cutting hand instruments and burs

1. JAGADEESH.K
P.G 3rd
year

2. “Instrument” : a tool, device or implement used for a specific
purpose or type of work.
used to examine, clean, cut & restore teeth.
The two main types are-
Hand instruments
Rotary instruments
Cutting instrument generally implies, unless otherwise specified,
a hand held instrument used to cut, plane, or cleave tooth
structure during the preparation of a cavity to receive a
restoration or other treatment.

3.  HISTORY OF HAND CUTTING
INSTRUMENTS
 Dr. Jonathen Taft- thick bulky chisels and excavators.
 heavy-handled made up of wood, ivory & inferior metals - as
wide as 1/4 inch at the cutting edge .
 Chisel entrance to the carious dentin and is removed by the
hand excavators .

4. STEEL-
ADVANTAGES DISADVANTAGE
S
Carbon steel sharpness
if unprotected
corrodes.
if dropped fractures
easily.
more sensitive to
chemicals
Stainless steel superior corrosion
resistance in
most conditions
looses keen edge
during use, much
more quickly

5.  2) Nichrome-
-An alloy of nickel-60-80%
chromium12-20%
iron-0-26%
ADV - can be subjected to high degree of
temperature.
does not oxidize easily.
DISADV -but does not readily maintain a sharp edge.

6.  3) STELLITE-
-An alloy of cobalt- 65-90%
chromium -10-35%
tungsten, molybednum, iron - small
quantities.
ADV - high resistance to action of acids.
- higher strength maintains cutting edge.
- high melting point .
 4)TARNO-
-An alloy of chromium.
-used for manipulation of cements.

7.  Hardening heat treatment :
1500° F (815°C)
 Tempering heat treatment:
350°F (176° C)
 Annealing

8. Operative dental instruments as classified by CHARBENEAU-
1.Cutting instruments-
a) Hand b) Rotary-Burs
Hatchets -Stones
Chisels -Disks
Hoes Others
Excavators
others
2. Condensing instruments
a) Pluggers
-Hand
-Mechanical

9. 3. Plastic instruments
a) Spatulas
b) Carvers
c) Burnishers
d) Packing instruments
4. Finishing and polishing instruments
a Hand
-Orangewood sticks
-Polishing points
-Finishing sticks
b.Rotary
-Finishing burs
-Mounted brushes
-Mounted stones
-Rubber cups
-Impregnated disks

10. 5.Isolation instruments
a. Rubber dam
b. Saliva ejector
c. Cotton roll holder
d Evacuating tips
6. Miscellaneous instruments
a. Mouth mirrors
b Explorers
c Probes
d Scissors
e Pliers
f others

12. 1)Excavators
a. Hatchet
b .Hoe
c. Spoon
d .Discoid
e. Cleoid
2)Chisels
a .Straight chisel
b .Monoangle chisel
c. Binangle chisel
d. Triple angle chisel
3)Special forms of chisels
a) Enamel hatchet
b) Gingival margin trimmer
c) Angle former
d) Wedelstead chisel
e) Offset hatchet
f) Triangular chisel
g) Hoe chisel

13. Cutting instruments:-
a. Excavators
-Hoe
-Angle former
-Ordinary hatchet
-Spoon excavator
b. Chisels
-Straight chisel
-Curved chisel
-Enamel hatchet
-Gingival margin trimmer
c. Others
-Knives
-Files
-Discoid
-Cleiod

14. 1) Examining the mouth and teeth-
a. Mouth mirrors
b. Probes
c. Scalers
2) Cutting teeth and removing caries
a. Excavators
b. Chisels, hatchets and hoes
3) Placing and condensing restorative materials
a. Plastic instruments
b. Condensers or pluggers
4) Carving and finishing instruments
5) Miscellaneous

15.  Rotary instruments
 Air abrasion
 Ultrasonic
 Lasers

17. 1) Handle/ Shaft-for grasping the instrument.
factors to be considered while handle selection-
a.weight- hollow
solid
b.diameter- small
large
c.serrations- knurled
smooth

18.  Any angulation in the instrument is placed.
Two Types of instruments
A) long handled instruments.
B) cone socket instrument.

20. Face end of the nib or working surface.
 Cutting edge working part of the instrument
Can be in the form of a bevel with different shapes.
 Blade angle
 Cutting edge angle

21. G.V. BLACK established a nomenclature
1. order - purpose or function of instruments
e.g. Scaler, excavator
2. sub order - position or manner of use e.g. push or pull
motion.
3. class - form of working end e.g. hatchet, chisel
4. sub class - shape of the shank e.g. Bin angle, mono
angle

25. BOLEY GAUGE
CENTIGRADE SCALE

28.  Direct cutting & lateral cutting instruments
 Contrangling
 Right and left instruments
 Double ended & Single ended instruments
 Single bevelled
 Bibevelled
 Triple bevelled
 Circumferentially bevelled

29.  DIRECT CUTTING & LATERAL CUTTING
INSTRUMENTS
 Single plane instruments
 Double plane instruments

30. For optimal anti rotational
design, the blade edge
must be within 3mm from
the axis of handle.
All dental instruments
need to satisfy this
principle of balance

31.  Depends on - length of blade
- degree of angulation in shank
 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.

35.  1 ) SINGLE BEVELLED INSTRUMENTS-
Cutting edge at right angle to the long axis of the shaft.
Distally bevelled Mesially bevelled

36. RING
Mesial bevel
Distal bevel

37.  If there is no angle in the shank or less than 12 degree then
they are used in push (direct cutting) and scraping motion
(bevelled to non bevelled side).
 If the angle exceeds 12 degree they used in push (mesially
bevelled) and pull (distally bevelled) motion.

38.  BIBEVELLED INSTRUMENT
TRIPLE BEVELLED INSTRUMENT

39.  Beveling the blade laterally (secondary cutting edge) together
with the edge of blade (primary cutting edge) forms three
distinct cutting edges.
 Most modern instruments are of this design.

40.  These are usually done in double planed instruments
where the blade is bevelled at all peripheries, e.g.
spoon excavator

43.  Self-limited in cutting enamel, cut only enamel undermined
by the loss of enamel.
 No vibration or heat accompanies the cutting, making it
painless and with no adverse effects to tooth tissues.
 Most efficient means of precise intricate cutting.
 Create the smoothest surface of all cutting instrument.
 The longest life span of all cutting instruments.

45. EXCAVATORS-
Designed for excavation and removal of carious dentine
and for sharpening of internal parts of cavities.
 hatchet excavators
 hoe excavators
 spoon excavators
 discoid
 cleoid

46.  Uses :preparing the
retentive areas in the anterior
teeth and sharpening the
internal line angles
 FOURMULA : 3–2-28.

47.  Uses : for planning the tooth
preparation walls and
forming line angles
FORUMLA : 4 ½-1 ½-22 .

49.  Discoid excavators:
Circular blade
 Cleoid excavators:
Circular blade with a
point

51.  They are intended mainly for cutting enamel and maybe
grouped as
Straight chisels
Monoangle chisels
Binangle chisels
Triple angle chisels
Formula : 12 – 7 – 0 ( Straight).
10 – 7 – 8 (Curved)
FORCE USED : FORWARD or STRAIGHT THRUST

52.  Straight chisel:
five possible
movements
 Monoangled chisel:
 Bin angle chisel
 Triple angle chisel
usually used to flatten the
pulpal floors

53. 1) Enamel hatchet
2) Gingival marginal trimmer
3) Angle formers
4) Wedelstaedt design
5) Off-set hatchets
6) Triangular chisels
7) Hoe chisels

54. Available as right/left.
Used for removing hard
caries, preparation of
retentive areas, & internal
line angles.
Formula : 10 – 7 – 14

56. It is a modified hatchet but differs
from hatchet in that
a. cutting edge is at an angle
other than 90°.
b. has a curved blade.
c. is a double planed
instrument.

57.  Identification:-
 Distal GMT: cutting edge
makes an acute angle with the
edge of the blade farthest from
the handle.
 Mesial GMT:- The cutting edge
makes an acute angle nearest to
the handle.
a.left-cuttimg mesial gingival margin
trimmer.
b.left-cutting distal gingival margin
trimmer

58.  Primary cutting edge is at
an angle (other than 90°) to
the blade
 Used to cut line and point
angles
 FORMULA :12 – 85 -5– 8

59.  It has a slight vertical
curvature in its shank
Mesially and distally
bevelled
 Uses: cleaving the
undermined enamel
Shaping the walls

60.  Whole blade is rotated 90
of turn forward or back
ward around its long axis
 Uses: They are useful to
create & shape specific
angulations for cavity
walls in inaccessible areas

61.  Triangular chisel
 Hoe chisel

62. 1.PEN GRASP,
2.MODIFIED PEN GRASP.
3.PALM AND THUMB GRASP .
4.MODIFIED PALM AND THUMB.

63. CORRECT
INCORRECT

68.  They are often called as oil stones
 course, medium and fine grits
 These also available in
1. flat
2. Grooved
3. Cylindrical
4. tapered

69.  Sharpening stones are made with
1. Arkansas stone
2. Silicon carbide
3. Aluminum oxide
4. Diamond

70.  Mechanical sharpening : Rx honing machine
This instrument moves a hone in a reciprocating motion at low
speed
Instrument is held at the appropriate angulations and supported
by a rest
 Hand piece sharpening :
mounted silicon carbide and aluminum oxide stones are used
for sharpening of instruments

73.  Move along hard plastic surface
 Finger nail test
 Visual inspection

75. a. Exploring instruments
b. Restoring instruments
c. Miscellaneous instruments

76.  Dry : Air syringes, tweezers
 Illuminate : battery operated lights, lights attached to dental
units, mouth mirrors
 Retract the soft tissues : mouth mirrors, cheek retractors,
Tongue depressors-retractors
 Probes : Straight, Right angled, Arch explorer, Interproximal
explorer
 Separators : Slow separators, Quick separators

77.  Straight
 Right angled
 Arch explorer
 Interproximal explorer

78.  Mixing instruments
 Plastic instruments
 Condensing instruments
 Burnishing instruments
 Carvers
 Files
 Knives

81.  There blades are
either bevelled or
knife edged
 Hollenback carvers

82.  Knives: They are designed
with a thin blade made of
various sizes & shapes.
 Files :The blade of files
have serrations (or) teeth up
to half
Movement given is
basically PUSH
(OR) PULL.

83.  Rubber dam kit
 Saliva ejectors
 Scissors
 Cotton holders
 Needles & Suture materials
 Matrix bands & Retainers
 BP handles & Blades
 Evacuating tips

84.  Definition :
 The term bur is applied to all rotary cutting instruments that have
bladed cutting heads. This includes instruments intended for such
purposes as finishing metal restorations and surgical removal of
bone, as well as those primarily intended for tooth preparation.
- (sturdevant)

85.  Early burs-hand made
 Machine made burs-1891-S.S.White
 STEEL BURS
Dull at high speed
Finishing & polishing
VHN: 800
 CARBIDE BURS
Used at high speed
Cavity preparation
VHN:1650-1700

86.  Combination burs
 Carbide heads are attached to steel shank and neck by welding
or brazing
 Baker curson bur: this bur consists of tungsten carbide blank
sintered on to the steel shank
 No blades are visible macroscopically but microscopic blades
are cut into the surface by stroking the tungsten carbide
longitudinally with a diamond stone

87.  Head
 Neck
 Shank or Attachment part

88.  Bladed or Abrasive
 Material used
 Size of head
 Shape of head
 Mode of attachment
 Length of head
 According to motion
 According to use

89.  Numbers are designated for bur sizes
 This numbering system was originated by the S.S White
Dental Manufacturing Company in 1891 for their first
machine made burs
 The original numbering system contains 9shapes and 11 sizes
the ½ and ¼ designations were added later when smaller
instruments were included in the system

90. Original Bur Head Sizes (1891 to 1954)

91. Standard bur head sizes: 1955 to present

92.  Basic head shapes are
1. Round
2. Inverted cone
3. Pear shaped
4. Straight fissure
5. Tapered fissure

93.  Bur tooth
 Rake angle
 Land
 Clearance angle
 Tooth angle
 Flute or chip space

94.  Bur tooth :it has two surfaces
1.Tooth face
2.back or flank
 Rake angle : it is the angle of
the face of the bur tooth makes
with the radial line from the
center of the bur to the blade
Rake angle can be positive,
zero, or negative
 Land : the plane surface
immediately following the
cutting edge

95. Clearance angle : it is the
angle between the back of the
tooth and its work
Primary clearance angle
Secondary clearance angle
Tooth angle : it is the angle
between the face and back (face
& land)
Flute or chip space: space
between two successive teeth
Generally 6-8 teeth are present

96.  Reduced use of cross cuts
 Extended head lengths
 Rounding of the sharp tip corners
 Reduced use of large diameter burs

97.  Rake angle
 Clearance angle
 Number of teeth or blades and their distribution
 Run out
 Finish of flutes
 Heat treatment
 Bur diameter
 Depth of cutting
 Influence of load
 Influence of speed

98.  RAKE ANGLE
Radial angle > negative rake
angle
Positive angle - more
clogging
 CLEARANCE ANGLE
Prevent friction
Less rapid dulling

99.  NO. OF BLADES
 Less blades remove more
material
 Less clogging
 Straight flutes-less temp
rise-larger chips
12 BLADE BUR 40 BLADE BUR BAKER-CURSON BUR

100. Run out
It is a dynamic test
It refers to the maximum
displacement of the bur head
from its axis of rotation while
the bur turns
Clinically acceptable
run out is 0.023mm
It mainly depends on the
1.Eccentricity of the bur
2.Precision of the handpiece
3.length of the bur shank

102.  1st
cut – flute is roughly
formed
 2nd
cut – cutting edge on
the bur flute
 Next cuts – roughness
on the flutes will be
removed

103.  Revelation type:
flutes come together at two
junctions near a diametrical
cutting edge
 Star cut :
flutes come together in a
common junction at the axis
of the bur

105.  Heat treatment :
 Used to harden the soft stainless steel burs
 This treatment is not used in tungsten carbide burs
 Influence of load :
Low speed – 1000 grams (2 pounds ) to 1500 grams
High speed – 60 to 120 grams (2 to 4 Ounces)
 Influence of speed :
Rate of cutting increases with rotational speed but it is not
directly proportional

106.  Diamond abrasive instruments
 Other abrasive instruments

107.  1st
introduced in USA-1945
 Small angular particles in
softer matrix
 Larger no. of cutting points
 ADVANTAGES:
Longer life
Better cutting effectiveness
DIAMOND ABRASIVES

108.  3 parts
 1.Metal blank
a) Head
b) Neck
c) Shank
 2.Powder diamond abrasive
 3.Metallic bonding material

109.  Diamond particles :
Natural and synthetic
Shape and size of the particles will
effect the cutting efficiency and
durability of the instruments
 Metallic bonding
material:
Diamonds attached to blank by
electroplating method

110.  1st
stage : Shank portion is coated with inert material
 2nd
stage : stainless steel blanks are then flash-plated or
strike–plated with a thin coating of nickel
 3rd
stage : It is performed in nickel–plating solution
commonly nickel sulfamate solution

111.  Microbrazing –technique :heat and vacuum are used for
attachment
 Sintering :mixture of diamond chips and powdered matrix
and metal (gold or copper alloy) are hot or cold compressed
on to the blank then it is heated

112. CLASSIFICATION
SHAPES & SIZES

113.  Size:
 Coarse(125-150µm),
 medium(88-125µm),
fine (60-74µm),
very fine(38-44µm),
finishing (10-38µm)
 Shape
 Hardness of the
particles
 Spacing
 Exposure
 Bonding of particles

114.  They are restricted to shaping, finishing and
polishing the restorations in the clinic and lab
1. Molded instruments
2. Coated instruments

115.  Abrasive particles are bonded to metal shank
through a binder
 1. Sintering
 2. Vitreous bonded abrasives are mixed with a glass or ceramic
matrix material , cold-pressed to the instrument shape , and fired
to fuse the binder
 3. Resin bonded abrasives are cold pressed or hot pressed and then
heated to cure the resin
 4. Rubber bonded abrasives are made in a manner similar to that
resin bonded

116.  Made by pressing uniform
mixture of abrasive and
matrix around end of shank
 Wearing causes
regeneration of particles
 TYPES:
Mounted & unmounted
stones, points
Hard & soft
 MATERIALS
Silicon carbide
(carborundum)
Aluminium oxide

117. FINISHERS
POLISHERS
Mounted stones

119.  Thin layer of abrasive is cemented
to a flexible blank
 They are softer & less wear
resistance
 Used for finishing and smoothing
procedures in indirect restorations
 MATRIX :
 Phenolic resins
 Rubber
 ABRASIVE MATERIALS :
Garnet
Quartz
Flint (sand)
Crocus
emery
Cuttlefish-polishing

120.  Cutting effectiveness :
 it is the rate of tooth structure removal (mm/min or mg/sec)
 Cutting efficiency :
 It is the percentage of energy actually producing the cutting
 it is possible to increase the effectiveness by reducing the
efficiency e.g. Dull bur cutting

121. Bladed cutting Abrasive cutting
Ductile material
Brittle material

122.  Most efficient for gross tooth removal
 Diamond abrasives : enamel
 Carbide burs : dentin
 Disadvantage:
In deep carious lesions-hand instruments preferable

123.  PULPAL PRECAUTIONS
remaining dentin thickness
Coolants
 SOFT TISSUE PRECAUTIONS
 EYE PRECAUTIONS
Glasses with side shields
High volume evacuation
 EAR PRECAUTIONS
85 Decibels-protection
Sound proofing
Ear plugs
 INHALATION PRECAUTIONS
Masks
Rubber dam

124.  Art and science of operative dentistry
Sturdevant’s
 Operative dentistry marzouk
 Text book of Operative dentistry
Baum-Philips-Lund
 Principles and practice of Operative dentistry
Charbeneau
 Text book of Operative dentistry
Vimal sikri
 Oprative dentistry Mc Gehee
 Operative dentistry Mc cabe
 www.ADA history .com

125. THANK YOU