Principles of Bonding (Ch. 5) 2025(1)

Principles Of Bonding

• Chapter 5 by Samantha Kelley CDA, RDH M.Ed, Associate Professor.

Learning Objectives

• List the uses of dental bonding.

• Define adhesion and its relation to dental bonding.

• Describe the role and components of bonding agents.

• Summarize mechanical adhesion in dental bonding.

• Discuss factors that interfere with bonding.

• Summarize basic steps of bonding.

• Define "smear layer" and its effect on dentin bonding.

• Discuss effects of acid etching on enamel and dentin.

• Evaluate bond strength and durability.

• Compare self-etch vs total-etch systems.

• Identify bonding systems with least post-operative sensitivity.

• Discuss differences in bonding to enamel, dentin, metal, and porcelain.

Adhesion

• Definition: The process of sticking two materials together.

• Types in Dentistry:

  • Mechanical Adhesion

  • Chemical Adhesion

Bonding

• Definition: Attaching restorative materials to the tooth via adhesion.

• Uses in Dentistry:

  • Cosmetic Resolutions (Veneers, Crowns, Bridges, Composite Resin)

  • Attachment of orthodontic brackets

  • Fixed retainers

Resin Bonded Bridges

• Types:

  • Maryland Bridge (with retainers or wings)

  • Traditional Fixed Bridge (with pontic and abutment).

Preparation of Materials

• Dental bonding is a multi-step process requiring pre-gathered materials.

Bond Strength

• Measurement:

  • Tensile force (pull apart).

  • Shearing force (90-degree applied force).

• Units: Measured in megapascals (MPa).

• Comparison: Enamel bonding shows high strength; dentin is weaker due to its composition.

Bond Durability

• Definition: Longevity of the bond in a moist environment.

• Influencing Factors:

  • Degradation of the bonding agent over time.

  • Forces of mastication and aging.

  • Coefficient of thermal expansion (CTE) causing fatigue failure.

  • Shrinkage of composite as it polymerizes, creating stress.

The Role of Chlorhexidine

• Enzymes in dentin may break down resin bond.

• Chlorhexidine tested as an enzyme inhibitor.

• Further studies are needed before clinical implementation.

Step 1: Tooth Preparation

• Essential for a strong bond:

  • Remove plaque/debris (using slurry of pumice)

  • Rinse thoroughly

  • Isolate tooth with a rubber dam.

Step 2: Acid Etch

• Purpose: Remove minerals from the surface to create a high-energy surface for improved wettability.

• Use of Phosphoric Acid: 10%-38% solution.

Wettability

• Wettable surfaces allow liquid to spread; non-wettable surfaces exhibit beading.

Acid Etch Process

• Types: Liquid or gel; rinsing times vary (5-30 seconds).

• Use of coloring agents aids visibility during the etching process.

Total Etch vs Self Etch

• Total Etch: Separate etching step, highly durable but may increase sensitivity.

• Self-Etch: Combines etchant with other components, simplifies process, reduces sensitivity.

Step 3: Application of Bonding Agent

• Components: Primer and adhesive (single-step systems available).

• Primer: Low viscosity resin; penetrates porosities created during etching.

• Adhesive: Chemically bonds to primer, enhances retention with restorative materials.

Step 4: Procedure-Specific

• Adapts based on the type of restoration (e.g., composite resin vs resin cement).

Tooth Structure Considerations

• Differences in mineral content between enamel/dentin affect bonding techniques.

Enamel Etching

• Removes surface portion, creates porosities.

• Rinse thoroughly, drying reveals a frosty surface appearance.

Dentin Bonding Challenges

• Higher water content leads to less mineralization.

• Smear layer occludes tubules; requires removal/modification for effective bonding.

• Over-etching and over-drying lead to weak bonds due to collagen fiber collapse.

Importance of Primer in Dentin Bonding

• Hydrophilic components penetrate wet dentin; hydrophobic components bond to resins above.

Contamination Prevention

• Isolation during procedures crucial; saliva/blood can alter bond strength.

• Maintain awareness of external factors (astringents, whitening agents, fluoride).

Microleakage

• Leakage occurs where restorations don't seal properly, leading to recurrent decay and failure.

• Percolation due to shrinkage of materials, allowing fluids/bacteria ingress.

Post-Operative Sensitivity

• Causes include trapped air in tubules, over-etching, and improper restoration placement.

• Self-etch systems generally reduce sensitivity.

Summary Questions

• Why use bonding?

• Importance of etching?

• Main differences between enamel and dentin procedures?

• Types of bonding systems?

• How to prevent contamination?

• What is microleakage and percolation?

• Key step to minimize post-operative sensitivity?

References

• Eakle, W. S., & Bastin, K. G. (2021). Dental materials: Clinical applications for Dental assistants and dental hygienists. Elsevier.

• Roberta Brown, CDA RDH MS

• Google images.