Enamel and Dentin Adhesion - Chapter 4

Enamel and Dentin Adhesion (2)

• Batterjee Medical College, a college for Science and Technology, is responsible for the presentation.
• The presenter is Dr. Rehab Alwakeb, from the Operative Dentistry Division.
• The presentation is based on Chapter 4, page 114 of the "Art and Science of Operative Dentistry" 6th edition.

Learning Objectives (ILOs)

• I: Differentiate between current strategies for resin adhesion to dentin.
• II: Discuss (with justification) the selection of the adhesive system appropriate for a prepared cavity.

Current Strategies for Adhesion of Resins to Dentin

• Contemporary adhesive systems include:
  • Etch-and-rinse systems (three-step)
  • Two-step systems
  • Self-etch systems (single-step, two-step)

Classification of Contemporary Adhesive Systems

• Diagrams illustrate the different steps and components (etchant, primer, bond resin, etc) of each system.

Three-Step Total Etch System

• The process involves acid-etching, rinsing, and then applying primer & adhesive.
• This creates etched dentin exposed collagen fibres.
• A composite is then applied.
• Formation of a hybrid layer & resin-tags results from this procedure.

Etchant, Primer, and Bonding Agent

• Etchant (E): Removes smear layer, exposes intertubular and peritubular collagen, and creates an accessible/decreased surface free energy.
• Primer (P): Includes bifunctional molecules (hydrophilic and hydrophobic), envelops external surface of collagen fibers and re-establishes free energy levels.
• Bonding agent (B): Contains hydrophobic monomers - Bis-GMA and hydrophillic monomers - HEMA, which then co-polymerize with the primer to create resin tags & hybrid layers that infiltrate into the intertubular spaces.

Two-Step Etch-and-Rinse (E+PB) System

• Rationale: Simplifies bonding procedure.
• Examples:
  • One-Step Plus (Bisco)
  • Prime & Bond NT (Dentsply Caulk)
  • Adper Single Bond Plus (3M ESPE)
  • OptiBond SOLO Plus

Drawbacks of Total Etch System

• Excessive Drying: Removing moisture via air drying during the rinsing phase results in collagen fiber network collapse, and prevents resin monomers from penetrating into the dentin.
• Excessive Wetting: Pooled moisture (excess water) dilutes the primer, resulting in reduced effectiveness.

Methods for Removing Excess Water After Rinsing

• Damp cotton pellet
• High-volume suction
• Disposable brush
• Laboratory tissue paper

Self-Etching Adhesives

• Described as non-rinsing conditioners.
• Two-types:
  • Two-step self-etching adhesives
  • One-step self-etching adhesives

2-Step Self-Etching Adhesives

• These systems do not necessitate rinsing
• The systems comprise self-etching primer, followed by application of adhesive & composite.
• No rinsing is needed.

Advantages of Self-Etching Adhesives Compared to Total Etch Systems

• Simplified Technique: Less technique sensitive
• No rinsing/drying steps
• Less post-operative sensitivity

One-Step Self-Etch Systems

• Contain all components in one bottle.
• Act as semi-permeable membranes.
• Do not provide an airtight seal for the vital deep dentin.

Overcoming Problems with Self-Etch Systems

• Use a hydrophobic binding layer on top of the self-etch system.
• Apply a thin layer of composite flowable liner.

SEP Classification

• SEPs (self-etch primers) are categorized by pH level:
  • Mild and ultra-mild
  • Moderate
  • Aggressive

Universal Adhesives

• Bond to various substrates in addition to dentin
  • Indirect ceramics, and resin-based restorations
• Considered moderate/mild self-etching.
• Enamel etching is mandatory.

Case-Based Discussion

• A 40-year-old patient seeks treatment for food collecting in tooth #47, which exhibits severe occlusal caries and displays hard discolored dentin on the pulpal floor.
• Composite restoration is the treatment of choice.

Clinical Questions

• Several patient cases are presented for which the best adhesive system must be identified and defended.