HAND INSTRUMENTS, classification, types and uses

hand instruments classification , types and uses , advantages , disadvantages

1. Presented by – Dr. Anurag Jain HAND CUTTING INSTRUMENTS IN OPERATIVE DENTISTRY

2. Contents • Introduction, history & 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 • Whats new?

3. 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.

4. HAND INSTRUMENTS IN OPERATIVE DENTISTRY

5. EARLY HAND OPERATED INSTRUMENTS - large, heavy handles and inferior metal alloys - cumbersome, awkward to use, ineffective - no uniformity of manufacture or nomenclature

6. 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.George Hollenback - invented pneumatic condenser.

7. Acc to Charbeneau - Principles & Practice of Operative Dentistry Six categories- according to use- 1. Cutting instruments hand- hatchets, chisels, hoes, excavators, others -rotary- burs, stones, disks, others 2. Condensing instruments pluggers - hand & mechanical 3. Plastic instruments spatulas, carvers, burnishers , packing instruments 4. Finishing & polishing instruments hand- orange wood sticks, polishing points, finishing strips rotary- finishing burs, mounted brushes, mounted stones, rubber cups, impregnated disks & wheels

8. 5. Isolation instruments rubber dam frame, clamps, forceps, punch saliva ejectors, cotton roll holders, evacuating tips & equipment 6. Miscellaneous mouth mirrors, explorers, probes

9. Exploring instruments- a. for drying- air syringe, tweezers (cotton pliers) b . for illuminating- source of light – overhead fixture - intra oral light - mirrors- to reflect light

10. c. For retracting soft tissues- hand mirrors, tongue depressors, cheek retractors, plastic instruments (restorative blunt headed instruments) d. Probe the potential lesions- explorers- straight, right angled, arch explorers, inter proximal e. Seperators

11. 2. To remove tooth structure- Hand cutting instruments a. excavators- hatchet, hoe, spoon, discoid, cleoid b. chisels- straight, mon angled, bin angled, triple angled c. special chisels- enamel hatchet, GMT, angle former, Wedelstaedt , off-set, triangular, hoe chisel Rotary cutting/ rotary abrasives a. speed- ultra low, low, medium, high, ultra high b. pressure c. heat d. vibration

12. 3. Ultrasonic instruments 4. Restorating instruments - mixing, plastic, condensing, burnishing, carvers - files, knives - finishing & polishing- finishing burs, papercarried abrasives, brushes, rubber, cloth, felt

13. Nomenclature, formula, design

14. Parts of hand cutting instruments • Shaft- used as a handle, 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 seperable blade (a) shank (b) handle (c)

15. Shank- 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- -Mon angle -Bin angle -Triple angle -Quaternary angle

16. Blade- is the part 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.

17. • Cutting edge- is the working part of the instrument. It is usually in the form of a bevel in different shapes. • Beveled- - single beveled - Bibeveled - Triple beveled - Circumferentially beveled • Regular bevel- - distal to shaft • Reverse bevel- - mesial to shaft eg:- binangle chisel

18. Blade angle- defined as the angle between the long axis of the blade and the long axis of the shaft. * Non cutting instruments- part corresponding to blade- is called NIB, end of the nib or working surface is called FACE 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.

19. • 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

20. • 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.

21. Instrument nomenclature ( G.V.Black ) 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’ (‘push’ can be omitted)

22. Instrument formula • To describe the parts of an instrument accurately. • 3 measurement, all expressed in metric system • Carved on one side of the instruments shaft, in the following sequence. 1. Width of the blade in 1/10 of a mm. 2. Primary cutting edge angle- Measured from line parallel to Long axis of handle in clockwise centigrade in percent of 3600 eg:- 85= 85% x 360= 3060 • If edge is perpendicular to blade, this number is omitted

23. 3. Blade length- in mm 4. Blade angle- relative to long axis of handle in clockwise centigrade * In some instances, an additional number on the handle- manufacturer’s identification number, to assist the manufacturer in cataloging and ordering

24. Cutting instrument bevels • Most hand instruments- single bevel, end of bladeforms primary cutting edge • Two additional edges- secondary cutting edges, extend from primary edge for length of blade • Bibeveled instruments- eg :- ordinary hatchets- 2 bevels that form cutting edge

25. • Spoon excavators and gingival margin trimmersscraping 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.

26. • 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, is moved from right to left. The opposite holds true for the left instrument of the pair.

27. • 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

28. • 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.

29. 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.

30. Instrument design • 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  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.

31. Direct cutting & lateral cutting instruments • 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 • 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

32. Contra angling 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 CONTRANGLING

33. • Short blade and small blade angle requires only binangle 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.

34. RIGHT AND LEFT INSTRUMENTS • Direct cutting instruments are made either right or left by placing a bend on one side of the blade. • If the instrument is held with the cutting edge down and pointing away from the operator, and the bevel is on the right side- right instrument, if bevel on the left- left instrument • For lateral cutting- move instrument from bevelled side to non- bevelled side of blade in lateral scrapping action • Lateral cutting instruments are made left and right by having curve or angle, which is at a right angle to the principal plane (shaft plane), either on right or left.

35. Single bevelled instruments Single planed intruments with cutting edge at right angle to the long axis of the shaft. • If bevelled on side away from the shaft distally bevelled . • If bevelled on side of the blade towards the shaft mesially bevelled • If these instruments have no angle in shank, or an angle of 12 o or less used in ‘push & scrapping motion’ • If angle in shank>12 o , used in ‘pull’ (distally bevelled ) & ‘push’ ( mesially bevelled ) motion.

36. Bi- bevelled instruments • Hatchets and straight chisels • Cut by pushing them in the direction of long axis of Blade Triple bevelled instruments • Bevelling in the blade laterally together with the end= form three cutting edge.

37. Cutting instrument application • Used to cut hard or soft tissues of the mouth EXCAVATORS- 1. Ordinary hatchet excavator- cutting edge of blade directed in the same plane as that of the long axis of the handle and is bibevelled . Used primarily on anterior teeth for preparing retentive areas and sharpening internal line angles, particularly in preparations for direct gold restorations.

38. 2. Hoe excavator- primary cutting edge of the blade perpendicular to the axis of the handle. Used for planing tooth preparation walls and forming line angles. Commonly used in class III and V preparations for direct gold restorations.

39. 3. Angle former- used for sharpening line angles and creating retentive features in dentin in preparation for gold restorations. Used in placing bevel on enamel margins. Mon-angled and has primary cutting edge at an angle to the blade. 4. Spoon excavators- used for removing caries and carving amalgam or direct wax patterns. Blades are slightly curved and cutting edges are either circular (discoid) or claw like ( cleoid ). Shanks are bin-angled or triple-angled to facilitate accessibility.

40. CHISELS Intended primarily for cutting enamel. 1. Straight chisel- • Straight shank and blade with bevel on only one side. • Primary edge perpendicular to the axis of the handle. • Shank and blade of chisel maybe slightly curved ( Wedelstaedt design) or bin-angled. • Primary cutting edges in a plane perpendicular to the axis of the handle and may have either a distal bevel or mesial bevel (reverse).

41. 2. Enamel hatchet- • Blade larger, heavier and beveled on only one side, rather than the ordinary hatchet • Cutting edge in a plane parallel with the axis of the handle • Used for cutting enamel and comes as right or left types for use on opposite sides of the preparation

42. 3. Gingival margin trimmer • To produce proper bevel on gingival enamel margins of proximo occlusal preparations. • Blade curved and primary cutting edge is at an angle • Right and left types- can be mesial or distal pairs • Second number in the formula- • 90-100- pair used on the distal gingival margin • 85-75- pair used to bevel the mesial margin • 100 & 75 pairs- for inlay/ onlay preparations with steep gingival bevels • 90 & 85 pairs- for amalgam preparations with gingival enamel bevels that decline gingivally only slightly

43. • The pair with the end of the cutting edge farthest from the shaft forming an acute angle is termed distal and is used to bevel a distal gingival margin or accentuate a mesial axiogingival angle. • The pair with the acute angle of the cutting edge closest to the shaft is called mesial and is used to bevel a mesial gingival margin or accentuate a distal axiogingival angle.

44. Hand instrument techniques Modified pen grasp- • Permits the greatest delicacy of touch • Similar to holding a pen, not identical • Pads of thumb, index and middle finger contact instrument, while tip of the ring finger and/or little finger is placed on a nearby tooth of the same arch as REST • Palm of the hand, facing away from operator

45. Inverted pen grasp- • Hand rotated so that palm faces more toward the operator • Used mostly for tooth preparations utilizing lingual approach on anterior teeth

46. Palm and thumb grasp- • Handle placed in the palm of the hand and grasped by all the fingers, while thumb is free of the instrument and rest provided by tip of thumb on nearby tooth of same arch or on a firm, stable structure

47. Modified palm and thumb grasp- • Used when its feasible to rest the thumb on the tooth being prepared or the adjacent tooth • Used universally • Used in areas of maxillary arch and best adopted when dentist is operating from rear chair positions

48. RESTS – • In modified pen grasp and inverted pen grasp, rests are established by placing ring or ring and little fingers on tooth of the same arch and as close to operating site as possible • Closer the rest- more reliable No rest One finger rest Two finger rest

49. Finger rest classified • Intra oral finger rest • Extra oral fulcrum Intra oral finger rest- 1. Conventional- finger rest is established on the tooth surface immediately adjacent to the working area 2. Cross-arch- finger rest is established on the tooth surfaces on the other side of the same arch 3. Opposite-arch- finger rest is established on tooth srfaces on the opposite arch ( Eg :- mandibular arch finger rest for instrumentation on maxillary arch) 4. Finger-on- finger- finger rest is established on the index finger or thumb of the non operating hand.

50. Extra oral fulcrums Two most commonly used- 1. Palm up 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 2. Palm down 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

51. Sharpening hand instruments • Dull cutting edges cause more pain, prolong operating time, less controllable, reduce quality and precision in tooth preparation • Resharpening requires little time and is very rewarding • Sharpening equipment- stationary sharpening stones - mechanical sharpeners - handpiece sharpening stones

52. Stationary sharpening stones • Block or stick of abrasive material - Stone • Oilstones- stationary stones, a coating of oil is given to aid in sharpening process • Oilstones - coarse grit - medium grit - fine grit

53. Coarse and medium grit stones- • Initial reshaping of a badly damaged instrument or for sharpening other dental equipment such as bench knives. • Coarser used as little as needed for reshaping and then final sharpening done with a fine stone. Fine grit stones- • Sharpening dental instruments to be used for tooth preparation

54. Stationary stones – - flat- sharpening instruments with straight cutting edges - grooved - cylindric - concave edges - tapered- permit using a portion of stone with curvature matching that of instrument Sharpening stones- made of – natural or synthetic

55. Four types of materials most commonly used- 1. Arkansas stone- - naturally occurring containing microcrystalline quartz. - Semitranslucent , white or gray color - Hard enough to sharpen steel, but not carbide instruments - Available in hard and soft varieties - Should be lubricated with light machine oil before use - Should be covered in thin film of oil when stored

56. 2. Silicon carbide ( SiC )- - Industrial abrasive - Grinding wheels, sand papers - Hard enough to cut steel, but not hard enough to sharpen carbide instruments - Available- coarse and medium - Moderately porous, require lubrication with a light oil to prevent clogging 3. Aluminium oxide- - Being increasingly used - Coarse & medium- speckled tan /bromide color - Fine- white, less porous, less lubrication

57. Diamond- - Hardest abrasive - Most effective - Capable of sharpening carbide and steel instruments Diamond hones- - Small blocks of metal with fine diamond particles impregnated in surface, held in place by electroplated layer of corrosion- resistant metal - Non porous, but lubrication extends life - Cleaved with mild detergent & medium bristle brush

58. Mechanical sharpeners- • Hand sharpening decreased due to more use of high speed rotary cutting instruments • Rx honing machine- example of mechanical sharpener • Move a hone in a reciprocating manner at a slow speed, while instrument is held at the appropriate angulation and supported by a rest.

59. Principles of sharpening • Sharpen instruments only after they have been cleaned and sterilized • Establish proper bevel (450) and the desired angle of cutting edge to the blade before placing the instrument against the stone, and maintain these angles while sharpening. • Use a light stroke or pressure against the stone to minimize frictional heat • Use rest or guide whenever possible • Remove as little metal from blade as possible • Lightly hone the unbeveled side of the blade after sharpening, to remove the fine bur that may be created. • After sharpening, resterilize the instruments along with other items on the instrument tray setup • Keep sharpening stones clean and free of metal cuttings

60. MECHANICAL TECHNIQUES • Blade is placed against the steady rest and proper angle of the cutting edge of the blade is established before starting the motor • Light pressure of instrument against reciprocating hone is maintained with a firm grasp on instrument • A trace of metal debris on the face of a flat hone along the length of the cutting edge is an indication that the entire cutting edge is contacting the hone. • Quick method • Handpiece stones used for instruments with curved blades.

61. STATIONARY STONE TECHNIQUE • Stationary sharpening stone- atleast 2 inches wide X 5 inches long • Should be medium grit • Thin film of oil lubricant placed on working surface • 45 degree angle of bevel and cutting edge should be used to the stone

62. Fundamental rules in using stationary stones • Lay stone on flat surface and do not tilt the stone while sharpening • Grasp the instrument firmly, usually with a modified pen grasp, so it will not rotate or change angles while being sharpened • To ensure stability during sharpening strokes, use the ring and little fingers as a rest and guide along a flat surface or along the stone. This prevents rolling or dipping of the instrument, which results in a distorted and uneven bevel.

63. • Use a light stroke to prevent the creation of heat and the scratching of the stone. • Use different areas of the stones surface while sharpening because this helps prevent the formation of grooves on the stone that impair efficiency and accuracy of the sharpening procedure

64. Sharpness test • Tested by lightly resting the cutting edge on a hard plastic surface. • If cutting edge digs in during an attempt to slide the instrument forward over the surface, the instrument is sharp. • If it slides the instrument is dull. • Only very light pressure is exerted in testing for sharpness • It cannot be overemphasized that sharp instruments are necessary for optimal operating procedures.

65. Thank you