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 intoThey are classified according to their use into
chisels and excavators. Chisels are used primarychisels and excavators. Chisels are used primary
for cutting or cleaving enamel. Excavators arefor cutting or cleaving enamel. Excavators are
used for removal of caries and refinement ofused for removal of caries and refinement of
internal parts of the preparation.internal parts of the preparation.

4. Cleaving underminedCleaving undermined
enamel using chiselenamel 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 aThese are instruments designed in a
similar way to ordinary carpenter's tools, andsimilar way to ordinary carpenter's tools, and
are mainly intended toare mainly intended to cleave underminedcleave undermined
enamel and to shape enamel walls.enamel and to shape enamel walls. TheirTheir
blades are relatively heavier and beveled onblades are relatively heavier and beveled on
one side only to suit cutting of the hardestone side only to suit cutting of the hardest
tooth tissue. The force used with these typestooth tissue. The force used with these types
of chisels is essentially a straight thrust.of chisels is essentially a straight thrust. TheyThey
include:include:

8. Straight Chisel:Straight Chisel:
It has aIt has a straight bladestraight blade in line with the handlein line with the handle
and shank. The cutting edge of instrument isand shank. The cutting edge of instrument is
runningrunning perpendicularperpendicular to long axis of theto long axis of the
handle. The cutting edge is on one side only tohandle. 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 abeveled. It is a single planed instrumentsingle planed instrument with awith 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 bladeIt is similar to straight chisel, but the blade
is placed at anis placed at an angleangle with the long axis of thewith the long axis of the
shaft. The cutting edge of the blade is either onshaft. The cutting edge of the blade is either on
thethe distal aspectdistal aspect of the blade «direct bevel» orof the blade «direct bevel» or
on itson its mesial aspectmesial aspect «reverse bevel», i.e.«reverse bevel», i.e. set ofset of
two instruments.two instruments.

11. Mon-Angle ChiselMon-Angle Chisel

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

13. Bin-angle ChiselBin-angle Chisel

14. Wedelstaedt Chisel:Wedelstaedt Chisel:
It is similar to the straight chisel, but it has aIt is similar to the straight chisel, but it has a
slight curvatureslight curvature in the shank, not to the extentin the shank, not to the extent
that the blade will make a real angle with thethat the blade will make a real angle with the
shaft. It is provided with either ashaft. It is provided with either a direct ordirect or
reverse bevelreverse bevel (distal or mesial). They are used(distal or mesial). They are used
mainly for cleaving undermined enamel andmainly 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-angleBin-angle

17. 2.2. Enamel Hatchet:Enamel Hatchet:
It is a chisel similar in design to theIt is a chisel similar in design to the
ordinary hatchet (bibeveled) except that theordinary hatchet (bibeveled) except that the
blade isblade is beveled on one side only.beveled on one side only. ItIt has itshas its
cutting edges in a plane that iscutting edges in a plane that is parallelparallel withwith
the axis of the handle andthe axis of the handle and perpendicularperpendicular
to the long axis of the blade. Itto the long axis of the blade. It
comes ascomes as rightright oror leftleft types with atypes with a three-figurethree-figure
formula.formula. Hatchets are used for cleavingHatchets are used for cleaving
undermined enamel inundermined enamel in proximal cavitiesproximal cavities andand
onon buccal and lingual wallsbuccal and lingual walls where it is notwhere 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 bevelThey are chisels made by grinding the bevel
at an angle of 80 degrees with the shaft, so thatat an angle of 80 degrees with the shaft, so that
the cutting edge will be at an angle with thethe cutting edge will be at an angle with the
bladeblade making itmaking it aa four-figure formulafour-figure formula
instrument.instrument. This design creates aThis design creates a pointed andpointed and
linearlinear cutting edge. They arecutting edge. They are single-planedsingle-planed
instruments, withinstruments, with rightright oror leftleft beveling. Anglebeveling. Angle
formers are also triple beveled, i.e. beveled atformers are also triple beveled, i.e. beveled at
the cutting edge as well as at the sides of theirthe cutting edge as well as at the sides of their
blades affording the instrument an additionalblades affording the instrument an additional
cutting potential to accentuate line and pointcutting 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 twoThey are modified enamel hatchets, with two
distinct differences:distinct differences:
 Their bladesTheir blades are curvedare curved either to theeither to the rightright oror
left;left; that makes themthat makes them double-planeddouble-planed
instruments and designed forinstruments and designed for lateral cutting.lateral cutting.
 Their cutting edges make anTheir cutting edges make an angleangle with thewith the
blade other than 90 degree which makes themblade other than 90 degree which makes them
have ahave a four-figure formula.four-figure formula.

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

27. There are two pairs of these instruments (itThere are two pairs of these instruments (it
contains acontains a set of four).set of four). Each pair has aEach pair has a rightright and aand a
leftleft beveled instrument. The cutting edge of onebeveled instrument. The cutting edge of one
pair makes an acute angle with the edge of thepair makes an acute angle with the edge of the
bladeblade furthest from the handlefurthest from the handle and are thus calledand are thus called
distal GMTdistal GMT (cutting edge angle is 90(cutting edge angle is 90 to 100to 100
centigrade).centigrade). A distal pair is used to cut on theA distal pair is used to cut on the
distal gingival margindistal gingival margin of the cavity. The cuttingof the cavity. The cutting
edge of the other pair makes an acute angle withedge of the other pair makes an acute angle with
the edge of the bladethe edge of the blade nearer to the handle;nearer to the handle; theythey
are called mesial GMT (cutting edge angle is 85are called mesial GMT (cutting edge angle is 85
toto 7575 centigrade)centigrade). A mesial pair is used to cut on. A mesial pair is used to cut on
thethe mesial gingival marginmesial 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 toIt is originally designed to trim the gingivaltrim the gingival
enamel marginsenamel margins of proximal portion of cavityof proximal portion of cavity
preparations where the enamel rods arepreparations where the enamel rods are
slanted or inclined gingivally. The anglesslanted or inclined gingivally. The angles
most commonly used for this purpose is 90most commonly used for this purpose is 90
(distal) and 85 (mesial).(distal) and 85 (mesial).
Squaring orSquaring or roundation of the axio-pulpalroundation of the axio-pulpal
line angleline angle of proximo-occlusal preparationsof 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 thePerforming the reverse bevel (gingival lock)reverse bevel (gingival lock)
indicated withindicated with cast goldcast gold restoration. It is placedrestoration. It is placed
on the gingival seat at the axio-gingival lineon the gingival seat at the axio-gingival line
angle. In this case, theangle. In this case, the reverse sidereverse side of GMT isof GMT is
used, i.e. mesial GMT is used in the distal andused, i.e. mesial GMT is used in the distal and
vice versa. GMT with cutting edge angle 100vice 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 theThey are mainly designed for the
excavationexcavation and removal ofand removal of decayed toothdecayed tooth
structuresstructures and forand for shaping internal partsshaping internal parts ofof
cavities. In other words, they are mainlycavities. In other words, they are mainly
designed to work ondesigned 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 equallyThe blades of these instruments are equally
bi-beveledbi-beveled on the right and left aspects of theon the right and left aspects of the
blade. Thus, the cutting edge runsblade. Thus, the cutting edge runs parallelparallel toto
the central axis of the shaft. They are used in athe central axis of the shaft. They are used in a
forward push motion in the direction of theforward push motion in the direction of the
length of the blade. They are used primarily onlength of the blade. They are used primarily on
anterior teeth in sharpening internal lineanterior teeth in sharpening internal line
angles, particularly in preparation forangles, particularly in preparation for directdirect
goldgold restorations. They may cut off a wall byrestorations. They may cut off a wall by
direct cutting action or may be used laterallydirect 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 aThe blade is place at a right angleright angle to theto the
central axis of the shaft. It is provided with acentral axis of the shaft. It is provided with a
distal bevel.distal bevel. It is used for the removal of harderIt is used for the removal of harder
varieties of caries. It is used for planning thevarieties of caries. It is used for planning the
internal walls and line angles of theinternal walls and line angles of the
preparations. It is commonly used in Classespreparations. It is commonly used in Classes
III and V preparations for direct goldIII and V preparations for direct gold
restorations. It may be differentiated from arestorations. It may be differentiated from a
chisel by having the blade angled more thanchisel by having the blade angled more than
12.5 centigrade (a chisel has a blade that is12.5 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 isThe blade of these instruments is curvedcurved
either to the right or to the left. Thus, theeither to the right or to the left. Thus, the
direction of the curve of the blade makes thedirection of the curve of the blade makes the
instrumentsinstruments rightright oror left,left, i.e.,i.e., lateral cutting,lateral cutting,
double planeddouble planed instruments. The cutting edge isinstruments. The cutting edge is
ground to a semi-circle forming a thin edgeground 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 theIt resembles the spoon excavator but the
blade isblade is circularcircular in shape. The cutting edgein shape. The cutting edge
extends around the whole periphery, exceptextends 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 forThey are used for excavation of soft dentin.excavation of soft dentin.

44. Discoid ExcavatorDiscoid Excavator

45. 5)5) Cleoid Excavator:Cleoid Excavator:
It is aIt is a «Claw-like»«Claw-like» instrument used toinstrument used to
excavate soft dentinexcavate soft dentin and toand to remove pulpremove pulp
chamberchamber during endodontic treatment. It isduring endodontic treatment. It is
most helpful for carving gold foil andmost helpful for carving gold foil and
amalgam, especially for the creation ofamalgam, 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 handThere 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 anThe conventional pen grasp is not an
acceptable instrument grasp.acceptable instrument grasp. With each grasp,With each grasp,
proper rest and guardproper rest and guard is mandatory.is mandatory.

48. Rests and Guards:Rests and Guards:
A proper instrument grasp must include a firmA proper instrument grasp must include a firm
restrest (support)(support) to steady the hand during operatingto steady the hand during operating
procedures. The support must be gained fromprocedures. The support must be gained from hardhard
tissue;tissue; soft tissue rests or too distant hard tissuesoft 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 thethe support is gained with finger rests with the
same hand holding the instrument. If this is notsame hand holding the instrument. If this is not
possible,possible, indirect restindirect rest may be gained using themay be gained using the
opposite hand where the index finger is rested onopposite hand where the index finger is rested on
the shank of the instrumentthe shank of the instrument oror the operating handthe operating hand
rests on the opposite hand which rests on stablerests on the opposite hand which rests on stable
oral structure.oral structure.

49. • GuardsGuards are hand instruments or other itemsare hand instruments or other items
such as interproximal wedges used tosuch as interproximal wedges used to protectprotect
soft tissuesoft tissue from contact with sharp cutting orfrom 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 fingersexcept that the thumb, index and middle fingers
contact the instrumentcontact the instrument while the tips of the ringwhile the tips of the ring
and little fingers are placed on theand little fingers are placed on the nearby toothnearby tooth
surfacesurface of the same arch as aof the same arch as a restrest (support). The(support). The
palm of the hand is facing away from thepalm of the hand is facing away from the
operator.operator.

55. • This in turn provides facility, great power andThis in turn provides facility, great power and
wide range of movement. If the hand is rotatedwide 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 thethis is called the inverted pen graspinverted pen grasp.. It is used inIt 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 aIt 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 theThe 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 thewhile the thumb is free of the instrument and the
restrest is provided by supporting the tip of theis 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 beingIf the thumb is rested on the tooth being
prepared; it is calledprepared; it is called Modified Palm-and-Modified Palm-and-
thumb graspthumb grasp.. It is usually used in the area ofIt is usually used in the area of
maxillary arch and is best adopted whenmaxillary 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 shouldThe edges of cutting instruments should
always be kept sharp as dull instruments are lessalways 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 qualityprolong 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, shinyThe presence of a "glint" or a bright, shiny
cutting edge indicates that the edge is dull orcutting edge indicates that the edge is dull or
rounded. Alternatively, the instrument can berounded. Alternatively, the instrument can be
pulled across hard plastic, such as the handle of apulled across hard plastic, such as the handle of a
plastic mouth mirror, or an evacuation tip. A dullplastic mouth mirror, or an evacuation tip. A dull
blade will slide across the plastic; a sharp bladeblade will slide across the plastic; a sharp blade
will cut into the surface, and its movement iswill 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 beseveral basic principles of sharpening should be
followed:followed:
Sharpening of the instruments is done onlySharpening 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 45Establish the proper bevel angle (usually 45
degrees) and the desired angle of the cuttingdegrees) and the desired angle of the cutting
edge to the blade before placing theedge 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 lessenUse a light pressure against the stone to lessen
frictional heat and remove as little metal fromfrictional 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 ofKeep the sharpening stone clean and free of
metal cuttings.metal cuttings.

65.  Sharpening equipments:Sharpening equipments:
Many types of sharpening equipments existMany types of sharpening equipments exist
including stationary sharpening stones andincluding stationary sharpening stones and
mechanical sharpeners.mechanical sharpeners.
I.I. Stationary sharpening stone:Stationary sharpening stone:
It is often called oilstone because of theIt is often called oilstone because of the
common practice of applying a little oil tocommon practice of applying a little oil to
aid the sharpening process. It could be madeaid the sharpening process. It could be made
of fine grit of Arkansas stone, siliconof 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 theIt moves at a slow speed while the
instrument is held at the appropriateinstrument is held at the appropriate
angulations and supported by a rest.angulations and supported by a rest.
Interchangeable aluminum oxide wheelInterchangeable aluminum oxide wheel
stones of different shapes and coarseness arestones of different shapes and coarseness are
available. It is easier, less time consumingavailable. It is easier, less time consuming
and can fill almost all instrument sharpeningand can fill almost all instrument sharpening
needs.needs.
 Alternatively, anAlternatively, an Arkansas wheel stoneArkansas wheel stone
rotating in a handpiece could be used inrotating in a handpiece could be used in
between treatments.between treatments.

71.  Advantages of hand over rotary cuttingAdvantages of hand over rotary cutting
instruments:instruments:
1.1. It will not cut into sound tooth structureIt will not cut into sound tooth structure
leading to more conservative cuttingleading to more conservative cutting
procedure.procedure.
2.2. It produces no vibration or heat generation; itIt 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 largeIt 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 interprismaticIt cleaves enamel at the interprismatic
substance; it thus ensures that the cutting issubstance; it thus ensures that the cutting is
performed in the direction of enamel rods andperformed in the direction of enamel rods and
that the cavosurface margin is formed of fullthat 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 usingRemoval 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 universallyRotary instruments are the most universally
used instruments for gross removal of toothused instruments for gross removal of tooth
structure and will thus be discussed later instructure 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 ofThis technique is based on the removal of
tooth material by an air-driven hand piecetooth material by an air-driven hand piece
equipped with aequipped with a diamond-coated working tipdiamond-coated working tip
that removes tooth material bythat removes tooth material by ultrasonicultrasonic
energy.energy. Different sizes and shapes of diamondDifferent sizes and shapes of diamond
tips have been designed, enabling easy access totips have been designed, enabling easy access to
occlusal and approximal tooth lesions. As theseocclusal and approximal tooth lesions. As these
tips are coated onlytips are coated only on one side,on one side, trauma of thetrauma 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 ofThe tooth structure is removed by means of
tinytiny aluminum oxidealuminum oxide particles (abrasive) ejectedparticles (abrasive) ejected
at great velocity by means of a high pressure gasat great velocity by means of a high pressure gas
stream directed at a definite angle. This abrasivestream directed at a definite angle. This abrasive
technique increases patient comfort by reducingtechnique increases patient comfort by reducing
heat, vibration, and noise, as commonlyheat, vibration, and noise, as commonly
experienced during mechanical preparation ofexperienced during mechanical preparation of
teeth when rotating burs are used.teeth when rotating burs are used.

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

81. 4.4. Laser equipments:Laser equipments:
Lasers are devices that produce beams ofLasers are devices that produce beams of
coherent and very high light intensity. Lasercoherent and very high light intensity. Laser
technology can remove tooth substratetechnology 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 tissueLasers are used mainly for soft tissue
applications (such as gingivectomy), surfaceapplications (such as gingivectomy), surface
modification (enamel etching) before bondingmodification (enamel etching) before bonding
and in curing of resin composite. They areand in curing of resin composite. They are
generally not used for tooth preparation becausegenerally not used for tooth preparation because
it is inefficient in removing large amounts ofit 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 theRotary equipments are chiefly used for the
removal of tooth structures and restorativeremoval of tooth structures and restorative
materials. However, some of them are used formaterials. However, some of them are used for
condensation of restorative materials ascondensation 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 asor for burnishing and finishing of restorations as
mechanical burnishers and finishing tools. Itmechanical burnishers and finishing tools. It
basically includes a power source and tools orbasically 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 electricIn the past rotary power from an electric
motor was transferred to a hand-piece by amotor was transferred to a hand-piece by a
belt and pulleys. Operating speed was lowbelt 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 lowexcept in dental laboratories where low
speed is desirable. New micro-motors deliverspeed is desirable. New micro-motors deliver
speed range of 20,000 - 60,000 rpm and arespeed 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 sourceAir turbine dental units driven by a source
of compressed air, developed in the lateof compressed air, developed in the late
1950s, eliminated the necessity of having an1950s, eliminated the necessity of having an
electric engine as a part of a standard dentalelectric engine as a part of a standard dental
unit. By having the turbine rotated by air, allunit. By having the turbine rotated by air, all
friction is eliminated, and speeds may befriction is eliminated, and speeds may be
increased to over 800,000 rpm. Air turbinesincreased to over 800,000 rpm. Air turbines
are the most popular and widely used types ofare 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 isThe 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 toMedium or intermediate speeds (12,000 to
200,000 rpm).200,000 rpm).
c.c. High or ultrahigh speeds (above 200,000High or ultrahigh speeds (above 200,000
rpm).rpm).

88. • Although intact tooth structure can be removedAlthough intact tooth structure can be removed
by an instrument rotating at low speed, it is aby an instrument rotating at low speed, it is a
traumatic experience for both the patient and thetraumatic experience for both the patient and the
dentist. Low speed cutting is ineffective, timedentist. Low speed cutting is ineffective, time
consuming, and requires a relatively heavy forceconsuming, and requires a relatively heavy force
of application. It produces heat and vibrationof 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 forTherefore, low speed range is most suitable for
caries removal and finishing and polishingcaries removal and finishing and polishing
procedures. At high speed, the surface speedprocedures. At high speed, the surface speed
needed for efficient cutting can be attained withneeded 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 lessRemove tooth structure faster with less
pressure and vibration.pressure and vibration.
2.2. The number of rotary cutting tools is reducedThe 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 treatedSeveral 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 theA handpiece is a device for holding the
rotating instrument, transmitting power torotating instrument, transmitting power to
them and positioning them intra-orally. Theythem 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 modeIt has a straight, tubular shape. Its mode
of attachment to the cutting tool could beof attachment to the cutting tool could be
through friction grip or a latch head. It isthrough friction grip or a latch head. It is
driven by electricity or air and used mainlydriven 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 angulationIt is tubular-shaped, with an angulation
between the head and the shank. The headbetween the head and the shank. The head
attachment could also be friction grip headattachment could also be friction grip head
or latch type. They are used for finishingor latch type. They are used for finishing
cavity preparation, to remove caries, andcavity preparation, to remove caries, and
for finishing and polishing of thefor finishing and polishing of the
restorations.restorations.

94. High-speed contra-angle handpiece:High-speed contra-angle handpiece:
It is tubular-shaped withIt is tubular-shaped with slightslight angulationangulation
between the head and the shank. It isbetween the head and the shank. It is powered bypowered by
airair (air-driven) and capable of rotational speeds(air-driven) and capable of rotational speeds
in excess of 200,000 rpm. The head attachmentin excess of 200,000 rpm. The head attachment
is friction gripis friction grip only. It is principally used foronly. It is principally used for
gross tooth structure removal and cavitygross tooth structure removal and cavity
preparation. However, due to small size of thepreparation. However, due to small size of the
turbine in the head, they have low torque and areturbine in the head, they have low torque and are
unsuitableunsuitable for some finishing and polishingfor some finishing and polishing
procedures.procedures.

96. • Many improvements of the contra-angleMany improvements of the contra-angle
handpiece include smaller head size, lower noisehandpiece include smaller head size, lower noise
levels and better chucking mechanisms. Sincelevels 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, cleansingwater spray feature to provide cooling, cleansing
and improved visibility. Modem contra-angleand improved visibility. Modem contra-angle
handpieces also include fiber-optic lighting ofhandpieces also include fiber-optic lighting of
the cutting site.the cutting site.

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

99. A.A. Burs:Burs:
The bur is considered a form of drill orThe bur is considered a form of drill or
milling cutter especially manufactured to suitmilling 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 ofthe shank, the neck and the head. Each of
these parts has its own function whichthese 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 theIt is that part of bur that fits into the
handpiece. There are three shank designshandpiece. There are three shank designs
available for, straight handpiece, latch typeavailable for, straight handpiece, latch type
handpiece, and friction grip handpiece. Inhandpiece, and friction grip handpiece. In
addition, modified burs with short shanks areaddition, 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 thatIt is the intermediate portion of the bur that
connects the head to the shank. The neck usuallyconnects the head to the shank. The neck usually
tapers from the shank towards the head. Its maintapers from the shank towards the head. Its main
function is to transmit rotational force to thefunction is to transmit rotational force to the
head.head.
3)3) Head:Head:
The head is the working part of the bur. TheThe head is the working part of the bur. The
shape of the bur head is strongly related to itsshape of the bur head is strongly related to its
intended use and technique of application. Bursintended use and technique of application. Burs
can be classified according to their material ofcan be classified according to their material of
construction, number of the blades, head shapesconstruction, number of the blades, head shapes
and sizes.and sizes.

105. Material of construction:Material of construction:
The dental burs may be made of eitherThe dental burs may be made of either carboncarbon
steelsteel oror tungsten carbide.tungsten carbide.
Carbide burs are quiteCarbide burs are quite more efficientmore efficient and haveand have
longer lifelonger life than steel burs. They also generatethan steel burs. They also generate
muchmuch less heatless heat during cavity preparationduring cavity preparation
because they are more effective cutters,because they are more effective cutters,
especially at high speeds; steel burs are usedespecially at high speeds; steel burs are used
only at low speed ranges. The superiority ofonly at low speed ranges. The superiority of
carbide burs over steel burs in cutting toothcarbide burs over steel burs in cutting tooth
structures is due to:structures is due to:

106. I.I. Their higher Vickers Hardness Number (aboutTheir higher Vickers Hardness Number (about
1700V.H.N.) as compared to steel burs (about1700V.H.N.) as compared to steel burs (about
600V.H.N .).600V.H.N .).
II.II. Their greater strength which allows them toTheir greater strength which allows them to
withstand cutting at higher speeds at higherwithstand cutting at higher speeds at higher
temperatures. It also increases the resistancetemperatures. It also increases the resistance
of their blades to dulling or turning out duringof their blades to dulling or turning out during
cavity preparation, and thus helps maintainingcavity preparation, and thus helps maintaining
their sharpness.their sharpness.
III.III. The superior treatment and careful designingThe superior treatment and careful designing
that they receive during manufacturing.that they receive during manufacturing.

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

108. Thank YouThank You