Sistemas Adesivos e Adesão - Adesão ao Esmalte

Adhesion to Enamel in Adhesive Systems

In this section, the composition of enamel is discussed before delving into the adhesion process. Enamel is primarily composed of inorganic substances, making it a relatively homogeneous tissue.

Composition of Enamel

• Enamel consists mainly of calcium phosphate crystals in the form of hydroxyapatite, with traces of sodium, potassium, fluoride, magnesium, carbonate, and chloride.

• Approximately 97% of enamel is inorganic, leading to its brittle nature despite being hard.

Adhesion Technique to Enamel

• Conventional adhesive systems involve acid conditioning with phosphoric acid application for around 30 seconds to demineralize the enamel surface.

• Acid treatment creates microporosities on the enamel surface, enhancing adhesive wetting for better adhesion efficiency.

Application Process for Adhesion on Enamel

This section details the steps involved in applying adhesives to enamel surfaces after acid conditioning.

Post-Acid Conditioning Steps

• After acid conditioning exclusively on enamel cavities, drying the surface with air results in a milky opaque appearance due to microporosities created by demineralization.

• Application of adhesive or primer-adhesive (for two-step conventional systems) penetrates these microporosities followed by photopolymerization for micro-mechanical bonding.

Demonstration: Adhesion Process on Enamel Cavities

A practical demonstration illustrating the adhesion process specifically on enamel cavities using conventional adhesive systems.

Application Procedure

• Apply phosphoric acid on the cavity area for about 30 seconds before rinsing thoroughly to remove desmineralization by-products.

• For three-step conventional systems post-acid conditioning involves primer application before adhesive; unnecessary when solely bonding to enamel.

Adhesive Systems: Self-Etch Approach

Exploring self-etch adhesive systems that eliminate separate acid conditioning steps by incorporating acidic primers directly onto enamel surfaces.

Self-Etch Application

New Section

In this section, the application of a two-step self-etching system in enamel is discussed, emphasizing the use of acid primer and adhesive without rinsing between steps.

Application of Two-Step Self-Etching System

• The first step involves applying Acid Primer to the enamel surface without photopolymerization.

• In a two-step self-etching system, there is no washing involved at any stage; it is not rinsed with water after each step.

New Section

This part focuses on the process of photopolymerization following the application of adhesive in systems with self-conditioning properties.

Photopolymerization Process

• After applying the adhesive in systems with self-conditioning properties where adhesive is present, photopolymerization takes place similar to conventional adhesive systems.

New Section

A comparison between the acidic primers' effectiveness in self-conditioning systems versus conventional systems regarding adhesion strength is highlighted.

Comparison of Acidic Primers

• Acidic primers have lower effectiveness in self-conditioning systems compared to conventional systems where acid is a separate step.

New Section

The importance of additional phosphoric acid application on enamel before using primers and adhesives in cavity preparations involving enamel is emphasized.

Importance of Phosphoric Acid Application

• It is recommended to apply phosphoric acid on enamel as an additional step before using primers and adhesives in cavity preparations involving enamel when utilizing self-conditioning systems.