cuting instrument applications in conservative dentistry
TRANSCRIPT
CUTING INSTRUMENT APPLICATIONS
•Used to cut hard & soft tissues of the mouth.Mainly we have:• Excavators.•Chisels.• Other cutting instruments.
EXCAVATORS*Ordinary hatchets*Hoes*Angle formers*Spoons
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.
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.
SPOON EXCAVATORS Bin angle spoon(13-7-14) Triple angle spoon (13-7-14)* Spoon (15-7-14)
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
CHISELS1) 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 hatchet3)Gingival margin trimmer
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.
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.
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.
OTHER CUTTING INSTRUMENTS Knife File Discoid-cleoid
instruments.
HAND INSTRUMENT TECHNIQUES Modified pen grasp Inverted pen grasp Palm-and-thumb & Modified palm-and-
thumb grasp
MODIFIED PEN GRASPSimilar to that of holding
a penPads 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.
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
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.
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.
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.
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
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
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
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.
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.