bonding-i / orthodontic courses by indian dental academy

BONDING IN ORTHODONTICS – II

INDIAN DENTAL ACADEMY

Leader in continuing dental education www.indiandentalacademy.com

www.indiandentalacademy.com

CONTENTS1. Evolution of bonding

agents2. Banding3. Indirect bonding4. Bonding to special

surfaces5. Bond strength6. Debonding 7. Decalcification and

demineralization8. Hazards of bonding

EVOLUTION OF BONDING MATERIALS

“An appliance which cannot be

made transparent or tooth-colored

should at least be made smaller.”

Schange’s adjustable clamp band Angle’s retraction screw

1871 - W.E. MAGILL – Zinc oxycloridewww.indiandentalacademy.com

Laborious, time-consuming, skill Partially erupted teeth Decalcification /discoloration Gingival irritation Unaesthetic Need of separators Closure of band spaces – “What you see

is not what you get”

6www.indiandentalacademy.com

3 major developments that made bonding of attachments to teeth possible –

1. BUONOCORE 1955 – improved retention of methyl methacrylate to enamel – 85% phosphoric acid for 30 seconds

2. BOWEN 1962 – bis Glycidyl methacrylate – more stable and greater strength

3. NEWMAN 1965 – first to acid etch and bond orthodontic brackets with epoxy resin

Orthodontic attachments had to be cemented on teeth instead of the intermediary bands-

Methylmethacrylate monomer –MMA – first material to be used

Catalyst – Benzoyl peroxide –BPO Powder-liquid system In use in restorative dentistry

•Poor adhesion - Polymerization shrinkage•Pulpal irritation

BUONOCORE (1955) –

Improved retention of methyl methacrylate to enamel – 85% phosphoric acid for 30 seconds

Not successful for orthodontic purposes –

• Occlusal force • Wide range of oral thermal change • Wet environment

G. V. NEWMAN (1965)

Bonded plastic brackets with epoxy resins

Start of direct bonding procedure

For short-term treatment with anterior brackets

Did not replace ‘metal-band’ system

First commercially available orthodontic adhesives

1. OIS Adhesive system – OIS company in 19692. Bracket Bond – GAC in 1970

MMA -BPO-amine catalyst system Weak Adhesion Early 70s - all adhesives consisted of MMA - it bonded

chemically to plastic brackets – in vogue

Fujio Miura and associates in 1971 –

Introduced – ORTHOMITE MMA - Tri–N–Butyl Borane (catalyst) Increased adhesive strength Coupling agent – ‘silane’

methacryloxypropyltrimethoxysilane Increased adhesive penetration

•Chemically bonded to adhesive•Affinity to enamel

Merits of MMA adhesives:

1. Plastic brackets 2. Good storage stability3. Increased working time – brush-on / dip-in4. Elimination of sealant - good penetration

into enamel surface5. Less damage during debonding

Demerits of MMA adhesives:

1. Fluctuating proportion of powder-liquid depending on operator

2. Poor mechanical interlocking to metal bracket bases

Metal brackets enter the scene

Plastic – worry about enamel-adhesive Enamel-adhesive & adhesive-bracket

Adhesive-bracket -Mesh, perforated pad , foil mesh Enamel-adhesive –

•Increased hardness of adhesive•MMA BisGMA •Filler material - TEGDMA

Bisphenol Glycidyl Dimethacrylate (Bis-GMA)

BOWEN 1962• Greater strength• Lower water absorption• Less polymerization shrinkage

2-paste system Strongest adhesives for metal brackets

FILLERS: Reduce viscosity of resin Reduce polymerization shrinkage Quartz, silica glass particles 3 - 20 microns - abrasion resistance 0.2 – 0.3 microns - smooth surface - less plaque

retentionAdhesives with large particle fillers

recommended for extra bond strength, but careful removal of excess is mandatory

Di/triethyl glycol dimethacrylate (TEGDMA)

Merit and demerit of Bis-GMA – hardness

Poor penetration due to increased viscosity – dilute with MMA

Plastic brackets could not be used – primer for partially dissolving added

Active life less than powder liquid system

In 1974 – ORTHOMITE II – 20% more HNPM – hydroxynapthoxypropylmethacrylate Eliminated silane

4 - META – methacryloxyethyl trimellitate anhydride

ORTHOMITE SUPER BOND

4 - META

Plastic & metal PRE-PRIMED brackets Base was primed with adhesive Bracket base covered with PMMA powder Base dipped in monomer and pressed onto

etched surface. Bond strength less than manual application

Orthodontic adhesives are variations of- Adhesives Direct-restorative materials used in

restorative dentistry

Late 20th century –direct restorative biomaterials

1. Resin-matrix – originated in U.S.2. Salt-matrix – U.K.

1. RESIN MATRIX: Classification -

According to organic matrix components -A. Acrylic resins – MMA Ex. ORTHOMITE, GENIEB. Diacrylate resins- BisGMA Ex.CONCISE, PHASE II

According to polymerisation mechanism –A. Chemically activatedB. Light-curedC. Dual-curedD. Thermocured

A. CHEMICALLY ACTIVATED:

Chemically-cured/ Auto-cured / Self-cured Used since beginning of bonding Most-widely used ortho adhesives Two-paste / one-paste Two-paste system: Initiator- Benzyl peroxide in monomer Activator- tertiary amine – dihydroxyethyl –p-

toluidine

Ex. Concise (3M)

Good bond strength

Laborious Time-consuming Increased air-exposure- oxygen

inhibition Defects – air entrapment, voids

One-paste system:

One adhesive component applied to bracket base and other on tooth surface – catalyst gradient

No-mixing Bracket positioned accurately - pressed firmly into

place Curing occurs – 30-60 secs Ex. Rely-a-bond, System 1+, Unite

Procedure simplified Fast Efficient

Little long term information available on bond strength Inhomogeneous polymerisation – sandwich technique Enamel and bracket side more polymerized Liquid activators – toxic, allergic reactions

B. LIGHT-CURED:

Visible-light curedCamphoroquinoneCure from incisal and gingival areas Increased working time Ideal for educational purpose DC same as Chemical-cure; same for metal and ceramic

brackets Photocuring time-consuming

C. DUAL-CURED:

Intiation – exposure to lightPropagation – chemically cured Advantages of light and chemically cured Improved surface and bulk material properties Highest DC, bond strength Ideal for bonding molar tubes

Most time-consuming Bulk defect due to mixing

D. THERMO-CURED:

Exposure to heat

Superior properties

Not for direct but only indirect bonding

Adhesives acting in the presence of water –

1. MOISTURE-RESISTANT – - can bond in presence of water - saliva, gingival fluid – contaminants - ex. Transbond MIP2. MOISTURE-ACTIVE – - need water for bonding - enamel surface intentionally made wet - Cyanoacrylate – no liquid, only paste - ex. Smartbond

CYANOACRYLATES:

Ethyl-cyanoacrylate – Smartbond-orthodontic bracket adhesive (1991)

Other uses•Automobiles,Circuit boards,Light aircraft•Fracture fixation•Skin sutures•Cardiac surgery•Guided tissue regeneration

Crabb and Wilson – 1971- compared with polycarboxylate cement – poor performance and bond strength, unsuitable for clinical use

Howells and Jones – 1994 – poor performance on storage in saline for a week

Krishnan et al – 1994 –equal to Bis-GMA when kept in 37oC for 24 hours

THOMAS W. - JCO 2000 - Compared the shear bond strength and debonding effects of Smart-Bond & Rely-a-bond

•Smart-Bond’s strength was significantly higher

•No danger of fracturing the enamel•Polycarbonate bracket - work only if

they are pretreated with water

Ideal characteristics of Bonding medium:

1. Non-toxic 2. Adequate working and setting time3. Moderate viscosity4. Ability to wet etched surface5. Sufficient tensile and compressive strength - retain bracket &

ease of debonding6. Resist decomposition in the oral environment7. Antimicrobial

Evaluation of antimicrobial properties of orthodontic composite resin combined with benzalkonium chloride

Othman et al,AJO Sep2002

The antimicrobial agent benzalkonium chloride added to a chemically cured composite resin

Anti microbial benefits and bond strength of the modified composite were evaluated.

Results:

No significant difference between the tensile bond strength between modified composite and the original product

The incorporated BAC added to anti microbial properties of original composite without altering it’s mechanical properties

2. SALT MATRIX: CEMENTS IN ORTHODONTICS:

Desirable properties:1. Adequate working and setting time2. High tensile, compressive and shear stress3. Resistant to dissolution4. Clinically acceptable bond strength5. Low Adhesive Remnant Index (ARI) on debonding6. Anticariogenic potential

ZINC PHOSPHATE:

Oldest of the luting cements Powder and liquid system Film thickness of 20 microns Efficient mixing characteristics

Mechanical adhesion Pulpal irritant - highly acidic May cause decalcification of enamel resulting in white

ZINC SILICOPHOSPHATE:

Addition of silicate glass Superior strength and fluoride releasing

property

Extremely acidic High solubility No longer used

ZINC POLYCARBOXYLATE CEMENT:

Introduced by Smith in 1968 First cement system that developed a

chemical bond to the tooth structure. Early 70s –Durelon – poor bond strength Combined desirable properties of Zn-

phosphate & ZOE

Acid-base reaction

Chemical bond to tooth Fluoride release Shorter setting time Viscous liquid – less efficient mixing characteristics -

PSEUDOELASTIC

GLASS IONOMER CEMENTS:

Developed and introduced in 1974 byWilson, Kent and Smith.

To combine strength and fluoride release of silicophosphate and adhesive efficiency of carboxylate

Group of materials that use silicate glass powder and an aqueous solution of Polyalkeonic acids

Setting reaction:

Surface of glass particles is attacked by acid Ca, Al, Na, Fl ions-leached into aqueous medium Next 24 hours a new phase forms in which aluminium ions

become bound within the cement matrix leading to a more rigid set cement

NaF uniformly dispersed in the set cement. Unreacted portion of glass particles sheathed by silica gel.

Unreacted powder particles surrounded by a silica gel in an amorphous matrix of hydrated Ca++ and Al+++ polysalts.

During initial reaction if mix contaminated by additional water or ambient air - dissolution of matrix - weak and more soluble cement

Adhesion- chelation of carboxyl groups of polyacids with Ca in apatite of enamel & dentin

Biological properties :

Chemical adhesion Bacteriostatic or bactericidal due to fluoride

release. Acid - less irritating to the surrounding tissues Enamel etching for luting bands not required Reduces demineralization Highest strength Least solubility Bonds to enamel and base metals

Drawbacks:

Moisture sensitivity Low early strength

Polymerizable resin functional groups added Impart additional curing process Allow the bulk of the material to mature through the acid-

base reaction.

RESIN MODIFIED GLASS IONOMER CEMENT

Nicholson (Quint Int 1977) “Resin modified GIC’s are those

materials that are modified by the inclusion of resin, generally to make them partly photocurable”

W.M. Tay (Dental update 95) “These are hybrid materials that retain

significant acid base reaction as a part of their overall curing process”

Advantages of RMGIC’s over GIC’s:

1. Sufficiently long working time controlled in command to a snap set by photocuring.

2. Improved setting characteristics.3. Protect the acid base balance from problem of

water balance.4. Rapid development of early strength.5. Fluoride release greater.6. Diametral strength high (20 Mpa compared to 6. 6 Mpa)

Disadvantages of RMGIC’s over GIC’s:

1. Biocompatibility is controversial.2. Setting shrinkage is higher leading to increased

microleakage and poor marginal adaptation Brands

• Fuji Ortho LC• Photacfil – ESPE • Vitrebond – 3M

In 1986 – White described a method of bonding orthodontic brackets to the enamel surfaces of teeth, with a glass ionomer cement.

Poor strength Isolation of newly bonded teeth Light arch-wires immediately after bonding

Bond strength and durability of glass ionomer cements used as bonding agents - AJO July 1989

-Klockowski, Davis, Joynt, Wieczkowski, and MacDo Compared GICs (Ketac-fil, Ketac-cem and Chelon)

with Rely-A-Bond (no-mix autopolymerising) which served as a standard in a clinical study.

Results:

Bond strength of GICs was significantly less when compared to Rely-A-bond.

Less reduction of bond strength of GICs on recycling – lesser than Rely-A-bond on recycling

Failures involved cohesion within cement or adhesion involving the enamel - easily scraped off from the enamel surface without causing much damage.

Cook -1990 compared the in vivo bond strength of a glass ionomer cement, Ketac (ESPE Premier Denbol Products, Norristown, Pa.), with a composite resin bonding agent – 12% failure rate

Fajen et al- 1990 evaluated the bond strength of three glass ionomer cements against a composite resin in vitro

Fricker - 1994, worked with Fuji II LC glass ionomer cement (GC Corp., Kyoto, Japan) –

•Same rate of success bonding brackets to enamel surfaces as he did with composite cements.

•Dentine conditioner was utilized for ten seconds

Kusy - discussed the damage to teeth on debonding after using composite bonding resins.

•“When is stronger better?” •Use of glass ionomer cements for orthodontic

bonding procedures - do not need etching or damage the enamel during debonding.

A new light-cured glass ionomer cement that bonds brackets to teeth without etching in the presence of saliva -AJO-DO SEP 1995

-Silverman, Cohen

Used a new Resin modified GIC Fuji Ortho LC Light-cured, resin-reinforced glass ionomer cement 3 mechanisms of setting

Advantages:

Saves significant amount of chair time. Eliminates working in a dry field. Eliminates etching and priming enamel surfaces. Fluoride release protects teeth against

decalcification. Repairs are quick and easy. Increased patient and operator comfort.

Evaluation of fluoride release from an orthodontic bonding system – AJO-DO Aug 1991

-Samir E. Bishara, Edward J. Swift, Jr., Daniel C. N. Chan,

Light-activated fluoride-releasing - FluorEver OBA Tensile bond strength was significantly less – 1/3 – 1/2 of

conventional (chan et al)

Fluoride ion release – 2.6ppm on day 1

0.42ppm on day 2

0.04ppm on day 43

However , decrease in enamel decalcification was observed.

BANDING

“Feel the pinch”

Advantages of banding

Stronger Protect against interproximal caries Easier to recement and deband

1. CUSTOM-MADE• Indirect• Direct

2. PRE-FORMED

1. CUSTOM-MADE BANDS:

1. Band-pinching2. Band-cementation

1. BAND-PINCHING: ‘Food-trap for cariogenic debris’ Exacting proximity between tooth and

band Poorly fitting band – ‘island in a sea of

cement’.

BANDING PROCEDURE

BAND MATERIAL:

Precious metalChrome-cobalt alloyStainless steel Size:

Thickness WidthIncisors 0.003 – 0.004” 0.125”

Premolars & Canines

0.004” 0.150”

Molars 0.005 – 0.006” 0.180 – 0.200”

REQUIREMENTS:1. Greatest strength and

durability with minimum of bulk

2. Soft enough to permit close adaptation

3. Strong enough to withstand stresses

4. Polishable5. Corrosion and tarnish

resistant6. Biocompatible

2. BAND-CEMENTATION:

Do not depend on cement for retention‘Drive fit’

Universal scaler parallel to band margin and not perpendicular

2. PRE-FORMED BANDS:

Band selection: Casts Variations – anatomy, tapered crowns, extra

cusps, restorations One size larger than the one that seems to fit

the tooth – prevents wasteful distortion of bands

Band fitting:

First - finger pressure - only on mesial and distal sides Amalgam plugger / band pusher – 2/3rd Bite pressure through biting stick – facial and lingual Final seating pressure –

•Maxillary – palatal side of tooth•Mandibular – buccal side of tooth

Checklist:

All cusps on banded teeth equally visibleBand margin –

•Just below marginal ridge•Above the contact point

Buccal attachment accurately positionedOpen occlusal margins crimped towards tooth

www.indiandentalacademy.com 78

Thank you

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bonding-i / orthodontic courses by indian dental academy

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