1. INSTRUMENTS IN
OPERATIVE DENTISTRY
Presented by,
Dr. Monisha Tiwari
MDS I Year
Guided by,
Dr. Rana .K. Varghese, Prof. and Head
Dr. Gururaj. M, Reader
Dr. Rishidev Yadav, Reader
Dr. Minal Daga,Sr. Lecturer
3. • Mechanism of cutting Instruments
• Hazards with cutting Instruments
• References
4. Introduction :
> In order to properly prepare a cavity ,the tooth
tissues ,enamel and dentin must be excised with
specific instruments in an efficiently ordered
sequence .
> Most cavity preparations required the use of both
rotary and hand instruments .
> Rotary burs and diamonds are used for gross
reduction ,creating angulation and final refinement of
the cavity preparation .
.
5. >The hand cutting instruments are used to
produce intricate details of the cavity
preparation and finish the restorative
material .
> In the use of hand cutting instruments
,there is no vibration ,pressure or pain
element as compared to high speed
instruments.
12. > According to Marzouck :
1.Exploring instruments :
- Tweezers
- Retractors
- Probes
- Separators
13. 2. Instruments for tooth structure
removal:
a. Hand cutting
-Excavators
-Chisels
-Special form of chisels
b. Handpiece
-Burs
-Ultrasonic
14. Classification (Acc. to Sturdevant)
1. Cutting (excavators ,chisels and others)
2. Non-cutting (amalgam condenser , mouth
mirrors , explorer and probes)
15. Nomenclature of instruments :
• In establishing a nomenclature for hand
instruments , Dr. Black prescribed four classes
,similar to a biological classification :
Order-
• Purpose of instrument .
16. Suborder-
• Position or manner of use .
Class-
• Form of working end.
Subclass-
• Shape of the shank.
19. a. Blade or Nib:
• Also may be appropriately termed the point or
head.
• This is the functional end of the instrument.
20. B . Shank:
• Connecting the shaft and blade or nib.
• The shank may be straight or single or
double or triple-angle.
21. C .Handle:
• Small ,medium or large diameter smooth,
knurled or serrated.
22. Material used to make hand instruments :
• Stainless steel
• Carbon steel
• Blades of tungsten carbide
23. Principles of cutting instrument :
1.Direct cutting and lateral cutting
instruments:
• A direct cutting instrument is one in which the
force is applied in the same plane as that of
the blade and the handle.
24. • It is called a “single planed” instrument .
USES:
• Single planed instruments can be used in
direct and lateral cutting.
25. LATERAL CUTTING :
• Lateral cutting instruments are those in which
the force is applied at a right angle to the
plane of the blade and the handle .
• These usually have a curved blade and are
called “double plane” instruments.
26. • Double planed instruments have an angle or
curve in a plane at an angle right angle to that
of the handle .
USES :
• It can be used only in lateral cutting .
27. 2.CONTRANGLING:
• In order to gain access, many instruments
have the shank bent at one or more points to
angle the blade relative to the handle .
• The extent of this arrangement depends on
the length of the blade and the degree of
angulation in the shank.
28. • Accordingly, the working point is moved out of
line with the axis of the handle.
• If this occur more than 3mm from the handle
axis , the instrument will be out of balance in
lateral cutting motions, and force will be
required to keep the instrument from rotating
in the hand .
29. • To solve this problem , modern instruments
are designed to have one or more angles in
the shank placing the working point within
3mm from the axis of the handle.
• This principle of design is called contrangling.
30. • The length of the blade required is
determined by the depth of the cavity and the
blade angle is determined by the accessibility
requirements.
31. • It follows, then ,that greater angles are
necessary for more posterior teeth and incisal
portions of proximal cavities in anterior teeth.
• So , in addition to balance ,contrangling will
provide better access and a clearer view for
the field of operation.
32. 3 . RIGHT AND LEFT INSTRUMENTS :
• Direct cutting instruments are made either
right or left by placing a bevel on one side of
the blade .
33. • If the instrument is held with the cutting edge
down and pointing away from the operator
and bevel is on the right side , it will be a
“right” instrument.
• If the bevel is on the left ,it will be a left
instrument .
34. • As mentioned before , these are single-planed
instruments , and for direct cutting acts the
non- bevelled side of the blade should be in
contact with the wall being shaved .
• For lateral cutting acts ,always move the
instrument in a scrapping action from the
beveled side to the non beveled side of the
blade.
35. 4.SINGLE BEVELLED INSTRUMENTS :
• These are all single planed instruments with
the cutting edge at a right angle to the long
axis of the shaft .
• They all are designed like carpenter’s chisel.
36. • If they are regularly beveled on the side away
from the shaft ,they are called “distally
beveled”.
• If they are beveled on side of the blade away
from the shaft ,they are called “mesially
beveled”.
37. • When these types of instruments have no
angle in the shank ,or an angle of 12 degree or
less, they are used in push (direct cutting) and
scrapping motions.
• If this angle in the shank exceeds 12 degree
,the instrument could be used in pull(distally
beveled) and push (mesially beveled) motions
38. 5. BIBEVELED INSTRUMENTS :
• Only hatchets and straight chisel can be
bibeveled.
• The blade is equally beveled on both sides ,
and they cut by pushing them in the direction
of the long axis of the blade.
39. 6. TRIPLE BEVELLED INSTRUMENTS :
• Bevelling the blade laterally , together with
the end, forms three distinct cutting edges.
• Most modern single planed instruments
especially the small ones , are triple beveled ,
affording the instrument an additional cutting
potential which is very useful.
41. 8.SINGLE ENDED AND DOUBLE ENDED
INSTRUMENTS:
• Most modern instruments are double ended,
Incorporating the right and left or the mesial
and distal form of the instrument in the same
handle .
42. • Single ended instruments are confined now to
those type of instruments have only one
specific function .
• Single planed instruments with no angle in the
shank have the potential for five cutting
movements-
43. • Vertical (parallel to the long axis of the blade)
• Right
• Left
• Push and
• Pull.
44. Cutting Instruments Bevels :
• Most hand cutting instruments have on the
end of the blade a single bevel that forms the
primary cutting edge.
• Two additional edges ,called secondary cutting
edges.
45. • Bi-beveled instruments, such as ordinary
hatchets , have two bevels that form the
cutting edge.
• Certain single-beveled instruments , such as
spoon excavators and gingival marginal
trimmers , are used with a scrapping or lateral
cutting motion .
46.
47. Black’s Instrument Formula
• It established an instrument formula that
describes the dimension and angulation of the
hand instrument.
48.
49. • The basic instrument formula consists of three
units those measurements are based upon the
metric system :
• The first unit of the formula describes the
width of the blade in tenths of millimeter.
• The second unit describes the length of the
blade in millimeter.
50. • The basic instrument formula consists of three
units those measurements are based upon the
metric system :
• The first unit of the formula describes the
width of the blade in tenths of millimeter.
• The second unit describes the length of the
blade in millimeter.
51. • The third unit describes the angle of the blade
forms with the axis of the handle. This angle is
expressed in “hundredths” of a circle or
centigrades.
• By this simple three unit formula , an
instrument such as the “binangle hatchet” has
a formula 15-8-12.
52. • This formula accurately describes the type,
dimension ,and angulation of this specific
instrument:
• 15-blade width 1.5 mm
• 8 –blade length 8 mm
• 12 –blade angled 12 centigrades from axis of
handle or shaft.
•
53. • When the cutting edge and face of an
instrument is at an angle other than a right
angle to the length of the blade , a fourth unit
is added to the basic three unit formula.
• This additional number , expressed in
centigrades , represents the angle formed
between cutting edge and central axis of the
shaft.
54. • It is placed in the second position of the formula.
• The gingival marginal trimmer has a formula 12-
92-10-8.
• The second unit “92” indicates that , in addition
to a blade width of 1.2mm,a blade length of
10mm,and a blade angle of 8 centigrades with
shaft axis , the cutting edge of the blade is at an
angle of 92 centigrades with the axis of the shaft.
56. CHISEL:
• It is characterised by a blade that terminates
in a cutting edge formed by a one-sided bevel.
• The cutting edge of the chisel is an right angle
to the plane of the instrument.
57.
58. STRAIGHT CHISELS :
• They have straight blade in line with the
handle and shank .
• The cutting edge is on one side only , with the
bevel of the blade running at a right angle to
the shaft.
59. • They are single-planed instruments with five
possible cutting movements .
60. MONOANGLE CHISELS :
• They are similar to straight chisels ,except the
blade is placed at an angle to the shaft.
• It may be mesially or distally bevelled .
61.
62. BINANGLE CHISELS :
• The chisel blade is placed at a slight angle with
the shaft as in the hoe .
• Like all chisels , it may be mesially or distally
bevelled.
• As the name indicates , there are the two
angle between the shaft and the blade .
63. • The three aforementioned chisels are all used
to cleave or split undermined enamel .
64. TRIPLE-ANGLE CHISEL :
• They have three angles in its shank and it is
usually used to flatten pulpal floors .
• It may be mesially or distally bevelled .
• The monoangle , binangle , or , triple angle
chisels are single-planed instruments.
65. • All possess three possible cutting movements
:vertical , right and left .
66. • The mesially bevelled chisels can cut in push
movements ,while the distally bevelled ones can cut in
pull motions .
USES :
• A chisel is an excavater primarily used for
planning or cleaving enamel and dentin.
Direction of motion :
• Push motion
68. • It is form of chisel in which the angle of the
blade is greater than 12.5 centigrades.
Uses:
• It is used to smooth and shape the floor and
form line angles in class III and class V
restorations.
69. • Also used for cutting mesial and distal
walls of molars and premolars.
Direction of motion :
• Pull motion.
72. • The hatchet shank has one or more
angles or curves.
• The blade is in same plane as this angle
or angles , parallel with the shaft.
73. • A chisel bladed instrument with the cutting
edge in the plane of the instrument is termed
as hatchet .
• These instruments are either paired ,one with
a left and other with a right bevel or they may
be right bevelled .
74. • Viewing the instrument from its working end
when the cutting edge is to the right, the
instrument is referred to as the “right” of the
pair.
• Conversely , with the cutting edge to the left
that instrument becomes the “left” of the pair.
75. Uses :
• Paired binangle enamel hatchets , right and
left , are used for planning and cleaving
enamel and dentin walls during cavity
preparation.
• Frequently , these are proximal and gingival
walls where access or position would dictate
their use.
76. Instrument formula :
• 15-8-12
Direction of movements:
• Vertical, push ,pull ,and either right or left
lateral cutting.
78. • It is like a straight chisel ,but with a slight
curvature in its shank.
• It is bevelled on one side of the blade
only.
79. • If this bevel is on the side toward the
curvature on the shank, it is mesially bevelled
,if it is on the side of the blade away from the
curvature ,it is distally bevelled.
• They are single planed instruments ,with three
cutting motions ; vertical ,right ,and left .
80. USES:
• It is used for cleaving undermined enamel and
for shaping walls .
• The mesially bevelled can be used in push
movements , and the distally bevelled can be
used in pull motions.
82. • This chisel has a blade which is triangular in
shape ,with the base of the triangle away from
the shaft .
• It has a terminal cutting edge like the straight
chisel .
83. 6. ANGLE FORMER :
• The cutting edge of the angle former is
sharpened at an angle to the axis of the blade.
• The angle of the cutting edge to the blade axis
of the angle former is usually 80 to 85
centigrades.
84. • The acute cutting angle being directed to the
right or to the left makes the angle former
always a paired instrument.
• The right of the pair is identified by an
intended ring on the shaft or shank .
85. Uses :
• To accentuate line and point angles in the
internal outline form in cavities for cohesive
gold to establish retention form.
• The action of the instrument is essentially one
of lateral scrapping.
• To place bevel on enamel margins.
88. • GMT are also a paired instruments and are
referred to as “left” and “right” .
• It is also a lateral cutting instrument so further
divided into two ; mesial and distal.
• It is a double–plane instrument having a
curved blade.
89. Uses :
• Used essentially for bevelling gingival
cavosurface margins , both mesially and
distally.
• Distal GMT is designed to plane or bevel the
cavosurface margins of distal proximal
amalgam and certain inlay preparations.
90. • Mesial marginal trimmer is used to plane the
mesial cervical margin.
92. • It is a double-plane instrument that is
modified hatchet.
• Its cutting edge is rounded.
• As its name , action is spooning or scooping
carious material.
93. • Like a double-plane instruments , the spoon is
designed for lateral scrapping.
• It is always a paired instrument , with the
curved of one blade directed from right to left
and that of the other from left to right.
94. Uses :
• Removal of carious dentin.
Instrument formula :
• 8-6-12
96. • The “cleoid” or “claw-like” and the “discoid” or
disk like ,hand cutting instrument is a
modified double-ended chisel.
• It provide sharp cutting edges similar in design
to the spoon ,but with the blade to the shaft .
97. Uses :
• For carious removal.
• Also used as a carving instrument for
amalgam and wax .
Instrument formula :
• 10-2-12
98. KNIVES :
• It is known as finishing knives, amalgam knives
,or gold knives.
• Most universal is the Bard-Parker knives.
• Some knives are made for the specific
purposes.
99. USES :
• Wilson’s knife ,used inter-proximally for
proximal and gingival manipulation of the
restorative materials .
• Stein’s knife ,which has a trapezoidal nib , is
used mainly for direct gold restoration and
margination.
100. • Also , used for trimming excess restorative
material on the gingival , facial, or lingual
margins of a proximal restoration or trimming
and contouring the surface of a class v
restoration .
101. FILES :
• The nib of the file can be foot-shaped ,
hatchet-shaped or parallelogram-shaped .
USES :
I. Used to trim excess restorative material.
II. Used for margination of restorations .
103. • It may be single or double ended instrument .
• Most of these instruments have angles and
curvatures in their shanks.
• The nibs have different shapes , e.g., rounded,
triangular, diamond, rectangular,
parallelogram etc.
104. • It may be smooth or serrated .
• It can be hand or mechanical in nature.
Uses :
• It is used to condense the restorative material
in to the prepared cavity.
106. • Within this class are an enormous number of
instruments .
• They all differ mainly in the shape of their nibs
and angulation or curvature in their shanks.
• They all have a flat sided nib with blunt edges
and corners.
107. • They may be made of stainless steel, ivorine or
plastic.
• They also can be plated with teflon to
minimize material adhesion to facilitate easy
cleaning.
108. USES :
• They all can be used for carrying and handling
materials after mixing while the materials are
in their plastic stage.
110. • These are basically cutting instruments with
their blades (nibs) either bevelled or knife-
edged (elongated bibevelling).
• The most universally used carvers are
Hollenback carvers, which possess double-
sided knife-edged, point-edged nibs, with
curved monangled or binangled shanks.
111. • They are very efficient in carving both
amalgam and wax.
• There are considerable number of special
forms of carvers, such as those with triangular
nibs , or diamond shaped nibs.
112.
113. Uses :
• To contour the restoration approximately
same to original tooth structure.
• Sharp cutting edges present in carvers are
used to shapen and form tooth anatomy from
a restorations.
114. • Hollenback carvers are used for carving
proximal surfaces.
• Diamond shape carvers are used for carving
occlusal surfaces.
116. • Burnishers are the kind of instruments
which make the surface shiny by rubbing.
• Burnishers have smooth rounded
working ends and come in single and
double-ended instruments.
118. • Ball burnisher
a. small
b .large
• Tear drop shape burnisher
• Peer shaped burnisher
• Bever tailed burnisher
119. Uses:
• Final condensation of amalgam .
• Initial shaping of occlusal anatomy of
amalgam.
• Shaping of metal matrix bands.
• Burnishing margins of cast gold restorations.
122. Rubber dam affords protection from
instrumentation and chemicals for the gingiva
and periodontal tissues when it is properly
applied.
Uses :
• To isolate the operating field .
128. Classification :
1.On the basis of sizes of mirror:
• No.2 - 5/8” dm
• No.4 - 7/8” dm
• No.5 - 15/16” dm
(No.4 and No.5 are commonly used sizes) .
129. 2.On the basis of mirror :
• Plain
• Convex
3.On the basis of surface :
• Front
• Rear
130. 4.On the basis of material :
• Plastic
• Metal
5. On the basis of joint :
• Cone socket
• One piece
131. 6. On the basis of number of surfaces:
• One sided
• Two sided
7. On the basis of shaft design :
• Bended
• Non-bended
•
132. USES :
• Mouth mirrors are used to provide a clear and
distinct vision of operating area .
FUNCTIONS :
• Help in direct visualization of the field of
operation .
133. • Reflect the operating light and thus
illuminate the operating area .
• Provide indirect visualization of obscure
areas of the mouth .
• Retract the soft tissues like the tongue ,
cheeks or lips .
135. • Explorer is commonly used as a
diagnostic aid in evaluating condition of
teeth especially pits and fissures.
Parts :
• Handle of explorer is straight which could
be plain or serrated .
136. • Shank of explorer is curved with one
/more angle.
• Working tip of explorer is pointed.
137. Types of explorer :
Straight explorer:
• It is bent perpendicular to the handle.
• This is used for examing occlusal surfaces of
teeth .
138. Shepherd’s Crook or curved explorer
• It has semilunar -shaped working tip
perpendicular to the handle.
• This is used for examing occlusal
surfaces.
139. Interproximal explorer :
• Commonly used for examination of
interproximal surfaces of teeth .
• It is pointed instruments used for tactile
examination of tooth surfaces and
restorations to identify any irregularities .
•
150. USES :
• For examination of initial proximal caries .
• Providing proper accessibility to proximal
area during preparation of teeth and polishing
of restorations .
• Helps in placement of matrix.
• Also used to remove foreign bodies .
151. Advantages of Hand Cutting
Instruments :
• They are self limited in cutting enamel ,i.e.
they will not cut sound enamel ,but will cut
only undermined enamel.
152. • Can remove large pieces of under-mined
enamel quickly thus saves time and effort.
• No vibration or heat is produced during
cutting.
• Are the most efficient way for precise intricate
cutting .
153. • Can create the smoothest surface of all cutting
instruments .
• Have the longest life span provided if they are
resharpened .
155. • Because potentially pathogenic micro-
organisms are everpresent , instrument must
be treated in such a manner as to eliminate
the transmission of potentially disease
producing forms of microbial life to another
patient.
• Sterlization implies the complete destruction
of all microbial life ,including spores and
resistant viruses .
156. Commonly, dental instruments are sterilized
by:
• Autoclaving (saturated steam under pressure)
• Application of dry heat,
• Application of gas (ethylene oxide)
157. • The autoclave is the most reliable sterlization
device available.
• Instruments , textiles ,and glassware can be
sterilized effectively in a reasonable period of
time.
158. • Steam under pressure of 15 pounds increases
the boiling point to a temperature of 121
degree celcius for 10 minutes at which all
known organisms are destroyed.
• In dentistry, disinfection commonly has been
accompalished by –
159. • Immersion in chemical solution
• Use of boiling water
• Use of hot oil (mineral and silicone)
• Flaming .
160. • When acceptable sterlization methods are not
possible to use ,disinfection can be carried out
by the following methods :
• Immersion in 100 degree celcius (boiling)
water for 30 minutes.
161. • Soaking in activated 2 % alkaline
glutareldehyde for atleast 10 minutes .
• Immersion in 1 % sodium hypochlorite (1.5
dilution of commercial liquid chlorine bleach)
for 10 minutes.
• One to 2 % formaldehyde for 20 to 30
minutes.
162. STORAGE :
• Storage of any hand cutting instruments
should be in a sterile , wrapped tray setup or
in an individual sterile wrapping .
164. • Rotary instruments are the most universally
used instruments for gross removal of tooth
structure .
• The term “rotary” applied to tooth cutting
instruments describes a group of instruments
that turn on a axis to perform work .
165. • Applied to dental procedures ,the character of
work performed is primarily:
Cutting
Abrading
Burnishing
Finishing and
Polishing tooth tissues or various restorative
materials.
166. • The rotational speed of an instrument is
measured in revolutions per minute (rpm).
• Three speed ranges are generally recognised
(According to Charbeneau) :
a. Conventional or low speed:
Below 10,000 rpm
167. b. Increased or high speeds-
10,000 to 150,000 rpm
c. Ultrahigh speeds-
Above 150,000 rpm
168. The following are the characteristics of rotary
instrumentation :
SPEED :
• Speed refers not only to the revolutions per
minute , but also to the surface feet per unit
time of contact that the tool has with the
work to be cut.
169. • For dental purposes we classify speeds as
follows (According to Marzouk ) :
A .Ultra-low speed (300-3000 RPM)
B .Low-speed (3000-6000 RPM)
C .Medium high speed (20,000-45,000 RPM)
170. D .High speed (45,000-100,000 RPM)
E .Ultra-high speed (100,000 RPM and more)
171. PRESSURE :
• It is resultant effect of two factors under the
control of the dentist .
1.Force(F):The gripping of the handpiece and its
positioning and application of the tooth .
172. 2.Area (A):The amount of surface area of the
cutting tool in contact with the tooth surface
during a cutting operation .
• Pressure relates as follows :
P =F/A
173. 3.Heat production:
• Heat is directly proportional to :
a. Pressure
b. RPM
c. Area of tooth in contact with the tool
174. VIBRATION :
• Vibration is not only a major annoying factor
for the patient ,but it also causes fatigue for
the operator, excessive wear of instruments
and most importantly , a destructive reactions
and the tooth and supporting tissues .
175. PATIENT REACTION :
• The factors that cause patient apprehension
consist primarily of heat production ,
vibrational sensation ,length of operating
time, and number of visits .
176. OPERATOR FATIGUE :
• The major causes for fatigue are :duration of
operation, vibration produced in the handpiece,
forces needed to control the rotating instrument,
apprehension on the part of the dentist, regarding
the possibility of producing a pulp exposure or
injuring adjacent oral, intra-and paraoral tissues , and
lack of patient co-operation .
177. SOURCES OF POWER :
• The introduction in the 1950’s of the air turbine as a
power source changed the shape of dental practice.
• The belt driven handpiece was rendered absolute for
operatory use .
• The air turbine remains the main power source .
178. INSTRUMENT DESIGN :
• Instrument design for rotary instrumentation
should be evaluated in two parameters: one
,the handpiece, which will hold and provide
power for the cutting tool; and two ,the
cutting tool itself (bur , stone , etc).
179. 1 .Handpiece :
• Handpieces come in a variety of sizes and
shapes :straight , contra-angled ,and right-
angled.
• Each is designed for a specific range of
functions
180. • They will retain the cutting tool by a screw-in
,latch, or friction grip type of attachment .
• The following criteria should be used in
evaluating handpieces :
181. A. Friction :
• It will occur in the moving parts of a
handpieces , especially the turbine.
B. Torque :
• Torque is dependent upon the type of bearing
used and the amount of energy supplied to
the hand piece.
•
182. 2.THE ROTARY TOOLS FOR THE REMOVAL OF
TOOTH STRUCTURE :
• These are the units actually responsible for the
removal of tooth structure and may be one of two
types : burs , which are cutting tools , and stones ,
which are abrading tools.
183. A . Dental cutting burs :
• The term bur is applied to all rotary cutting
instruments that have bladed cutting heads.
184. Every bur will have a three parts :
• The head- it is the portion carrying the cutting
blade.
• The shank – portion connecting the head to
the attachment part.
• The attachment part –the portion which will
be engaged within the handpiece.
185. • It includes :
i. Instruments intended for finishing metal
restorations .
ii . Surgical removal of bone .
iii . Instruments primarily intended for
tooth preparation.
186. Historical development of dental
burs :
• First machine made bur introduced in 1891.
• Early burs were made of steel .
• Carbide burs were introduced in 1947.
187. I .Composition and manufacture :
• Dental burs can be classified by their
composition in two types ;
a. Steel bur
b. Tungsten carbide bur
188. ii. General designs of dental burs:
• The dental bur is a small milling (cutting)
instrument.
189.
190. a. Bur tooth :
• This terminates in the cutting edge, or blade.
b. Rake angle :
• It is most important design characteristic of
bur blade .
191. • The rake angle is the angle that the face of the
bur tooth makes with the radial line from the
center of the bur to the blade.
• Negative rake angle minimizes fracture of
cutting edge and increases tool life.
• It is said to be negative when rake face is
ahead of the radius .
192.
193. • This angle can be negative if the face is
beyond or leading the radial line (referring to
the direction of rotation ).
• It can be 0 if the radial line and the tooth face
coincide with each other(radial rake angle).
194. • The angle can also be positive if the radial line
leads the face ,so that the rake angle is on the
inside of the radial line .
c. Land :
• The plane surface immediately following the
cutting edge.
195. d. Clearence angle :
• The angle between the back of the tooth and the
work.
• If a land is present on the bur, the clearance angle is
divided into :primary clearance which is the angle
the land will make with work , and secondary
clearance which is the angle between the back of the
bur tooth and the work.
196. • When the back surface of the tooth is curved,
the clearance is called radial clearance.
f. Flute or chip space :
• The space between successive teeth .
197. CLASSIFICATION OF BURS :
• According to Marzouk :
1 .According to their mode of attachment to
the handpiece dental burs can be classified
as:
A . Latch type
B . Friction grip type
198. 2 .May be classified according to the handpiece
they are designed for , i.e ;
A . Contrangle bur
B . Straight hand piece bur
199. 4.According to the length of the blade ,bur can
be classified as :
A . Long
B . Short ( pedominiature)
C . Regular
200. 5.According to their shapes and sizes, they may
be classified as follows:
a .Round burs :
• They are numbered from ¼ , ½ , 1,2,to 10.
• They are round in shape.
• They are used for initial tooth penetration and
for the placement of retention grooves .
201. B .Wheel burs:
• They are numbered as 14 and 15.
• They are wheel shape.
• They are used to place grooves and for gross
removal of tooth structure .
202. C .Inverted cone burs :
• They are numbered from 33 ¼,33 ½, 34,35 ,to
39.
• They are an inverted cone shape.
• They used mainly for cavity extension and
occasionaly for establishing wall angulations
and retention forms .
203. D .Plain cylindrical fissure bur :
• They are numbered from 55 to 59.
• The bur teeth can be cut parallel to the long
axis of the bur, which are designed straight or
cut obliquely to the long axis of the teeth,
which are called spiral.
204. E .Cross cut cylindrical fissure bur :
• They are numbered 555,556 ,to 560.
• Their teeth can also be cut parallel to the long
axis of the bur(straight)or obliquely(spiral).
• They are used for gross cutting ,cavity
extension and creation of walls .
205. F . Plain tapered fissure bur :
• They are numbered from 168,169,to 172.
• They have a tapered cylindrical head; their
teeth can be straight or spiral.
206. G . End-cutting burs :
• They are numbered from 900 to 904.
• They are cylindrical in shape , with just the
end carrying blades .
• They are very efficient in extending
preparations apically without axial reduction .
•
207.
208.
209. Factors influencing the cutting efficiency of
burs :
1.Rake angle :
• The more positive the rake angle is, the greater is the
bur’s cutting efficiency.
• Also burs with radial rake angles cut more effectively
than designs with negative rake angles.
211. • This angle provides clearance between the
work and the cutting edge to prevent the
tooth back from rubbing on the work.
• There is always a component of frictional force
on any cutting edge as it rubs against the
surface , following the dislodgement of the
chip.
212. 4. Run-out :
• It refers to the maximum displacement of the
bur head from its axis of rotation while the
bur turns .
213. • The average value of clinically acceptable run-
out is about 0.023mm.
• Run-out is depend not only on the
eccentricity of the bur itself but also depend
on the precision on the dental handpiece.
214. 5.Depth of cutting :
• As the depth of cutting is decreased, the force
intensity on each small portion of the bur
tooth still cutting is correspondingly increased
and accordingly the average displacement per
flute revolution should also be increased.
215. Procedures For Tooth Tissue Removal With
Rotary Instruments :
• The practical application of rotary procedures
associated with cavity preparation is best
categorized by the following classifications :
216. • Penetration
• Extension
• Excavation
• Refinement
• With some exceptions ,penetration is most
effectively carried out at ultra speeds of
rotation.
217. DENTAL ABRASIVE STONES :
• Abrasives
• Such as carborundum (green) or alumdum
(white or pink)
• Fixed directly into bur shank.
• Abrasive particles are held together by means
of “binder”(base)of variable nature.
218. According to the composition of the abrasive
particles ,dental stones can be classified as
follows:
• Diamond stones
• Carbides
• Sand
• Aluminium oxide
• Garnet
•
219. • Types of dental stones :
Mounted
Unmounted
220. FINISHING AND POLISHING INSTRUMENTS :
• Most of these are rotary type instruments :
1.Finishing burs :
• It should be atleast 12 fluted .
• However, some of them are upto 40 fluted.
221. • They may be made of stainless steel (for amalgam) or
tungsten carbide (for composite resin).
• They do not grossly cut the restorative materials, but
only remove the excesses, creating a smoother
surface.
• Such burs come in different shapes, e.g,. rounded
,apple-shaped, pear-shaped, flame-shaped , tapered,
cylindrical, inverted cone .
•
222. 2. Paper-carried abrasives :
• These are usually sand, cuttle , garnet or boron
carbide glued to paper discs or strips .
• The paper discs should be attached to a
mandrel(screw-in or screw headed) for rotary
finishing.
• The paper strip carried abrasives are used by hand in
a back and forth motion similar to a shoe polishing
action.
223. 3. Brushes :
• They come in different forms ,e.g , wheels, cylinders ,
cones etc.
• They can be screwed in the handpiece , attached to a
mandrel ,or have their own frictional attachment
extension .
• Brushes can be used be alone or with intermediate
abrasive pastes .
224. 4. Rubber :
• Plain ,rubber ended rotary tools are essential for
polishing procedure.
• They come in variety of shapes ,e.g.,cups wheels ,
cones etc.
• They can be attached to the handpiece either via
mandrel, a screw-in device , or their own frictional or
latch extension .
•
225. HAZARDS WITH CUTTING INSTRUMENTS
• For patients there are pulpal dangers from the
tooth preparation and restoration procedures.
• There also are soft tissue dangers .
• Everyone is potentially susceptible to eye , ear
and inhalation dangers .
226. REFERENCES :
• Art and Science of Operative Dentistry,
Sturdevant,5th edition.
• Fundamentals of Operative Dentistry,
James.B.Summitt,2nd edition.
• Picards manual of Operative Dentistry,
8th edition.
227. • Operative dentistry ,Modern Theory and
Practice , M.A.Marzouk , First Edition.
• Principles and practice of Operative Dentistry ,
Gerald T. Charbeneau , third edition.
