FIXED PROS - Principles of Tooth Prep

Question 1

what is an indirect restoration? give 4 examples.

Answer 1

a restoration which is not placed directly into the patients mouth e.g. a crown, veneers, onlays or inlays

Question 2

why is a crown an indirect restoration?

Answer 2

• take an impression
• produce restoration within the labs

Question 3

what are 4 cons of indirect restorations?

Answer 3

more appointments
more expensive
more stages involved - time consuming
more professionals involved

Question 4

why are indirect restorations needed?

Answer 4

aesthetics
comfort
function
stability

Question 5

what 3 things need to be considered when preparing?

Answer 5

• room needs to be created for the restoration and cement
• needs taper - narrow at the bottom
• consider the path of insertion with proximal contact - ideal to be parallel to taper

Question 6

what are the 7 principles of preparation?

Answer 6

1. preservation of tooth tissue
   - protect pulp, periodontium and prevent fracture
2. retention and resistance
3. structural durability
4. the material choice
5. marginal integrity and position
6. biological considerations
7. aesthetics

Question 7

what happens if there isn’t enough space and a crown is placed?

Answer 7

cause pain
opposing tooth or crown may fracture due to forces
complain due to crown being high

Question 8

what if the tapering leads to a wider top and narrower bottom?

Answer 8

it becomes an undercut
- leaves overhand of tooth tissue
- over prepared
- weakens the tooth risking fracture or pulpal exposure
- crown will not fit properly

Question 9

describe difference between retention and resistance

Answer 9

retention - prevents movement of vertical forces

resistance - prevents movement of lateral or apical forces

Question 10

what is retention and resistance influenced by?

Answer 10

the taper, surface area, height and design

the greater the taper, the less the retention and resistance

the larger the surface area and height, the better the retention and resistance

design - grooves and boxes

Question 11

what is the best degree of taper?

Answer 11

6-12 degree

Question 12

what bur is used, already possessing the 6 degree angle?

Answer 12

long diamond bur

Question 13

what is the minimum recommended height for the tooth tissue?

Answer 13

3mm

allows placement of crown without occlusal interference

Question 14

what are the differences in cement selection?

Answer 14

passive vs active

• can have adhesive properties rather than passive cement

Question 14

what should be the depth of a groove?

Answer 14

no less than half the burs diameter

Question 15

what comes under structural durability?

Answer 15

to be able to withstand:
- occlusal forces
- changes in the oral environment
temperature, pH, mastication of food
- minimal maintenance

Question 16

what are the 4 different materials to choose from?

Answer 16

metal ceramic
gold
non precious metal
all ceramic

Question 17

why do the margins need to be accurate?

Answer 17

to allow the crown to fit flush onto the tooth
- prevent plaque retentive factors forming
- reduce exposed cement

Question 18

what are the different types of margin design?

Answer 18

horizontal margin
- shoulder design - metal ceramics crowns
- requires 1.2mm margin width

• chamfer design - gold crowns
• requires 1.5mm margin width

vertical margin
- knife edge
- a thin, fine edge which fades away - metal crowns

Question 19

what should be regarded in terms of biological consideration?

Answer 19

• preservation of the periodontium
• preservation of the pulp
• biological width

Question 20

how do you preserve the periodontium?

Answer 20

good oral hygiene
supragingival margins
sufficient marginal reduction

Question 21

how can the aesthetics of the periodontium be affected?

Answer 21

if there is recession and increased crown height ratio

Question 22

what is the biological width?

Answer 22

the distance from depth of sulcus to the alveolar crest

Question 23

why can biological width be difficult to manage when taking impressions and placement?

Answer 23

• may be gingival inflammation
• increase probing depth
• increase chance of attachment loss when extra coronal margins are placed subgingivally

Question 24

how much can a extra coronal margin increase recession by?

Answer 24

1mm: 2.65x

Question 25

…/5 teeth can become non-vital following crown preparation

Answer 25

1/5

Question 26

how do you assess the abutment tooth?

Answer 26

Assessing the abutment tooth
Clinical
Caries
Quality of restoration
Pocketing
Mobility
Occlusion
Radiographs - bone levels, apical status, root form and shape

Question 27

what is the unit?

Answer 27

a term to indicate the no of pontics or retainers associated with the bridge

also indicates the length of bridge