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PRESENTED BY-HARMEET
BONDING AGENTS
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CONTENTS
Introduction Concepts of adhesion Adhesion and its ten commandments Orthodontic bonding agents CompositesNewer systems Fluoride-releasing compositeMoisture-resistant adhesiveMoisture-active adhesives
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Dentin bonding agents CementsGlass ionomer cementResin-ionomer hybridsZinc phosphate cementZinc polycarboxylate cements Bond failure Conclusions References
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INTRODUCTION
Adhesive bonding is important for orthodontics, especially in terms of the fixation of bands and brackets to teeth.
Dental cements and resins are used intraorally to secure fixed orthodontic devices.
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Many new bonding agents have been developed such as composite resins, conventional glass ionomer cements, resin-modified glass-ionomer cements and polyacid modified composites (compomers) with different polymerization mechanism such as chemically, light or dual curing
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BASIC CONCEPTS OF ADHESION
The word adhesion is derived from the Latin word adhaerere, which means ad – to, and haerere – to stick.
Adhesion refers to the attraction between the atoms and molecules at the contacting surfaces of different materials - De Bruyne and Howwink, 1951
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Bonding of the resins to tooth structure is the result of four possible mechanisms
Mechanical adhesion-interlocking of the adhesive with irregularities in the surface of the substrate, or adherend.
Adsorption adhesion-chemical bonding between the adhesive and the adherend. The forces involved may be primary (ionic and covalent) or secondary hydrogen bonds, dipole interaction , van der Waals or valence forces.
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Diffusion adhesion-interlocking between mobile molecules, such as the adhesion of two polymers through diffusion of polymer chain ends across an interface.
Electrostatic adhesion-an electrical double layer at the interface of a metal with a polymer that is part of the total bonding mechanism
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Adhesion and its Ten Commandments
THE ADHESIVE1. Shall resist ambient environment, at the same
time protecting the interfaces2. Shall be fluid enough3. Shall set hard and tough4. Shall tolerate/dissolve tiny amounts of impurities5. Shall not cure slowly, unduly shrink or allow
discontinuities
Claude G. Matasa .AJO-DO Volume 1989 Apr (355 - 356): Adhesion and its Ten Commandments
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THE SUBSTRATES/INTERFACES6. Shall be clean7. Shall be firm8. Shall allow air to escape THE SYSTEM9. The adhesive has to "love" both
substrates10. Shall have a thin "glue-line"
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ORTHODONTIC BONDING AGENTS
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COMPOSITES A composite, consist of a
mixture of two or more components, a combination of hard, (inorganic) filler particles bonded to soft (organic) dimethacrylate polymer
Two basic types of dental resins
Acrylic Resins Diacrylate Resins
greater strength, lower water absorption and less polymerization shrinkage
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COMPOSITION
THE RESIN MATRIX Most composite consist of
monomers of molecular weight of 100-1000g/ mole
Viscous aromatic dimethacrylate monomer (Bis-GMA)
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Large molecular size, lower volatility, lower polymerization shrinkage, more rapid hardening and production of a stronger and stiffer resin.
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Bis-GMA is thinned with a variety of other monomers
Diethylene glycol dimethacrylate (DEGMA) and tri- ethylene glycol dimethacrylate (TEGDMA)
A typical formulation would be 75% Bis-GMA and 25% TEGDMA.
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Alternative monomer systems in which all or part of the Bis-GMA is replaced by aliphatic or aromatic urethane dimethacrylates (UDMA)
They have lower viscosities, hence requiring reduced proportions of TEGDMA and have more effective light curing, lower water sorption and greater toughness.
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FILLER Advantages Polymerization shrinkage The coefficient of thermal expansion Water absorption is reduced Abrasion resistance is enhanced The mechanical properties such as
tensile strength, compressive strength, modulus of elasticity and hardness
Fillers also enhance the rigidity
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QUARTZ Advantage chemically stable and
strong but its disadvantage is its hardness
GLASSES- barium or lithium aluminium silicate glasses, borosilicate glass or barium, strontium, zinc glasses.
They have proper strength, hardness, chemical and optical properties
COLLOIDAL SILICA
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COUPLING AGENT
A bond between filler particle and matrix in the set composite is achieved by use of a silane-coupling agent (methacryloxypropyl trimethoxy silane).
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FUNCTIONS OF COUPLING AGENT Increase the physical and mechanical
properties of the material. Increase the content of the filler
particles, so that it resists abrasion. A bond between filler and matrix
allows the distribution of stresses generated under function.
It prevents water from penetrating the interface between resin and filler.
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MECHANISM OF ACTION OF
COUPLING AGENT
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INITIATORS AND ACCELERATORS Light cured composite –
Camphorquinone Chemical cured composites are
activated by organic amines (accelerator) reacting with peroxide (initiator)
INHIBITOR Hydroquinone - 0.1%.
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PIGMENTS Numerous shades are supplied from
white to yellow gray.
ULTRAVIOLET ABSORBER
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CLASSIFICATION OF THE COMPOSITES
1. Based on the filler
2. Based on the method of
polymerization
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MACROFILLED (TRADITIONAL) COMPOSITES
Developed in 1960s. Quartz/ glass filler particles with the
particle size of 10-50µm and filler content is 60 -80 % by weight.
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MICROFILLED RESINS Introduced in the late 1970's Submicron particles (colloidal silica)
having particle size between 0.03 and 0.5µm with an average particle size of 0.04µm.
Filler loading in these composites is therefore limited to about 20 to 50 percent by volume or 35 to 60 percent by weight.
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SMALL PARTICLES COMPOSITES Developed in 1980s. Filler content is 80-85 percent by
weight and 60 to 77 percent of the composite by volume.
Average particle size is 1-5µm, the range is between 0.5 and 10µm.
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HYBRID OR BLEND COMPOSITES Developed in late 1980s. They are called as hybrids or blended
composites because they contain a blend of both conventional glass and quartz particles together with some submicron, particulate silica.
Filler loadings - 75 percent conventional size (1-50µm) and 8 percent submicron size (0.04 average µm)
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Failure rates for steel mesh-backed brackets direct-bonded with highly filled diacrylate resins may be as low as 1% to 4%.
Buzzitta et al found that a highly filled diacrylate resin with large filler particles gave the highest values of in vitro body strength for metal brackets
(Buzitta VAJ, Hallgren SE, Powers IM: Bond strength of orthodontic direct-bonding cement-bracket systems
as studied in vitro, Am J Orthod 81:87, 1982).
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POLYMERIZATION ACTIVATION CHEMICALLY ACTIVATED (ALSO TERMED
CHEMICALLY CURED, AUTOCURED OR SELF-CURED):TWO-PASTE OR ONE-PASTE
LIGHT-CURED (ALSO TERMED PHOTOCURED)
DUAL-CURED (CHEMICALLY ACTIVATED AND LIGHT- CURED)
THERMOCURED
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SELF CURE TWO -PHASE (TWO-PASTE) ADHESIVE
SYSTEMS 1—2% BP (benzoyl peroxide) in the
monomer portion as a free radical initiator.
The activator - tertiary amine, most commonly dihydroxyethyl-p-toluidine (DHEPTI) which leads to better color stability than the traditional dimethyl-p-toluidine (DMPTl).
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DISADVANTAGES The manipulative process is
problematic, relatively time— consuming and cumbersome
Mixing of the two components introduces potentially critical defects such as surface porosity and air voids in the bulk material
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ONE-PHASE ADHESIVE SYSTEMS No-mix adhesives
These materials (e.g., Rely-a-Bond, System 1+) set when one paste under light pressure is brought together with a primer fluid on the etched enamel
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ADVANTAGES Efficient application Limited time requirement DISADVANTAGES Little long-term information is
available on their bond strengths In vitro tests have shown that liquid
activators of the no-mix systems are definitely toxic and allergic reactions have been reported in patients.
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LIGHT-CURE (VLC)
1,2-diketone such as camphoroquinone and an amine reducing agent such as N,N-dimethyl-amino-ethyl methacrylate (DMAEMA)
The concentration of CQ photosensitizer is in the range 0.17—1.03 mass% of the resin phase and that of DMAEMA reducing agent is 0.86—1.39 mass%.
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Transbond XT composite (3M Unitek, Monrovia, USA).
This is composed of 14% BIS-GMA, 9% BIS-EMA, and 77% load particles.
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In a study by Eliades et al the DC value for a light-cured adhesive bonded to a metallic bracket and irradiated from the incisal and cervical edges was comparable to DC values for a chemically cured adhesive and its light- cured counterpart bonded to transparent ceramic brackets
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ADVANTAGES
Bond strength for light-cured materials is comparable in vitro to those of chemically cured composites
Quick set Advantageous when extra long
working time is desirable
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In 1984 Andreasen et al found that shear bond strength of light-cured resin and 40-second light exposure had the same bond strength as self-cured resin .However light-cured resin with a 20-second light exposure was found to be weaker than Concise.
In 1987 King et al reported that tensile or shear bond strength of self-cured resin (Concise and Right-On) was stronger than the tensile or shear bond strength of lightcured resin (Heliosit, Heliosit-Ortho, and Silix) with light exposure for 60, 40, or 20 seconds
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In 1989 Greenlaw et al disclosed that shear bond strength of light cured resin (Heliomat) was only one half of that of the chemically cured resin (Unite)
(Wang and Meng .Bond strength between light- and self-cured resin. AJO-DO on Volume 1992 )
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DUAL-CURED SYSTEMS
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J. Clifton Alexander & Anthony D. Viazis compared the bond Strengths and Fracture Modes of Three Orthodontic Adhesives - a light-cured composite, a chemically cured composite, and a new dual-cure system— along with their fracture modes. The results showed that there was no significant difference between the metal brackets bonded with - a light-cured composite and the metal brackets bonded with dual-cure system, or between the metal and ceramic brackets bonded with dual-cure system
(J. Clifton Alexander & Anthony D. Viazis: Bond Strengths and Fracture Modes of Three Orthodontic Adhesives .JCO Volume 1993 Apr 207 - 209)
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THERMOCURED SYSTEMS
Introduced for indirect orthodontic bonding and restorations.
These adhesives present substantially increased polymerization rates
Their use is currently limited because of the increased temperature required to initiate polymerization and the necessity for adapting an indirect bonding setup.
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NEWER SYSTEMS
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FLUORIDE-RELEASING COMPOSITE The fluoride within this material is
not bound, but rather encapsulated within the composite, which allows the fluoride to be released by a diffusion/dissolution mechanism over a prolonged period to the adjacent enamel.
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ADVANTAGES
1. It is available as a light-activated composite.
2. Material's unique properly of fluorescing under ultraviolet light
(Sonis and Snell: Fluoride-releasing, visible light-activated bonding system.AJO-DO Volume 1989 Apr 306 – 311
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MOISTURE-RESISTANT ADHESIVE
Conventional acid-etching and priming adhesive system require dry conditions and in isolated fields because of their hydrophobic properties
It is available in a primer formulation that replaces the conventional bonding agents
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The main reactive component of this product is a methacrylate-functionalized polyalkenoic acid copolymer
Excess interfacial water ionizes carboxylic groups, forming hydrogen- bonded dimers.
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Shear bond strength was compared among three materials: conventional primer, moisture-insensitive primer and self-etch primer Bond strength was tested under laboratory conditions with brackets bonded on both dry enamel and enamel contaminated with natural saliva. Self-etch primer showed maximum bond strength under both dry and wet conditions. Conventional primer was comparable with the former under dry conditions but did not offer clinically adequate bond strength in cases of moisture contamination. Both MIP and self-etch primer showed adequate bond strength superior to that of conventional primer in case of moisture contamination.
Rangaswamy Rajagopal .A Comparison of Shear Bond Strength and Debonding Characteristics of Conventional, Moisture-Insensitive, and Self-etching Primers In Vitro. Angle Orthodontist, Vol 74, No 2, 2004
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MOISTURE-ACTIVE ADHESIVES Moisture-active
adhesives require rather than tolerate the presence of moisture for proper polymerization
The surface must be intentionally wetted prior to application
Requiring no bonding agent
Based on a cyanoacrylate
formulation (Smartbond)
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SETTING REACTION Involves two steps. In the first step isocyanate groups
react with water, forming an unstable carbamic acid component, which rapidly decomposes to carbon dioxide and the corresponding amine.
In the second step the amine reacts with residual isocyanate groups, cross- linking the adhesive through substituted urea groups.
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ADVANTAGES Useful in conditions where moisture
control is difficult DISADVANTAGES In the presence of excess water the first
step of the reaction, namely the formation of amine and carbon dioxide, is enhanced, resulting in reduced film-fracture toughness because of the formation of deleteriously brittle polymer films.
CO2 released has only limited diffusion through the adhesive films
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DENTIN BONDING AGENTS
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Dentine bonding agent is essentially an unfilled or lightly filled resin, similar in composition to the resin in composites except that hydrophilic molecules have been added
Make the surface of the substrate more amenable to accepting a bond
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FIRST GENERATION DENTIN BONDING AGENTS
The Ist generation adhesives were developed in the late 1950s
The first commercial system of this type (Cervident- SS White) added a surface-active comonomer N- phenylglycine glycidyl methacrylate
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DRAWBACKS
It was common to see debonding at the dentinal interface within several months due to poor bonding strength.
( bond strengh was only 2-3MPa) Postoperative sensitivity
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SECOND GENERATION DENTIN BONDING AGENTS
In the early 1970s, a distinct 2nd generation of adhesives was developed
Primarily use polymerizable phosphates added to BIS-GMA resins.
Products attempted to use the smear layer as a bonding substrate
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Clearfil Bond System F was introduced in Japan was generally recognized as the first product of the second generation of dentin adhesives.
It was a phosphate-ester material (phenyl-P and HEMA in ethanol
DRAWBACKS These second-generation dentin
bonding systems typically had in vitro bond strengths of only 1 to 5 MPa
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THIRD GENERATION DENTIN BONDING AGENTS
In the late 1980s, two component primer-adhesive systems were introduced.
Bonding strength to dentin increased significantly to 8-18 MPa
Kuraray introduced Clearfil New Bond in 1984.
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System utilized a conditioning step either to modify or remove smear layer
This system uses a dentin conditioner of 2.5 percent nitric acid in combination of ferric oxalate or aluminium oxalate.
Step was followed by sequential treatments of NTG-GMA and PMDM also referred to as F-N-P system
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This multistep procedure can be described as. Etch+ Prime + Bond APPLICATION OF DENTINE CONDITIONER APPLICATION OF THE PRIMER APPLICATION OF ADHESIVE PLACEMENT OF RESIN BASED COMPOSITE
Examples Mirage bond, Scotch bond 2 Prisma Universal bond 2 and 3 Scotch bond Multipurpose (3M)
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FOURTH GENERATION DENTIN BONDING AGENTS
It was developed by Fusayama and Nakabayashi in Japan in the 1980s
Also known as etch and rinse technique
Total-etch, multiple-bottle
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THREE ESSENTIAL COMPONENTS
Phosphoric acid etching gel – 35%phosphoric gel
Primer containing reactive hydrophilic monomers,2% NPG-GMA and 16%BPDM in ethanol , acetone or water.
An unfilled or filled resin (hydrophobic monomers : Bis GMA combined with hydrophilic monomer :HEMA
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EXAMPLES All bond-2 (BISCO), Prime and bond Comfort bond (Heraeus Kulzer)
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FIFTH GENERATION DENTIN BONDING AGENTS
Total-etch, single-bottle Hydrophilic and hydrophobic resins
simultaneously dissolved in solvents like alcohol or acetone,displacing water and achieving an intimate contact to dentinal structures.
It contains PENTA, TEGMA and the elastomeric resin UDMA in acetone.
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ADVANTAGES These materials adhere well to
enamel, dentin, ceramics, and metal. Bond strengths to dentin are in the
range of 20-25 Mpa. These bonding agents, easy to use
and predictable. Postoperative sensitivity has been
reduced appreciably.
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EXAMPLES One step (BiSCO) Single bond (3M) Clearfil SE bond
(Kuraray medical Inc.) Opti bond solo (KERR) Xeno III(Denstply) .
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SIXTH GENERATION DENTIN BONDING AGENTS
The self-etching primers (SEPs), was introduced in Japan.
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This system can be described as• EPB (methacrylated phosphates)
They are of 2 types : SELF ETCHING PRIMER AND
ADHESIVE (Type I) SELF ETCHING ADHESIVES (Type II)
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SELF ETCHING PRIMER AND ADHESIVE
Two bottles Liquid 1 acidic primer and Liquid 2
adhesive . Acidic primer applied to tooth
surface followed by the adhesive Solvent is water.
SELF ETCHING ADHESIVES Two bottles, containing acid primer
and adhesive .A drop of each liquid is mixed and applied to the tooth surface
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UDMA /HEMA –wetting agent 4 META – binding to calcium or
collagen GLUTARALDEHYDE – disinfectant ACETONE – removing humidity WATER – helps in etching process
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ADVANTAGES SIMPLIFIED TECHNIQUE LESS TECHNIQUE SENSITIVE LESS LIKELY TO CAUSE DISCREPANCY
BETWEEN THE DEPTH OF DEMINERALIZATION AND DEPTH OF RESIN INFILTERATION
LESS POST OPERATIVE SENSTIVITY
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Self-etch adhesives can divided into 3 categories according to their acidity:
Strong Self-etch adhesives Mild self-etch adhesives Intermediary Strong Self-Etch
Adhesives
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System comes with etchant, primer, adhesive and microbrush sealed in a triple lollipop-shaped aluminium foil package (blister pack).
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SEVENTH GENERATION DENTIN BONDING AGENTS
These are recently introduced group of adhesives which has simplified the 6th generation 2 bottle self etch adhesives into one bottle, single step, self-etching adhesives
Etchant + primer +Adhesives combined
The first adhesive to be introduced under this category is L- bond
Major drawaback was low bond strength values i.e < 15 Mpa
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BOND STRENGTH OF DIFFERENT DENTINE BONDING AGENTS
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Several in vivo studies have been published concerning the bond failure rates with CM and SEP
Finding indicated that SEP can be effectively used for bonding of orthodontic brackets. Furthermore, the mean bracket bonding time with SEP per tooth was significantly shorter than with the CM
Selma Elekdag-Turk , Devrim Isci , Tamer Turk and Fethiye Cakmak Six-month bracket failure rate evaluation of a self-etching primer. European Journal of Orthodontics 30 (2008) 211–216
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Self-etching primer has significantly less bond strength when compared conventional etching & priming 2 step procedure.
(Vicente A, Bravo LA, Romero M. Self-etching primer and a non-rinse conditioner versus phosphoric acid: alternative methods for bonding
brackets. Eur J Orthod. 2006 Apr;28(2):173-8)
Bergeron and colleagues concluded that the resin-enamel bond strength of seven different self-etching primers, including Prompt L-Pop, was similar to or better than that of multiple-step systems.
Bergeron, C.; Vargas, M.A.; Gelinas, P.; and Van Meerbeek, B.: Bond strength of self-etching adhesives to enamel (abstr.), J. Dent. Res. 79:442, 2000
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Study evaluated the use of a new self etch primer as compared with the conventional bonding procedure. The findings indicated that the use of a self-etch primer to bond orthodontic brackets to the enamel surface provided lower, but clinically acceptable, shear bond forces (mean, 7.1 ± 4.4 MPa).
Samir E. Bishara. Effect of a self-etch primer/adhesive on the shear bond strength of orthodontic brackets. Am J Orthod Dentofacial Orthop 2001;119:621-4)
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RECENT MODIFICATION IN DENTIN BONDING
AGENTS
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FLUORIDE RELEASING BONDING AGENTS
Fluoride in incorporated as silanized NaF porticles or pre-reacted glass particle fillers.
It has been shown that fluoride incorporated into adhesive resins increased the dentin bond strength and it did not decrease after long term water immersion.
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NANO-FILLED ADHESIVES
These nanofillers are generally amorphous silicon dioxide which are 100 times smaller than the fillers in hybrid composites which results in optimal optical properties. Fillers with size ranging from approximately 5 – 100 nm have been developed
( Moszner and Klapdohr, 2004 ).
ADVANTAGES Increased adhesive strength to both enamel and dentin Increased marginal intergrity Sufficient film thickness for one cost, one cure
technique. Deeper penetration into dentinal tubules
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ANTIBACTERIAL SELF-ETCHING PRIMER
12-Methacryloyloxydodecylpyridinium bromide (MDPB) is an antibacterial agent incorporated into a self-etching adhesive system to inhibit bacterial attachment and plaque accumulation on the tooth surface
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Composition MDP, MDPB, HEMA, hydrophilic
dimethacrylate, water Example Clearfil PROTECT Bond
(Yuichi Kitasako & Hidenobu Senpuku. Growth-Inhibitory Effect of Antibacterial Self-Etching Primer on Mutans Streptococci Obtained from Arrested Carious Lesions. J Esthet Restor Dent 16:176–184, 2004)
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BONDING TO AMALGAM
Micromechanical retention
Metal-bonding adhesives
Intermediate resins
Björn U. Zachrisson, Tamer Büyükyilmaz, Yngvil Ørstavik Zachrisson Angle Orthodontist 1995 No. 1, 35 - 42: Improving orthodontic bonding to silver amalgam
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METAL-BONDING ADHESIVES Superbond C&B (4-META resin) Amalgambond ( Orthomite Super-
Bond D liner)
Panavia Ex (10-MDP & Bis-GMA resin)
Clearfil Porcelain Bond. BOND STRENGTH -30Mpa – sand
blasted metal surfaces or tin plated noble metals
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INTERMEDIATE RESINS All-Bond 2 Primers A+B
Scotch-Bond Multi-Purpose (SBMP) system.
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1.The mean tensile bond strengths to sandblasted amalgam ranged from 3.4 to 6.4 MPa, which was significantly lower than the bond strength of Concise to etched enamel.
2The strongest bonds to sandblasted amalgam were obtained with Superbond C&B. This bond strength was significantly higher than that of Panavia Ex and Concise
3 The bond strength of Concise to amalgam was significantly improved with the intermediate application of All-Bond 2 Primers A + B.
4.The All-Bond 2 primers significantly improved the Concise bonds to amalgam compared to the Scotchbond Multi-Purpose system.
5.Sandblasting the amalgam surface prior to bonding produced higher mean bond strengths with Concise than roughening with a diamond bur, but the difference was not statistically significant
. Björn U. Zachrisson, Tamer Büyükyilmaz, Yngvil Ørstavik Zachrisson Angle Orthodontist 1995 No. 1, 35 - 42: Improving orthodontic bonding to silver amalgam
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Bonding to Gold
In contrast to bonding to porcelain and amalgam, excellent bonding to gold crowns does not yet seem to be available to orthodontic clinicians
Different new technologies, including sandblasting, electrolytic tin-plating or plating with gallium-tin solution (Adlloy), the use of several different types of intermediate primer, and new adhesives that bond chemically to precious metals and all have been reported to improve bonding to gold in laboratory setting
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SANDBLASTING
Bjorn U. Zachrisson, Tamer Buyukyilmaz. JCO Recent Advances in Bonding to Gold, Amalgam, and Porcelain Volume 1993 Dec(661 - 675)
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TIN PLATING
New low-voltage tin platers also facilitate intraoral bonding to noble metals.
The deposition of a layer of tin on the gold surface permits a chemical and mechanical bond between resin and metal
Most commonly, the tin is electrolytically deposited with a unit such as the MicroTin or Kura Ace Mini
An alternative method is to rub on a solution of gallium and tin (Adlloy) with a pure tin bar
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BONDING TO PORCELAIN
Porcelain etchant is 9.6% HF acid in gel form, applied for two to four minutes
A silane bonding agent such as Ormco Porcelain Primer Scotchprime or Clearfil Porcelain Bond is then painted onto the porcelain surface and allowed to dry. This coupling agent alters the surface so that chemical and mechanical bonding are possible.
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CEMENTS
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GLASS IONOMER CEMENT
It was introduced in 1972 by Wilson & Kent
Hybrid of silicate & polycarbonate cement
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COMPOSITION
POWDER Silica (si02)-42% Alumina (AIP3)-28.6 % Aluminium fluoride (AIF3)-
1.6 % Calcium fluoride (CaF3)-15.7
% Sodium fluoride (NaF)-9.3 % Aluminium phosphate
(AIP04)-3.8 %
LIQUID Polyacrylic
acid Tartaric acid Water
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MANUFACTURING
Ground to yield a frit (particles of glass).
Cooled in water
Quartz, alumina, calcium fluoride, cryolite), aluminum fluoride and aluminum phosphate are
fused between 1100°C and 1300 °C
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CHEMISTRY OF SETTING The setting reaction of conventional
glass ionomer cement is acid (liquid)-base (powder) reaction leading to the formation of polycarboxylate salts that comprise the cement matrix.
The reaction occurs in three distinct stages:
DissolutionGelationFinal maturation stage
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MANIPULATION
PREPARATION OF THE TOOTH SURFACE
PROPORTIONING (Powder Liquid Ratio)
PLACEMENT AND PROTECTION OF THE MATERIAL
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PROPERTIES Surface hardness is about 48 KHN. Film Thickness Ideally it should be in
the range of 25-35 µm in thickness. The compressive strength increases
over 24 hours to 90 to 140 Mpa The modulus of elasticity is about 7
GPa
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Adhesion Glass-ionomer cements exhibit bonding to enamel & dentin
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Bonding Technique1. Isolate the teeth using cotton
rolls only.2 Pumicing and drying .3. Mix the cement somewhat
thicker than the manufacturer's recommendation. The mixture should have a creamy consistency, but if the surface sheen disappears, the cement is too thick.
4. After positioning the bracket, press it firmly against the tooth
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5. Remove excess cement with a small spoon excavator during the gel phase.
6. Depending on the mixing ratios and the temperature of the refrigerated mixing slab, an archwire can usually be tied in within four minutes of positioning the bracket.
7. Debonding is much easier than with composite resins.
DR. PAUL ANDREW .Direct Bonding with Glass lonomer Cement .JCO Volume 1990 Aug(509 - 511):
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LIGHT CURED GIC HEMA is added to the liquid (1) The mean shear bond strength of the light-cured
glass ionomer is greater than that of the chemically cured glass ionomer at 1 and 24 hours.
(2) The mean shear bond strength of both glass ionomers increases from 1 to 24 hours.
(3) The mean shear bond strength of the lightcured glass ionomer is not significantly different from 1 to 24 hours, but the shear bond strength of the chemically cured glass ionomer cement is different
Compton, Meyers, Hondrum, and Lorton Comparison of shear bond strength of glass ionomer cements - of a light-cured glass ionomer and a chemically cured glass ionomer for use as an orthodontic bonding agent. AJO-DO Volume 1992 Feb
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GLASS IONOMER CEMENTS CONTAINING
CHLORHEXIDINE AND CETRIMIDE
GICs containing chlorhexidine diacetate and cetrimide were effective in inhibiting bacteria associated with caries, and incorporation of 1% cetrimide was optimal to give the appropriate antibacterial and physical properties
Mohanavelu Deepalakshmi Evaluation of the antibacterial and physical properties of glass ionomer cements containing chlorhexidine and cetrimide: An in-vitro study. Indian J Dent Res, 21(4), 2010 552
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(Glass Ionomer Cements Used in Bonding Materials for Metal Orthodontic Brackets An in vitro Study", Oen, J. O. et al., European Journal of Orthodontics, 13, 187-191 (1991).
(Tensile Bond Force of Glass Ionomer Cements in Direct Bonding of Orthodontic Brackets: An in vitro Comparative Study", F. Rezk-Lega and B. Ogaard, American Journal of Orthod. Dentofac. Orthop., 100, 357-361 (October 1991)
The bond strength of glass ionomer cements was tested in vitro and compared to composite resins .
Bond strength for each of the composite resins was in excess of the bond strength for any of the tested glass ionomer cements.
Glass ionomer cements are advantageous in their ability to release fluoride over prolonged periods of time
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Traditional GICs have several disadvantages like:Short working timeLong setting time (not command set)Cracking on desiccationPoor resistance to acid attackLow fracture toughnessLow abrasion resistanceInitial sensitivity to moistureHigher bond failure rate (20%)
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RESIN MODIFIED GLASS IONOMERS CEMENT
It was introduced by Antonucci in 1988
10%-20% of a photocurable
monomer Set by an acid-base reaction and by
free-radical addition polymerization
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COMPOSITION
POWDER Ion leachable
glasses Photo initiators Polymerizable
resin
LIQUIDPolyacrylic acid WaterMethacrylate
monomer HEMA
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Study by Bishara et al 1998
Resin-modified glass ionomer may result in unacceptable bond failure rates.
The bond strength of the resin-modified
glass ionomer can be increased using an enamel acid etch technique, although it was still significantly lower than Transbond.
Bond strengths achieved with resin-modified glass ionomer. when combined with etching may be adequate in low loading clinical situations, but this would
have to be confirmed in a controlled clinical trial.
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POLYACID-MODIFIED COMPOSITE RESIN OR
COMPOMER Compomers are single-component
systems consisting of aluminosilicate
glass in the presence of carboxyl-modified resin monomers and light-activated conventional resin monomers.
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COMPOSITION
Powder contains aluminium fluorosilicate glass, sodium fluoride and chemical and light cured initiators.
The volume percent filler ranges from 42% to 67% and the average filler particle size ranges from 0.8 to 5.0 µm
Liquid contains polymerizable methacrylate/ carboxylic acid monomer and diacrylate monomer
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SETTING MECHANISM
Primarily by light, but acid-base reaction also occurs
MANIPULATION Single-paste packaged in unit-dose
ampules.
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ADVANTAGES They have excellent esthetics. Low solubility High bond strength High fracture toughnessDRAWBACKS They require bonding agents to bond
with the tooth structure. They have generally been shown to
have less fluoride release than glass ionomers.
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Mitchell et al compared the shear bond strength of 3 glass-ionomer cements to a composite adhesive when the brackets were debonded after 10 minutes and after 24 hours stored at 37°C and 100% humidity. They found that the composite adhesive was significantly stronger at both time periods. They also found that the resin-modified glass-ionomer cement was significantly stronger than the conventional glass-ionomer cement.
Mitchell CA, O’Hagan E, Walker JM. Probability of failure of orthodontic brackets bonded with different cementing agents. Dent Mater 1995;11:317-22..
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Fruits et al compared the shear strengths of 4 fluoride- releasing glass-ionomer and composite adhesives bonded to dentin. They also found that the resin-composite material has significantly greater (from 2 to 5 times) shear bond strength after 24 hours storage than any of the 3 glass-ionomer materials tested
Fruits TJ, Duncanson MG Jr, Miller RC. Bond strengths of fluoride releasing restorative materials. Am J Dent 1996;9:219-22.
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ZINC PHOSPHATE CEMENT
Zinc phosphate cement is one of the oldest luting cements used in dentistry
POWDERZinc oxide - 90 percentMagnesium oxide - 10 percentSilica or alumina - Small amounts
LIQUID Phosphoric acid - 45-60 percentWater - 30-55 percentAluminium - 2-3 percentZinc - 0-8 percent
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MANIPULATION
Mixing time is 60 to 90 seconds.
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PROPERTIES
Compressioe strength-l04 MPa Tensile strength is 5.5 Mpa Modulus of elasticity is 13 GPa It has low solubility in water Film Thickness Biologic Effects The freshly mixed
zinc phosphate (at 2 minutes) is highly acidic with a pH of 2
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ADVANTAGES Zn phosphate cement has good
handling properties. It can be mixed easily and set to a relatively strong mass
The longevity of the cement in the mouth is quite good
The set cement has a strength that is adequate for clinical service, so manipulation is less critical compared to other cements.
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DISADVANTAGES It does not bond with the tooth structure The acidity of the cement is its biggest
disadvantage, which may cause pulpal irritation
The cement has no anticariogenic effect, like silicates
The cement appears opaque, hence cannot be used as an anterior restorative material
It lacks antibacterial action The cement is brittle.
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Superior performance of a glass ionomer cement in routine orthodontic cementation during a 2-year period. A significant difference in recementation rate was observed when comparing zinc phosphate and glass ionomer cements. No decalcifications were noted on any of the molars that were cemented with glass ionomer cement.
(Maijer and Smith .Comparison between zinc phosphate and glass ionomer cement.AJO-DO Volume 1988 Apr (273 - 279)
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ZINC POLYCARBOXYLATE CEMENTS
Zinc polycarboxylate cement was discovered by Smith in 1968
COMPOSITION Powder Zinc oxide with approximately 10 percent
magnesium oxide, or sometimes tin oxide. Silica, alumina or bismuth salts and small amounts of stannous fluoride (4-5%)
Liquid The liquid is usually a copolymer of polyacrylic
acid with other unsaturated carboxylic acids, such as itaconic and maleic acid
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PROPERTIES
Compressive strength of the fully set cement is 50-85 MPa
The diametric tensile strength is - 6 MPa.
The elastic modulus is around 4-6 GPa
Film thickness of polycarboxylate cement is slightly more than that of ZnPO.
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ADVANTAGES They bond to enamel and dentin as well
as some of the metallic cast restorations They have a low irritancy Their strength, solubility and film
thicknesses are comparable to that of zinc phosphate cement
DISADVANTAGES Their properties are highly dependent
upon handling procedures They have short working times An exacting technique is required to
ensure bonding
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BOND FAILURES
1. Adhesive-enamel bond failure
2. Adhesive-bracket bond failures
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CAUSES OF ADHESIVE-ENAMEL BOND FAILURES
1. Contamination2. Insufficient rinsing of etchant3. Inadequate drying of enamel surface4. Over-etching demineralizes enamel5. Faulty bonding materials, materials with
expired date6. No activator was placed on enamel
surface when a no-mix adhesive was used
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CAUSES OF ADHESIVE-BRACKET BOND FAILURES
1.Excessive force exerted on bracket from occlusion or excessive force from appliance
2.Movement of bracket during initial setting of adhesive
3.Contaminated bracket mesh (oil from hands, glove powder or rebonded bracket)
4.Adhesive not buttered into base firmly5.Activator not placed on bracket in paste-primer
system6.Inadequate cure of light cured resin composite
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CONCLUSIONS
Introduction of newer bonding agents have changed the practice of orthodontics Modifications of technical devices, sealants and adhesives, attachments and procedures are continuing. Careful study of the available information by the orthodontist is mandatory in keeping up with progress. However, cautious interpretation of in vitro studies is recommended because the in vivo results do not always reflect and verify the laboratory findings. Long-term follow-up studies are needed in several areas.
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Buzitta VAJ, Hallgren SE, Powers IM: Bond strength of orthodontic direct-bonding cement-bracket systems as studied in vitro, Am J Orthod 81:87, 1982).
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Rangaswamy Rajagopal .A Comparison of Shear Bond Strength and Debonding Characteristics of Conventional, Moisture-Insensitive, and Self-etching Primers In Vitro. Angle Orthodontist, Vol 74, No 2, 2004.
Selma Elekdag-Turk, Devrim Isci, Tamer Turk and Fethiye Cakmak. Six-month bracket failure rate evaluation of a self-etching primer. European Journal of Orthodontics 30 (2008) 211–216
Vicente A, Bravo LA, Romero M. Self-etching primer and a non-rinse conditioner versus phosphoric acid: alternative methods for bonding brackets. Eur J Orthod. 2006 Apr;28(2):173-8
A Murfitt PG, Quick AN, Swain MV, Herbison GP A randomised clinical trial to investigate bond failure rates using a self-etching primer. Eur J Orthod. 2006 Oct;28(5):444-9
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Bergeron, C.; Vargas, M.A.; Gelinas, P.; and Van Meerbeek, B.: Bond strength of self-etching adhesives to enamel (abstr.), J. Dent. Res. 79:442, 2000
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THANK – YOU