DHYG 113 Restorative Dentistry I 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 Reduction of microleakage 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 Biofilms – contaminated by oral fluids 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