Oper.i 09

Dr. lama khaled El Banna

Faculty of Oral and Dental Medicine

Al – Azhar University
operative dentistry

2. College of DentistryCollege of Dentistry
Operative Dentistry IOperative Dentistry I
Instruments & Instrumentation -2-Instruments & Instrumentation -2-

Dr. Hazem El AjramiDr. Hazem El Ajrami

3. Types of hand cutting instruments:Types of hand cutting instruments:
They are classified according to their use into They are classified according to their use into
chisels and excavators. Chisels are used primary chisels and excavators. Chisels are used primary
for cutting or cleaving enamel. Excavators are for cutting or cleaving enamel. Excavators are
used for removal of caries and refinement of used for removal of caries and refinement of
internal parts of the preparation. internal parts of the preparation.

4. Cleaving undermined Cleaving undermined
enamel using chisel enamel using chisel

5. I.I.Chisels: Chisels:
They include: They include:
1.1.Chisels. Chisels.
2.2.Enamel Hatchet. Enamel Hatchet.
3.3.Angle Formers. Angle Formers.
4.4.Gingival Margin Trimmers.Gingival Margin Trimmers.

7. 1.1.Chisels:Chisels:
These are instruments designed in a These are instruments designed in a
similar way to ordinary carpenter's tools, and similar way to ordinary carpenter's tools, and
are mainly intended to are mainly intended to cleave undermined cleave undermined
enamel and to shape enamel walls. enamel and to shape enamel walls. Their Their
blades are relatively heavier and beveled on blades are relatively heavier and beveled on
one side only to suit cutting of the hardest one side only to suit cutting of the hardest
tooth tissue. The force used with these types tooth tissue. The force used with these types
of chisels is essentially a straight thrust. of chisels is essentially a straight thrust. They They
include: include:

8. Straight Chisel:Straight Chisel:
It has a It has a straight blade straight blade in line with the handle in line with the handle
and shank. The cutting edge of instrument is and shank. The cutting edge of instrument is
running running perpendicular perpendicular to long axis of the to long axis of the
handle. The cutting edge is on one side only to handle. The cutting edge is on one side only to
be used as distal or mesial and it could be triple-be used as distal or mesial and it could be triple-
beveled. It is a beveled. It is a single planed instrument single planed instrument with a with a
three-figure formula.three-figure formula.

9. Straight ChiselStraight Chisel

10. Mono-angle Chisel:Mono-angle Chisel:
It is similar to straight chisel, but the blade It is similar to straight chisel, but the blade
is placed at an is placed at an angle angle with the long axis of the with the long axis of the
shaft. The cutting edge of the blade is either on shaft. The cutting edge of the blade is either on
the the distal aspect distal aspect of the blade «direct bevel» or of the blade «direct bevel» or
on its on its mesial aspect mesial aspect «reverse bevel», i.e. «reverse bevel», i.e. set of set of
two instruments.two instruments.

11. Mon-Angle Chisel Mon-Angle Chisel

12. Binangle Chisel:Binangle Chisel:
Its name indicates that there are Its name indicates that there are two angles two angles
between the blade and the shaft. It is also between the blade and the shaft. It is also
mesially or distally beveled. All mesially or distally beveled. All
aforementioned chisels have three possible aforementioned chisels have three possible
cutting movements: vertical, right and left. cutting movements: vertical, right and left.

13. Bin-angle Chisel Bin-angle Chisel

14. Wedelstaedt Chisel:Wedelstaedt Chisel:
It is similar to the straight chisel, but it has a It is similar to the straight chisel, but it has a
slight curvature slight curvature in the shank, not to the extent in the shank, not to the extent
that the blade will make a real angle with the that the blade will make a real angle with the
shaft. It is provided with either a shaft. It is provided with either a direct or direct or
reverse bevel reverse bevel (distal or mesial). They are used (distal or mesial). They are used
mainly for cleaving undermined enamel and mainly for cleaving undermined enamel and
shaping cavity walls in Class III and V cavities. shaping cavity walls in Class III and V cavities.

15. Widelstaedt ChiselWidelstaedt Chisel

16. WidelstaedtWidelstaedt
StraightStraight
Bin-angle Bin-angle

17. 2.2.Enamel Hatchet: Enamel Hatchet:
It is a chisel similar in design to the It is a chisel similar in design to the
ordinary hatchet (bibeveled) except that the ordinary hatchet (bibeveled) except that the
blade is blade is beveled on one side only. beveled on one side only. ItIt has its has its
cutting edges in a plane that is cutting edges in a plane that is parallel parallel with with
the axis of the handle and the axis of the handle and perpendicular perpendicular
to the long axis of the blade. Itto the long axis of the blade. It
comes as comes as right right or or left left types with a types with a three-figure three-figure
formula. formula. Hatchets are used for cleaving Hatchets are used for cleaving
undermined enamel in undermined enamel in proximal cavities proximal cavities and and
on on buccal and lingual walls buccal and lingual walls where it is not where it is not
possible to use chisels. possible to use chisels.

18. Enamel HatchetEnamel Hatchet

21. Enamel HatchetEnamel Hatchet

22. 3.3.Angle former:Angle former:
They are chisels made by grinding the bevel They are chisels made by grinding the bevel
at an angle of 80 degrees with the shaft, so that at an angle of 80 degrees with the shaft, so that
the cutting edge will be at an angle with the the cutting edge will be at an angle with the
blade blade making itmaking it a a four-figure formula four-figure formula
instrument. instrument. This design creates a This design creates a pointed and pointed and
linear linear cutting edge. They are cutting edge. They are single-planed single-planed
instruments, with instruments, with right right or or left left beveling. Angle beveling. Angle
formers are also triple beveled, i.e. beveled at formers are also triple beveled, i.e. beveled at
the cutting edge as well as at the sides of their the cutting edge as well as at the sides of their
blades affording the instrument an additional blades affording the instrument an additional
cutting potential to accentuate line and point cutting potential to accentuate line and point
angles. angles.

23. Angle FormersAngle Formers

24. Angle FormersAngle Formers

25. 4.4.Gingival Margin Trimmers (GMT):Gingival Margin Trimmers (GMT):
They are modified enamel hatchets, with two They are modified enamel hatchets, with two
distinct differences: distinct differences:
Their blades Their blades are curved are curved either to the either to the right right or or
left; left; that makes them that makes them double-planed double-planed
instruments and designed for instruments and designed for lateral cutting.lateral cutting.
Their cutting edges make an Their cutting edges make an angle angle with the with the
blade other than 90 degree which makes them blade other than 90 degree which makes them
have a have a four-figure formula.four-figure formula.

26. Mesial (A) and distal (B) GMT Mesial (A) and distal (B) GMT
compared to enamel hatchet (Ccompared to enamel hatchet (C) )

27. There are two pairs of these instruments (it There are two pairs of these instruments (it
contains a contains a set of four). set of four). Each pair has a Each pair has a right right and a and a
left left beveled instrument. The cutting edge of one beveled instrument. The cutting edge of one
pair makes an acute angle with the edge of the pair makes an acute angle with the edge of the
blade blade furthest from the handle furthest from the handle and are thus called and are thus called
distal GMT distal GMT (cutting edge angle is 90 (cutting edge angle is 90 to 100 to 100
centigrade). centigrade). A distal pair is used to cut on the A distal pair is used to cut on the
distal gingival margin distal gingival margin of the cavity. The cutting of the cavity. The cutting
edge of the other pair makes an acute angle with edge of the other pair makes an acute angle with
the edge of the blade the edge of the blade nearer to the handle; nearer to the handle; they they
are called mesial GMT (cutting edge angle is 85 are called mesial GMT (cutting edge angle is 85
to to 75 75 centigrade)centigrade). A mesial pair is used to cut on . A mesial pair is used to cut on
the the mesial gingival margin mesial gingival margin of the cavity. of the cavity.

28. Gingival Margin Trimmers
mesial
distal

29. Uses of GMT:Uses of GMT:
It is originally designed to It is originally designed to trim the gingival trim the gingival
enamel margins enamel margins of proximal portion of cavity of proximal portion of cavity
preparations where the enamel rods are preparations where the enamel rods are
slanted or inclined gingivally. The angles slanted or inclined gingivally. The angles
most commonly used for this purpose is 90 most commonly used for this purpose is 90
(distal) and 85 (mesial).(distal) and 85 (mesial).
Squaring or Squaring or roundation of the axio-pulpal roundation of the axio-pulpal
line angle line angle of proximo-occlusal preparations of proximo-occlusal preparations
to avoid stress concentration of the isthmus. to avoid stress concentration of the isthmus.

30. A: Right mesial (a) and distal (b) GMT, B: Distal
GMT used to trim distal gingival seat, C: same GMT
used for roundation of the axio-pulpalline angle and
D: distal GMT used to place gingival bevel in mesial
portion of the preparation.

31. Performing the Performing the reverse bevel (gingival lock) reverse bevel (gingival lock)
indicated with indicated with cast gold cast gold restoration. It is placed restoration. It is placed
on the gingival seat at the axio-gingival line on the gingival seat at the axio-gingival line
angle. In this case, the angle. In this case, the reverse side reverse side of GMT is of GMT is
used, i.e. mesial GMT is used in the distal and used, i.e. mesial GMT is used in the distal and
vice versa. GMT with cutting edge angle 100 vice versa. GMT with cutting edge angle 100
(distal) and 75 (mesial) are used to produce a (distal) and 75 (mesial) are used to produce a
steep gingival bevel (to increase retention). steep gingival bevel (to increase retention).

33. II.II.Excavators:Excavators:
They are mainly designed for the They are mainly designed for the
excavation excavation and removal of and removal of decayed tooth decayed tooth
structures structures and for and for shaping internal parts shaping internal parts of of
cavities. In other words, they are mainly cavities. In other words, they are mainly
designed to work on designed to work on dentin. They include:dentin. They include:
1)1)Hatchet excavator (Ordinary Hatchet).Hatchet excavator (Ordinary Hatchet).
2)2)Hoe excavator.Hoe excavator.
3)3)Spoon excavators.Spoon excavators.
4)4)Discoid excavator «Disc-Like».Discoid excavator «Disc-Like».
5)5)Cleoid excavator. Cleoid excavator.

34. 1)1)Hatchet Excavator (Ordinary Hatchet):Hatchet Excavator (Ordinary Hatchet):
The blades of these instruments are equally The blades of these instruments are equally
bi-beveled bi-beveled on the right and left aspects of the on the right and left aspects of the
blade. Thus, the cutting edge runs blade. Thus, the cutting edge runs parallel parallel to to
the central axis of the shaft. They are used in a the central axis of the shaft. They are used in a
forward push motion in the direction of the forward push motion in the direction of the
length of the blade. They are used primarily on length of the blade. They are used primarily on
anterior teeth in sharpening internal line anterior teeth in sharpening internal line
angles, particularly in preparation for angles, particularly in preparation for direct direct
gold gold restorations. They may cut off a wall by restorations. They may cut off a wall by
direct cutting action or may be used laterally direct cutting action or may be used laterally
with a scraping motion. with a scraping motion.

36. Hatchet Excavator

37. 2)2)Hoe Excavator:Hoe Excavator:
The blade is place at a The blade is place at a right angle right angle to the to the
central axis of the shaft. It is provided with a central axis of the shaft. It is provided with a
distal bevel. distal bevel. It is used for the removal of harder It is used for the removal of harder
varieties of caries. It is used for planning the varieties of caries. It is used for planning the
internal walls and line angles of the internal walls and line angles of the
preparations. It is commonly used in Classes preparations. It is commonly used in Classes
III and V preparations for direct gold III and V preparations for direct gold
restorations. It may be differentiated from a restorations. It may be differentiated from a
chisel by having the blade angled more than chisel by having the blade angled more than
12.5 centigrade (a chisel has a blade that is 12.5 centigrade (a chisel has a blade that is
angled up to 12.5 centigrade). angled up to 12.5 centigrade).

39. Hoe ExcavatorHoe Excavator

40. 3)3)Spoon Excavators:Spoon Excavators:
The blade of these instruments is The blade of these instruments is curved curved
either to the right or to the left. Thus, the either to the right or to the left. Thus, the
direction of the curve of the blade makes the direction of the curve of the blade makes the
instruments instruments right right or or left, left, i.e., i.e., lateral cutting, lateral cutting,
double planed double planed instruments. The cutting edge is instruments. The cutting edge is
ground to a semi-circle forming a thin edge ground to a semi-circle forming a thin edge
(circumferential bevel)(circumferential bevel). They are designed for . They are designed for
removal of soft carious dentin. removal of soft carious dentin.

41. Spoon ExcavatorSpoon Excavator

43. 4)4)Discoid excavator «Disc-Like»:Discoid excavator «Disc-Like»:
It resembles the spoon excavator but the It resembles the spoon excavator but the
blade is blade is circular circular in shape. The cutting edge in shape. The cutting edge
extends around the whole periphery, except extends around the whole periphery, except
the part which joins the blade with the shank. the part which joins the blade with the shank.
They are used for They are used for excavation of soft dentin.excavation of soft dentin.

44. Discoid ExcavatorDiscoid Excavator

45. 5)5)Cleoid Excavator:Cleoid Excavator:
It is a It is a «Claw-like» «Claw-like» instrument used to instrument used to
excavate soft dentin excavate soft dentin and to and to remove pulp remove pulp
chamber chamber during endodontic treatment. It is during endodontic treatment. It is
most helpful for carving gold foil and most helpful for carving gold foil and
amalgam, especially for the creation of amalgam, especially for the creation of
proximal fossa and marginal ridges. proximal fossa and marginal ridges.

46. Cleoid ExcavatorCleoid Excavator

47. Instrument Grasps: Instrument Grasps:
There are four grasps used with the hand There are four grasps used with the hand
instruments:instruments:
1.1.Modified pen.Modified pen.
2.2.Inverted pen.Inverted pen.
3.3.Palm and thumb.Palm and thumb.
4.4.Modified palm and thumb.Modified palm and thumb.
The conventional pen grasp is not an The conventional pen grasp is not an
acceptable instrument grasp. acceptable instrument grasp. With each grasp, With each grasp,
proper rest and guard proper rest and guard is mandatory. is mandatory.

48. Rests and Guards:Rests and Guards:
A proper instrument grasp must include a firm A proper instrument grasp must include a firm
rest rest (support) (support) to steady the hand during operating to steady the hand during operating
procedures. The support must be gained from procedures. The support must be gained from hard hard
tissue; tissue; soft tissue rests or too distant hard tissue soft tissue rests or too distant hard tissue
rests does not afford reliable control. Normally, rests does not afford reliable control. Normally,
the support is gained with finger rests with the the support is gained with finger rests with the
same hand holding the instrument. If this is not same hand holding the instrument. If this is not
possible, possible, indirect rest indirect rest may be gained using the may be gained using the
opposite hand where the index finger is rested on opposite hand where the index finger is rested on
the shank of the instrument the shank of the instrument or or the operating hand the operating hand
rests on the opposite hand which rests on stable rests on the opposite hand which rests on stable
oral structure. oral structure.

49. •Guards Guards are hand instruments or other items are hand instruments or other items
such as interproximal wedges used to such as interproximal wedges used to protect protect
soft tissue soft tissue from contact with sharp cutting or from contact with sharp cutting or
abrasive instruments. abrasive instruments.

51. Modified pen grasp:Modified pen grasp:
It is similar to that used in holding a pen, It is similar to that used in holding a pen,
except that the thumb, index and middle fingers except that the thumb, index and middle fingers
contact the instrument contact the instrument while the tips of the ring while the tips of the ring
and little fingers are placed on the and little fingers are placed on the nearby tooth nearby tooth
surface surface of the same arch as a of the same arch as a rest rest (support). The (support). The
palm of the hand is facing away from the palm of the hand is facing away from the
operator. operator.

55. •This in turn provides facility, great power and This in turn provides facility, great power and
wide range of movement. If the hand is rotated wide range of movement. If the hand is rotated
so that the palm faces more toward the operator; so that the palm faces more toward the operator;
this is called the this is called the inverted pen graspinverted pen grasp. . It is used in It is used in
the lingual surface of anterior teeth. the lingual surface of anterior teeth.

57. Palm-and-thumb grasp:Palm-and-thumb grasp:
It is similar to that used for holding a It is similar to that used for holding a
knife while paring the skin from an apple. knife while paring the skin from an apple.
The handle of the instrument is placed in the The handle of the instrument is placed in the
palm of the hand and grasped by all the fingers, palm of the hand and grasped by all the fingers,
while the thumb is free of the instrument and the while the thumb is free of the instrument and the
rest rest is provided by supporting the tip of the is provided by supporting the tip of the
thumb on a nearby tooth of the same arch. thumb on a nearby tooth of the same arch.

59. •If the thumb is rested on the tooth being If the thumb is rested on the tooth being
prepared; it is called prepared; it is called Modified Palm-and-Modified Palm-and-
thumb graspthumb grasp. . It is usually used in the area of It is usually used in the area of
maxillary arch and is best adopted when maxillary arch and is best adopted when
operator is working from a rear-chair position. operator is working from a rear-chair position.

61. Instrument Sharpening:Instrument Sharpening:
The edges of cutting instruments should The edges of cutting instruments should
always be kept sharp as dull instruments are less always be kept sharp as dull instruments are less
controllable, cause more pain to the patient, controllable, cause more pain to the patient,
prolong the operating time and reduce the quality prolong the operating time and reduce the quality
and precision of the tooth preparation.and precision of the tooth preparation.

62. Sharpness tests:Sharpness tests:
The presence of a "glint" or a bright, shiny The presence of a "glint" or a bright, shiny
cutting edge indicates that the edge is dull or cutting edge indicates that the edge is dull or
rounded. Alternatively, the instrument can be rounded. Alternatively, the instrument can be
pulled across hard plastic, such as the handle of a pulled across hard plastic, such as the handle of a
plastic mouth mirror, or an evacuation tip. A dull plastic mouth mirror, or an evacuation tip. A dull
blade will slide across the plastic; a sharp blade blade will slide across the plastic; a sharp blade
will cut into the surface, and its movement is will cut into the surface, and its movement is
stopped. stopped.

63. Sharpening principles:Sharpening principles:
In the use of any sharpening equipment, In the use of any sharpening equipment,
several basic principles of sharpening should be several basic principles of sharpening should be
followed: followed:
Sharpening of the instruments is done only Sharpening of the instruments is done only
after they have been cleaned and sterilized. after they have been cleaned and sterilized.
Establish the proper bevel angle (usually 45 Establish the proper bevel angle (usually 45
degrees) and the desired angle of the cutting degrees) and the desired angle of the cutting
edge to the blade before placing the edge to the blade before placing the
instrument against the sharpening equipment. instrument against the sharpening equipment.

64. Use a light pressure against the stone to lessen Use a light pressure against the stone to lessen
frictional heat and remove as little metal from frictional heat and remove as little metal from
the blade as possible. the blade as possible.
Use a rest or guide whenever possible. Use a rest or guide whenever possible.
After sharpening, resterilize the instrument. After sharpening, resterilize the instrument.
Keep the sharpening stone clean and free of Keep the sharpening stone clean and free of
metal cuttings.metal cuttings.

65. Sharpening equipments:Sharpening equipments:
Many types of sharpening equipments exist Many types of sharpening equipments exist
including stationary sharpening stones and including stationary sharpening stones and
mechanical sharpeners. mechanical sharpeners.
I.I.Stationary sharpening stone:Stationary sharpening stone:
It is often called oilstone because of the It is often called oilstone because of the
common practice of applying a little oil to common practice of applying a little oil to
aid the sharpening process. It could be made aid the sharpening process. It could be made
of fine grit of Arkansas stone, silicon of fine grit of Arkansas stone, silicon
carbide or aluminum oxide. carbide or aluminum oxide.

67. II.II.Mechanical sharpener: Mechanical sharpener:
It moves at a slow speed while the It moves at a slow speed while the
instrument is held at the appropriate instrument is held at the appropriate
angulations and supported by a rest. angulations and supported by a rest.
Interchangeable aluminum oxide wheel Interchangeable aluminum oxide wheel
stones of different shapes and coarseness are stones of different shapes and coarseness are
available. It is easier, less time consuming available. It is easier, less time consuming
and can fill almost all instrument sharpening and can fill almost all instrument sharpening
needs.needs.
Alternatively, an Alternatively, an Arkansas wheel stone Arkansas wheel stone
rotating in a handpiece could be used in rotating in a handpiece could be used in
between treatments. between treatments.

71. Advantages of hand over rotary cutting Advantages of hand over rotary cutting
instruments: instruments:
1.1.It will not cut into sound tooth structure It will not cut into sound tooth structure
leading to more conservative cutting leading to more conservative cutting
procedure. procedure.
2.2.It produces no vibration or heat generation; it It produces no vibration or heat generation; it
is thus painless and more biological. is thus painless and more biological.
3.3.It has efficient cutting; as it can remove large It has efficient cutting; as it can remove large
area of undermined enamel in one stroke, area of undermined enamel in one stroke,
thus saving time and effort. thus saving time and effort.

72. 4.4.It cleaves enamel at the interprismatic It cleaves enamel at the interprismatic
substance; it thus ensures that the cutting is substance; it thus ensures that the cutting is
performed in the direction of enamel rods and performed in the direction of enamel rods and
that the cavosurface margin is formed of full that the cavosurface margin is formed of full
length sound enamel rods. length sound enamel rods.
5.5.It produces smoother, better finished surfaces. It produces smoother, better finished surfaces.
6.6.Have longer life span. Have longer life span.

74. Powered cutting equipmentPowered cutting equipment
Power sources:Power sources:
Removal of tooth structure can be done using Removal of tooth structure can be done using
any of the following power sources: any of the following power sources:
1.1.Rotary equipments.Rotary equipments.
2.2.The ultrasonic equipment (Sono-abrasion).The ultrasonic equipment (Sono-abrasion).
3.3.The air abrasion equipment.The air abrasion equipment.
4.4.Laser equipments. Laser equipments.

75. 1.1.Rotary equipments:Rotary equipments:
Rotary instruments are the most universally Rotary instruments are the most universally
used instruments for gross removal of tooth used instruments for gross removal of tooth
structure and will thus be discussed later in structure and will thus be discussed later in
details. details.

76. 2.2.The ultrasonic equipment (Sono-abrasion): The ultrasonic equipment (Sono-abrasion):
This technique is based on the removal of This technique is based on the removal of
tooth material by an air-driven hand piece tooth material by an air-driven hand piece
equipped with a equipped with a diamond-coated working tip diamond-coated working tip
that removes tooth material by that removes tooth material by ultrasonic ultrasonic
energy. energy. Different sizes and shapes of diamond Different sizes and shapes of diamond
tips have been designed, enabling easy access to tips have been designed, enabling easy access to
occlusal and approximal tooth lesions. As these occlusal and approximal tooth lesions. As these
tips are coated only tips are coated only on one side, on one side, trauma of the trauma of the
approximal side of adjacent teeth is prevented. approximal side of adjacent teeth is prevented.

78. 3.3.The air abrasion equipment:The air abrasion equipment:
The tooth structure is removed by means of The tooth structure is removed by means of
tiny tiny aluminum oxide aluminum oxide particles (abrasive) ejected particles (abrasive) ejected
at great velocity by means of a high pressure gas at great velocity by means of a high pressure gas
stream directed at a definite angle. This abrasive stream directed at a definite angle. This abrasive
technique increases patient comfort by reducing technique increases patient comfort by reducing
heat, vibration, and noise, as commonly heat, vibration, and noise, as commonly
experienced during mechanical preparation of experienced during mechanical preparation of
teeth when rotating burs are used. teeth when rotating burs are used.

80. •However, their use is limited mainly because However, their use is limited mainly because
loss of dentist's tactile sense, high cost and loss of dentist's tactile sense, high cost and
problems involving removal of the dust problems involving removal of the dust
particles. They are mainly used in particles. They are mainly used in
enameloplasty and caries removal from pits and enameloplasty and caries removal from pits and
fissures, with pit & fissure sealant, in fissures, with pit & fissure sealant, in
micromechanical roughening of surfaces to be micromechanical roughening of surfaces to be
bonded and in minimally invasive dentistry or bonded and in minimally invasive dentistry or
microdentistry. microdentistry.

81. 4.4.Laser equipments:Laser equipments:
Lasers are devices that produce beams of Lasers are devices that produce beams of
coherent and very high light intensity. Laser coherent and very high light intensity. Laser
technology can remove tooth substrate technology can remove tooth substrate
effectively and precisely by means of a thermo-effectively and precisely by means of a thermo-
mechanical ablation process (micro-explosions). mechanical ablation process (micro-explosions).
Lasers are used mainly for soft tissue Lasers are used mainly for soft tissue
applications (such as gingivectomy), surface applications (such as gingivectomy), surface
modification (enamel etching) before bonding modification (enamel etching) before bonding
and in curing of resin composite. They are and in curing of resin composite. They are
generally not used for tooth preparation because generally not used for tooth preparation because
it is inefficient in removing large amounts of it is inefficient in removing large amounts of
tooth structure and its high cost. tooth structure and its high cost.

83. Rotary equipments: Rotary equipments:
Rotary equipments are chiefly used for the Rotary equipments are chiefly used for the
removal of tooth structures and restorative removal of tooth structures and restorative
materials. However, some of them are used for materials. However, some of them are used for
condensation of restorative materials as condensation of restorative materials as
amalgam or gold foil as mechanical condensers, amalgam or gold foil as mechanical condensers,
or for burnishing and finishing of restorations as or for burnishing and finishing of restorations as
mechanical burnishers and finishing tools. It mechanical burnishers and finishing tools. It
basically includes a power source and tools or basically includes a power source and tools or
attachments that are fitted in the hand-piece. attachments that are fitted in the hand-piece.

84. Rotary Power Sources:Rotary Power Sources:
I.I.Electric Motors:Electric Motors:
In the past rotary power from an electric In the past rotary power from an electric
motor was transferred to a hand-piece by a motor was transferred to a hand-piece by a
belt and pulleys. Operating speed was low belt and pulleys. Operating speed was low
(5000 - 15,000 rpm). It is seldom used (5000 - 15,000 rpm). It is seldom used
except in dental laboratories where low except in dental laboratories where low
speed is desirable. New micro-motors deliver speed is desirable. New micro-motors deliver
speed range of 20,000 - 60,000 rpm and are speed range of 20,000 - 60,000 rpm and are
alternatively used nowadays. alternatively used nowadays.

86. II.II.Airotors: Airotors:
Air turbine dental units driven by a source Air turbine dental units driven by a source
of compressed air, developed in the late of compressed air, developed in the late
1950s, eliminated the necessity of having an 1950s, eliminated the necessity of having an
electric engine as a part of a standard dental electric engine as a part of a standard dental
unit. By having the turbine rotated by air, all unit. By having the turbine rotated by air, all
friction is eliminated, and speeds may be friction is eliminated, and speeds may be
increased to over 800,000 rpm. Air turbines increased to over 800,000 rpm. Air turbines
are the most popular and widely used types of are the most popular and widely used types of
rotary equipment. rotary equipment.

87. Rotary Speed Ranges: Rotary Speed Ranges:
The rotational speed of an instrument is The rotational speed of an instrument is
measured in revolutions per minute (rpm). measured in revolutions per minute (rpm).
Three speed ranges are generally recognized: Three speed ranges are generally recognized:
a.a.Low or slow speeds (below 12,000 rpm). Low or slow speeds (below 12,000 rpm).
b.b.Medium or intermediate speeds (12,000 to Medium or intermediate speeds (12,000 to
200,000 rpm).200,000 rpm).
c.c.High or ultrahigh speeds (above 200,000 High or ultrahigh speeds (above 200,000
rpm). rpm).

88. •Although intact tooth structure can be removed Although intact tooth structure can be removed
by an instrument rotating at low speed, it is a by an instrument rotating at low speed, it is a
traumatic experience for both the patient and the traumatic experience for both the patient and the
dentist. Low speed cutting is ineffective, time dentist. Low speed cutting is ineffective, time
consuming, and requires a relatively heavy force consuming, and requires a relatively heavy force
of application. It produces heat and vibration of application. It produces heat and vibration
which are the main source of patient discomfort. which are the main source of patient discomfort.
Therefore, low speed range is most suitable for Therefore, low speed range is most suitable for
caries removal and finishing and polishing caries removal and finishing and polishing
procedures. At high speed, the surface speed procedures. At high speed, the surface speed
needed for efficient cutting can be attained with needed for efficient cutting can be attained with
smaller and more versatile cutting instruments. smaller and more versatile cutting instruments.

89. The advantages of using high speed are:The advantages of using high speed are:
1.1.Remove tooth structure faster with less Remove tooth structure faster with less
pressure and vibration. pressure and vibration.
2.2.The number of rotary cutting tools is reduced The number of rotary cutting tools is reduced
because smaller sizes are more often used. because smaller sizes are more often used.
3.3.The operator has better control. The operator has better control.
4.4.Due to the lower level of vibration produced, Due to the lower level of vibration produced,
the patient is less apprehensive. the patient is less apprehensive.
5.5.Several teeth in the same arch can be treated Several teeth in the same arch can be treated
at the same appointment. at the same appointment.

90. Handpieces:Handpieces:
A handpiece is a device for holding the A handpiece is a device for holding the
rotating instrument, transmitting power to rotating instrument, transmitting power to
them and positioning them intra-orally. They them and positioning them intra-orally. They
are developed as two basic types: are developed as two basic types:
I.I.Straight handpieces:Straight handpieces:
It has a straight, tubular shape. Its mode It has a straight, tubular shape. Its mode
of attachment to the cutting tool could be of attachment to the cutting tool could be
through friction grip or a latch head. It is through friction grip or a latch head. It is
driven by electricity or air and used mainly driven by electricity or air and used mainly
for laboratory procedures. for laboratory procedures.

92. II.II.Contra-angle hand pieces:Contra-angle hand pieces:
Low-speed contra-angle handpiece: Low-speed contra-angle handpiece:
It is tubular-shaped, with an angulation It is tubular-shaped, with an angulation
between the head and the shank. The head between the head and the shank. The head
attachment could also be friction grip head attachment could also be friction grip head
or latch type. They are used for finishing or latch type. They are used for finishing
cavity preparation, to remove caries, and cavity preparation, to remove caries, and
for finishing and polishing of the for finishing and polishing of the
restorations. restorations.

94. High-speed contra-angle handpiece: High-speed contra-angle handpiece:
It is tubular-shaped with It is tubular-shaped with slight slight angulation angulation
between the head and the shank. It is between the head and the shank. It is powered by powered by
air air (air-driven) and capable of rotational speeds (air-driven) and capable of rotational speeds
in excess of 200,000 rpm. The head attachment in excess of 200,000 rpm. The head attachment
is friction grip is friction grip only. It is principally used for only. It is principally used for
gross tooth structure removal and cavity gross tooth structure removal and cavity
preparation. However, due to small size of the preparation. However, due to small size of the
turbine in the head, they have low torque and are turbine in the head, they have low torque and are
unsuitable unsuitable for some finishing and polishing for some finishing and polishing
procedures. procedures.

96. •Many improvements of the contra-angle Many improvements of the contra-angle
handpiece include smaller head size, lower noise handpiece include smaller head size, lower noise
levels and better chucking mechanisms. Since levels and better chucking mechanisms. Since
1955, contra-angle handpieces have had air-1955, contra-angle handpieces have had air-
water spray feature to provide cooling, cleansing water spray feature to provide cooling, cleansing
and improved visibility. Modem contra-angle and improved visibility. Modem contra-angle
handpieces also include fiber-optic lighting of handpieces also include fiber-optic lighting of
the cutting site. the cutting site.

98. Rotary tools:Rotary tools:
These are rotary tools or attachments that These are rotary tools or attachments that
are fitted in the handpiece to achieve the are fitted in the handpiece to achieve the
desired procedure. They may be one of two desired procedure. They may be one of two
types: types: burs, burs, which are cutting tools, and which are cutting tools, and
abrasives abrasives which are abrading tools. which are abrading tools.

99. A.A.Burs:Burs:
The bur is considered a form of drill or The bur is considered a form of drill or
milling cutter especially manufactured to suit milling cutter especially manufactured to suit
dental purposes.dental purposes.
Bur design:Bur design:
Each instrument consists of three parts; Each instrument consists of three parts;
the shank, the neck and the head. Each of the shank, the neck and the head. Each of
these parts has its own function which these parts has its own function which
influences its design. influences its design.

101. 1)1)Shank: Shank:
It is that part of bur that fits into the It is that part of bur that fits into the
handpiece. There are three shank designs handpiece. There are three shank designs
available for, straight handpiece, latch type available for, straight handpiece, latch type
handpiece, and friction grip handpiece. In handpiece, and friction grip handpiece. In
addition, modified burs with short shanks are addition, modified burs with short shanks are
available for use in inaccessible areas. available for use in inaccessible areas.

104. 2)2)Neck:Neck:
It is the intermediate portion of the bur that It is the intermediate portion of the bur that
connects the head to the shank. The neck usually connects the head to the shank. The neck usually
tapers from the shank towards the head. Its main tapers from the shank towards the head. Its main
function is to transmit rotational force to the function is to transmit rotational force to the
head.head.
3)3)Head: Head:
The head is the working part of the bur. The The head is the working part of the bur. The
shape of the bur head is strongly related to its shape of the bur head is strongly related to its
intended use and technique of application. Burs intended use and technique of application. Burs
can be classified according to their material of can be classified according to their material of
construction, number of the blades, head shapes construction, number of the blades, head shapes
and sizes. and sizes.

105. Material of construction:Material of construction:
The dental burs may be made of either The dental burs may be made of either carbon carbon
steel steel or or tungsten carbide. tungsten carbide.
Carbide burs are quite Carbide burs are quite more efficient more efficient and have and have
longer life longer life than steel burs. They also generate than steel burs. They also generate
much much less heat less heat during cavity preparation during cavity preparation
because they are more effective cutters, because they are more effective cutters,
especially at high speeds; steel burs are used especially at high speeds; steel burs are used
only at low speed ranges. The superiority of only at low speed ranges. The superiority of
carbide burs over steel burs in cutting tooth carbide burs over steel burs in cutting tooth
structures is due to: structures is due to:

106. I.I.Their higher Vickers Hardness Number (about Their higher Vickers Hardness Number (about
1700V.H.N.) as compared to steel burs (about 1700V.H.N.) as compared to steel burs (about
600V.H.N .). 600V.H.N .).
II.II.Their greater strength which allows them to Their greater strength which allows them to
withstand cutting at higher speeds at higher withstand cutting at higher speeds at higher
temperatures. It also increases the resistance temperatures. It also increases the resistance
of their blades to dulling or turning out during of their blades to dulling or turning out during
cavity preparation, and thus helps maintaining cavity preparation, and thus helps maintaining
their sharpness. their sharpness.
III.III.The superior treatment and careful designing The superior treatment and careful designing
that they receive during manufacturing. that they receive during manufacturing.

107. •Carbide burs, however, are much more Carbide burs, however, are much more
expensive and they are brittle; they expensive and they are brittle; they
fracture readily if subjected to high impact fracture readily if subjected to high impact
forces (allowed to drop, or if subjected forces (allowed to drop, or if subjected
to bending in the cavity). to bending in the cavity).

108. Thank YouThank You