Week 4- restorative instruments

Question 1

two types of powered rotary instruments

Answer 1

air-driven systems

electric-driven systems

Question 2

advantages of air driven systems

Answer 2

cheaper to start up, replace, weigh less

Question 3

advantages of electric driven systems

Answer 3

quieter
high torque with little stalling
smoother cut
more attachments for burs

Question 4

three rotary speed ranges

Answer 4

slow speed

Question 5

true/false: carbide burs are more easy to break in slow speed hand pieces?

Answer 5

true

Question 6

advantages of high speed handpiece

Answer 6

diamond/carbide burs remove tooth sx faster, less pressure
reduced # of cutting instruments
operator has better control
instruments last longer
less vibrations for patient
several teeth in same arch in same visit

Question 7

true/false: most handpieces need oiling after sterilization

Answer 7

true

Question 8

laser equipment used for:

Answer 8

tx of soft tissues and modification of hard tooth structures

Question 9

disadvantages of laser equipment:

Answer 9

expensive
do not create good margin
hard to use
do not remove existing restorations

Question 10

this equipment is good for stain removal and debriding pits/fissures before sealant application

Answer 10

contemporary air abrasion equipment

Question 11

how does contemporary air abrasion equipment work?

Answer 11

uses transfer of energy from stream of powder particles from surface of tooth/restoration to produce fractured surface layer -> roughness for bonding

Question 12

true/false: steel burs can be used in high speed handpieces?

Answer 12

false; will bend…can only be used in slow speed

Question 13

fits into handpiece and provides bearing surface for control

Answer 13

shank

Question 14

connects head to shank

Answer 14

neck

Question 15

working part of rotary instrument that has cutting edge

Answer 15

head

Question 16

carbide is stiffer than steel but has one disadvantage

Answer 16

more brittle

Question 17

round bur used for:

Answer 17

initial entry into tooth
extension of prep
prep retention features

Question 18

inverted cone bur used for:

Answer 18

provide undercuts in preps

Question 19

pear shaped bur used for:

Answer 19

tooth preps for amalgam

Question 20

straight fissure bur used for:

Answer 20

amalgam preps, indirect restorations

Question 21

trends in bur design

Answer 21

less use of crosscuts (notches in blade to increase cutting efficiency)
extended heads of fissure burs
rounding of sharp tip angles

Question 22

true/false: the more blades on the bur, the smoother the cutting at slow speeds?

Answer 22

true

Question 23

number of blades on a bur is always _____

Answer 23

even

Question 24

concentricity

Answer 24

direct measurement of bur head symmetry, determines if there is a blade longer than others

Question 25

runout

Answer 25

test measuring accuracy with which all blade tips pass thru single point when instrument rotated (cannot be LESS than concentricity)

Question 26

most important design characteristic of bur

Answer 26

rake angle

Question 27

rake angle

Answer 27

angle between rake face and radius of bur | should be negative

Question 28

negative rake angle

Answer 28

rake face in front of radius of bur | minimize fractures and increase tool longevity

Question 29

rake face

Answer 29

side of blade toward direction of cutting

Question 30

clearance face

Answer 30

side of blade away from direction of cutting

Question 31

edge angle

Answer 31

angle between rake face and clearance face | larger = more tool longevity

Question 32

clearance angle

Answer 32

angle btw tooth structure and clearance face | smaller = higher edge angle = longevity

Question 33

true/false: cutting effectiveness takes into account heat or noise

Answer 33

false | just measures rate of tooth structure removal

Question 34

cutting efficiency

Answer 34

% of energy actually producing cutting

Question 35

true/false: cutting efficiency reduced when energy is wasted as heat or noise?

Answer 35

true

Question 36

abrasive cutting often leads to:

Answer 36

plastic deformation

Question 37

brittle fracture often results from:

Answer 37

high speed cutting

Question 38

diamond abrasive instruments composed of:

Answer 38

abrasive instruments held in matrix of softer material

Question 39

where does cutting occur in diamond abrasive instruments?

Answer 39

numerous places where hard particles protrude from matrix

Question 40

true/false: diamond abrasive materials not good for cutting dentin/enamel?

Answer 40

false

Question 41

diamond instrument parts:

Answer 41

metal blank (bur without blades) powered diamond abrasive metallic bonding material (holds diamond powder onto blank)

Question 42

why can't you use air alone?

Answer 42

damage odontoblasts | water helps with pulp insulation

Question 43

disadvantage of air driven system

Answer 43

does not stop immediately after you stop rheostat ; careless soft tissue injury

Question 44

______ are most prone to injury of patient

Answer 44

large discs

Question 45

how to avoid third degree burns when cutting?

Answer 45

sharp burs that don't require extreme high speeds to cut