. - Used to cleave or split undermined enamel. - Reverse bevel instrument. 4) Triple angle chisel:- - Used to flatten the pulpal floor.
  38. 38. Hatchet:- - Cutting edge of the instrument is parallel to the axis of the instrument. - Cutting edge of the instrument is at right angle to the axis of blade. - Mono angled - Length of blade is very small - Bibevelled - Single ended - Used with push stroke Use:- - Preparing retentive areas on anterior teeth. - Sharpening internal line angles in DFG restorations.
  39. 39.  Enamel hatchet:- - Cutting edge of the instrument is parallel to the axis of the instrument. - Cutting edge of the instrument is at right angle to the axis of blade. - Binangle hatchet - Monobeveled - Single plane instrument - Paired instrument - Bevel on right side – Right side instrument - Bevel on left side – Left side instrument
  40. 40.  Used with push stroke (planing or direct cutting motion as well as lateral cutting motion).  Used for smoothening buccal and lingual walls of proximal box.  Used for breaking enamel of proximal box.  Used for smoothening gingival seat (lateral scraping motion).
  41. 41.  Gingival marginal trimmer:- - Cutting edge of the instrument is parallel to the axis of the instrument. - Cutting edge of the instrument is at an angle other than a right angle to the blade. - Modified hatchet - Binangle instrument - Monobeveled - Double plane instrument (better lateral scraping efficiency/ scooping effect).
  42. 42.  2 pairs: 1. MESIAL PAIR (RIGHT AND LEFT) 2. DISTAL PAIR (RIGHT AND LEFT) - 4 unit instrument formula - Mesial pair – 10- 80- 6- 8 ( < 80 ) - Distal pair – 10- 95- 6- 8 ( > 95) - Used to give gingival cavo surface bevel. - Used for rounding or bevelling axio- pulpal line angle.
  43. 43.  Angle former:- - The instruments are made by grinding the bevel at an angle of 80 degree with the shaft, thus forming an acute angle with the long axis of the blade. This creates a pointed and a linear cutting edge. - 4 unit instrument formula - Paired instrument- right and left - Ring on the shank – right side - 3 cutting edges (blade is bevelled on the sides as well as the end). Use:-To exaggerate line and point angles in DFG restorations to establish the retention form.
  44. 44.  Wedelstaedt chisel:- - Shank and blade are curved. - Bevelled on one side of blade only. - If bevel is on the side towards the curvature of the shank:- Mesially bevelled. - Away from the curvature of the shank:- Distally bevelled - Used for cleaving undermined enamel and for shaping walls. - Single instrument with 3 cutting motion:- vertical, right and left.
  45. 45. Off- angle hatchet:- - Instruments in which blade is rotated by 45 degrees from the plane of the long axis of the instrument. - Used to create and shape specific angulations for cavity walls, especially in areas of difficult access. Triangular chisel:- - Blade is triangular in shape with the base away from the shaft. - Has a terminal cutting edge like straight chisel.
  46. 46.  Spoon excavator:- - Modified hatchet. - Double ended instrument. - Bin angle/ Triple-angle instrument. - Paired (right and left). - Double plane instrument. - Circumferentially beveled. - Cutting edge either circular (discoid) or claw like (cleoid). Use:- Spooning or scooping of softened carious material. - Carving amalgam or direct wax patterns.
  47. 47. Other instruments:-  Knives:- Finishing knives, Amalgam knives, or Gold knives. Used for trimming excess restorative material on the gingival, facial or lingual margins of a proximal restoration or trimming and contouring the surface of class V restorations.  Files:- Used for smoothening of overhanging restorations (amalgam and gold).
  48. 48.  Diagnostic instruments:- 1 ) Mouth mirror:- - Is an instrument having a mirror head top and a detachable handle. - Also called as odontoscope. Types:- A) Front surface:- - Is one where the reflecting surface is on the top of the glass piece. - Gives better visibility. - Absence of intervening glass. - No double image. - Mercury coating on top is liker to be lost due to scratching. B) Rear surface (regular) - Reflecting surface is on the back surface of the mirror lens. - Surface is less easily scratched. - Produces a double or ghost image.
  49. 49. C) Magnifying mirror (concave):- - Reflecting surface is on the front surface of the mirror lens. - Produces magnified but slightly distorted image. - Concave surface mirror magnifies the image, requiring the clinician to learn to accommodate movement. - Concave mirror rarely used except for seeing enlarged internal details of the cavity. - The instrument movements are smaller than the clinician visual perception. - For endodontic surgeries. D) Disposable mirror:- - Made of plastic.
  50. 50.  Uses:- Indirect illumination. - Mouth mirror could be held at an angle to reflect the light onto the working area. - Retraction : Mirror head used to retract the patient’s lip or cheek or tongue so that the clinician is able to view tooth surfaces. - Protects from injury. - Indirect vision. - Guard. - Trans illumination. Different sizes of mouth mirror:- No. 2 (5/8 inch) No. 4 (7/8 inch) No. 5 (15/16 inch)
  51. 51. 2 ) Probe:- - Sharp pointed hand instrument used to explore teeth and restoration surfaces in order to detect caries, overhanging edges and other defects. - May be single-ended or double-ended. Uses:- - For detecting and assessing carious lesion in the tooth - Detecting demineralized dentin. - Releasing debris from the tooth. - Removing slight excess fill up around cavo-surface margins - Identifying hypersensitive areas in the tooth - Assessing marginal fit of the restoration
  52. 52.  Types:- - Straight. - Interproximal probe - No.2 cow horn (arch explorer) - No.17 back action - No. 23 shepherd’s hook - Orban –type explorer
  53. 53. 3) Periodontal probe:- - Detect and measure the depth of periodontal pockets. - In operative dentistry:- Used to determine the dimensions of instruments and of various features of preparations or restorations.
  54. 54. 4) Forceps:- - Tweezers/ Cotton forceps - Hemostats - Articulating paper forceps Tweezers:- - Hand instrument with two narrow and pointed, straight or curved beaks used to grasp small objects. - Consist of:- 2 long arms. Locking device. 2 long arms joined at one end. Other end remains apart.
  55. 55.  Uses: - Useful in carrying things to and from mouth. - Carrying cotton rolls, cotton pledges, sponge pellets to and around the cavity. - Carrying saliva soaked cotton rolls from the oral cavity to the waste disposal unit. Locking tweezer - Has a locking device to maintain the beaks in a closed position until released. - This avoids the unnecessary anxiety of the operator at the possibility of slippage of whatever is carried by the tweezer.
  56. 56.  Mixing instruments:- Cement spatula Agate spatula Spatulas:- - Flat and wide nibs with blunt edges. - Straight Shank - Different sizes and different degrees of stiffness in their nibs to suit their various uses. - Made of Stainless steel. Plastic. - Doubles ended instrument. Blunt end – for manipulating impression materials. Sharp end - for mixing cements. - Used for manual mixing of cements supplied as powder and liquid.
  57. 57. 2) Plastic carrying/ filling instruments:- - It is an instrument used for carrying the mixed base cements which are in soft (plastic) stage or the restorative cement from a cement spatula to the cavity. - Usually one end is flat and other end is cylindrical. - Flat end is used for carrying the cement. - Cylindrical end is used for manipulating and positioning the cement. - Made of: Stainless steel Plastic - Also can be plated with teflon to minimize material adhesion.
  58. 58. 3) Packing instrument:- Amalgam carrier:- - Amalgam carrier is a stainless steel instrument used for carrying mixed amalgam to the cavity. - Use:- 1) Hollow tip of an amalgam carrier is inserted into the mixed amalgam to pack the carrier with amalgam. 2) It is then carried into the cavity and plunger is pressed injecting cylindrical pellets of amalgam.
  59. 59. 4) Condensing instruments: - To pack material into prepared cavity. - Types: A) Amalgam condenser - Hand - Mechanical – Vibratory and Impact B) Gold condenser - Hand - Mechanical. Hand condenser:- - Are double-ended instruments with the nibs (condensing tips) coming in different size and shapes. - Force varies inversely with the area of the face.
  60. 60. Nibs may be:- I) Of different shapes:- - Round - Elliptical - Diamond - Triangular - Parallelogram - Rectangular II) Sizes vary considerably; - Large round condenser - Small round condenser III) Depending on working end; (condenser face). - Serrated – For spherical amalgam - Non-serrated (smooth) – For admixed amalgam
  61. 61. 5) Burnishing instruments:- - Hand instrument with rounded edges used to polish or burnish the surface of metallic restorations by rubbing. - Burnishing is the process of rubbing, usually performed to make a surface shiny or lustrous. - Double-ended. - Nibs are : Spherical. Ball shaped. Egg shaped. Apple shaped. Beaver tail shaped. Conical. Hour glass Fish tail. Bullet shaped etc. › Nibs are smooth-faced. › Different angulations and curvature in their shank.
  62. 62.  Amalgam burnishers - Small ball burnisher. - Beaver tail or egg burnisher. - Anatomic burnisher. Other uses:- - Shape metal matrix bands so that they impart more desirable contours to restorations. - To “bend” cast gold near the margins to narrow the gap between the gold and the tooth (beaver tail).
  63. 63. 6) Carving instruments:- - Hand instrument with a blade or nib used to contour the surface of filling material in their plastic state, waxes, models and patterns. e.g.- Hollenback carver (Knife- edged- elongated bibeveled) - Diamond (Frahm’s) carver – Bibeveled cutting edge - Wards ‘C’ carver - Discoid- cleoid - Interproximal carver › Hollenback, Diamond and Wards - One blade is parallel to the long axis of the instrument and the other is perpendicular to the long axis of the instrument.
  64. 64.  Instrument grasps:- Definition:- These are the manners of holding the instruments which if not held properly it will result in loss of efficiency and accumulation of unnecessary strain on the operator. Adv:- Instrument can be held in different areas for maximum comforts of the operator. - Better operator efficiency. › Different grasps: 1) Pen grasp 2) Modified pen 3) Inverted pen 4) Palm and thumb 5) Modified palm and thumb
  65. 65.  Pen grasp:- - Instrument is held between thumb and first finger with middle finger below acting as a support. - Either the third or third and fourth fingers are placed on adjoining tooth as rest. - Position of middle finger is important – 1) For obtaining thrust 2) Preventing the instrument from slippage during manipulation. - It involves wrist movement. Adv:- - More flexibility of movement. - Less power. - Greatest versatility of movement. - More comfortable. - Limits application of pressure. Disadv:- Bracing is difficult because only the ring and little fingers are used.
  66. 66.  Modified pen grasp:- - Permits greatest delicacy of touch. - Pads of thumb, index and middle finger contact the instrument, while the tip of the ring finger (or tips of the ring and little fingers) is placed on a nearby tooth surface of the same arch as a rest. - The pad of the middle finger is placed near the “topside” of the instrument for good control and cutting pressure. - The fingers and the thumb engage the instrument as a grappling hook. - The base of the index finger and the tip of the middle finger reciprocate, with the thumb placed midway between them. - The palm of the hand generally faces away from the operator. - Involves forearm which turns inward (pronates) or outward (supinates).  Adv:- - More effective - Controlled power to the instrument.
  67. 67. Inverted pen grasp:- - The palm is rotated upwards with the pad of the thumb and index fingers close to each other but the middle finger is farther down the shank. - Used mostly for the tooth preparation utilizing the lingual approach on maxillary anterior teeth.
  68. 68.  Palm and thumb grasp:- - The handle of the instrument is held between the palm and four fingers firmly with the tip of the thumb acting like a rest. - Power grasp. Adv:- - More control and precision. - Limited movement. - Enhance bracing (a forward thrust with the arm of wrist can be controlled by the opposing action from the thumb, which is braced against the teeth). - Gives the possibility of applying pressure precisely. Example: holding a hand piece for cutting incisal retention for Class III preparation on maxillary incisor.
  69. 69.  Modified palm and thumb grasp:- - The handle of the instrument is held by all four fingers whose pads press the handles against the distal area of the palm, as well as the pad and first joint of the thumb. - The rest is tip of thumb on tooth being prepared or adjacent teeth. Adv:- - Most valuable aid in operating inside and outside the mouth. - Allows greater ease of instrument movement. - More control against slippage during thrust stroke compared to palm and thumb grasp. - Grasping the handle under the first joint of the ring and little finger acts as a stabilizer. - More delicate manipulation.
  70. 70.  Rest:- - Is to stabilize the hand and instrument by providing a firm fulcrum as movement are made to activate the instrument. - Is required for steady hand during operative procedures. Adv:- - A good finger rest prevents injury and laceration of the gingiva and surrounding tissues. The ring finger is preferred as finger rest.
  71. 71. - When modified pen and inverted pen grasps are used, rests are established by placing the ring or ring and little fingers on a tooth (or teeth) of the same arch and as close to the operating site as possible (more reliable). - In palm and thumb grasp, rests are created by placing the tip of the thumb on tooth being operated on, or on an adjacent tooth, or on a convenient area of the same arch. - When it is impossible to establish a rest on tooth structure, soft tissue must be used (not reliable).
  72. 72. Finger rests classified - Intra oral finger rest - Extra oral fulcrum Intra oral finger rest:- 1. Conventional : Finger rest is established on the tooth surfaces immediately adjacent to the working area.
  73. 73. 2. Cross- arch : Finger rest is established on the tooth surfaces on the other side of the same arch.
  74. 74. 3. Opposite-arch : Finger rest is established on tooth surfaces on the opposite arch (e. g:- mandibular arch finger rest for instrumentation on the maxillary arch).
  75. 75. 4. Finger – on – finger : Finger rest is established on the index finger or thumb of the non operating hand.
  76. 76.  Extra oral fulcrums : Two most commonly used- (1) Palm-up Palm-up fulcrum is established by resting the backs of the middle and ring fingers on the skin overlying the lateral aspect of the mandible on the right side of the face.
  77. 77. (2) Palm-down Palm- down fulcrum is established by resting the front surfaces of the middle and ring fingers on the skin overlying lateral aspect of the mandible on the left side of the face.
  78. 78.  Guards - Hand instruments or other items such as interproximal wedges used to protect soft tissue from contact with sharp cutting or abrasive instruments. - May be mouth mirror, check retractor, lip retractor or even the operator’s own finger of the other hand. - This should be placed in the direction of movement of instrument. - Advantages: › Avoid accident slippage of instrument. › Prevent injuries.
  79. 79.  Sharpening is done by reducing the thickness of the metal at the cutting edge, while maintaining the angle and shape of the bevel. DETECTION OF A DULL CUTTING INSTRUMENT 1) Visibility of a reflection off the cutting edge. Sharp edge – not reflect light Dull edge – reflect light/ presence of a “glint”. 2) Obvious irregularities in the cutting edge 3) Won’t shave thumb nail. 4) Won’t cut tooth structure.
  80. 80.  Instruments with dull cutting edge causes:- - More pain - Prolong operative time - Less controllable - Reduce quality and precision in tooth preparation  Goal of sharpening instrument - Maintain and restore a knife like cutting edge - Preserve the shape and proportional dimensions of the instrument - Increase work efficiency of the instrument
  81. 81.  VARIOUS TYPES OF SHARPENING EQUIPMENTS 1) STATIONARY STONES/ OIL STONES : - Arkansas stone - Silicon carbide - Aluminium oxide - Diamond 2) MECHANICAL SHARPENERS - Rotary (Hand piece) - Honing machine
  82. 82.  Stationary stones/ oil stones : - Available in variety of grits, shapes and materials. Grit Coarse (Initial reshaping of badly damaged instrument) Medium Fine (Final sharpening) Shapes Flat – sharpening instruments with straight cutting edges. Grooved – curved edges. Cylindrical – concave edges. Tapered – using portion of the stone with a curvature matching that of the instrument.
  83. 83.  Arkansas stone:- - Naturally occurring mineral containing micro crystalline quartz. - Used in fine sharpening stones. - Semi transparent, white or grey in colour. - Hard enough to sharpen steel but not carbide instruments. - Should be lubricated with machine oil which helps in fineness of sharpening and prevents clogging avoids creation of heat.
  84. 84.  Silicon carbide:- - Widely used as an industrial abrasive. - Used for grinding wheels, sand papers and sharpening stones. - Hard enough to cut steel but not to sharpen carbide instruments. - Available in medium and coarse grits. - Black or greenish black in color and require lubrication with oil.  Aluminium oxide:- - Used to manufacture sharpening stones. - Available in coarse, medium and fine grits.
  85. 85.  Diamond:- - Hardest available abrasive. - Effective for cutting and shaping hard materials. - Used in sharpening carbide and steel instruments. - Diamond hones are small blocks of metal with fine diamond particles impregnated in the surface.
  86. 86. Mechanical sharpeners:- 1) Honing machine:- - This instrument moves a hone in a reciprocating motion at a slow speed, while the instrument is held at the appropriate angulation and supported by a rest. - This type of sharpener is very versatile, and can fill almost all instrument sharpening needs. 2) Hand piece sharpening stones:- - Mounted silicon carbide and aluminium oxide stones for use with straight and angle hand piece are available in various sizes and shapes. - Used to sharpen instruments with curved blades.
  87. 87.  PRINCIPLES OF SHARPENING - Sharpen the instrument only after they are cleaned and sterilized. - Establish the proper bevel angle (450) and desired angle of the cutting edge to the blade before placing the instrument. Maintain these angles while sharpening. - Use light strokes or pressure against the stone to minimize frictional heat. - Use a rest or guard. - Remove as little metal from the blade as possible. - Lightly hone the unbevelled side of the blade after sharpening, to remove the fine bur that may be created. - After sharpening, resterilize. - keep the sharpening stones clean and free of metal cuttings.
  88. 88.  Sharpness test:- - Tested by lightly resting the cutting edge on a hard plastic surface, such as the handle of a plastic mouth mirror or an evacuator tip. - A dull blade will slide across the plastic; a sharp blade will cut into the surface, stopping movement. - A specially made, sterilizable, sharpness- testing stick is also available (Dalron Test stick, Thompson Dental).
  89. 89. Advantages of sharp instrument: - Few strokes - Less effort. - Increase tactile sensitivity and operator control. - Prevent gouging of the root surfaces.
  90. 90.  STERILIZATION AND DISINFECTION Sterilization: Destruction of both the vegetative form and bacterial spores. Disinfection: Destruction of only vegetative form. Procedures involved in instrument processing: 1) Presoaking 2) Cleaning 3) Corrosion control and lubrication 4) Packaging 5) Sterilization 6) Sterilization monitoring 7) Drying or cooling 8) Storage 9) Distribution 10) Sharpening
  91. 91.  SUMMARY AND CONCLUSION The removal and shaping of tooth structure are essential aspects of restorative dentistry. Modern high speed equipments has eliminated the need for many hand instruments for tooth preparation, but hand cutting instruments are still important for finishing many tooth preparations and thus hand cutting instruments remain an essential part of the armamentarium for quality restorative dentistry.
  92. 92.  REFERENCES: - Sturdevant’s art and science of operative dentistry (4th Edition) - Principles and Practice of operative Dentistry – By Gerald T. Charbenau (2nd edition) - Operator dentistry of modern theory and practice – M.K. Marzouk (1st edition) - Pickard’s manual of operative dentistry (5th Edition)

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