Introduction to Operative Dentistry Third Year

1. General instruments &
instrumentation

4. General classification
1. Diagnostic or exploring instruments
2. Cutting instruments
3. Isolating instruments
4.Condendsing instruments
5.Plastic instruments
6. Finishing& polishing instruments a-Hand
b-Rotary
7.Miscellaneous instruments

5. Restoring teeth back to normal

7. Parts of hand cutting
instrument

8. Black's formula
Three figure instrument:
1. Width of blade in 1/10 mm
2. Length of blade in mm
3. Angle between long axis of blade &long
axis of handle

9. Four figure instrument
1. Width of blade in 1/10mm
2. Cutting edge angle
3. Length of blade in mm
4. Angle between long axis of the blade &
long axis of the handle

10. 3 Figure instrument

11. Hand cutting instruments are chisels
or excavators

12. Excavator
Chisel
-Used in dentin
-Scooping or
peeling off soft
carious dentin
-Lighter in weight
-Gentle force
- Include spoon,
discoid, celoide,
Hatchet
-Used in enamel
-Cleavage of
undermined
enamel
-Heavier in weight
-Firm strokes
- Include chisel,
enamel hatchet,
G.M.T, Angle
former,
weadelsteadt
chisel

13.  Direct cutting instrument: direction of cutting is the
same as direction of application of force
 Lateral cutting instrument: direction of cutting is ┴
to direction of application of force
 Single plane instrument: main parts of the
instrument conform to one single plan
 Double plane instrument: main parts are in two
plans
 Reverse beveled instrument. Left hatchet and
mesial chisel indicated by a ring in the shaft

15.  Contra-angling: additional angle or angles
added to the shank on the opposite side of
the shaft in order to make the cutting edge
within 2-3 mm from the long axis of the
instrument→ balance, visibility, accessibility

16. 4 Figure instrument

18. Spoon and discoid excavator

19. Spoon excavator

20. Discoid excavator

21. Gingival marginal trimmer and enamel hatchet

24. Instrument maintenance, sharpness using Arkansas stones

25. Rotary Instruments
 According to the attachment to the hand piece it is
 1- Latch type→ conventional speed
 2-friction grip→ conventional or high speed
 Speed ranges
-low 2000-5000 rpm
-medium
-high
-ultra high

26. Latch and frictional grip

27.  Cutting efficiency: Ability of the cutting instrument
to cut maximum amount of tooth structure in
minimal time with minimal effort.
 Factors affecting the cutting efficiency:
 1- speed used
 2- pressure
 3- bur design & shape
 4-use of a coolant
 5-eccentricity or run out
 6- Tissue to be cut

28. –Eccentricity or Run-out
Maximum displacement of the bur
head away from the central axis of
rotation. The bur is said to be
eccentric if this displacement is
greater than 0.025mm. This leads to
vibration and loss of controlled
cutting.

29.  Heat generation:
Not all the energy delivered at the cutting bur
is dissipated in the form of actual cutting
part of the energy is dissipated in the form of
heat generation because of friction at the
cutting site.
Generated heat→ to the atmosphere- to the
hand piece- to the tooth structure→ adverse
effects on the pulp

30.  According to material of construction
 1- steel bur
 2-Tungestin carbide bur
 steel is less efficient, used for removal of
hard caries and finishing of restorations
 Tungsten Carbide bur harder, higher
melting, better manufacturing

31. Bur Design

32. Rake Angle
Increasing +ve rake
angle increases the
cutting efficiency but
within limits
+ve
-ve
radial

33. Cross Cutting( increasing number of blades without affecting
clearance space)

39. Coolant
Air-water spray, multi-directed, copious
amount, 37̊ c so as to dissipate heat,
lubricate, increase bur life, cleaning effects
and reduce the need for local anesthesia

41. Burs versus Stones

42. Burs and Stones

43. Foot driven dental drilling