PRESENTED BY-HARMEET

BONDING AGENTS

CONTENTS

Introduction Concepts of adhesion Adhesion and its ten commandments Orthodontic bonding agents CompositesNewer systems Fluoride-releasing compositeMoisture-resistant adhesiveMoisture-active adhesives

Dentin bonding agents CementsGlass ionomer cementResin-ionomer hybridsZinc phosphate cementZinc polycarboxylate cements Bond failure Conclusions References 

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.

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

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

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.

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

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

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"

ORTHODONTIC BONDING AGENTS

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

COMPOSITION

THE RESIN MATRIX Most composite consist of

monomers of molecular weight of 100-1000g/ mole

Viscous aromatic dimethacrylate monomer (Bis-GMA)

Large molecular size, lower volatility, lower polymerization shrinkage, more rapid hardening and production of a stronger and stiffer resin.

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.

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.

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

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

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). 

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.

MECHANISM OF ACTION OF

COUPLING AGENT

INITIATORS AND ACCELERATORS Light cured composite –

Camphorquinone Chemical cured composites are

activated by organic amines (accelerator) reacting with peroxide (initiator)

INHIBITOR Hydroquinone - 0.1%. 

PIGMENTS Numerous shades are supplied from

white to yellow gray.

ULTRAVIOLET ABSORBER

CLASSIFICATION OF THE COMPOSITES

1. Based on the filler

2. Based on the method of

polymerization

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.

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.

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.

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)

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).

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

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).

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

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

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.

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%.

Transbond XT composite (3M Unitek, Monrovia, USA).

This is composed of 14% BIS-GMA, 9% BIS-EMA, and 77% load particles.

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

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

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

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 )

DUAL-CURED SYSTEMS

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)

 

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. 

NEWER SYSTEMS

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.

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

 

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

The main reactive component of this product is a methacrylate-functionalized polyalkenoic acid copolymer

Excess interfacial water ionizes carboxylic groups, forming hydrogen- bonded dimers.

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

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)

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.

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

DENTIN BONDING AGENTS

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

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

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

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

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

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.

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

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)

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

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

EXAMPLES All bond-2 (BISCO), Prime and bond Comfort bond (Heraeus Kulzer)

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.

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.

EXAMPLES One step (BiSCO) Single bond (3M) Clearfil SE bond

(Kuraray medical Inc.) Opti bond solo (KERR) Xeno III(Denstply) .

SIXTH GENERATION DENTIN BONDING AGENTS

The self-etching primers (SEPs), was introduced in Japan.

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)

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

UDMA /HEMA –wetting agent 4 META – binding to calcium or

collagen GLUTARALDEHYDE – disinfectant ACETONE – removing humidity WATER – helps in etching process

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

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

System comes with etchant, primer, adhesive and microbrush sealed in a triple lollipop-shaped aluminium foil package (blister pack).

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

BOND STRENGTH OF DIFFERENT DENTINE BONDING AGENTS

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

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

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)

RECENT MODIFICATION IN DENTIN BONDING

AGENTS

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.

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

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

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)

 

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

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

INTERMEDIATE RESINS All-Bond 2 Primers A+B

Scotch-Bond Multi-Purpose (SBMP) system.

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

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

SANDBLASTING

Bjorn U. Zachrisson, Tamer Buyukyilmaz. JCO Recent Advances in Bonding to Gold, Amalgam, and Porcelain Volume 1993 Dec(661 - 675)

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

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.

CEMENTS

GLASS IONOMER CEMENT

It was introduced in 1972 by Wilson & Kent

Hybrid of silicate & polycarbonate cement

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

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

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

MANIPULATION

PREPARATION OF THE TOOTH SURFACE

PROPORTIONING (Powder Liquid Ratio)

PLACEMENT AND PROTECTION OF THE MATERIAL

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

Adhesion Glass-ionomer cements exhibit bonding to enamel & dentin

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

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):

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

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

(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

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%)

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

COMPOSITION

POWDER Ion leachable

glasses Photo initiators Polymerizable

resin

LIQUIDPolyacrylic acid WaterMethacrylate

monomer HEMA

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.

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.

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

SETTING MECHANISM

Primarily by light, but acid-base reaction also occurs

MANIPULATION Single-paste packaged in unit-dose

ampules.

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.

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..

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.

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

MANIPULATION

Mixing time is 60 to 90 seconds.

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

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. 

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.

 

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)

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

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.

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

BOND FAILURES

1. Adhesive-enamel bond failure

2. Adhesive-bracket bond failures

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

 

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  

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.

REFERENCES

Dental Hard Tissue and Bonding – G. Eliades, D C Watts . 

Sturdevats Art and Science of Operative Dentistry- Theodore M. Roberson,

Harald O. Heymann and Edward J swift Orthodotics – Current Principles And

Technique –Graber , Varnsdall And Vig Philips – Science Of Dental Materials –

Anusavice Orthodontic Materials – Wiliam .A. Brantley 

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).

Wang and Meng. Bond strength between light- and self-cured resin. AJO-DO on Volume 1992.

J. Clifton Alexander & Anthony D. Viazis: Bond Strengths and Fracture Modes of Three Orthodontic Adhesives .JCO Volume 1993 Apr 207 – 209 

Sonis and Snell: Fluoride-releasing, visible light-activated bonding system.AJO-DO Volume 1989 Apr 306 - 311.

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

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 

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

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 

D. T. Millett & MOrtha; L.-A. McCluskey. A Comparative Clinical Trial of a Compomer and a Resin Adhesive for Orthodontic Bonding

Maijer and Smith .Comparison between zinc phosphate and glass ionomer cement.AJO-DO Volume 1988 Apr (273 - 279). 

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.

Fruits TJ, Duncanson MG Jr, Miller RC. Bond strengths of fluoride releasing restorative materials. Am J Dent 1996;9:219-22. 

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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