Inlays/Onlays

Question 1

describe the impact of caries management on a tooth

Answer 1

• large restorations are linked with cracked teeth

Question 2

what risks increase tooth fracture?

Answer 2

• large restorations - larger height:base
• not crowned root canalled teeth
• group function - molar stress occlusions
• clenched jaw, bruxism

Question 3

how can you strengthen weakened cusps?

Answer 3

bonding
cuspal coverage

Question 4

how much does bonding increase the fracture resistance following caries removal?

Answer 4

60%

Question 5

what are the limitations of bonding and direct composites?

Answer 5

• polymerisation shrinkage
• harder to achieve contact points

Question 6

what is the average stress applied to the tooth at the tooth-composite interface?

Answer 6

3-8MPa

Question 7

what is the configuration factor?

Answer 7

the number of bonded surface
divide
number of unbounded surfaces

Question 8

the higher the configuration factor =

Answer 8

the higher the chance of the tooth having stress placed on it

Question 9

what is there a chance of if the stresses on the tooth overcome the strength of the bond?

Answer 9

marginal leakage

Question 10

what does marginal leakage run the risk of? (2)

Answer 10

sensitivity
secondary caries

Question 11

define inlay

Answer 11

an intracoronal restoration constructed in the laboratory and cemented into a tooth

Question 12

what are benefits of inlays being made in the lab?

Answer 12

can achieve good contact points
any shrinkage occurs within the labs

Question 13

problems with inlays

Answer 13

• require tapered form
• don’t cover the cusps - no cuspal protection

Question 14

what is a wedging effect?

Answer 14

when an inlay is placed in the tooth
but exerts force out on the tooth

• risk fracture

Question 15

are inlays best for low height:base ratio? or high height:base ratio?

Answer 15

low height:base ration

because they dont offer cuspal protection, simply slot within the cavity space

• prone to fractures with a high height:base ratio

Question 16

give indications for inlays

Answer 16

• small to medium cavities
• low caries rate patient
• good cuspal support
• canine guidance

Question 17

do onlays offer cuspal protection?

Answer 17

yes

Question 18

with inlays and onlays, what 6 things must be considered when choosing the materials?

Answer 18

• aesthetics
• preserving natural tooth tissue
• retention and resistance
• structural durability of restoration
• biological considerations
• marginal integrity and positioning

Question 19

how much natural tooth tissue is estimated to be removed with a full coverage crown?

Answer 19

67-75%

Question 20

how much natural tooth tissue is estimated to be removed with an onlay?

Answer 20

39% - better preservation than crown

Question 21

is there cuspal reduction with onlays?

Answer 21

yes

Question 22

define onlay

Answer 22

a restoration constructed in the lab
cemented into a tooth that may contain a intracoronal aspect
but also covers one or more cusps

Question 23

is there a large wedging effect from onlays?

Answer 23

not as much as inlays

the stress goes onto the onlay and not onto underlying tooth tissue

Question 24

7 indications for onlays

Answer 24

• larger restorations
• sound buccal and lingual walls needing cuspal protection
• endo teeth
• low caries rate
• weakened cusps
• parafunction
• group function

Question 25

3 materials for onlays

Answer 25

gold
composite
ceramic

Question 26

survival rate for gold inlays/onlays?

Answer 26

96% for 10 years

Question 27

survival rate for lithium disilocate onlays

Answer 27

100% for 8 years

Question 28

why may you choose ceramic inlays? give 2 reasons why you wouldn’t use them

Answer 28

• CAD-CAM more cost effective than lab work
• good success rate
• submargination and hypersensitivities noted

Question 29

which materials are best for - preserving tooth tissue.

Answer 29

1. gold - less prep
2. ceramic

Question 30

which materials are best for - least damage to opposing enamel

Answer 30

1. gold/ composite
2. porcelain
3. ceramic

Question 31

which materials are best for - aesthetics

Answer 31

1. porcelain, composite, ceramic
2. gold

Question 32

give 3 general preparation guidelines

Answer 32

• no undercuts
• limit paths of insertion - in and out one direction
• resistance to occlusal force

Question 33

how do you remove undercut

Answer 33

remove more tooth tissue
or
restore with composite - take away divergent walls

Question 34

gold - ideal taper, margin and occlusal reduction?

Answer 34

taper - 6 degrees
margin - chamfer, 0.5mm
occlusal reduction - 1mm, 1.5mm cusp

Question 35

composite and ceramic - space requirements, taper, margins, finish?

Answer 35

space requirement
- 1.5-2mm wide and depth
- 2mm occlusal coverage - porcelain only

taper
- 15-20 degrees

margin
- 90-120 cavo-surface
- 1mm - heavy chamfer/rounded shoulder

finish
- rounded internal angles

Question 36

what are adhesive onlays? what’s the chamfer depth?

Answer 36

known as table top or occlusal veneers
- doesn’t have an intracoronal component
- with gold onlay or lithium dislocate

1mm chamfer depth

Question 37

indications for adhesive onlays

Answer 37

• cuspal coverage for cracked tooth syndrome
• TSL - erosion/attrition
• short or over tapered crowns
• amelogenesis

Question 38

when would you NOT want to use adhesive onlays?

Answer 38

• poor OH
• subgingival margins
• lack of moisture control
• lack of enamel margins
• parafunction

Question 39

when preparing an inlay/onlay, what do you need to consider in the meantime?

Answer 39

temporisation
take an impression