Cariology Lecture 11

Dr. Michael Buonocore

American dentist and researcher

Worked at Eastman in Rochester

Focused on improving restorative retention

What did restorations rely on before adhesives?

Mainly mechanical retention (undercuts grooves)

Why was reliance on mechanical retention bad?

Led to unnecessary removal of sound tooth structure

What was wrong with early acrylic resins?

Poor retention and marginal leakage

Buoncores paper in 1955

A simple method of increasing the adhesion of acrylic filling materials to enamel surfaces

What did Buonocore introduce in 1955?

Acid etching with phosphoric acid

What does acid etching do?

Creates microporosities in enamel for resin retention

Increases surface energy and roughness

What are characteristics of adhesive resin?

Low viscosity resin penetrates microporosities

Polymerized resin tags form micromechanical bonds

Provides foundation for restorative resin

What was resin’s impact on dentistry?

Reduced need for aggressive cavity designs

Enabled conservative dentistry

Foundation for bonding systems and composites

Basis for modern adhesive protocols

What is the cornerstone of adhesive dentistry?

Acid etching

What was the inspiration behind adhesive dentistry?

By observing how paint adhered better to boat hulls when the surface was roughened or primed

How is bonding to enamel achieved?

By etching to create microporosities filled with resin tags

How is bonding to dentin achieved?

By hybrid layer formation

Resin infiltration into demineralized collagen

What do adhesives rely on?

Both micromechanical interlocking and chemical interaction in some systems

How many adhesive process classifications?

3

How many types of etch and rinse are there?

Two

Three step and two step

What is etch and rinse (total etch)?

Separate phosphoric acid etching step

What are the steps in three step etch and rinse?

Etch

Primer

Adhesive

What are the steps of two step etch and rinse?

Etch

Primer and adhesive combined

What is self etch?

Acidic primer/adhesive etches and primes simultaneously

How many types of self etch?

Two

Two step and one step

What are the steps of two step self etch?

Self etch primer

Adhesive

What is the step in one step self etch?

All in one etch, prime, and bond

What are universal/multimode adhesives?

Can be used as etch and rinse, self etch, or selective etch

Etch and rinse systems

Widely used and highly reliable for enamel bonding

Separate phosphoric acid etching ensures strong enamel micromechanical retention

What are the challenges of etch and rinse systems?

Technique-sensitive on dentin

Risk of over etching and sensitivity

What is etch and rinse system best for?

Situations requiring strong enamel margins like Class IV, Class II, and occlusal margins

Self etch systems

Simplify procedure by combining etching and priming

Less aggressive on dentin, reducing risk of sensitivity

Bonding to enamel may be weaker compared to etch and rinse

Mild self-etch adhesives preserve hydroxyapatite for chemical bonding

Useful in cases with more dentin exposure and less enamel margin

Universal adhesives

Most versatile

Contain functional monomers (MDP) for chemical bonding to hydroxyapatite and metals

Compatible with direct and indirect restorations

Selective enamel etching recommended for optimal enamel bond strength

Simplifies inventory and improves clinical flexibility

How long do you do selective etching with phosphoric acid on enamel?

15-30 seconds

How long do you do selective etching with phosphoric acid on dentin?

15 seconds

Do you want dentin dry?

No, slightly moist for etch and rinse

What does etch do?

Causes selective dissolution of enamel, leading to a porous surface

Cleanses enamel of tenacious debris leading to better wetting

Increases surface energy of enamel allowing the resin to readily wet the surface

Who introduced bonding to dentin in 1978?

Fusayama

When did dentin bonding gain international popularity?

In the early 1990s

Was dentin bonding successful from the start?

No

It went through tremendous developing to become effective

What is the percentage of inorganic content in dentin?

70%

What is the percentage of organic content in dentin?

20%

What is the percentage of water content in dentin?

10%

What tooth structure has tubules?

Dentin

What are primers?

Adhesion promoting agents

Contain hydrophilic monomer and solvent

How is the hybrid layer formed by a primer?

The solvent displaces the water in the dentin structure carrying with it the monomer

How does primer allow chemical bonding to the adhesive resin layer?

Priming transfers they hydrophilic surface of dentin into a hydrophobic structure

What is adhesive resin?

A low viscosity resin that stabilizes the hybrid layer and forms the resin tags

The resin tags are microscopic projections that extend into the dentinal tubules and has major role in the bonding procedure

How can microleakage be prevented?

Prevented by proper etching, bonding, and curing

How to minimize postoperative sensitivity

By avoiding over etching dentin and ensuring adequate adhesive penetration

How to prevent adhesive failure

By strict adherence to manufacturers protocol

How to prevent wear enamel bond

By selective enamel etching when using self etch or universal adhesives

How to avoid contamination by saliva or blood

Rubber dam isolation