Fixed - L1 - Margin & Burs

Question 1

Conventional diamond burs are made by …?

Answer 1

…plating small industrial mineral diamond particles on stainless steel shanks by a galvanic process

Question 2

What are limitations of diamond burs?

Answer 2

1. heterogeneity of grain shapes (irregular)
2. difficulty of automation
3. short lifetime

Question 3

Why do diamond burs have short lifetimes?

Answer 3

1. repeated sterilization (loss of particles)
2. ultrasonic cleaning solns w/ pH greater than 11 corrodes the nickel matrix (loss of particles)
3. potential smearing of Nickel ions from metallic binder onto the dental substrate

Question 4

What are the types of bur designs?

Answer 4

1. parallel
2. tapered
3. modified-(round, flat)-end)
4. end cutting
5. round
6. barrel
7. egg
8. flame
9. wheel

Question 5

Per ISO standards, the diameter of a rotary instrument is defined as the…?

Answer 5

widest part of the cutting surface

Question 6

Objective of restorative therapy…?

Answer 6

to protect dentin, pulp, and other structures

Question 7

Damages during tooth prep could occur to…?

Answer 7

adjacent teeth, soft tissues, and dental pulp

• we are more concerned w/ mechanical dmg to pulp

Question 8

Increase in frictionally generated heat is influenced by…?

Answer 8

1. pressure
2. duration of applied force (intermittence)
3. condition of burs
4. rotational speed
5. use of coolant!
6. remaining dentin thickness

Question 9

what is the adequate force for the burs?

Answer 9

1-4oz of force

Question 10

What condition should the burs be in?

Answer 10

use NEW burs consistently

Question 11

What should the rotational speed of the HS handpiece be?

Answer 11

200,000rpm

Question 12

What should the remaining dentin thickness be?

Answer 12

2mm ideal, 0.5mm increases risk of toxic injury by 25%

Question 13

3 - 25% of teeth develop _____ as a result of tooth prep for CCC.

Answer 13

pulpal necrosis

Question 14

Whenever possible, margin should always be placed _____.

Answer 14

supragingivally

Question 15

Exceptions to placing margin supragingivally?

Answer 15

1. cervical erosion (sensitivity)
2. subgingival restorations
3. prox. contact extends to the gingiva
4. additional retention & resistance is needed
5. surveyed FDP where undercuts are planned for clasp retention

Question 16

What are the types of margin designs?

Answer 16

chamfer, shoulder, feather edge beveled shoulder

• we only use the first 2
• last one is most conservative

Question 17

What is CVD?

Answer 17

Chemical vapor deposition (CVD); technique most modern/urban companies are using to help form a more even and uniform grain shapes in diamond burs.

Question 18

what happens when you lose the diamond particles on the tip of the bur?

Answer 18

bur will create more heat

Question 19

what are the 5 variables of bur design?

Answer 19

1. TYPE (shape)
2. LENGTH (total & cutting)
3. SIZE (HEAD/(Ø)
4. GRIT (texture)
5. HANDPIECE

Question 20

which variable of bur design is most important?

Answer 20

GRIT

Question 21

what are the most common types of burs for fixed?

Answer 21

parallel and tapered burs

Question 22

goal of using burs in fixed?

Answer 22

to generate the most type of cuts w/ the lease amt of burs

Question 23

what does grit depend on?

Answer 23

the size of the diamond particles

Question 24

Color for the burs & Grit type:
gray - ?
white - ?
green - ?
red - ?
black - ?
yellow - ?

Answer 24

white - ultra fine
yellow - super fine
red - fine
gray - medium
green - coarse
black - super coarse

Question 25

range of length for bur design? (include total & cutting)

Answer 25

total: 14.5 - 25mm cutting: 0.08 - 10mm

Question 26

range of size (head/(Ø)?

Answer 26

0.5 - 8.0mm

Question 27

range of grit for bur design?

Answer 27

Ultra fine (8μ) to Super Coarse (150μ)

Question 28

type of handpiece for fixed burs?

Answer 28

FG, Latch, Straight, Stryker

Question 29

what type of bur makes it easier to avoid J-margins?

Answer 29

modified round-end taper

Question 30

Per ISO standards, the diameter of a rotary instrument is defined as the _____.

Answer 30

widest part of the cutting surface

Question 31

Tell me about the length, cutting length, head size, and grit of the modified round-end taper bur?ƒ

Answer 31

``` TYPE: Modified Round End Taper LENGTH: 31 FG (19mm) CUTTING LENGTH: 8.0 mm HEAD SIZE Ø: 016 = 1.6mm GRIT: Coarse Medium Fine ```

Question 32

what do worn burs do?

Answer 32

have more touching area, so generate more friction, thus having more energy

Question 33

Depth of the prep affects what?

Answer 33

dentin permeability and odontoblast process amputation recovery

Question 34

incisal/occlusal remaining dentin thickness?

Answer 34

4mm combined enamel-dentin thickness in young teeth (5-7mm in older subjects)

Question 35

axial reduction of dentin?

Answer 35

0.3mm thickness remaining in young bicuspids when prep was 1.2 deep margin w/ TOC of 20 degrees

Question 36

Avoid full coverage on vital teeth before the age of...?

Answer 36

18

Question 37

Margin design is controlled by what?

Answer 37

your maneuvering of the bur shape