Adhesive Dentistry

Definition

Adhesive Dentistry refers to the procedures involved in joining dental materials to tooth structure (enamel and dentin) through chemical and micromechanical forces. This approach allows for the preservation of healthy tooth structure, as it does not require the extensive "undercut" preparations needed for traditional materials like Amalgam.

Core Concepts

Enamel Bonding

Enamel bonding is achieved through Acid Etching (typically with 37% phosphoric acid). This process removes about 10 microns of the enamel surface and creates microporosities. When a low-viscosity resin (bonding agent) is applied, it flows into these pores, creating Resin Tags that provide a powerful mechanical bond.

Dentin Bonding and the Hybrid Layer

Bonding to dentin is challenging because dentin contains significant water and organic Collagen.

Hybrid Layer: Formed when the adhesive resin infiltrates the demineralized collagen network of the dentin.
Smear Layer: A layer of debris created during tooth preparation that must be either removed or modified to achieve a successful bond.

Bonding Strategies

Current adhesive systems are categorized by how they handle the tooth surface:

Etch-and-Rinse (Total Etch): A separate phosphoric acid step is used to etch both enamel and dentin. It provides the strongest bond to enamel but can lead to post-operative sensitivity if the dentin is over-dried.
Self-Etch: Uses acidic primers that etch and prime simultaneously. This creates a thinner hybrid layer but significantly reduces sensitivity by not fully exposing the dentinal tubules.
Universal Adhesives: Multimode systems that allow the clinician to choose the etching strategy based on the specific clinical situation.

Clinical Applications

Adhesive dentistry is the foundation for:

Composite Resins (Fillings)
Dental Veneers
Inlays and Onlays
Bonded Dental Bridges (Maryland Bridges)

Factors Affecting Bond Strength

Moisture Control: Contamination by saliva or blood is the leading cause of bond failure. The use of a Rubber dam is highly recommended.
Curing Light Intensity: Proper polymerization of the resin is critical for long-term stability.
Material Compatibility: Ensuring the adhesive is compatible with the restorative resin or cement.