Biomimetic Dentistry Flashcards
What are guided preps and how do they work (veneer work)
“working from final form”
Biomimetic concept to preserve enamel
Prep the teeth with depth-cutting burs through the provisionals, this ensures you’re only taking off a very small amount of enamel.
What is the principle of biomemetic restorations (3)
Restore teeth to full function by creating hard tissue bond that allows functional stress to path through tooth
- adhesive indirect restos distribute stress, unlike traditional alloy restos and cemented crowns
- coronal tissue of the tooth acts as support for the bonded tooth-resto complex
Factors influencing enamel bonding (3)
- Surface wettability of adhesive agents
- Surface contamination
- Water
Why is dentine harder to bond to? (3)
- more water than enamel
- hydroxyapatite is randomly arranged in an organic matrix whereas enamel is patterned
- Smear layer makes wetting of dentine by the adhesive more difficult
What does dentine bond strength depend on
Depth- less effective deeper you go due to change in diameter of tubules (permeability)
Age- less collagen, less tubules
When are calcium chelators used? Example?
Biomemetic
Remove smear layer without demineralising the dentin layer
used when dentine bonding as alt to phos acid
Ex. EDTA
2 reasons why you should bond into moist dentine
- prevent collagen collapse
- acetone in the bond is hydrophillic, will chase the water into tubules -> better bond strength
Why may dentine bonding fail? (3)
- contamination with fluids
- structural changes in dentine
- Lower penetration of bonding agent due to premature evaporation of solvent -> thickening
Purpose of IDS (5)
- Create interdiffusion / hybrid layer
- Protects tooth from contamination, bacterial leakage, and remnants of temp cement
- Reduces hydrodynamic water mvmt in tubules, minimising sensitivity
- Thickness of hybrid layer prevents collagen collapse during imps/cementation
- Allows for maturation of hybrid layer during provisionalisation
Why is IDS “immediate”?
What structure does it mimic?
- Bond btw monomers and dentine mimics the DEJ
- “immediate” bc freshly prepped dentine is uncontaminated, thus ideal for resin infiltration
What types of preps strongly benefit from IDS (2)
Short clinical crowns
Tapered preps
Should final impressions be taken before or after IDS
After
Otherwise resto will not fit properly, poor margins
Why should you wait 1-2 weeks before bonding to IDS
Need time for hybrid layer maturation
- less susceptible to polymerisation shrinkage
Should light cure or dual cure DBA be used with IDS?
LC DBA’s if IDS used
Dual-cure have higher levels of polymerisation and colour instability- thats why we only use dual cure when LC not possible (posts, opaque crown)
How to identify exposed dentine in veneer preps
Shortly etch (2-3s) the tooth surface and rinse
- enamel will be frosty
- dentine will be glossy
after this etch, if there is dentine, it will need to be re-prepped to expose fresh layer of dentine before being etched again for DBA application
Adhesive technique of IDS
- Etch immediately after prep (phosphoric acid)
- rinse, suction excess water
- Primer, wait to evaporate
- DBA applied, excess solvent suctioned, LC
- glycerine jelly applied, bond cured again through jelly (polymerizes oxygen inhibition layer)
What is the best bonding generation for IDS
Gen 4-
3 bottles
total etch technique
research says is most favourable
however 2 bottle can still be used
Why is glycerine jelly used in IDS to cure the bond
polymerizes the oxygen inhibition layer
- Prevents interaction with impression materials, esp polyether
What provisionals to avoid after IDS
Maximum 2 weeks
- Avoid resin-based cements
- NO EUGENOL
- Temp bond instead (ProTemp)
- Cover tooth with vaseline
How to prepare ceramic restoration for insertion (the actual onlay, inlay, crown, etc) (5)
biomimetic
- ask lab to send it w model- check model for damage
- Try in- contact, margins, fitting surface must be ideal
- onlay etched with HF 9.5% 60s, rinsed for 30s
- fitting surface of onlay then etched again with phos ac for 2 min and rinsed
- silane applied to resto, evaporated
How to prepare tooth for cementation
biomimetic dentistry
- Clean tooth using pumice
- selective etch for 15s, rinse, dry
- adhesive applied to tooth and resto but not cured
- resin cement applied to fit surface, crown seated, excess removed, LC
- glycerine applied to margins, LC
Advantages of eMax (5)
- most aesthetic
- no metal
- translucent - Durability
- less likely to chip than zirc - Ability to mill
- Conservative preps
- Versatility
- veneers
- onlays
- anteior cantilevers
- single crowns
Disadvantages of emax (4)
- $$$
- not suitable for dark teeth
- Not ideal for posteriors
- Not suitable for long bridges
What condition is this
MIH
Tx plan for this case (4)
- Immediate
- Perio and remove any plaque traps. OHI - Transitional
- Evaluate outcome of perio and OHI
- Prescribe diagnostic wax up
- Direct provisional restos, aesthetic try-in - Reconstruction
- Silicone impression
- Emax veneers
- Occlusal splint - Maintenance
- 6 mo review
- OH reinforced
- Splint assessment
What are the different thickness’ for emax veneers
Press/cad can be used for bruxists
What style of preps is preferred for emax veneers
Typically C
D can be used for bruxists
What is biomimetic tooth reduction?
Like working from final form
- diagnostic wax up based on aesthetic prescription
- Mockups in mouth
- preps based on the exact requirements from planned results (prepping into the mockups)
When are emax onlays mainly indicated
compromised posterior teeth with intact buccal and lingual walls
(MOD)
Emax onlay prep design (4)
- Prep margins should not be placed in contact areas
- min 1.5mm non-working cusps, 2mm working cusps (always need cuspal coverage)
- No bevels or retentive feats
- rounded shoulder margins, min 1mm
How to address subgingival defects prior to onlay
This is a violation of BW
- Deep Margin Elevation
- box the composite subgingivally to raise the margins - Crown lengthening (surgery or ortho extrusion)
Why are subgingival defects bad / deep preps subgingivally? (3)
- Poor access for impressions, cementation, polishing
- Poor moisture control
- BW invasion
Why is conservative new onlay prep preferred to conventional (3)
Increased fracture resistance
Reduced stress concentrations
More favourable fracture modes
What should you do if you took off old onlay and prep looked like the right?
Why?
Build up with composite so it looks like left
Uniformity in structure, both of tooth and the onlay will allow for better diversion of stresses = more fracture resistant
