From THE DENTAL ADVISOR: Bonding agents overview

Dental bonding agents continue to evolve. Both total-etch (4th- and 5th-generation) and self-etch (6th- and 7th-generation) bonding systems are in use. New bonding systems include self-etching products with dual-cured capabilities as well as simplified total-etch systems.

This issue of THE DENTAL ADVISOR reports the characteristics and compares 65 bonding agents. Clinical tips are given for a number of clinical techniques for restorative procedures requiring bonding. Effects of contamination on bond strengths to dentin are also discussed.

Types

4th-generation

• Multiple bottles
• Separate etching with phosphoric acid — called total-etch or etch and rinse
• Separate primer and adhesive
• Both light- and dual-cured formulations
• Either acetone or ethanol solvent

5th-generation

• Single bottle or unit dose
• Separate etching with phosphoric acid — called total-etch or etch and rinse
• Combined primer and adhesive in one bottle
• Both light- and dual-cured formulations
• Either acetone or ethanol solvent

6th-generation (Type I, self-etching primer + adhesive)

• Two bottles, Liquid 1 — acidic primer, Liquid 2 — adhesive; acidic primer applied to tooth first, followed by adhesive
• No etching with phosphoric acid
• Light-cured formulation
• Water solvent
• Several products (Clearfil LINER BOND 2V, Nano-Bond, Prelude SE) have separate catalysts for dual curing
• Compatible with self-cured composites

6th-generation (Type II, self-etching adhesive)

• Two bottles or unit dose containing acidic primer and adhesive; a drop of each liquid is mixed and applied to the tooth
• No etching with phosphoric acid
• Light-cured formulation
• Water solvent

7th-generation

• Single bottle containing acidic primer and adhesive — no mixing
• No etching with phosphoric acid
• Light-cured formulation
• Water solvent
• Some products (Clearfil DC BOND, Futurabond DC, Xeno IV Dual Cure) have separate catalysts for dual curing

Glossary of terms

• Adhesive — resin used to bond the composite to the primed tooth surface.
• Dual-cured bonding agent — bonding agent that can be light-cured or self-cured.
• Etchant — typically phosphoric acid used to clean and demineralize the tooth surface, used primarily for 4th- and 5th-generation bonding agents.
• Inverted cone tensile test — test for measurement of tensile bond strength developed by Dr. John Powers at the University of Michigan in 1986.
• Light-cured bonding agent — use of a light-curing unit is required; bonding agents typically contain camphorquinone (CQ) as the polymerization photoinitiator.
• Modified smear layer — result of self-etching primers that modify and combine with the smear layer rather than removing it.
• Primer — hydrophilic monomer used to wet and penetrate the tooth surface.
• Self-cured bonding agent — bonding agent with catalyst that allows self curing without light activation.
• Self-etching (acidic) primer — primer with acid groups producing low pH that interact with tooth structure and resin adhesives.
• Smear layer — layer of tooth structure produced when enamel and dentin are ground with a diamond or carbide bur. This layer must be removed or modified for good bond strengths.
• Ultradent bond strength test — test for measurement of shear bond strength (SBS) developed by Ultradent Products.

To read more, including Contaminants, Core Materials, and Advances in Bonding Agents, visit www.dentaladvisor.com.