Adhesive Materials

DHYG 113

Restorative Dentistry I

Objectives

Describe the difference between micromechanical and macromechanical bonding

Discuss the benefits of bonded restorations Compare the differences of enamel and dentin in

regards to etching and bonding Discuss the terms: ortho-phosphoric acid,

enamel tags, smear layer, primer and adhesive Summarize the differences between glass

ionomer cements and dentinal bonding

Why use adhesives?

Strong adhesion increases retention of appliance or restoration

Eliminates need to remove tooth structure (undercuts) for mechanical retention

Seals margins, reducing chance of recurrent decay

Adhesion or Bonding

Joining together of two objects using a glue or cement

Micromechanical bonding – Superglue Surface irregularities too small to be

seen Macromechanical bonding

Larger scale – wood glue

Acid Etch and Composites

Materials developed in the 50’s, ’60’s, ’70’s and 80’s Bonded ortho brackets Bonded bridges (Maryland bridge) Porcelain, plastic & composite veneers –

etched & bonded to facial surfaces Composite materials used to reshape teeth Periodontal splints, stabilize jaw fractures

Uses in Dentistry

Retention of restorations Undercuts not necessary Bond weak restoration to stronger tooth

Reduction of microleakage Reduce postoperative sensitivity

Reduction of recurrent decay Sealed margins more resistant to decay

Uses in Dentistry

Bond Porcelain Veneers

Before After

Attach Ortho Brackets

Surface Factors

Cleanliness Don’t want adhesive to bond to surface debris

– poor bonding Should be chemically compatible or adhesive

will not “wet” adequately Biofilms – contaminated by oral fluids

Enamel pellicle Reduces or prevents bonding Use rubber dam to keep surface dry

Testing Adhesion

Adhesive Failure – comes cleanly off tooth Orthodontic bracket may have been

contaminated

Cohesive Failure – bonding material fails Cement layer remains on both tooth &

bracket

Acid Etching

Etch is usually 37% ortho-phosphoric acid 15-30 seconds

Creates microscopically rough enamel surface Micropores Enamel tags

More effective to bond polymer resin to ends of enamel rods than to long axis of rods

Properly etched enamel appears ‘frosty’

Resin Systems Resins “wet” the etched surface and flow into the

microscopic irregularities

Enamel bonding resin – adhesive Set by polymerization Next step is to place the composite material –

chemically bonds to the resin

Dentinal Bonding

Micromechanical bonding and secondary atomic bonds

Bond to enamel and dentin to prevent leakage and recurrent decay

Etching removes dentin “smear layer” and decalcifies layer of dentin Dentin is rinsed, but not thoroughly dried

One Step Dentin Bonding

Etch/prime and adhesive in one bottle

2-Step Dentinal Bonding

Optibond solo

Prime and bond Primer and

Adhesive combined May take longer

than 3-step systems

3-Step Dentin Bonding

Etch Apply primer – wetting agent Apply adhesive – low viscosity resin Place the composite

Deep cavities – may use protective material to protect pulp from irritation

Polycarboxylate Cement

Chemically adhesive – ionic bonds between negative charge in cement and positive charge in tooth

Zinc oxide powder + polyacrylic acid dissolved in water = Polycarboxylate cement

Glass Ionomer Cements

Dentin surface “conditioned” with polyacrylic acid solution to remove smear layer and result in better bonding

No separate adhesive is used – chemically adhesive

Glass ionomers are the materials of choice for high caries risk & both dentin and enamel margins – fluoride-releasing

Glass Ionomer Material

Fuji Triage high-fluoride-release,

command-set glass ionomer

Suitable as a surface-protection

material for a root sensitivity.

Intermediate restorative material

for cases of rampant caries. It

light cures in 1 minute or can

self cure.

Desensitization

Gluma desensitizer