A presentation on cutting instruments used in conservative dentistry

1. CUTING INSTRUMENT APPLICATIONS
•Used to cut hard & soft tissues of the mouth.
Mainly we have:
• Excavators.
•Chisels.
• Other cutting instruments.

2. EXCAVATORS
*Ordinary hatchets
*Hoes
*Angle formers
*Spoons

3. ORDINARY HATCHET(3-2-28)
*It has the cutting edge
directed in the same
plane as that of the
long axis of the handle
&is bibeveled.
* Used primarily on
anterior teeth for
preparing retentive
areas & sharpening
internal line angles.

4. HOE(4 ½ -1 ½ -22)
*cutting edge perpendicular to the
axis of the handle.
*used for planing tooth preparation
walls& forming line angles.
* Commonly used in classIII &
class V preparation for direct
gold restoration.

5. SPOON EXCAVATORS
 Bin angle spoon
(13-7-14)
 Triple angle spoon
(13-7-14)
* Spoon (15-7-14)

6.  spoon excavators are used for
>removing caries
>carving amalgam or direct wax pattern
*cutting edge of the spoon excavator are
>Discoid(circular)
>Cleoid(clawlike)
*shank may be bin angled or triple angled

7. CHISELS
1) Depending upon the shank angle& blade, it may be
>straight (12-7-0)
>Wedelstaedt(11 ½ -15-3)
>Bin angle(10-7-8)
2)Enamel hatchet
3)Gingival margin trimmer

8.  Straight chisel has a
shank & blade with the
bevel on one side.
 primary edge is
perpendicular to the
long axis of the handle.
 Bin-angle
&Wedelstaedt chisel
may have either a
distal bevel or a
mesial(reverse)bevel.

9. ENAMEL HATCHET(10-7-14)
 it is a chisel with larger
&heavier blade beveled
on only one side.
 cutting edge parallel
with the axis of handle.
 Use for cutting enamel
& comes as right or left
types.

10. GINGIVAL MARGIN TRIMMER
(12 ½-100-7-14)
 designed to produce
proper bevel on
gingival enamel
margins of proximo-
occlusal preparations.
 cutting edge is
angled(other than
perpendicular) to the
axis of the blade.
 comes as right and left
types.

11. OTHER CUTTING INSTRUMENTS
 Knife
 File
 Discoid-cleoid
instruments.

12. HAND INSTRUMENT TECHNIQUES
 Modified pen grasp
 Inverted pen grasp
 Palm-and-thumb &
 Modified palm-and-
thumb grasp

13. MODIFIED PEN GRASP
Similar to that of holding
a pen
Pads of thumb ,index ,&
middle fingers contact
the instrument, while
the tip of the fingers is
placed on a nearby
tooth of the same arch
as rest.
Palm generally is facing
away from the
operator.

14. INVERTED PEN GRASP
 Finger positions same
as that of the modified
pen grasp
 Hand is rotated
however, so that the
palm faces more
towards the operator.
 Used mostly for lingual
approach of the
anteriors

15. PALM-AND-THUMB GRASP
 Handle is placed in the
palm and grasped by
all the fingers, while
thumb is free and the
rest is provided by
supporting the tip of the
thumb on a nearby
tooth of the same arch
or on firm stable
structure.

16. MODIFIED PALM-AND-THUMB GRASP
 Handle of the
instrument is held by all
the fingers whose pads
press the handle
against the distal area
of the palm & the pad &
first joint of the thumb.
 This grip fosters control
against slipage.

17.  RESTS:- the closer the
rest areas are to the
operating area, the
more reliable the are.
 GUARDS:- are hand
instruments or other
items such as
interproximal wedges,
used to protect soft
tissue from contact with
sharp or abrassive
instruments.

18. SHARPENING HAND INSTRUMENTS
 Requires because
instruments with dull
cutting edge cause
*More pain
*prolong operating
time
*more difficult to
control
*reduce quality in
tooth preparation

19. STATIONARY SHARPENING STONES
(OILSTONES)
 Available in coarse ,
medium& fine grit.
 Commonly used stones
are:- arkansas stone,
silicon carbide, aluminium
oxide& diamond.
 Technique;
 Thin film of light oil should
be placed on working
surface.
 grasp the instruments with
modified pen grasp,
 Use light stroke
 Establish proper 45degree
angle of the bevel and the
cutting edge of the stone

20. MECHANICAL SHARPNERS
 example:- the Rx
Honing Machine.
 This instrument moves
a hone in a
reciprocating motion at
a slow speed, while the
instrument is held at
the appropriate
angulation
 Interchangable hones
of different shapes and
coarseness are
available

21. PRINCIPLES OF SHARPENING
 Sharpen instruments only after they have been
clean & sterilized
 Establish the proper bevel angle usually of
45degree
 Use light stroke or pressure to minimze frictional
heat.
 Use a rest or guide
 Remove as little metal as possible
 After sharpening, resterilize the instrument
 Keep sharpening stones clean.

22. SHARPNESS TEST
 Tested by lightly resting the cutting edge on a hard
plastic surface.
 If it digs in during sliding, the instrument is sharp.
 if it slides , the instrument is dull.