Lecture 1 Tools

Question 1

Carious

Answer 1

Bacterial infection
diseased tissue has to be removed
precise cavity preparation

Question 2

Non carious

Answer 2

Loss of surface tooth structure due to mechanical or chemical factors
ex: attriction, abrasion, erosion, abfraction

Question 3

Direct restoration

Answer 3

dental material placed in a soft state directly in cavity preparation to restore contour before it sets and hards
ex: amalgam and composite

Question 4

Indirect restoration

Answer 4

restoration fabricated outside the oral cavity then cemented or bonded to the tooth
ex: crown, CAD/CAM

Question 5

Low speed hand piece

Answer 5

Less than 12,000 RPM
no water
less efficient but more controlled
uses: remove deep caries when close to the nerve, cleaning and polishing

Question 6

Medium Speed

Answer 6

12,000-20,000 RPM

not used

Question 7

High Speed

Answer 7

Greater than 200,000 RPM
uses water because great amt of heat generated
Most efficient cutting– less vibration and pressure that leads to less patient discomfort
Uses: teeth preparation and removal of old restorations

Question 8

Rotary instruments

Answer 8

Bladed instruments- excavating and finishing
Diamond (abrasive) instruments
Other abrasives (discs)

Question 9

Bladed instruments

Answer 9

1. Excavating/cutting burs– 6 or 8 blades
2. Finishing burs– 8+ blades
   Red: 10-12
   Yellow: 16-20
   White: 30
   Greater number of blades=smoother finish

Question 10

Carbide for blade cutting

Answer 10

• WC blanks ground to desired shape
• stronger/harder than SS but brittle
• WC with SS shaft or all WC
  uses: intracoronal preps

Question 11

Diamond for abrasive cutting

Answer 11

-metal blanks with small diamond particles within a softer matrix
Yellow: superfine (smoothest)
Red: fine
Blue: medium
Green: coarse
Black: supercoarse
uses: extracoronal preparations

Question 12

Round burr

Answer 12

1/4 to 11
1/4=0.5 mm
4=1.4 mm

Question 13

331/2-40

Answer 13

Inverted cone
flat ended
usually short
creates converted walls

Question 14

229-333

Answer 14

Pear shaped
round and tapered
Creates Convergent walls

Question 15

330

Answer 15

Length: 1.5 mm
Taper: 8 degrees– Convergent walls
Diameter: 0.8 mm
pear shaped

Question 16

245

Answer 16

Length: 3.0 mm
Tapered 4 degrees– convergent walls
diameter: 0.8 mm
pear shaped

Question 17

55-59

Answer 17

Plain cylindrical fissure
no taper (// sides)
diameter= 1 mm
Flat ended
(designate 200 series for rounded corners)

Question 18

169-172

Answer 18

Plain tapered fissure

tapered to create Divergent walls

Question 19

900 series

Answer 19

End cutting

Question 20

500 or 700 series

Answer 20

cross cut

Question 21

Brittle fracture

Answer 21

crack formation upon tensile loading
enamel is brittle

no energy absorbed before fracture

Question 22

Ductile fracture

Answer 22

Plastic deformation of the material by shearing
bladed cutting more efficient with a ductile material (deform then shear)
ex: gold alloys

Question 23

Abrasive cutting

Answer 23

more efficient with brittle materials (microcracks)

not efficient with ductile materials because they undergo plastic deformation (displace material instead of cutting it)

Question 24

Bade design

Answer 24

1. Rake face
2. Clearance face
3. Chip space

Question 25

Rake face

Answer 25

surface that forms the chips | surface of the blade towards the direction of cutting

Question 26

Clearance face

Answer 26

surface that clears away chips | away from the direction of cutting

Question 27

Edge angle

Answer 27

btwn rake and clearance surface

Question 28

rake angle

Answer 28

btwn radial line and rake face | radial line is perpendicular to the tangent

Question 29

clearance angle

Answer 29

angle that provides clearance btwn cutting edge and tooth structure

Question 30

Positive rake angle

Answer 30

When the radial line is ahead of the rake face (blade is behind the perpendicular) Higher cutting efficiency Larger chips produced but the chip space is smaller chips clog space breaks easier

Question 31

Negative rake angle

Answer 31

Radial line is behind the rake face decreased cutting efficiency smaller chips produced but no clogging of chip space cutting edge spared since carbide burs are brittle less likely to fracture

Question 32

Clearance angle

Answer 32

between clearance edge and tangent angle that provides clearance between tooth and cutting edge prevents blade from rubbing on tooth bigger clearance angle=less friction=dulling minimized=bur life lengthened

Question 33

3 unit formula

Answer 33

when the cutting edge of the Blade and the long axis of the Blade are perpendicular

Question 34

4 unit formula

Answer 34

cutting edge of Blade and long axis of Blade are NOT perpendicular

Question 35

Blacks instrument 3 number formula

Answer 35

1st number: width of the blade in tenth of a mm (10=1mm b/c 1/10 of 10=1) 2nd number: length of blade in mm 3rd number: angulation of blade to long axis of the handle in 100th of a circle (Centigrade-- always less than 50)

Question 36

Four number Formula

Answer 36

1st- width of a blade in tenth of a mm 2nd- PRIMARY CUTTING ANGLE (relative to the long axis of the handle); new number always Greater than 50 3rd-blade length in mm 4th-blade angle relative to long axis of handle in centigrade

Question 37

Direct cutting

Answer 37

force applied perpendicular to cutting edge cutting edge in contact with wall being planed hold // to the wall being planed ex: enamel hatchet

Question 38

Indirect cutting/Lateral cutting/scraping

Answer 38

Force exerted // to cutting edge Motion: Beveled to non beveled side (away from bevel) ex: enamel hatchet and gingival margin trimmer

Question 39

Enamel hatchet

Answer 39

cutting edge // to long axis of handle direct and lateral cutting double ended instrument with right and left bevels Chisel family

Question 40

Gingival margin trimmer

Answer 40

blade curved and not mille din a single plane curved blade accentuates lateral cutting cutting edge makes an angle to the long axis of the blade Lateral cutting Chisel family