BONDING
PRESENT
FUTURE
PAST
PRESENT
FUTURE
COMPOSITE RESIN
BONDING AGENT
TOOTH
COMPOSITE RESIN
BONDING AGENT
ETCHING
TOOTH
Adhesion
The state in which two surfaces are held together by interfacial forces which may consist of valence forces or interlocking forces or both
Adhesion is the latin word which means – ‘’To stick to’’
Adhesive is a material, frequently a viscous liquid, that joins two surfaces together and solidifies, and therefore is able to transfer a load from one surface to the other. Dentin Bonding or adhesion Micromechanical coupling or union of restorative materials to dentin, particularly composites, via an intermediary adhesive resin layer.
Allow more conservative cavity preparation since reliance on traditional retentive features is reduced.
Dentin bonding agents
Difunctional or multifunctional organic molecules that contain reactive group which interacts with dentin and the monomer of the restorative resin.
mechanisms of adhesion.
1. Mechanical : Interlocking of the adhesive with irregularities on the surface of the substrate or adherend.
2. Adsorption adhesion : Chemical bonding between the adhesive and the adherend.Forces may be primary (ionc and covalent ) ,secondary (hydrogen, diple interaction) and vanderwaal’s valence forces. 3. Diffusion adhesion : Interlocking between mobile molecules such as adhesion of two polymers.
4. Electrostatic adhesion :An electrical double layer at the interface of a metal with a polymer that is part of the total bonding mechanism.
CLINICAL USES OF DENTIN BONDING SYSTEMS:
1. Bonding of directly placed resin based restorative
materials.
2. Bonding of indirectly placed restorative materials.
3. Bonding of ceramic restorations.
4. Bonding of amalgam restorations.
5. Bonding of prefabricated and cast posts.
6. Bonding orthodontic brackets.
7. Bonding periodontal splints
8. Repair existing restorations.
9. Sealing of pits and fissures of posterior teeth.
10.Treatment of cervical sensitive dentine.
11. Reattachment of fractured tooth fragments.
12. Pulp capping.
13. Reinforce fragile roots internally.
14. Seal apical restorations placed during endodontic surgery.
IDEAL REQUIREMENTS OF DENTIN BONDING
AGENTS
1961 Phillips and Ryge:
High bond strength to dentin .
Biocompatibility to dental tissue including the pulp.
Minimize microleakage at the margins of the restorations.
Prevent recurrent caries and marginal staining.
Easy to use and minimally technique sensitive.
Good shelf life.
Be compatible with a wide range of resins.
Non toxic and non sensitizing to the operators or patients.
Bonding agents should seal the tooth surfaces from oral fluids.
HISTORY OF DENTINAL
BONDING
Oscar Hagger( 1951): GPADMA.
Buonocore: (1955): Acid etching technique
Bowen ( 1957) : Development of BISGMA.
Schmidt and Purrmann( 1958) P Cadurit.
Causton( 1965) :how primers work.
Gwinnet and Silverstone( 1975) described three
patterns of etching of enamel.
Nakabayashi et al( 1982) Hybrid layer
Fusayama ( 1987) Concept of total etching and
bonding.
John Kanca ( 1990s) Wet bonding technique
Ferrari et al( 1997- 2003) Development of one bottle
bonding systems.
Sixth and Seventh generation bonding systems.
Steps in Forming Good Adhesion
(1) Clean adherend
(2) Good wetting
(3) Intimate adaptation
(4) Bonding
(5) Good curing
Requirements of good bonding
1.Good Wetting; degree of spreading of a liquid drop on a solid surface Low contact angle : Good
wetting
High contact angle : Poor wetting
2. Surface energy
Adhesive: Low surface energy
Adherend: High surface energy
Hydroxyapatite and glass ionomer cement :High
surface energy
Collagen and composite :low energy surfaces
3. Surfaces joined should be clean
4.Good penetration
Liquid with low viscosity, low surface tension, low
contact angle
Acid etching
1955‐ Michael Buonocore
Effects of acid etching
Increases surface area and energy
Irregularities, depressions‐25 µm
Exposes proteinaceous material
ETCHING PATTERNS
Type I:
Type II:
Type III:
Dissolution of prism cores without dissolution of prism peripheries.
Dissolution of peripheral enamel without dissolution of prism cores.
Mixed pattern.
SUBSTANCES USED
PHOSPHORIC ACID
Citric acid ‐10%
Polyacrylic acid‐40%
Maleic acid
Nitric acid‐2.5%
With ferric oxalate
With aluminium oxalate
Pyruvic acid + glycine
Hydrochloric acid
Lactic acid
Monohydroxy carboxylic acid
α‐ketocarboxylic acid
Phosphoric acid as an etchant
Buonocore :acid etching with 85% phosphoric acid for 30 sec
50 % phosphoric acid for 60 seconds
Monocalcium phosphate monohydrate precipitate (prevents further
dissolution)
Concentrations below 25%
Dicalcium phosphate
removed)
monohydrate precipitate ( can not be
Concentrations above 40%
Dissolve less calcium and etch patterns with poorer definitions
37% for 15 sec is considered appropriate.
DENTIN BONDING
SMEAR LAYER
TOTAL ETCH
SELF ETCH
SMEAR LAYER
Produced by
instrumentation Composition
cut dentin debris
Bacteria
hydroxyappatite and altered denatured collagen.
Reduces dentin permeability 86%
Smear Layer
• Thickness
– 0.5 ‐ 5.0 microns • Will not wash off
• Weak bond to tooth
– 2 – 3 MPa
• Very soluble – weak acids
Van Meerbeek in: Summitt,
Fund Oper Dent 2001
TOTAL ETCH
SELF ETCH
Dynamics of Dentin Bonding
The key element for adhesion is the intimate bond that develops b/w the adhesive & the substrate.
↓ ↓ surface energy _ ↓ ↓ wetting
etching of dentin
↓
↓surface free energy
(exposure of collagen fibres)
↓
less wettability of adhesives
And the difficulty we face is,
Dentin ‐ Hydrophilic
Resin ‐ Hydrophobic
PRIMER
Primer
Increases the surface energy of the substrate
Better wettability of adhesive resin
In addition to primer the other important component is the SOLVENT that helps to carry the primer to the dentin
this solvent can be
‐acetone ‐alcohol (ethanol)
‐water
Primer • Hydrophilic monomers
– dissolved in acetone, alcohol, or water
• Displaces water • Promotes infiltration into collagen
• Lightly air dry
– drive off solvents, water
• Transforms hydrophilic to hydrophobic
Van Meerbeek in: Summitt,
Fund Oper Dent 2001
Primer • Bifunctional monomer
– Link
• hydrophilic collagen
• hydrophobic resin
– Example
• HEMA
CH3
H2C=C-C-O-CH2-CH2-OH
O
Adhesive Resin
• Unfilled or lightly‐filled monomers
– Bis‐GMA, UDMA, TEGDMA
• Stabilize the hybrid layer
– fills up remaining pores
• Resin tags • Links primer to composite resin
Van Meerbeek in: Summitt,
Fund Oper Dent 2001
Dentin Bonding
• Development
– seven generations
– chronologic
• Classification First Generation
(1950‐1970’s)
• Hydrophobic monomers • Very low bond strengths
– 2 to 3 MPa
• First commercial dentinal adhesive
•
Cervident ‐ SS White (1965)
–
–
claimed chemical bond to calcium
retention only 50% at 6 months
•
Class 5
Harris, J Prosthet Dent 1974
Second Generation (late 70’s to mid 80’s)
´Phosphorous‐ester monomers «
«
«
enhanced surface wetting
claimed chemical bond to calcium
smear layer predominately intact ²
fear of etching dentin
´Low bond strengths
«5 to 6 MPa
´Retention 70% at 1 year
«Class 5
Van Meerbeek in: Summitt,
Fund Oper Dent 2001
Third Generation
(mid‐80’s)
• Mechanism of action
– mildly acidic hydrophilic monomer
– modified/altered smear layer
• Moderate bond strengths
• Improved short / long term success
Van Meerbeek in: Summitt,
Fund Oper Dent 2001
Fourth Generation
(early 1990’s)
• Multi‐step – condition dentin
• remove smear layer
– primer
– adhesive
• High bond strengths
– Retention 98 to 100 % at 3 yrs
• Class 5
Van Meerbeek in: Summitt,
Fund Oper Dent 2001
Fifth Generation
(late 1990’s)
• Attempt to simplify
– reduce number of bottles
• combined primer and adhesive • High bond strengths
Van Meerbeek in: Summitt,
Fund Oper Dent 2001
Sixth Generation
(late 1990’s)
• Combined conditioner and primer
– moderate bond strengths Seventh Generation
(most recent)
• “All‐in‐one” adhesives
– combined conditioner, primer and adhesive
– one‐step • No mixing
• Low bond strengths
Van Meerbeek, Oper Dent 2003
Click here for abstract
Currently Available Generations
• Fourth Generation
– Three‐step Etch & rinse
• Fifth Generation
– Two‐step Etch & rinse
• Sixth Generation
– Two‐step Self‐etch
• Seventh Generation
– One‐step Self‐etch
• no mix Adhesive Categories
• Etch & Rinse
– Three‐Step
• conditioner, primer, adhesive
– Two‐Step
• conditioner, (primer & adhesive)
• Self‐Etch
– Two‐Step
• (conditioner & primer), adhesive
– One‐Step
• (conditioner & primer & adhesive)
Pros/Cons of Etch & Rinse
•
•
•
•
Separate acid etch
Potential to over‐etch dentin
Post‐conditioning rinse necessary
Multiple long‐term clinical studies available
Pros/Cons of Self‐Etch
•
•
•
•
Good dentin conditioning
Possible reduction in post‐op sensitivity??
No post‐conditioning rinse
Reduced application time
Pros/Cons of Self‐Etch
•
•
•
•
Limited clinical indications
Limited clinical data Relatively lower bond strengths
Many require refrigeration
Dentin Wetness
Etch & Rinse
• After conditioning dentin
– dentin must be wet
• prevent collagen collapse
• Too little water
– collagen collapse
• Ineffective resin penetration
• Leads to nanoleakage
Wet Bonding
• Acetone and ethanol based primers
– displace remaining water
– carry monomers into collagen
– gently air‐dried
• leaving monomers behind
• Examples
– One‐Step
– Prime & Bond NT
Dry Bonding
´Water‐based primers
«effective on wet or dry dentin
²self‐rewetting effect ²re‐expand collapsed collagen
´Permits check of “frosted”
enamel
´Examples
«Scotchbond Multi‐Purpose
«Optibond
Van Meerbeek in: Summitt,
Fund Oper Dent 2001