Enamel and Dentin Adhesives

Enamel and Dentin Adhesives
Col Kraig S. Vandewalle USAF Dental Evaluation & Consultation Service

Official Disclaimer The opinions expressed in this presentation are those of the author and do not necessarily reflect the official position of the US Air Force or the Department of Defense (DOD). Devices or materials appearing in this presentation are used as examples of currently available products/technologies and do not imply an endorsement by the author and/or the USAF/DOD.

Overview Principles of adhesion Principles of bonding
Historical development Classifications Features Conclusions

Advantages of Adhesion
Help offset polymerization shrinkage reduce marginal leakage staining sensitivity caries Adhesion conservation of tooth structure internal splinting Esthetic restorations

Indications for Adhesion
Direct resin composite restorations caries, fractures, reshaping, masking Bond all-ceramic restorations veneers, inlays, onlays, crowns Bond amalgam Resin-retained fixed-partial dentures

Indications for Adhesion
Pit and fissure sealants Orthodontic brackets Treat dentinal hypersensitivity Core build-ups Repair fractured porcelain and composite

Basic Mechanism of Adhesion (resin-based)
Exchange process replacement of minerals from hard tissue by resin monomers micromechanically interlocked Primarily mechanical retentive interlocking

Variations in Tooth Structure
Enamel more predictable bonding more homogeneous structure higher inorganic content higher surface energy Dentin less predictable bonding higher variability higher organic content Van Meerbeek in: Summitt Fund Oper Dent 2001

Enamel Composition Primarily inorganic hydroxyapatite Organic 2% Water
By volume 12% Inorganic 86% Van Meerbeek in: Summitt Fund Oper Dent 2001

Enamel Bonding Developed by Buonocore-1955 Etching various acids
traditionally phosphoric acid creates micropores 5 – 50 microns deep increases surface energy increases wettability Van Meerbeek in: Summitt Fund Oper Dent 2001

Surface Wetting Tooth surface contamination Clean surface
saliva, smear layer Clean surface increase surface energy decrease contact angle Van Meerbeek in: Summitt Fund Oper Dent 2001

Enamel Bonding Low-viscosity monomers Predictably high bond strengths
examples Bis-GMA UDMA TEGDMA HEMA Predictably high bond strengths > 20 MPa Van Meerbeek in: Summitt Fund Oper Dent 2001

Dentin Structure Dentin composition Dentinal tubules
Changes in dentin structure Smear layer Dentinal wetness

Dentin Composition Inorganic 50% Organic 25% Water 25%
By volume Water 25% Van Meerbeek in: Summitt Fund Oper Dent 2001

Dentinal Tubules Radiate from pulp Largest near pulp
2.5 microns at pulp 0.8 microns at DEJ Concentrated near pulp 45,000/mm2 at pulp 20,000/mm2 at DEJ Van Meerbeek in: Summitt Fund Oper Dent 2001

Tubule Composition Peritubular dentin Intertubular dentin
surrounds tubule hypermineralized Intertubular dentin between tubules less mineralized Odontoblastic process Dentinal fluid Van Meerbeek in: Summitt Fund Oper Dent 2001

Changes in Dentin Structure
Sclerotic normal aging abrasion erosion Reparative caries dental procedures Hypermineralization Less receptive to bonding Van Meerbeek in: Summitt Fund Oper Dent 2001

Smear Layer Produced by instrumentation Composition
cut dentin debris bacteria Reduces dentin permeability 86% Van Meerbeek in: Summitt Fund Oper Dent 2001

Smear Layer Thickness Will not wash off Weak bond to tooth
microns Will not wash off Weak bond to tooth 2 – 3 MPa Very soluble weak acids Van Meerbeek in: Summitt Fund Oper Dent 2001

Dentinal Wetness Increases Historically, more difficult to bond
dentinal depth removal of smear layer Historically, more difficult to bond Van Meerbeek in: Summitt Fund Oper Dent 2001

Dentin Bonding Development Classification seven generations
chronologic Classification Van Meerbeek in: Summitt Fund Oper Dent 2001

First Generation (1950-1970’s)
Hydrophobic monomers Very low bond strengths 2 to 3 MPa First commercial dentinal adhesive Cervident - SS White (1965) claimed chemical bond to calcium retention only 50% at 6 months Class 5 Harris J Prosthet Dent 1974

Second Generation (late 70’s to mid 80’s)
Phosphorous-ester monomers enhanced surface wetting claimed chemical bond to calcium smear layer predominately intact fear of etching dentin Low bond strengths 5 to 6 MPa Retention 70% at 1 year Class 5 Van Meerbeek in: Summitt Fund Oper Dent 2001

Third Generation (mid-80’s)
Mechanism of action mildly acidic hydrophilic monomer modified/altered smear layer Moderate bond strengths Improved short / long term success Van Meerbeek in: Summitt Fund Oper Dent 2001

Fourth Generation (early 1990’s)
Multi-step condition dentin remove smear layer primer adhesive High bond strengths Retention 98 to 100 % at 3 yrs Class 5 Van Meerbeek in: Summitt Fund Oper Dent 2001

Fifth Generation (late 1990’s)
Attempt to simplify reduce number of bottles combined primer and adhesive High bond strengths Van Meerbeek in: Summitt Fund Oper Dent 2001

Sixth Generation (late 1990’s)
Combined conditioner and primer moderate bond strengths Combined conditioner, primer and adhesive lower bond strengths Van Meerbeek Oper Dent Click here for abstract

Seventh Generation (most recent)
“All-in-one” adhesives combined conditioner, primer and adhesive one-step No mixing Low bond strengths Van Meerbeek Oper Dent Click here for abstract

Currently Available Generations
Fourth Generation Three-step Etch & rinse Fifth Generation Two-step Etch & rinse Sixth Generation Two-step Self-etch One-step Self-etch mix Seventh Generation no mix

Classification of Newer Systems
Interaction with tooth surface Number of clinical application steps 1) Etch & rinse (i.e., total-etch) 2) Self-etch 3) Resin-modified glass ionomer Van Meerbeek Oper Dent Click here for abstract

Adhesive Categories Etch & Rinse Self-Etch Glass Ionomer Three-Step
conditioner, primer, adhesive Two-Step conditioner, (primer & adhesive) Self-Etch (conditioner & primer), adhesive One-Step (conditioner & primer & adhesive) Glass Ionomer conditioner, resin-modified glass-ionomer mixture

Etch & Rinse (Three-Step)
Conditioner Primer Adhesive resin Examples Scotchbond Multi-Purpose Optibond FL

Conditioner Chemical alteration of surface
acids phosphoric, citric, maleic, nitric Removes dentinal smear layer exposes collagen fibrils Simultaneous enamel etch Rinse keep moist Van Meerbeek in: Summitt Fund Oper Dent 2001

Primer Hydrophilic monomers Displaces water
dissolved in acetone, alcohol, or water Displaces water Promotes infiltration into collagen Lightly air dry drive off solvents, water Transforms hydrophilic to hydrophobic Van Meerbeek in: Summitt Fund Oper Dent 2001

Primer Bifunctional monomer Link Example hydrophilic collagen
hydrophobic resin Example HEMA H2C=C-C-O-CH2-CH2-OH CH3 O

Adhesive Resin Unfilled or lightly-filled monomers
equivalent to enamel bonding Bis-GMA, UDMA, TEGDMA Stabilize the hybrid layer fills up remaining pores Resin tags Links primer to composite resin Van Meerbeek in: Summitt Fund Oper Dent 2001

Hybrid Layer Conditioner demineralizes dentin
Interdiffused with low-viscosity monomer displaces water bifunctional Resin mechanically interlocks collagen Van Meerbeek in: Summitt Fund Oper Dent 2001

Etch & Rinse (Two-Step)
Conditioner Combined primer and adhesive higher technique sensitivity higher solvent-to-monomer ratio risk of applying too thin apply multiple layers Examples Single Bond Optibond Solo Plus Prime & Bond NT Hashimoto Oper Dent 2004 Click here for abstract

Pros/Cons of Etch & Rinse
Separate acid etch good enamel etch pattern Potential to over-etch dentin except sclerotic dentin Post-conditioning rinse necessary sensitive to level of dentin wetness Multiple long-term clinical studies available Van Meerbeek Oper Dent Click here for abstract

Dentin Wetness Etch & Rinse
After conditioning dentin dentin must be wet prevent collagen collapse Too little water collagen collapse Ineffective resin penetration Leads to nanoleakage Sano Oper Dent Click here for abstract

Wet Bonding Acetone and ethanol based primers Examples
displace remaining water carry monomers into collagen gently air-dried leaving monomers behind Examples One-Step Prime & Bond NT Kanca Quintessence Int Click here for abstract

Effect of Dentin Wetness
One-Step (Bisco) 16 14 12 10 Bond Strength (MPa) 8 6 4 2 moist dry 1 sec dry 5 secs dry 5 secs + rewet Perdigao Am J Dent Click here for abstract

Overwet Phenomena Too much water Phase separation
not completely displaced Phase separation blister and globule formation Tay Dent Mater Click here for abstract

Disadvantages to Wet Bonding
Cannot check for enamel “frosted” etch Technique sensitivity not too wet or too dry Solvents evaporate from bottle may reduce monomer penetration Van Meerbeek in: Summitt Fund Oper Dent 2001

Dry Bonding Water-based primers Permits check of “frosted” enamel
effective on wet or dry dentin self-rewetting effect re-expand collapsed collagen Permits check of “frosted” enamel Examples Scotchbond Multi-Purpose Optibond Van Meerbeek in: Summitt Fund Oper Dent 2001

Class V Clinical Studies Etch & Rinse Three-Step
Scotchbond MP (3M ESPE) 100% retention at 3 yrs Van Meerbeek Quint Int 1996 98-100% retention at 3 yrs Trevino JDR 1996 100% retention at 2 yrs Alhadny Am J Dent 1996

Class V Clinical Studies Etch & Rinse Two-Step
Optibond Solo (Kerr) 93.3% retention at 3 yrs Swift JADA 2001 Prime & Bond 2.1 (Caulk) 89.4% retention at 3 yrs

Laboratory Study Three-Step vs Two-Step Etch & Rinse
Shear Bond Strength 30 Two-Step Three-Step 25 20 MPa 15 10 5 Opti Opti FL Single MP + Excite Syntac Solo+ Bond Pecora J Prosthet Dent Click here for abstract

Laboratory Study Three-step vs Two-step Etch & Rinse
Microtensile Bond Strength 60 50 40 uTBS 30 20 10 24 hr 4 yr Single Bond Scotchbond Optibond Optibond FL MP Solo De Munck J Den Res Click here for abstract

HEMA usually water based
Self-Etch Components Acidic monomers MDP Di-HEMA-Phosphate MA 154 Phenyl-P MAC-10 4-MET(A) BisGMA UDMA TEGDMA GDMA HEMA usually water based Crosslinking monomers List of common self-etch components – they are currently all methacrylate based monomers. Typically all solvents are water. Solvent

Self-Etch (Two-Step) Combined conditioner and primer Adhesive resin
Examples Clearfil SE AdheSE Click here for table of self-etching adhesives

Self-Etch (One-Step) Combined Examples conditioner primer adhesive
Prompt L-Pop One-up Bond F Touch and Bond iBond Xeno III Click here for table of self-etching adhesives

Pros/Cons of Self-Etch
Good dentin conditioning simultaneous infiltration depth of demineralization Possible reduction in post-op sensitivity?? No post-conditioning rinse not sensitive to level of dentin wetness Reduced application time Hara Am J Dent 1999

Clinical Studies (Post-Operative Sensitivity)
Class 1 or 2 composite restorations Clearfil SE self-etch Prime & Bond NT etch & rinse Tested for post-op sensitivity No difference Baseline, 2 weeks, 6 weeks, 6 months Perdigao JADA Click here for abstract Baseline, 2 weeks Perdigao Quint Int Click here for abstract

Application Time 120 100 80 60 40 20 iBond Excite PQ1 Xeno III AdheSE
Etch&Rinse Self-Etch Seconds 120 100 80 60 40 20 iBond Excite PQ1 Xeno III AdheSE Tyrian Clearfil SE One-up Bond Single Bond Prompt L-Pop Optibond Solo Scotchbond MP Prime&Bond NT Source: USAF DIS N=3

Pros/Cons of Self-Etch
Limited clinical indications Limited clinical data Relatively lower bond strengths Many require refrigeration Van Meerbeek Oper Dent Click here for abstract

Shear Bond Strength to Dentin
Etch&Rinse Self-Etch MPa Source: USAF DIS Horizontal lines connect nonsig diff at 0.05 level N=10

Class V Clinical Studies Self-Etch Two-Step
Clearfil SE Bond (Kuraray) 100% retention at 2 yrs Peumans J Dent Res abstr #0911 93% retention at 2 yrs Turkun J Dent 2003

Class V Clinical Studies Self-Etch One-Step
Prompt L-Pop (3M ESPE) 65% retention at 1 yr Brackett Oper Dent 2002 79% retention at 2 yrs van Dijken Am J Dent 2004

Special Considerations
Incompatibilities self-cure composites with simplified adhesives two-step etch & rinse one-step self-etch Acidic monomers react with basic catalyst of overlying composite Adhesive permeability leads to superficial water blisters via water trees Click here for details

Adverse Acid-Base Reaction
Simplified Adhesives Composite Adhesive Primer Dentin Three-step Etch & Rinse Two-step Self-Etch Acidic Monomers Two-step Etch & Rinse One-step Self-Etch BPO+Amine Neutral O2 Inhibited Layer Suh 2002

Water Trees Simplified adhesives Act as semi-permeable membrane
Conduct fluid Osmotic blistering along the composite-adhesive interface slows self-curing of composite Click here for details

Water Tree Formation Composite Hybrid Layer Trapped Moisture Dentin
Lindemuth 2004 Composite Water Tree Formation Hybrid Layer Trapped Moisture Dentin

Failure over time Hydrolytic Degradation of Resin – Dentin Bond
Lindemuth 2004 Hydrolytic Degradation of Resin – Dentin Bond Failure over time

Dual Cure Dual- and self-cure composites Separate activator Examples
cores cements Separate activator Examples Optibond Solo Plus Prime and Bond NT

Features Fluoride release Unit-dose

Fluoride Release Anti-caries effect? Examples no proof of efficacy
in resin-based adhesives Examples FL-Bond One-up Bond F PQ1 Tenure Quick Optibond Solo Plus

Unit Dose Improved infection control Convenience
Minimizes loss of volatile components over time Higher cost Examples Optibond Solo Plus Excite Prime and Bond NT Prompt L-Pop

Resin-modified Glass-Ionomer
Weak conditioner pretreatment polyacrylic acid removes smear layer exposes collagen Mechanical bonding hybrid layer Chemical bonding carboxyl groups with calcium in tooth

Resin-modified Glass-Ionomer
Two-step weak conditioner mix and apply glass ionomer adhesive Fluoride release Example Fujibond LC

Pros/Cons of Resin-Modified Glass-Ionomer
Chemical and mechanical bonding Fluoride release Limited clinical data Class V study Fuji Bond LC 96% retention at five years Class 5 Tyas Oper Dent 2002

Average Annual Failure Rate Class V Restorations
% Standard Deviation Peumans Dent Mater Click here for details

Adhesive Preferences with Light-Cured Composites
Adhesive Preferences with Light-Cured Composites* Civilian Practitioners Total-etch 70% Self-etch 62% Other 3% *Multiple responses DPR 2005

Van Meerbeek Oper Dent 2003 Click here for abstract
Conclusions Etch & rinse favorable long-term data Self-etch promising?? do not require rinsing demineralize and infiltrate to same depth reduced technique sensitivity reduced application time potential decreased post-operative sensitivity?? Van Meerbeek Oper Dent Click here for abstract

Conclusions Trend toward simplified application
reduced number of steps not necessarily better Van Meerbeek Oper Dent 2003

Purchasing Considerations (Federal Dental Services)
4th generation etch & rinse three-step several available 5th generation etch & rinse two-step multiple available 6th generation self-etch two-step Clearfil SE Bond self-etch one-step ???? Click here for synopsis of self-etching adhesives

Acknowledgements Questions/Comments Dr. Dave Charlton
Lt Col Steve Klyn Questions/Comments Col Kraig Vandewalle DSN

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