Inlays/Onlays Flashcards
describe the impact of caries management on a tooth
- large restorations are linked with cracked teeth
what risks increase tooth fracture?
- large restorations - larger height:base
- not crowned root canalled teeth
- group function - molar stress occlusions
- clenched jaw, bruxism
how can you strengthen weakened cusps?
bonding
cuspal coverage
how much does bonding increase the fracture resistance following caries removal?
60%
what are the limitations of bonding and direct composites?
- polymerisation shrinkage
- harder to achieve contact points
what is the average stress applied to the tooth at the tooth-composite interface?
3-8MPa
what is the configuration factor?
the number of bonded surface
divide
number of unbounded surfaces
the higher the configuration factor =
the higher the chance of the tooth having stress placed on it
what is there a chance of if the stresses on the tooth overcome the strength of the bond?
marginal leakage
what does marginal leakage run the risk of? (2)
sensitivity
secondary caries
define inlay
an intracoronal restoration constructed in the laboratory and cemented into a tooth
what are benefits of inlays being made in the lab?
can achieve good contact points
any shrinkage occurs within the labs
problems with inlays
- require tapered form
- don’t cover the cusps - no cuspal protection
what is a wedging effect?
when an inlay is placed in the tooth
but exerts force out on the tooth
- risk fracture
are inlays best for low height:base ratio? or high height:base ratio?
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
give indications for inlays
- small to medium cavities
- low caries rate patient
- good cuspal support
- canine guidance
do onlays offer cuspal protection?
yes
with inlays and onlays, what 6 things must be considered when choosing the materials?
- aesthetics
- preserving natural tooth tissue
- retention and resistance
- structural durability of restoration
- biological considerations
- marginal integrity and positioning
how much natural tooth tissue is estimated to be removed with a full coverage crown?
67-75%
how much natural tooth tissue is estimated to be removed with an onlay?
39% - better preservation than crown
is there cuspal reduction with onlays?
yes
define onlay
a restoration constructed in the lab
cemented into a tooth that may contain a intracoronal aspect
but also covers one or more cusps
is there a large wedging effect from onlays?
not as much as inlays
the stress goes onto the onlay and not onto underlying tooth tissue
7 indications for onlays
- larger restorations
- sound buccal and lingual walls needing cuspal protection
- endo teeth
- low caries rate
- weakened cusps
- parafunction
- group function
3 materials for onlays
gold
composite
ceramic
survival rate for gold inlays/onlays?
96% for 10 years
survival rate for lithium disilocate onlays
100% for 8 years
why may you choose ceramic inlays? give 2 reasons why you wouldn’t use them
- CAD-CAM more cost effective than lab work
- good success rate
- submargination and hypersensitivities noted
which materials are best for - preserving tooth tissue.
- gold - less prep
- ceramic
which materials are best for - least damage to opposing enamel
- gold/ composite
- porcelain
- ceramic
which materials are best for - aesthetics
- porcelain, composite, ceramic
- gold
give 3 general preparation guidelines
- no undercuts
- limit paths of insertion - in and out one direction
- resistance to occlusal force
how do you remove undercut
remove more tooth tissue
or
restore with composite - take away divergent walls
gold - ideal taper, margin and occlusal reduction?
taper - 6 degrees
margin - chamfer, 0.5mm
occlusal reduction - 1mm, 1.5mm cusp
composite and ceramic - space requirements, taper, margins, finish?
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
what are adhesive onlays? what’s the chamfer depth?
known as table top or occlusal veneers
- doesn’t have an intracoronal component
- with gold onlay or lithium dislocate
1mm chamfer depth
indications for adhesive onlays
- cuspal coverage for cracked tooth syndrome
- TSL - erosion/attrition
- short or over tapered crowns
- amelogenesis
when would you NOT want to use adhesive onlays?
- poor OH
- subgingival margins
- lack of moisture control
- lack of enamel margins
- parafunction
when preparing an inlay/onlay, what do you need to consider in the meantime?
temporisation
take an impression
