Download adhesion in dentistry

ADHESION
Is defined as the state in which two surfaces are
held together by interfacial forces which consist of
valence forces or interlocking forces or both
Is defined as attachment of one substance to another
 Adherend :
The surface or substrate to which adhesive is applied
 Adhesive:
A material that can join substances together, resist
separation and transmit loads across the bond
Adhesive
Adherend
DENTIN BONDING AGENTS:
 Are di-functional or multifunctional organic molecules
that contain a reactive group which interacts with
dentin and monomer of restorative material
MECHANISM OF ADHESION
 1. Mechanical theory:
State that the solidified adhesive interlocks
micromechanically with the roughness and irregularities
of the surface of the adherend.
2. Adsorption theory:
This includes all kinds of chemical bonds between the
adhesive and adherend including primary & secondary
bonds
 Diffusion theory:

Proposed that adhesion is a result of bonding between mobile
molecules .

Polymers from each side of the interface can cross over and
react with molecules on other side.

Eventually interface disappears and two parts merge into one.
 Electrostatic theory:
 States that an electrical double layer forms at the
interface between a metal & a polymer.
 The interfacial phenomena to occur, the two materials
being joined must be sufficiently close & have intimate
contact.
 Sufficient wetting of adhesive will occur only if it’s ST is
less than Surface free energy of adherend
ADVANTAGES OF ADHESIVE TECHNIQUE
 1) Minimal tooth preparation…………
 2) Reduces microleakage at restoration tooth
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interface…..
3) Better transmission & distribution of functional
stresses across restoration tooth interface
4) Reinforcement of weakened tooth structure
5) Repair of restoration is possible
6) Replacement of debonded restoration with little
loss of tooth structure……
Requirements of good bonding:
(Dental materials and their selection: William J O’ Brien Third edition.Sturdevant.)
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 FOR SUBSTRATE
 3. SURFACE TENSION OF LIQUID
 4. SURFACES JOINED SHOULD BE CLEAN
 Liquid with low viscosity, low surface tension, low contact
angle & substrate should have high surface energy.
Indications of adhesive dentistry:
 Restoring carious and fractured tooth structure,
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abrasion, erosion, cervical restorations
Indirect resin based restoration.
All ceramic restoration.
Prefabricated/ cast posts.
Ortho brackets.
Perio splints
Pit and fissure sealants.
Re attachment of fractured tooth.
History of dentinal bonding:
Oscar Hagger( 1951): GPA DMA.
Buonocore: (1955): Acid etching technique …….
Bowen ( 1957) : Development of BISGMA.
Nakabayashi et al( 1975) Hybrid layer
Fusayama ( 1979) Concept of total etching and
bonding.
.
Ferrari et al( 1997- 2003) Development of one bottle bonding
systems.
Sixth and Seventh generation bonding systems.
Ideal requirements of dentin bonding agents:
High bond strength to dentin
Provide bond strength to dentin similar to that of
enamel
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.
Enamel adhesion:
 Bonding to enamel is achieved mainly by micro mechanical
retention after acid etching which removes the smear layer
and dissolves hydroxy apatite crystals in the outer surface.
 The formation of resin tags with enamel surface is the
basis.
 Resin tags : 2 types
 Macrotag: formed between enamel rod peripheries.
(2-5µ)
 Microtag: fine network of tags across the end of each
rod where HA are dissolved.
 More important & contribute to bond strength….
Macrotags
 Microtags
Etching:
 Process of increasing surface reactivity by de-
mineralising the superficial calcium layer and thus
creating the enamel tags.
 Enamel etching transforms smooth enamel into
irregular enamel with a high surface free energy.
Pattern of enamel etching:
 Type I: removal of enamel prism core, prism periphery
intact
 Type II: Prism periphery removed
 Type III: Mixed pattern
Enamel etching patterns
Effect of acid etch on enamel:
 Kind of acid used
 Acid concentration
 Etching time
 Form of etchant
 Rinse time
 Way in which etching is activated– Rubbing, agitation,
repeated application
 Primary or permanent dentition
 Flouridated, demineralised or stained enamel.
Etchants:
 INORGANIC ACIDS
 Phosphoric Acid 30%-40%
 Nitric Acid
 ORGANIC ACIDS
 Maliec acid
 Citric acid
 Oxalic acid
Phosphoric acid:
 Buonocore suggested 85% PA
RECOMMENDED 30-40%
 This is because calcium dissolution & etching depth
increases as the conc of PA increases until it reaches
40%. At higher conc, a reverse effect is seen.
 Etching time:
 Not less than 15 secs
Washing time:
5-10secs
ETCHING RESULTS IN:
1. Cleanses debris from enamel
2. Produces a complex 3D microtopography at enamel
surface.
3. Increases enamel surface area for bonding
4. Produces micro-pores for resin.
5. Exposes more reactive surface layer thus increasing its
wettability
Steps of enamel etching:
 1) oral prophylaxis
 2) Clean & wash the teeth with water
 3) Isolation
 4) Apply acid etch in the form of liquid or gel for 10
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15secs
5)Wash etchant for 5-10secs
6) frosty white appearance on drying
7) Repeat procedure if contaminated
8) Apply Bonding agent
9) Formation of micro & macro tags constitute the
fundamental of enamel resin adhesion
Hybrid layer
 Defined as structure formed in dental hard tissue due
to de-mineralisation of dentinal surface followed by
infiltration of monomer & its polymerisation.
 It is the zone in which resin of adhesive system micro
mechanically interlocks with dentinal collagen.
Tubule wall hybridization
Refers to extension of hybrid layer into tubule wall.
Hermetically seals pulp dentin complex.
Lateral tubule hybridization
Refers to formation of tiny hybrid layer into the walls of lateral
tubule.
This hybrid layer typically surrounds central core of resin called
micro resin tag
.
Reverse Hybrid layer:
Seen when acid etch dentin is treated with NaOCL. Hybrid
layer is surrounded by more inorganic material unlike the
normal hybrid layer where collagen is encapsulated by resin.
Ghost hybrid layer:
Formed due to incorporation of air bubbles at the substrate
adhesive interface
These micro space are then open to micro leakage.
Resin tag
Dentinal
tubule
Hybrid
layer
Composition of dentin bonding agents
Etchants
Primers
Adhesives
Initiators and accelerators
Fillers
The various acid etchants used are:
Organic
Maliec acid
Tartaric acid
Citric acid
EDTA
Acidic monomers
Polymeric
Polyacrylic acid
Mineral acids
Hydrochloric acid
Nitric acid
Hydrofluoric acid
Primers
Also called adhesion promoters.
Monomers used is HEMA-HYDROXY ETHYLE METH
ACRYLATE
The solvents used in primers
Acetone
Ethanol
water.
Acetone – H2O
Eg: Tenure- quick
Acetone- ethanol
Eg: All bond 2 ( Bisco)
Ethanol- water
Eg: Gluma comfort bond
Scotchbond
Adhesives
Bis GMA, UDMA, TEGDMA, Methacrylated phosphates
Initiators and Accelerators
Light cured: camphoroquinone and an organic amine.
Dual cured bonding agents :catalyst to promote self curing.
Fillers:
•Most unfilled
•inorganic fillers 0. 5% to 40% by wt.
•microfillers, or nanofillers, and submicron glass.
Advantages ….
Classification of dentin bonding agents:
I Generation Bonding agents
Buonocore :GPA-DMA could bond to HCl etched
dentin
Bowen 1965 :N- Phenylglycine glycidyl methacrylate(
NPG- GMA)
.
Dentin Bonding Systems
Agents used in this generation:
NPG-GMA.
Glycerophosphoric acid dimethacrylate.( GPA-DMA).
Cyanoacrylates
Polyurethanes
Commercial product
Cervident( S.S White, Lake wood, NJ) First
commercially available bonding agent.
Cosmic bond( Amalgamated Dental Company)
Palakav( Kulzer, USA).
Dentin Bonding Systems
II generation bonding agents:
1978, the Clearfil Bond System F( Kuraray, Osaka, Japan)
Systems
Scotch bond dual cure( 3M ESPE).
Bondlite ( Kerr).
Prisma Universal Bond.
Mechanism of action:
Major Disadvantage : Interaction occurred at the smear
layer
Dentin Bonding Systems
Third Generation Dentin Adhesives
mid to late 1980s
Two approaches :
Modification of smear layer to improve its properties
Removal of smear layer partially without disturbing the plugs
that occluded the dentinal tubules
Dentin Bonding Systems
3 step process
Advantages:
Better clinical performance.
Disadvantages
.
Dentin Bonding Systems
The agents used were:
Scotch bond2 ( 3M Dental)
Gluma( Bayer/ Miles)
Tenure( Den- Mat)
Prisma Universal Bond 3( Caulk/ Dentsply),
Syntac( Ivoclar Vivadent)
XR Bond( Kerr)
Clearfil New Bond( Kuraray)
Dentin Bonding Systems
Fourth Generation Bonding agents:
Total etch concept : Fusayama in 1979
Dentin Bonding Systems
Bonding via resin tag formation in the tubules of
conditioned dentin.
Formation of precipitate on pre treated dentin
surfaces followed by chemical or mechanical bonding
of resin.
Chemical union to either
organic or inorganic
components of dentin.
Hybrid layer : Nakabayashi
3 step total etch
4 Th Generation
Etchant
+
Primer
+
Adhesive
Dentin Bonding Systems
Advantages:
Bond strength: 18 Mpa
Can bond to mineralized tissue as well as metal,
amalgam, composite and porcelain.
Disadvantages:
Multiple steps: Technique sensitive.
Unless the primer and adhesive are applied
consecutively, the overlying composite resin will not
bond to the surface.
light cure to dual cure.
Dentin Bonding Systems
Agents used in this generation
All bond 2( Bisco Dental)
Amalgam- bond( Parkell)
Clearfil Liner Bond( Kuraray)
Imperva Bond( Shofu Dental)
Optibond( Kerr)
Scotch bond multipurpose( 3M Dental)
Dentin Bonding Systems
FIFTH GENERATION
BONDING AGENTS
3 step total etch
4 Th Generation
Etchant
Etchant
+
+
Primer
Primer
+
Primer
and
adhesive
Adhesive
Adhesive
2 step
5 Th Generation
Dentin Bonding Systems
Mechanism of action :
micromechanical retention by
Penetration into partially opened tubules
Hybrid layer
Chemical interactions using first and second order
bonding
Moist bonding technique
Dentin Bonding Systems
Moist bonding technique
use acetone based primer
In case surface is dried – rewetting agents
Dentin Bonding Systems
Advantages:
Good bond strength.
Time saving and relatively simpler to use.
Some agents have incorporated fluoride and elastomeric
components to improve marginal integrity.
Disadvantages:
Post operative sensitivity
(most common in situations that magnify effects of composite
polymerization shrinkage.)
Dentin Bonding Systems
Fifth Generation adhesives
Prime and Bond
Prime and Bond 2.1
Prime and Bond NT( Dentsply Caulk, Milford,
Delaware.
Prime and Bond 2.0( Dentsply De Trey, Konstanz,
Germany)
Single Bond( 3M ESPE)
Optibond Solo
Optibond Solo plus( Kerr Corporation, Orange
California)
Pq1(Ultradent products, South Jordan)
Excite( Ivoclar Vivadent.
Bond 1(Jeneric/Pen
Dentin Bonding Systems
Dentin Bonding Sy tems
Prime and Bond NT
Is the successor of Prime bond
2.1.
Contains nanofillers of diameter
of 7 micrometers.
Stabilize the hybrid layer
Additional crosslinkage by
penetrating the channels between
collagen fibrils to provide
nanoretention
Dentin Bonding Systems
SIXTH GENERATION
BONDING AGENTS
.
Sixth Generation
Type 1
Etchant
+
Self
etching
primer
+
Primer
Adhesive
Sixth Generation
Type ii
Etchant
+
Primer
All in one
adhesive
+
Adhesive
Mechanism
Dentin Bonding Systems
2 gen- smear layer modifying
6 th gen- smear layer dissolving
Dentin Bonding Systems
Advantages of Sixth Generation Bonding agent:
Single dose packaging possible. So less chance of
cross infection.
Possibility for particle filled adhesive.
Low technique sensitivity
Dentin Bonding Systems
Disadvantages of sixth Generation Bonding Agents:
Less effective bonding of enamel.
Initial bond might deteriorate with aging, which could
lead to premature failures.
Bonding to Sclerotic and caries affected dentin might be
problematic
May inhibit set of self cure or dual cure resin materials.
Insufficient long term research.
Dentin Bonding Systems
Type I Two step/ Non rinsing conditioner/ Self etch
primer systems:
NRC Non Rinse Conditioner( Dentsply De Trey,
Konstanz, Germany) followed by Prime and Bond NT(
Dentsply)
Clearfil SE Bond
Clearfil Liner Bond IIV.
Tryian( BISCO, Inc, Schaumburg,)
Simplicity( Apex Dental Materials, Inc, Sandwich, IL)
UniFil Bond(GC America, Alsip, IL)
OneCoat Self-Etching Bond(Coltene Whaledent,
Cuyahoga Falls )
AdheSE( Ivoclar Vivadent).
Dentin Bonding Systems
Type II 6 th Generation Bonding agent :One step/
Self etching adhesives/ All in one systems
In reality, many of these are not all in- one systems at
all but require premixing of chemical components
(Prompt-L-Pop) or the use of chemically activating
pellets or brushes that come with the kit (Touch &
Bond, Brush & Bond).
Dentin Bonding Systems
6th Generation Type II.
•Prompt L Pop( 3M)
•Touch and Bond ( Parkell)
•Brush and Bond( Parkell)
•Xeno III( Dentsply Caulk)
•One up Bond F( J Morita, Kuraray)
Universal adhesive for
composites and
compomers
Disposable application
system – excellent
hygiene
Prompt L pop:
10 second curing step
It has 3 compartments
Compartment 1: Containing methacrylated phosphoric
acid, esters photoinitiators, stabilizers.
Compartment 2: Contains water, complex fluoride and
stabilizers.
Compartment 3: Has a microbrush.
Features:
Single step application
Visual confirmation of
polymerization.
Fluoride releasing
A
A and B Mixed
Polymerization completed
Dentin Bonding Systems
Seventh Generation Bonding systems:
They are truly all in one self etch adhesives that
require no mixing.
Eg:
I bond( Heraeus Kulzer).
G Bond( GC America).
GC s G bond:
4 MET monomer :strong consistent bond to dentin
Phosphoric acid ester monomer : Consistent bond to enamel.
Nanointeraction technology
Non-conventional interface with the dentin – a “Nano Interaction
Zone” (NIZ)
Forms insoluble calcium compound.
Dentin Bonding Systems
Advantages of seventh generation:
Fast and easy to use.
Disadvantages:
Marginal staining and debonding may occur in some of
the systems.May not bond durably to enamel.
May not be compatible with self cure and dual cure
composites.
Lack of polymerization.
Water trees phenomenon.
phase seperation between hydrophilic and hydrophobic
components
Dentin Bonding Systems
MOIST BONDING VS DRY BONDING
Moist dentin
Dry
dentin
Dentin Bonding Systems
Dry Bonding: use the adhesive systems with
water based primers
Moist Bonding:use the adhesive systems with
acetone based primers
Azeotrophism
How wet or how dry?
.
Dentin Bonding Systems
Clinical problems that can decrease bond strength
Problem
Solution
Dentin surface too dry
Use moist cotton pellet to
rehydrate surface
Dentin surface too wet
Gently air dry to achieve
glistening surface
Contamination with saliva and
blood
Rinse, re etch if contamination is
moderate or greater
Contamination with caries
detector, handpiece lubricant or
hemostatic agent
Rinse and reetch
Contamination by eugenol
Avoid eugenol containing
provisional materials and
temporary cements.
Remaining caries affected dentin Remove caries
Surface does not glisten after
application of primer
Apply additional coats of
primer
Self cured composite debonds
from adhesive
Use dual cure bonding agent
with self cured composite or
resin cement
Bonding agent under cured
Cure recommended time with
properly maintained light
curing unit, be sure the
bonding agent is compabtible
with light curing unit.
Recent bleaching procedure
Wait one week after bleaching.
Flourosed teeth
Double the etching time
Smooth single surface lesions
lack of bonding
Create surface roughness and
mechanical undercuts