Operative Instruments in Endodontics including hand and power driven instruments. Recent advances in instruments in conservative dentistry and endodontics.

1. Instruments in
Operative Dentistry
Dr. Ashok Ayer
Assistant Professor
Department of Conservative Dentistry and Endodontics
College of Dental Surgery
B. P. Koirala Institute of Health Sciences, Dharan, Nepal

2. Outline:
 Hand Instruments
 Introduction
 Classification
 Materials
 Application
 Techniques
 Sharpening
 Powered cutting equipments
 Rotary cutting instruments
 Cutting Mechanism
 Hazards

3. Introduction:
 G.V. Black
 Nomenclature & numbering of hand instruments
1. Cutting instruments/ excavators
2. Noncutting
Designs of some early hand instruments
 1728 – Pierre Fauchard invented the bow drill
 1891 – Edward C Acheson –produced carborundum tools
 1935 – W H Drendes - Diamond cutting instruments

4. MATERIALS
 CARBON STEEL:
 HARDER THAN STAINLESS STEEL
 MAINTAINED BETTER SHARPNESS
 CORRODE IN MOIST CONDITIONS
Carbon steel

5.  Stainless Steel
 Preferred materials
 Remains bright under most conditions
 Loses keen edge during use much more
quickly
 Chromium: corrosion resistance
 Carbon: hardness
Stainless Steel

6.  TUNGSTEN CARBIDE
 INSERTS OR BLADES TO PROVIDE MORE
DURABLE CUTTING EDGES (BRITTLE).
 THEY MAY BE SOLDERED TO STEEL
HANDLES
 SOME INSTRUMENTS ARE MADE WITH
CARBIDE TO PROVIDE MORE DURABLE

7.  OTHER ALLOYS OF NICKEL, COBALT, OR
CHROMIUM ARE USED IN THE
MANUFACTURE OF HAND INSTRUMENTS.
 THEY ARE RESTRICTED TO INSTRUMENTS OTHER THAN
THOSE FOR CUTTING TOOTH STRUCTURE

8. Hardening and Tempering Heat
Treatments
Heat treatment Furnace
The hardening heat treatment hardens the
alloy, but it also makes it brittle, especially
when the carbon content is high.
Tempering heat treatment relieves strains and
increases toughness.

9. Classification of Instruments:- by
Sturdevant HAND
INSTRUMENT
cutting
excavators
ordinary
hatchets
hoes
Angle
formers
spoons
chisels
straight
curved
bin-angle
Enamel
hatchet
Gingival
margin trimmers
others
files
scalers
carvers
Non cutting
Amalgam
condenser
mirrors
explorers,
probes
others

10.  ORDER
 PURPOSE OF THE INSTRUMENT
 E.G. EXCAVATOR, SCALER
 SUB-ORDER
 MANNER OF USE
 E.G. PUSH, PULL
 CLASS
 FORM OF BLADE
 E.G. HATCHET, CHISEL
 ANGLE
 NUMBER OF ANGLES IN THE SHANK: MONOANGLE, BIANGLE,
TRIPLE-ANGLE, QUADRANGLE
 E.G. BIANGLED HATCHET EXCAVATOR,
According to G. V. Black

11. Classification of Instruments:- by Charbeneau
 Cutting instruments
Hand- hoes, chiesel etc
Rotary- burs, discs etc
 Condensing instruments
Pluggers
 Plastic instruments
Carvers, Burnishers
 Finishing and polishing instruments
Discs, Strips
 Isolation instruments
Cotton roll, Rubber dam
 Miscellaneous-
Mirrors, Explorers

12. CLASSIFICATION BY MARZOUK
EXPLORING
INSTRUMENTS
REMOVAL OF
TOOTH STRUCTURE
RESTORATION
OF TEETH
To dry
To illuminate
Retraction
Probes
Separators
Mixing
Plastic
Condensing
Burnishing
Carvers
Files
Knives
Finishing
& polishing
Hand cutting
Rotary cutting

13. Design

14. Blade
 Working part of the instrument
 Usually in the form of a bevel (acute angle) that
cuts into the tooth structure.
 On non cutting instruments e.g. condensers the
part corresponding to the blade is called the nib or
face.

15. Shank
 Connect the handle to the working end of the instrument.
 Normally smooth, round and tapered.
 Mon-angle, bin-angle, triple angle
 Balance is accomplished by designing the angle of the shank so
that the cutting edge of the blade must not be off axis by more
than 1-2 mm (Sturdevant’s)/2-3 mm (Summitt)

16.  Balance allows for the concentration of force onto
the blade without causing rotation of the
instrument.
 Instruments with long blades may required two or
three angles in the shank to bring the cutting edge
near to the long axis of the handle
 Such shanks are termed contra angled.

17. Handle/ Shaft
 Serrated for better gripping and control of the
instrument.
a. Standard Stainless steel handle: Diameter 6.4 mm
approx.
b. Padded handles: Diameter 8mm approx.
c. Larger diameter handles: 9.5 mm
 More ergonomic
 Less likely to develop carpal tunnel syndrome
 Occupy more space in instrument tray

18.  Handles are in conjunction with the shank
or it may be separable.
 Separate type is known as cone-socket
handle and allows for replacement of several
working ends e.g. mirrors and condensers.

19. cone-socket handle (mirror)
mirror

20. Numeric formulas
 Describing the dimensions and angle of the working end.
 Three number formula
 Four number formula:
 Cutting edge is not perpendicular to the long axis of the
blade.
 Gingival marginal trimmer
 Angle former

21. Instrument shank and
blade design
85

22. Bevels
 Most hand cutting instruments have on the end of the
blade a single bevel that forms the primary cutting edge.
 Additional two secondary cutting edges that extend from
the primary cutting edge for the length of the blade.
 Allows cutting in 3 directions; facial and lingual walls of
the proximal cavity

23.  Bibeveled instrument have two bevels that form
the cutting edge;
 e.g. hatched excavator

24.  Single beveled instrument such as spoon
excavator and gingival margin trimmer are
used with lateral cutting movement.

25.  Enamel hatchet also as a single beveled instrument
used with direct cutting motion, a planning or
lateral cutting designated for right (R) and left (L) to
the instrument formula.

26. The cutting edge is perpendicular to
the axis of the handle
e.g. binangle chisel.
Instrument with slight blade curvature
e.g.Wedelstaedt chisel.

27. Hand cutting
instrument
Excavators Chisels
Removal of caries and
refinement of the
internal parts of the
preparation.
Used primarily for cutting
enamel.

28. Excavators
1. Ordinary Hatchets
2. Hoes
3. Angle formers
4. Spoons

29. Ordinary Hatchets
 It has the cutting edge of the blade directed
 In the same plane as that of the long axis of the handle
and
 Is bibeveled.

30.  Used primarily on anterior teeth for
 Preparing retentive areas and
 Sharpening internal line angles, particularly in
preparations for direct gold restorations .

31. Hoe excavators
 Primary cutting edge of the blade perpendicular
to the axis of the handle
 Planing tooth preparation walls and forming line
angles.
 It is commonly used in Classes III and V
preparations for direct gold restorations.

32.  Hoes with longer and heavier blades, with the
shanks contra-angled.
 For use on enamel or posterior teeth.

33.  The blade angle of the hoe: > 12.5 centigrades
 The blade angle of chisel: ≤ 12.5 centigrades

34. Angle former
 It is mon-angled and has the primary cutting edge
at an angle (other than 90 degrees) to the blade.
 It is available in pairs (right and left )

35.  Used primarily for sharpening line and point angles
and creating retentive features in dentin in
preparation for gold restorations
 Also may be used in placing a bevel on enamel
margins

36. Spoon excavators
 Its blades are slightly curved, the shanks may be bin-angled
or triple-angled to facilitate accessibility.
Spoon excavators
discoid cleoid
The cutting edges are
circular
The cutting edges are
claw like.

37. Left cutting and right cutting
Used mainly for removal of caries and refinement of
internal opening in a cavity preparation

38. bin-
angled
spoon
triple-
angled
spoon

39. Cleoid spoon

40. Discoid spoon
Discoid is disc shaped, with cutting edge around the blade

41. Chisels:
 Straight, Monoangle, Biangle, Wedelstaedt chisels
 Enamel Hatchets
 Gingival Marginal Trimmers

42. Straight Chisel
 The straight chisel has a straight shank and blade,
with the bevel on only one side.
 Its primary edge is perpendicular to the axis of
the handle.
(12-7-0)

43.  The shank and blade of the chisel also may be
slightly curved (Wedelstaedt design)
11½-15-3
Biangled chisel

44.  Force used with chisels : straight thrust
 The bin-angle and Wedelstaedt chisels:
 Primary cutting edges in a plane perpendicular to the
axis of the handle.
 Distal bevel or a mesial (reverse) bevel.
Used for cleaving undermined enamel and for shaping
walls.
Instrument with three cutting motion: vertical, right and
left.

45.  The blade with a distal bevel is designed to plane a
wall that faces the blade's inside surface
 The blade with a mesial bevel is designed to
plane a wall that faces the blade's outside surface

46. Enamel Hatchet
 It is a chisel similar in design to the ordinary hatchet
excavator except that the blade is larger, heavier, and is
beveled on only one side
 Cutting enamel
 Right or Left cutting ends of the double- ended hatchet.
10-7-14

47. Gingival margin trimmer
 Blade is curved
 Bevel for cutting edge: outside of the curve
 Face of instrument: inside of the curve

48. 12½-100-7-1412½-75-7-14
Mesial Distal

49.  Cutting edge angle: 100 and 75 :
Inlay & Onlay preparations.
 Cutting edge angle: 90 and 85 :
Amalgam preparations.

50. Uses:
 Beveling of the gingival margins of proximo-
occlusal preparations.
 Beveling of the axio-pulpal line angle
 Performing a gingival lock (reverse bevel), placed
on the gingival seat

51. Usage of hand cutting instruments
 Horizontal strokes:
 Long axis of blade directed between 45 & 90
degree to the surface being planed or scraped
 Vertical or chopping strokes:
 Pulling stroke
 Hoe: beveled end or distal bevel
 Pushing stroke
 Hoe: contrabeveled end or mesial bevel.

52.  The cutting edge of the hand instrument should
always be kept sharp as
 Dull instruments may cause:
1. Loss of control.
2. More pain.
3. Prolonged time for the operative procedure.
4. Reduce the quality and precision of tooth
preparation.

53.  Stationary sharpening stone e.g. Arkansas
stone, silicon carbide.

54. Mechanical sharpener; moves at low speed while
the instrument is held at the opposite angle and
supported by a rest i.e. easier and less time
consuming.
E.g. Rx Honing Machine
Mechanical sharpener

55. Principles of Sharpening
 Sharpen instruments only after they have been cleaned
& sterilized
 Establish the proper bevel angle (usually 45 degree)
and the desired angle of the cutting edge to the blade.
 Use light stroke pressure
 Use a rest or guide whenever possible.
 Remove as little metal as possible

56. Non cutting Instruments
 Diagnostic instruments
 Mirror
 Probe or explorer
 Twizzer
 Plastic instruments
 Amalgam instruments
 Condensers
 Burnisher
 Carver
 Amalgam carrier

57. MOUTH MIRROR
Most common sizes used are the No. 4 (⅞ inch diameter)
and No. 5. (15/16 inch diameter)
No. 2 (5/8 inch diameter): when working on posterior teeth
with a rubber dam.
For clarity, reflective surface on the external surface of the
glass: Front surface mirror.

58. Uses for the mouth mirror. A, Indirect vision. B, Light reflection.
C, Retraction. D, Tissue protection.
A
D
C
B

59. Explorers
 To feel tooth surface for irregularities
 To determine the hardness of exposed dentin
1. Shepherd’s hook: No. 23
2. Cowhorn explorer: No. 2
3. No. 17: back action

60. Tweezer/ cotton forceps:
 Cotton forceps are used for picking up small items,
cotton pellets

62. Plastic filling Instruments
 To carry and shape tooth colored restorative material:
Composite resin and glass ionomer
 For placing of base and lining material
 Hard plastic or metal.
 Composite placement instrument
 Designed specifically for the placement of composite
restorative materials.
 Anodized aluminum
 Teflon
 Titanium nitride layer on instruments

63. A: ash49 B:ash6 C:dycal applicator D:cement spatula.

64. Amalgam Carriers
 An instrument with a hollow cylinder that is filled
with amalgam.
 Sizes:
 Mini: 1.5 mm diameter
 Regular: 2.0 mm
 Large: 2.5 mm
 Jumbo: 3.0-3.5 mm

65. Amalgam Condensers
Various Amalgam condensers

66. Carvers
 Hand instruments with a blade or nib used to contour the
surface of filling material in their plastic state, waxes,
models and patterns.
 Hollenback carver (knifed edged- elongated- bibevelled)
 Diamond (Frahm’s) carver : Bibevelled cutedge.
 Ward’s ‘C’ carver
 Discoid Cleoid
 Interproximal carver

68. Burnishers
 Burnishing of the amalgam on the margins of the cavity,
 Shaping metal matrix band to have more desirable contours for
restoration.
 To bend cast gold restoration (inlay or onlay) near the margin of
the prepared cavity to narrow the gap between gold and the
tooth.

69. Burnishers

70. Disposable brush
 Used with etching and bonding procedures associated
with composite resins.

71. Accessory Instruments
 Scissors
 Used for cutting dental dam material, retraction cord,
and stainless steel crowns.
 Crown and bridge scissors
 Dappen Dish
 Hold certain liquid dental materials during a procedure.

72.  Howe Pliers
 Also referred to as 110 pliers. Useful for holding items, for
carrying cotton products to and from the oral cavity,
removing the matrix band, and placing and removing the
wedge.
 Guards
 Interproximal wedges to protect soft tissues from contact
with sharp rotary cutting instruments.

73. Preset restorative tray

74. There are four grasps used with the hand
instruments:
Modified pen.
Inverted pen.
Palm and thumb.
Modified palm and thumb.

75. M o d i f i e d p e n g r a s p
pen grasp Modified pen grasp

76. Inverted pen grasp
 If the hand is rotated so that the palm faces more toward
the operator.
 Used in the lingual and labial surfaces of anterior teeth.
inverted pen grasp

77. Palm and thumb grasp
 The handle of the instrument is placed on the palm of the
hand and grasped by all the fingers while the thumb is free of
the instrument and rest on the nearby tooth of the same arch.
 Preparing incisal retention in a class III preparation on a
maxillary incisor.

78. Palm and thumb grasp
 The same as in palm and thumb grasp but the
thumb is rested on the tooth being prepared.
 Used in the upper arch.

79. Powered cutting equipments

80. CHARACTERISTICS:
SPEED
 SURFACE FEET PER UNIT TIME OF CONTACT THAT THE TOOL
HAS WITH THE WORK TO BE CUT OR REVOLUTIONS PER
MINUTE
 ACCORDING TO MARZOUK:
1. ULTRA LOW SPEED: 300-3000 RPM
2. LOW SPEED: 3000-6000 RPM
3. MEDIUM HIGH SPEED 20,000-45,000 RPM
4. HIGH SPEED 45,000-1,00,000 RPM
5. ULTRA HIGH SPEED > 1,00,000 RPM

81.  According to Charbenau:
1. Conventional or low speed: below 10,000 RPM
2. Increased or high speed: 10,000-1,50,000 RPM
3. Ultraspeed: above 1,50,000 RPM
 According to Sturdevant:
1. Low or slow speeds: below 12,000 RPM
2. Medium/Intermediate speeds: 12,000 to 2,00,000
RPM
3. High/ Ultrahigh speeds: above 2,00,000 RPM

82. Pressure:
 P=F/A
 Low speed: 2-5 pounds of force
 High speed: 1 pound of force
 Ultra high speed: 1-4 ounces of force
Heat Production
 Directly proportional to the Pressure, RPM, and
area of tooth in contact
 113˚ F : Pulpitis & pulp necrosis.
 130˚ F : Permanent damage of pulps.

83.  Brown et al: Temperature of dentin at a distance of
0.5 mm from a high speed bur cutting dry to be
245˚F (118˚C).
 Even in non vital teeth, dry cutting at high speed
should be avoided, since the thermal stresses will
cause microfractures in the enamel. This could
contribute to marginal failure of the restoration.
 Higher water velocity.
Clean head system

84. Greater flow of water coolant is required to prevent
clogging when diamonds are used under increased
pressure.
42 psi is the optimal air pressure to achieve peak
performance
Optic
Drive air
Spray water
Exhaust air
Spray air
Optic
Drive air
Spray water
Exhaust air
Spray air
6-pin
5-hole

85. VIBRATION:
 EQUIPMENT USED & THE SPEED OF ROTATION
 EXCESSIVE VIBRATION: ANNOYANCE TO THE PATIENT,
OPERATOR FATIGUE AND RAPID WEAR OF INSTRUMENTS.
TORQUE:
 ABILITY OF THE HAND PIECE TO WITHSTAND LATERAL
PRESSURE ON THE REVOLVING TOOL WITHOUT DECREASING
ITS SPEED OR REDUCING ITS CUTTING EFFICIENCY.

86. Friction:
 Occurs in the moving parts of the hand piece especially the
turbine.
 Friction is reduced by equipping the hand piece with ball
bearings, needle bearings, glass and resin bearings.
 Ceramic Ball Bearings:
 40% lighter and 3 times harder than conventional
bearings, they offer an extended turbine life, reduced
operation noise, and less vibration.

87. Handpieces:
Two basic types of handpieces, the straight handpiece
and contra angle handpiece.
The straight is used more frequently for laboratory
work, while contra angle used in the oral cavity.
High speed techniques are generally preferred for
cutting enamel and dentin.

88. Penetration through enamel and extension of the
cavities outline are more efficient at high speed.
Small diameter burs should be used in the high
speed handpiece.
 High speed generates considerable heat during
cutting, even with small diameter burs and should
be used with water coolant and high efficiency
evacuation

89. Design:
This model is the choice for limited access or
when treating children.
Rear-facing exhaust vents direct air flow away
from the surgical site for patient protection

90. Commonly used couplings

93. Zero Suck Back Technology
Prevents the intake of aerosol and other
particles when it is stopped.
Drive air flows into an Anti Suck Back
Diffuser (ASBD) within the capsule.
Air in the ASBD is pressurized through
centrifugal force created by the
impeller rotation.
Through the centrifugal force and
rotation of the impeller, air continues
to flow into the ASBD and remains
pressurized even after drive air is
stopped.
The pressurized air in the ASBD is
released to the outside at the
bottom of the head

94. Low-Speed Handpiece
 Design
Straight in appearance.
Standard length and “short.”
Speed ranges from 10,000 to 30,000 rotations
per minute (rpm).
Operates the rotary instrument in either a
forward or backward movement.

95.  Uses of the low-speed handpiece
 Intraoral
 Removal of soft decay and fine finishing of a
cavity preparation.
 Finishing and polishing of restorations.
 Coronal polishing and removal of stains.
 Extraoral
 Trimming and contouring temporary crowns.
 Trimming and relining of removable partials and
dentures.
 Trimming and contouring of orthodontic
appliances.

96. Low-Speed Attachments
Straight attachment receives a long-shank laboratory
bur, the contra-angle attachment, and the prophy
angle attachment.
Contra-angle attachment receives latch type rotary
instruments and mandrel.

97.  Prophylaxis Angle
Used during polishing procedures to hold the
prophy cup and bristle brush.
Two types
 Plastic disposable “prophy” angle
 Metal “prophy” angle

98. High-Speed Handpiece
Cellular Glass Optics

99.  Uses of the high-speed handpiece
Removes decay.
Removes an old or faulty restoration.
Reduces the crown portion of the tooth for the
preparation of a crown or bridge.
Prepares the outline and retention grooves for a new
restoration.
Finishes or polishes a restoration.
Sections a tooth during a surgery.

100. Ultrasonic Handpiece
 Design
Attached to the dental unit.
Powered by electricity.
Attachments are similar in appearance to scaling
instruments.
Delivers a pulsating spray of water.

101.  Uses of the ultrasonic handpiece
Removes calculus.
Removes stain.
Removes bonding materials from a tooth surface
after orthodontic appliances are removed.
Removes cement after orthodontic bands are
removed.

102. Laser Handpiece
 Design
Uses a laser light beam instead of rotary
instruments.
The laser is conducted through a fiber-optic cable.
Resembles a standard handpiece.
Maintains a water-coolant system.
Maintains an air-coolant system

103.  Uses:
 Cauterizes soft tissue.
 Vaporizes decayed tooth structure.
 Advantages:
 Usually painless.
 Patient usually does not require anesthesia.
 Proceed with procedure faster.
 Disadvantage:
 Cannot be used on teeth with existing restorations.

104. AIR-ABRASION HANDPIECE
 Design
 Small version of a sandblaster.
 Compressed air at pressure of 7 to 11 atm (40
to 140 psi)
 Produces a high-pressure delivery of aluminum
oxide particles (of 20 to 50 pm) through a small
probe.

105. Uses:
 Prepares teeth for sealants.
 Removes external stains.
 Class I through class VI preparations.
 Endodontic access.
 Crown margins.
 Prepares a tooth surface for the cementation of a cast
restoration, such as a crown or veneer.

106. Disadvantages:
More effective on hard normal dentine than soft
dentine affected dentine
When using composite, the air abrasion doesn’t
provide the micromechanical roughness needs for
retention thus needs acid-etchant.
Loss of tactile sensation.

107. Possible iatrogenic damage especially on the
cementum and root dentine.
Can induce asthma –> thus needs high volume suction
Can’t remove amalgam restoration.
Can’t perform massive reduction for crown.

108. Laboratory Handpiece
 Design
 Operates at speeds up to 20,000 rpm.
 Uses laboratory burs.
 Provides greater torque than handpieces used
intraorally.

109. Rotary instruments
Cutting Abrasive
Carbide burs
Made from
1- tungsten carbide
2- steel carbide
1- Diamond burs
2- Discs
3- Stones
4- Rubber wheels

110.  According to composition:
1. Steel burs
2. Tungsten Carbide burs
 According to mode of attachment to handpiece
1. Latch type
2. Friction grip type
 According to handpiece they are designed for;
1. Clockwise
2. Anticlockwise

111. Rotary instruments consist of three parts :
1- shank
2- neck (shaft)
3- head
head shaft Shank

112. Shank design
Long shank – used for straight
hand piece (low speed)
Short latch shank – used for contra-angle (low speed)
Friction grip shank - used for high speed hand piece

115. Dental Burs
A group of instruments that can turn on an axis with different
speed of rotation to perform different types of work.
The characteristics of this work are either cutting , abrasive,
finishing or polishing.
Steel burs cut human dentin at low speeds, but dulls rapidly at
higher speeds or when cutting enamel
Steel necks bends easily causing vibration

116. Carbide burs
 Burs possess blades that shear (cut) tooth
structure.
 They are used for making precise
intracoronal preparation features such as
placing groove, and boxes.
 Used for smoothing surface in enamel and
dentin
 They are not used for bulk reduction
because to producing undulations on the
tooth surface

117. Shapes:
 Round Bur:
 Initial entry into the tooth
 Extension of the preparation
 Retentive features and caries removal
 Inverted cone bur
 Undercuts in the tooth preparation
 Pear shaped bur
 Tooth preparation for amalgam, gold foil.
 Straight fissure bur
 Tooth preparation for amalgam
 Tapered fissure bur
 Tooth preparation for indirect restorations.

118. Basic bur head shapes

119. Regular –cut
Fine Cut
Coarse-cut

120.  Its used for highly smoothing of prepared surfaces of tooth
 Because of its blades in a diagonal to the instrument shaft
 Its have a torpedo shape
Twelve-fluted carbide bur

121. Plain fissure bur
Its tapered and cylinder shape its used for placing
groove and boxes and they also used for finishing of
preparation.
Groove seating

122. Bur numbering systems
 In the united states the burs have been traditionally
described in term of arbitrary i.e. numerical code
eg, 2 =1 mm diameter round bur,
34 = 0.8mm inverted,
57 = 1mm diameter straight fissure
 Number 500 is added to indicate cross cutting
 Number 900 is added to indicate end-cutting only
 So no. 57 ,557 and 957 are all had the same head size

123. Iso system(international standard organization)
FDI (Federation dentaire internationale)
 Usually tend to use head shape name and size
(in tenth of a millimeter)
 Eg. Round 010 = 1mm diameter
 Straight fissure plain 010 = 1mm diameter
 Inverted cone 008=0.8mm diameter

125. Shapes & diameters of regular carbide burs used for tooth preparation
 Round
Bur size: 1/16 1/8 ¼ ½ 1 2 3 4 5 6 7 8 9 11
Diameter: 0.30 0.40 .50 .60 .80 1.0 1.2 1.4 1.6 1.8 2.1 2.3 2.5 3.1
 Inverted cone
Bur size: 33½ 34 35 36 37 39 40
Diameter (mm): .6 .8 1.0 1.2 1.4 1.8 2.1
 Straight Fissure:
Bur size: 55½ 56 57 58 59 60
Diameter (mm): .60 .80 1.0 1.2 1.4 1.6
Straight fissure, round end:
Bur size: 1156 1157 1158
Diameter (mm): .80 1.0 1.2
Tapered fissure:
Bur size: 168 169 170 171
Diameter (mm): .80 .90 1.0 1.2

126.  Tapered fissure, rounded end
Bur size: 1169 1170 1171
Diameter (mm): .90 1.0 1.2
 Pear:
Bur size: 329 330 331 332
Diameter (mm): .60 .80 1.0 1.2
 Long inverted cone, rounded corners (amalgam preparation)
Bur size: 245 246
Diameter (mm): .80 1.2
 End-cutting:
Bur size: 956 957
Diameter (mm): .80 1.0

127.  Bur head design:
 The number of blades on a bur is always even
 Number of blades on an excavating bur may vary from 6 to
8 t0 10.
 Finishing bur: 12 to 40 blades

128. Concentricity:
 Measurement of the symmetry of the bur head.
 Runout:
 Test measuring the accuracy with which all blade tips
pass through a single point when the instrument is
rotated.
 Average value of clinically acceptable run-out is about
0.023 mm
 Is the primary cause of vibration

129. Bur blade design

130.  Rake angle:
 Angle that the face of the bur tooth makes with the
radial line.
 Radial rake angle: radial line & the tooth face coincide.
Negative rake angle: blade face is leading the radial line
 Increases the life expectancy of the bur & provides for the most effective
performance in low and high speed ranges.
Positive rake angle:
 Produce acute edge angle

131.  Edge angle:
 In the range of 90˚ to provide strength to the blade &
longevity of cutting efficiency of the bur.
 Land: plane surface immediately following the cutting edge.
 Flute/ Chip space:
 Space between successive bur teeth or the blades of the bur.
 Provides an exit for removal of the fractured matter and
creates a clearance angle.

132.  Clearance angle:
 Angle between the back of the blade and the tooth surface.
 If a land is present on the bur:
1. Primary clearance angle: the angle the land will make with work.
2. Secondary clearance angle: the angle between the back of the bur
tooth and work.
3. Radial clearance angle: is formed when the back surface of the bur
tooth is curved.
 Provides clearance between the work & the cutting edge to prevent
the tooth back from rubbing on the work.

133. Abrasive instruments
Head consists of small angular particles of hard substance
embedded in a soft binder (ceramic, metal, shellac,
rubber).
 Diamond abrasives
 Other abrasives –Silicon carbide (carborundum),
aluminium oxide, garnet, quartz, pumice, cuttlebone.
 Deposited by Electroplating, sintering or microbrazing.

134. These are made from diamond chips bonded to blanks
(heads). Diamonds used for grinding enamel and
dentin surfaces
Diamond burs may divided according to :
1- coarseness ( medium grit - fine grit )
2- shape
Diamond stones
Medium grit
Fine grit

135. Diamond particle size:
1) Coarse: 125~150 um
2) Medium: 88~125 um
3) Fine: 60~74 um
4) Very fine:38~44 um
Diamond instruments consists of three parts:
 A metal blank,
 The powdered diamond abrasive
 A metallic bonding material that holds the
diamond powder onto the blank

136.  Color coding:
Coarse: 120-150µ
Standard: 106-125µ
Fine: 53-63µ
Extra- fine: 20-30µ
TF: Taper flat end; TR: Taper round end; TC: Taper conical
end; FO: Flame Ogival end; SF: Straight flat end; SO:
Straight Ogival end; BR: Ball round; WR: wheel round edge;
Green
Blue
Red
Yellow

138. Discs, Mandrel, Stones, and Wheels

139. Moulded abrasive instrument –
 Manufactured by pressing a uniform mixture of abrasive
and matrix around roughened end of shank,
 Points and stones; finishing & polishing
Coated abrasive instrument –
 Disks that have a thin layer of abrasive cemented to a
flexible backing.
 surface contouring, finishing

140. SmartPrep Instruments
SmartPrep Instruments (Smart Bur, Polymer Bur)
 Medical polymer that has the ability to remove decayed dentine
while keeping the healthy dentin.
 Its hardness is less than healthy dentine while harder than the
carious dentin.
 Ability to self-limit(selectively)
It will only cut what is carious and if it’s in contact with
healthy dentin the bur will only wear away (when extensive
force isn’t used).

141. Advantages:
 Conservative
 Minimal to none disease transfer (because its single
use only).
 No need for Local Anesthesia.
 For Students to start with first clinical cases.

142. Disadvantages:
Single-patient-use = Expensive.
Technique sensitive ( too much pressure and you will cut
the healthy dentine)
The bur breaks down when it touches enamel.
 It can sometimes leave large amounts of decayed tissue
(use caries dye to locate the left amount.
 Access should be done by a different type of bur that can
penetrate the enamel.

143. Cutting Mechanisms
 Bladed Cutting:
 Brittle fracture: crack production, by tensile loading.
 High speed cutting, especially of enamel
 Ductile fracture: plastic deformation, by shear.
 Low speed cutting.
 Abrasive Cutting:
 Diamonds are most efficient when used to cut
brittle materials, are superior to burs for removal of
the dental enamel.
 Burs are generally preferred for cutting ductile
materials such as dentin.

144. CUTTING RECOMMENDATIONS
 Use of contra-angled handpiece, air-water spray
for cooling, high operating speed (above 200,000
rpm), light pressure.
Carbide burs are better for end- cutting, produce
lower heat, and have more blade edges per diameter
for cutting.
 Diamonds are more effective than burs for both
intracoronal & extracoronal tooth preparations,

145. CHEMO-MECHANICAL CARIES REMOVAL
Carisolv (Chemo‐mechanical caries removal )
Composition:
 0.5% sodium hypochlorite and 0.1 M amino acids “Glutamine,
leucine and lycine”
This is a technique used to remove caries and decay with minimal
invasive techniques.
 Hypochlorite: dissolves the decayed dentine
 Amino acid: buffering solution to prevent damage to the healthy
tissue.
[The amino acid and hypochlorite will react with the denatured
Collagen Tissue of dentine (Infected dentine) making soft and easily
removed with hand instruments.]

146. Advantages:
 Less anesthesia is used
 Useful for children, dental‐phobic patients.
 Useful for removing root or coronal caries in easily accessible
areas.
 Removes the smear layer and doesn’t affect the bond strength of
the adhesive materials.
 No histological effect on the pulp even with direct contact.

147. Ozone treatment
 Ozone gas has a high oxidation potential and is
effective against bacteria, viruses, fungi, and protozoa.
 Capacity to stimulate blood circulation, platelets, and
immune response.
 Ozone is used in dentistry in gaseous, ozonated water
and as ozonated oils
 Ozone has been proven to halt root caries and also
reverse lesions (pit and fissure carious lesions) by
allowing the natural remineralisation process to proceed.
 Remineralised lesions are known to be more resistant to
further dissolution than sound tooth surfaces.

148.  Disruption of the protected ecological niche of the micro-
flora allows remineralisation from the saliva.
 Intracanal irrigants in endodontic treatment.
 Treatment of alveolitis, avascular osteonecrosis of the jaw,
and herpes virus infection.
 Inhibits plaque formation: periodontal surgical and
maintenance phase.
 Used in dental unit water line to disinfect water.
 Advantage of ozone therapy is it is an atraumatic,
biologically based treatment.

149. O3 delivered from the HealOzone unit:
(2100 ppm O3, 615 ml/min) through a hand
piece with a silicone cup that sealed the
tooth.
Once sealed, the device automatically
delivered the O3 for the treatment group
for 10 seconds followed by 10 seconds
vacuum.
Recall:
After one and three months.
Prophylaxis of teeth
Re-examination using the DIAGNOdent® and
ECM readings.
Ozone treatment repeat on each of these two
recall visits.

150. HAZARDS WITH CUTTING
INSTRUMENTS
PULPAL PRECAUTIONS:
 MECHANICAL VIBRATION, HEAT, DESICCATION, LOSS OF
DENTINAL TUBULE FLUID, AND OR TRANSECTION OF
ODONTOBLASTIC PROCESSES.
 PULPAL SEQUELAE (RECOVERY OR NECROSIS) TAKE FROM 2 WEEKS
TO 6 MONTHS OR LONGER, DEPENDING UPON EXTENT AND
DEGREE OF TRAUMA.

151. The remaining tissue is effective in protecting the pulp
in proportion to the square of its thickness.
 Steel burs produce more heat than carbide burs because
of inefficient cutting.
Dull instruments will plug debris, do not cut efficiently
and result in heat production.

152. When used without coolants, diamond instruments
generate more damaging heat than carbide burs.
Air alone as coolant: much lower heat capacity than
water, desiccates dentin, damage odontoblasts.

153. Soft tissue precautions:
 Lips, tongue and cheeks of the patient.
 Good access and visibility.
 Isolation of the operating site: rubber dam, retraction type saliva
ejector tip.
 Wait for the instrument to stop or extremely careful while removing the
handpiece from the mouth.
 Large disc
 Sudden reflex by the patients.
 Hand excavators: soft caries removal in the deep preparation may lead
to mechanical pulp exposure: round bur at low speed.

154. Eye Precautions
 Airborne particles, old restorations, tooth structure,
bacteria, debris.
 Strong high volume evacuation.
Ear Precautions:
 Loud noise: mental and physical distress, increase accident
proneness, reduce overall eficiency.
 Noise level in excess of 75 db, 1000 to 8000 cps(frequency)
may cause hearing damage.

155. Inhalation Precautions
 Amalgams or composites produce submicron particles and
vapor.
 Alveolar irritation and tissue reactions.
 During cutting or polishing: thermal decomposition of
polymeric restorative materials (sealants, acrylic resins,
composites) : Monomers.
 Mask : do not filter either mercury or monomer vapors

156. Conclusion:
The removal and shaping of the tooth structure are
essential aspects of restorative dentistry. Modern high
speed instruments has eliminated the need of many
hand instruments, but hand cutting instruments are
still important for finishing many tooth preparations
and thus they remain as an essential part of the
armamentarium for quality restorative dentistry.

157. References:
1. Sturdevant’s Art & Science of Operative Dentistry :4th edition
2. Fundamentals of Operative Dentistry; James B. Summitt; 3rd edition.
3. Operative Dentistry of Modern Theory and Practice: M K Marzouk
4. Black GV. A work on Operative Dentistry. Chicago: Medico-Dental
Publishing, 1908
5. Dental Hand Instruments, 2003: Elsevier Science (USA). ISBN 0-
7216-9770-4
6. Fundamentals of Tooth Preparation: Shillingburg
7. Journal of Interdisciplinary Dentistry / Jul-Dec 2011 / Vol-1 / Issue-2