2. Adhesion Flashcards
Factors that influence adhesion (6)
- reactive groups
- surface tension
- surface energy
- wettability
- capillary action
- substrate
What are the reactive groups in tooth tissues?
- HAP
- Collagen
What are the reactive groups in HAP? (2)
(OH)-
Ca2+
What are the reactive groups in collagen? (3)
- COOH
- NH2
- CONH2
What are the reactive groups in adhesive?
Bis-GMA (CH2)
What are the reactive groups in composite resin? (3)
- Bis-GMA (CH2)
- CH3
- C-COO
What kind of adhesion do we get between tooth tissues and adhesive?
Micromechanical
- due to etch
What kind of adhesion do we get between composite resins and adhesive?
Chemical (long chain molecules)
What is surface energy?
Characteristic of the solid we want to adhere to
What kind of surface energy do we want for the tooth?
High surface energy to attract the liquid (adhesive)
What is surface tension?
- property of liquids
- force of internal molecules to pull from the external ones (forming drops)
- resistance of fluid to deform or break
What kind of surface tension do we want for adhesive?
low surface tension so it spreads more easily
What happens when theres high surface energy?
Forms drops
What is wettability?
Ability of a liquid to wet a solid
What does wetability depend on?
- surface energy
- surface tension
How is wettability measured?
by the angle formed between the tangent to the surface of a liquid and its adherent/adhesion surface
A bigger wetability angle means?
Less wetability
A smaller wettability angle means?
More /better wetability
Better wetability has ____ surface tension and _____ surface energy and ____ capillary action and ____adhesion
- Low surface tension
- High surface energy
- Good capillary action
- Good adhesion
What influences good capillary action?
- Low surface tension and high surface energy (=good wetability)
- viscosity
What is capillary action?
- Ability of the liquid to penetrate into thin tubules
- due to adhesive and cohesive forces between liquid and surface
Capillary action only occurs when…
adhesive forces are greater than cohesive forces
What surface energy does enamel have? why?
High SE
- a lot of inorganic matter (HAP)
- low water content & organic matter (almost no collagen)
What happens when enamel is treated with acid?
- Microporosites are created that act as tubules
- increase SE
What surface energy does dentin have? why?
Lower SE than enamel
- more organic content (collagen) and H20
- hydrophilic
Is dentin hydrophobic or hydrophillic?
Hydrophilic
Why is dentin a worse substrate for adhesion than enamel?
- large number of tubules that can act as capillaries - in dentinal fluid has pressure that affects resin penetration
- size and diameter of tubules decreases moving away from pulp chamber
- lower SE than enamel
- more organic content
What are resins (adhesives) propterties as a substrate?
- adhesive
- hydrophobic AND hydrophilic characteristic
What are the dental adhesive qualities ? (8)
- Good biocompatibility to dental tissue
- wetting capacity
- bond strength to dental tissues
- bond strength to restorative materials
- good mechanical behavior
- easy to handle
- durability
- good shelf life (few years)
What are the dental adhesive components? (8)
- Hydrophillic resins
- Hydrophobic resins
- Acidic resin
- Solvent
- Photoinitiators
- Catalyst
- Inorganic filler
- Radio-opacifiers
What are the hydrophillic resin components? (4)
- HEMA: hydroxy-ethyl-methacrylate
- TEGDMA: lower viscosity
- 4-META: 4 methacryloyl-oxy-ethy-trimellitate-anhydride
- PMDM: p-dimethylacrylate promellitic acid
What are the hydrophobic resin components? (2)
BIS-GMA
UDMA
What are the acidic resin components?
Self etching adhesives
pH: 1.5-2.5
What are the photo-initiator components?
Camphorquinone molecules - start polymerization by light
- not necessary if self-cured
What are the catalyst components?
TBB - tributylborane
*necessary for some reactions in certain adhesives
What are the inorganic filler components?
Microfilled glass (small amounts) or colloidal silica *nowadays nanoparticles
What are the radio-opacifier components? (2)
Bismuth oxide (prone to discoloration) or Barium sulphate
What does the concentration of camphorquinone affect?
aeshtetics of a restoration
- exceeding critical concentration = yellow discoloration
- unreacted molecules may return back to ground state
What is PPD?
1-phenyl-1, 2-propanedione
- to improve polymerization kinetics
- reduce yellowing effect of photointiator
- camphorquinone cant be removed completely but adding other co-photointiators helps avoid the problem
Adhesives can be classified by: (4)
- etching
- polymerization system
- generations
- steps
How are adhesives classified by etch?
Total vs Self vs Selective
How are adhesives classified by polymerization system? ?
- light
- self
- dual
What is self polymerizing adhesive?
Pure chemical reaction
- 2 bottles with benzoyl peroxide and tertiary amine
How are adhesives classified by generations?
1st: Chemical adhesion (methacrylate)
2nd: Hydrophobic resins
3rd: Enamel etching. Hydrophilic+ hydrophobic, smear layer
4th: Total etch. Hybrid layer
5th: 1 step
6th. Self etch (2000). 2 bottles
7th: Self etch 1 step
Which generation has the best adhesion we can achieve ?
4th
Describe 1 gen adhesive
Very weak bond to dentin
Describe 2 gen adhesive (3)
- weak needing retentive preps
- hydrophobic resin
- prone to water degradation
Describe 3 gen adhesive (5)
- Enamel etching only
- 2 component primer and adhesive system
- bonding to metals
- reduced sensitivity
- hydrophobic and hydrophillic
Describe 4 gen adhesive (5)
- Best adhesion
- 3 steps
- total etch (conventional)
- little sensitivity
- Hybridization: hybrid layer discovery + etch (E&D)
What is the 3 step adhesive?
- step 1: orthophosphoric acid (etch)
- step 2: primer (first bottle)
- step 3: bonding (second bottle)
Describe 5 gen adhesive (5)
- single component
- moist bonding
- hybridization
- no mixing (2 steps)
- little sensitivity
What is the 2 step adhesive?
Etch
Adhesive (primer and bonding in same bottle)
Describe 6 gen adhesive (5)
- multicomponent
- 2 step
- self etch & prime
- hybridization
- very little sensitivity
Describe 7 gen adhesive (6)
- single component and step
- self etch & prime
- desensitizing / very little - no sensitivity
- bonds to metal
- moisture independent
How are adhesives classified by steps?
Conventional: 2&3 steps
Self etch: consecutive, mixing, 1 step
What are the steps for conventional adhesive?
- Total etching orthophosphoric acid 37 (15 s)
- Wash & Dry
- Cavity cleaning for dentin (clorhexidine)
- Adhesive
Cavity cleaning with CHX?
- Optional
- Antimicrobial
- Delays the activity of metalloproteinases (dentin enzymes): cause hybrid layer degradation
How is adhesive applied in conventional technique?
- Application with a brush
- Should ensure a hermetic film is formed. 1 or 2 coats.
- Avoid material excess/ Accumulation in angles
What are the steps for 3step conventional adhesive? (6)
- 1st: Etching - Orthophosforic acid 37%
- 2nd: Primer (10s) rubbing slightly on the dentin but not enamel.
- Soft air (if alcohol, dry longer)
- 3rd: Bonding.
- Soft Air
- Polymerize (10s)
*dont polymerize between primer and bonding
Hydrophobic/hydrophillic adhesive application order?
- hydrophillic
2. hydrophobic
How many bottles are in the 3 step total etch?
2: primer + bonding
3 step conventional adhesive characteristics? (5)
- Best hybrid layer
- Higher adhesion
- More steps: > Time > % error
- Washing and drying
very critical - Union between hydrophilic and
hydrophobic resins not very strong
Possible errors that can occur in 3 step adhesive? (3)
- Cleaning: if the etch isn’t removed, adhesion wont work
- Put adhesives in the right order
- Remember no light curing between them
2-step conventional technique?
1 bottle
- Orthophosphoric acid 37%, (+wash for double time)
- Apply adhesive (10s)
Dry (20s)
Lightcure
2 step conventional technique worse behaviour? (3)
- Hydrophilic resin: more difficult infiltration.
- Worse evaporation of the solvent ( trapped debris).
- The interface is too hydrophilic : tendency to absorb water with the risk of hydrolytic degradation over time.
- water absorption & weaker bond b/w tooth and resin
2 step conventional technique advantages?
- Studies show worst values than other techniques but good enough for clinical use.
- A weak interface is not created between the hydrophilic and hydrophobic resins.
- It saves time
2 step conventional adhesive characteristics? (4)
- < time
- < failure
- No interface between the two resins
- Weaker adhesion than with 3 step
Self etch adhesive aims? (2)
- Obtain a resin with a low pH w/similar effects as
Orthophosphoric acid. - This acidic resin should dissolve the smear layer and decalcify D+E
Self etch adhesive components? (6)
Acidic resins Water: in the same bottle as the acidic resins Hydrophilic resins (HEMA, TEDGMA..) Hydrophobic resins: BIS-GMA Fillers, catalysts
same as before
Strong acidic resin adhesive properties? (2)
- pH = or <1.5
- E + D deep demineralization = than ortho-phosphoric but no waste products elimination
Intermediate acidic resin adhesive properties? (4)
- pH = 1.5 -2
- Softer dentin decalcification leaving too many crystals of HAP around the collagen fibers.
- Hybrid layer thickness 1 mm or less
- Fewer Tags
Soft acidic resin adhesive properties?
-pH >2
• It is the current trend
• It works in a very superficial dentin level , creating really thin hybrid layers.
• When resins with ph= 2.5 – 3 are used , only a very superficial collagen layer is exposedà
Nanometer hybrid layer is formed “ nanointerdifusion area “
• They have incorporated monomers (10 MDP , 4 META , phenylphosphate ) that through their
carboxyl and phosphate groups are able to create chemical unions with the HA, increasing this
way the micromechanical bond.
Self etching adhesive action in enamel
mechanical locking occurs but at much lower level than orthophosphoric acid
Self etching adhesive action in dentin (2)
Primer partially dissolves the smear layer, so its added to the adhesive
interface.
Thick smear layer is counterproductive: recommended to finish the cavity with fine grit diamond burs -
reduce smear layer thickness
Self etch adhesive demineralization?
Not as deep as orthophosphoric acid.
Slower so we must leave it for longer, 30 s.
How does self etch adhesive work?
The adhesive resin penetrates into what the acidic resin has etched
Does self etching adhesive ever etch excessively?
- Never because the adhesive etches the surface.
Infiltrates and etches the surface at the
same time on the same area.
Whats the problem with self etch adhesive?
Acidity of the resin blocks the HA as
it etches and sometimes defective hybrid layers are formed: poorly
etched or poorly infiltrated.
Self etch adhesive presentations? (2)
1 bottle & 2 bottles
*2 bottles works better
Self etch adhesive: consecutive?
- 2 bottles
1. acidic resin
2. after a few seconds , bonding
Self etch adhesive: mixed?
*2 bottles
Contents are mixed before applying them.
Self etch 1 bottle problem?
Hydrophobic resin
and water could not be in the same bottle and the water is essential…
BIS-GMA has been replaced by other high molecular weight resins water -tolerant
(HEMA…)
Which self etch adhesive works better?
2 bottles
Self etching adhesive technique - prisimless layer?
must be removed so that the acidic resin has a better
access to infiltrate the prisms improving the bonding at that level
Self etching adhesive steps - 2 bottles (5)
- 1st Leave the acidic resin 30s (1st bottle)
- blow air
- Hydrophobic
resin 10-20s (2nd bottle) - blow air
- light cure 10-20 sec
Self etching adhesive steps - 2 bottles mixed (3)
- drop of each bottle, mixed together
- apply mixture on the tooth’s surface 30s
- dried and cured 10-20s
Self etching adhesive steps - 1 bottle (3)
- Rub the sponge applicator, several layers
- air
- cure 10s
Self etching adhesives indications
- Cavity with a large exposure of deep dentin.
- With high risk of causing postoperative sensitivity.
- Cavity margins without enamel.
- Risk of contamination (no isolation).
- Situations where adhesion to dentine is more important than adhesion to
enamel. - Cervical injuries
How do we treat cervical injuries? (3)
- just root (self etch),
- root and enamel (bevel on enamel and then apply adhesive),
- just enamel (conventional adhesive)
Self etching one step adhesives, characteristics
!For a better action: They must be more acidic and more
hydrophilic than 2 step adhesives.
!As they are more hydrophilic ( + + HEMA) ,the adhesive interface
tends to absorb water from the moisture of the dentine, acting as
a semipermeable membrane.
!This creates small bubbles of water in the adhesive interface that
promote resin hydrolysis, so binding degradation may occur over
time.
!Some manufacturers are trying to replace the HEMA.
!The self-etching one-step adhesives present etching defects or
infiltration defects underneath the hybrid layer.
Self etching one step adhesives, indications
!Situations that don’t need adhesive’s full potential and require a very fast
application
!Children , special patients , uncooperative , restless
!Coating sensitive areas or worn areas
!Prevention of root caries
!Any other situations they are the worst option.
Must increase polymerization time.
Self etch adhesive area vs innfiltrated?
etched area always matches infiltrated area
Self etch adhesive sensitivity?
Less sensitivity
Self etch adhesive sealing?
Better sealing interface
Self etch adhesion forces?
weaker
Self etch smear layer?
No smear layer removed - bacterial contamination
What is the universal adhesive strategy?
Union in the minimum number of steps to different substrates - dental and non-dental
What are the included components in universal adhesives?
- polyalkenoic acid
- vinyl silane
- acidic bifunctional monomers (mainly phophate esters)
- especialy when presentedin a single bottle
What does polyalkenoic acid do? (2)
- found in universal adhesive
- forms chemical bonds to dentin by the binding of the carboxylic groups of the acid with calcium ions of the tooth structure
What does vinyl silane do? (2)
- found in universal adhesive
- Joins to ceramic
What are the indications for universal adhesive? (5)
- direct light cure restoration
- intraoral repair
- sealing of cavities prior to amalgam restorations
- sealing of cavities and stump preparations prior to temporary cementation of indirect restorations
What is the gold standard adhesive in terms of durability?
3 step ethanol-water based etch and rinse adhesive
What is the adhesive that is close to the goldstandard? (2)
2 step
additional benefits: - ease of manipulation
- reduced technique sensitivity
What are the steps for adhesive on feldspathic porcelain?
- HF acid etch (9-10%) 2 mins
- Rinse with water
- Orthophosforic acid 37% on enamel and rinse off
- ultrasonic bath: distilled water or alcohol
- Dry
- silane 60s
- Evaporate excess: air or heat
- Apply adhesive
What are the steps for adhesive on Lithium disilicate
- HF acid etch (5%) 20-30s
- Rinse with water
- Orthophosforic acid 37% on enamel and rinse off
- ultrasonic bath: distilled water or alcohol
- Dry
- silane 60s
- Evaporate excess: air or heat
- Apply adhesive
What are the steps for adhesive on Old composite/composite indirect restorations?
- Gritblasting with 50 micron aluminum oxide OR 30-50 micron silica coated particles (Cojet sand)
- Rinse with water + dry
- Orthophosforic acid 37% on enamel and rinse +dry
- Special primer (cojet) 30-60s
- Dry
- Apply adhesive resin
What are the steps for adhesive on metal?
- Gritblasting with 50 micron aluminum oxide OR 30-50 micron silica coated particles (Cojet sand)
- Rinse with water + dry
- Orthophosforic acid 37% on enamel and rinse +dry
- Special primer (alloy) 30s *not over titanium
- Dry
- Apply adhesive resin
What is in the porcelain repair kit?
- etchant gel
- porcelain bond activator
- primer and bond
- alloy primer
-opaquer
(to hide visible metal) - accessories
When do we use the porcelain repair kit?
Broken crowns - porcelain or PFM
Steps to repair fractured surfaces of porcelain (6)
- Preparation
- Facing material Preparation: use diamond point, removge later and bevel in marginal area
- Metal prep: Roughen metal surface with diamond point
- Etch:
- K-etchant gel to facing material surface 5s then wash and dry
* if adhereant surface is uncut enamel apply K etchant gel 10s then wash and dry
* dry with oil free air
* if using precious metal apply ALLOY primer according to manufacturers instructions - silane treatment
- 1 drop of clearfil SE bond primer and clearfil porcelain bond activator and mix
- apply to facing material and metal surfaces with sponge or brush tip 5s
* make sure no saliva or exudate contacts
* if adherent surfact extents to tooth then 20s
- evaporate with oil free air important to dry well for adhesion - Bonding
- Clearfil SE bond bond on entire cavity wall with sponge or brush
- use air to spread it uniformly
- light cure 10s - opaquer
- opaque resin for metal to prevent it showing
- light cure 40s - light cure composite filling
- place composite, cur4e, finish and polish according to manufacturers instructions
What do you do if your adhesive is contaminated with saliva? (2)
- clean with water and air
- new adhesive application
What do you do if your adhesive is contaminated with Blood? (3)
- critical
- Remove with bur
- etch, rinse and new adhesive application again
What do you do if your dentin is contaminated by caries detector?
- remove with bur
- rinse and dry
- begin adhesion
How do you avoid contamiantion with adhesives?
Use complete isolation
What adhesive do we use if theres a lot of enamel exposure but little dentin or no deep dentin?
- conventional total etch
- simplified (less steps) total etch
What adhesive do we use if theres lots of enamel and alot of dentin/deep?
Selective etch on enamel with self etch adhesive
What adhesive do we use if its a ceramic crown/veneer cementation?
Conventional total etch on the tooth
What adhesive do we use if its A lot of dentin without enamel borders?
self etch
