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Dr. Menni to sez

Hey Mo, learn’m ‘bout

dental tools today!

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- Thomas Carlyle

Man is a tool using animal.Nowhere do you find him without tools;

Without tools he is nothing, with tools he is all.

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2 Lectures

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used in dentistry

hand rotary

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Dr. A. F. Peete

St. George, SC

late 19th century

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Single-ended

Double-ended

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Carbon 1.0 - 1.2%

Manganese 0.2%

Silicon 0.2%

Iron 98.4 - 98.6%

Carbon 0.6 - 1.0%

Chromium 18%

Iron 81 - 81.4%*

1930’s

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Chisel of stainless steel with carbide insert

to produce the cutting edge.

Carbide - an intermetallic compoundof carbon and another material 

“ Tungsten” carbide - used in cutting instruments (blades) 

“ Silicon” carbide - used as abrasives 

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 Annealing

Hardening

Tempering

- 3 basic & sequential steps

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 Annealing reduces the steel to its extreme degree of softness. The

metal is heated to a dull redness and cooled slowly. A greater degree

of softness is produced by excluding the atmosphere by covering it

and allowing it to cool slowly. Annealing relieves strains and makes

the metal as ductile as possible for machining and shaping.

Main Entry: duc·tile

Pronunciation: ' d&k- t &l , - "t I l

Function: adjective

Etymology: Middle French & Latin; Middle French, from Latin ductilis, from duc

1 : capable of being drawn out or hammered thin <ductile iron>

2 : easily led or influenced

3 : capable of being fashioned into a new form

synonym see PLASTIC

-duc·til·i·ty /"d&k- ' t i - l &- tE/ noun

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The metal is then hardened to its limit by heating it to a full cherry-red color

which allows the carbon to freely migrate through-out the piece

and plunging it immediately into cold water. In this state it is extremelybrittle. The more carbon present, the harder and more brittle it becomes.

Note: Gold casting alloy is hardened by slow bench

cool ing and annelled (softened) by quenching a hot

casting in water.

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The relief of strains produced by the hardening process to an

extent needed for a particular tool (varies). Tempered steel is less brittle.

This is accomplished by reheating to a lower temperature (than for

hardening) and plunging it into cold water, oil, or mercury.

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Temperature abuse of hand instrumentswill alter the original properties of the alloy

and make the instrument unserviceable

for the intended purpose.

Don’t flame a cutting/carving instrument becauseyou will destroy its cutting ability and toughness.

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4  Parts Of A Hand Cutt ing Instrument

Handle (shaft)

Shank

Blade (or nib)

Cutting Edge (or “face” in the case of a nib)

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blade

(nib)shank handle

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Face (2) 

Secondary

Cutting edge

SecondaryCutting

edge

side

bevel

endbevel

primary

cuttingedge

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Likewise with a spoon excavator !

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The Good, the Bad and the Ugly:

Proper and Improper End Bevels

Cutting edge

 Angle of the bevel

inefficient efficient

and

durableefficient

but

not durable

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 - a small pointed or projecting part

… but without a blade or cutting edge

Examples in instruments we use:

• amalgam condensers• burnishers

• plastic instruments 

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Straight - no angle

Monangle - one angle

Binangle - two angles

Triple angle - three angles

curved

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15-8-12

G.V. Black’s Instrument Numbering Formula

Enamel Hatchet:  15-8-12 

15 = width of blade

(tenths of mm.) 

8 = length of blade 

(mm) 

12 = angle of blade

from long axisof handle

centigrade !

He’s Watching Yo

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 Astronomical scaleCentigrade scale

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Measuring

 Angle of cutting edge

Measuring

 Angle of blade

14°

Instruments with four numbers

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15 - - 8 - 12

Instruments with four numbers

Primary cutting edge is

NOT 90° to blade. 

 Angle of primary cutting edge (centigrade °)

placed in second position.

95

margin trimmers & angle formers

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distal margin trimmer

Mesial Margin Trimmerless than

90° more than

90°

mesial margin tr immer

80

90

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Unsupported enamel

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c. 20°

Margin Trimmer In Action

Explorer 23-17

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p

“ E P k”

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“ Exam Pack”

mirror

explorer

perio probe

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Cone Socket Front-Surface Mirror

EVIL RearSurfaceMirrors

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EVIL Rear Surface Mirrors

Spoon Excavator

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Spoon Excavator

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Binangle Chisel

“2 angles”1

2

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Curved Chisel (Wedelstaedt)

Wh t i it?

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What is it?

1 2

3

Triple Angle Hoe

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…fair material for testing.!

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Palm & Thumb

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with finger rest !

with f inger rest ! uh-oh!

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Questions about hand instruments

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