Fundamentals of Enamel and Dentin Adhesion

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Questions and Answers

What is a primary advantage of bonded tooth-colored restorations in restorative dentistry?

They eliminate marginal gaps between restoration and tooth structure. (correct)

They rely solely on mechanical retention.

They increase microleakage.

They require extensive tooth preparation.

Which mechanism of adhesion involves the formation of resin tags within the tooth surface?

Micro-Mechanical bonding (correct)

Adsorption

Thermal bonding

Chemical bonding

What characteristic must an adhesive have to promote good adhesion?

Low surface tension (correct)

High surface tension

Low viscosity

High contact angle

Which of the following is NOT a requirement for good adhesion?

The adhesive should have high surface energy. Signup and view all the answers

The term 'adherend' refers to which of the following?

The surface or substrate that is adhered to. Signup and view all the answers

What are the two main components involved in chemical bonding during adhesion?

Hydroxyapatite and type I collagen Signup and view all the answers

Which bonding mechanism is characterized by the chemical interaction with the tooth structure's components?

Adsorption Signup and view all the answers

What is one of the goals of having a bonded restoration in operative dentistry?

To minimize postoperative sensitivity. Signup and view all the answers

What is the preferred concentration of phosphoric acid used for acid etching enamel?

37% Signup and view all the answers

Which of the following statements about etched enamel is true?

It has increased surface free energy. Signup and view all the answers

What determines the bond strength of composite resins to etched enamel?

The development of resin tags. Signup and view all the answers

What is a common challenge when bonding to dentin compared to enamel?

Presence of filigree collagen fibers. Signup and view all the answers

What effect does acid etching have on enamel?

Creates micro-pores. Signup and view all the answers

Why are gel etchants preferred over liquid etchants for enamel bonding?

They provide better control in placement. Signup and view all the answers

After etching enamel, how long should the rinsing time be compared to the etching time?

Twice the etching time. Signup and view all the answers

What is the impact of the bond strength range of 20 to 50 Mpa in dental procedures?

Provides adequate retention for a variety of procedures. Signup and view all the answers

Study Notes

Fundamentals of Enamel and Dentin Adhesion

The presentation covers fundamental concepts of enamel and dentin adhesion.
A key reference is the "Art and Science of Operative Dentistry" 6th edition, chapter 4, page 114.
Learning objectives (ILOs) include understanding adhesion mechanisms of dental resins, determining enamel bonding procedures, identifying dentin adhesion challenges, and discussing current resin-dentin adhesion strategies.
Introduction: Adhesion is crucial for restorative materials. Bonded tooth-colored restorations offer advantages over traditional methods, eliminating the need for extensive preventive procedures like those developed by G.V. Black.
Bonded restorations encourage initial seal (preventing secondary caries), strengthening remaining tooth structure, and conservation (reducing mechanical preparation needed).

Basic Terminology

Adhesion/Bonding: The state where two surfaces are held together by interfacial forces (valence, interlocking, or both).
Adhesive: The bonding agent that joins surfaces, resists separation, and transmits loads across the bond.
Adherend: The surface or substrate to which the adhesive is applied.

Bonding Mechanisms

Micro-Mechanical: Resin penetration and creation of resin tags within tooth surfaces.
Adsorption: Chemical bonding with tooth's inorganic (e.g., hydroxyapatite) or organic components (primarily type I collagen).
These mechanisms often work in combination.

Requirements for Good Adhesion

Surface Energy: Tooth surfaces need to be clean and wettable with high surface energy for proper adhesion.
Low Surface Tension: Adhesion products should have low surface tension to effectively spread on the surface, having a low contact angle.
Intimate Adaptation: A close fit between the adhesive and the tooth surface is necessary.
Polymerization: The adhesive material needs proper curing/polymerization to strengthen the bond.
Strong Bond Strength: Sufficient bond strength between the adhesive and the tooth surface is needed to resist de-bonding.

Bonding to Enamel

Acid Etching: A critical step in enamel bonding; it creates micropores on the enamel surface, increasing surface energy, allowing for strong resin tags formation. Buonocore introduced it in 1955.
Acid Concentration: Currently, 37% phosphoric acid is the preferred concentration.
Etching Time: 15 seconds is the recommended etching time.
Rinsing Time: The rinsing time should be double the etching time, using a continuous stream of air-water spray.
Application Technique: Acid etchants may be available in liquid or gel forms; gel forms are more commonly preferred for improved control during application.
Bonding Agents: These agents flow into the microporosities and, upon light activation, form resin tags that lock them into the tooth surface. Bond strength usually ranges from 20 to 50 MPa.

Bonding to Dentin

Challenges Compared to Enamel: Dentin has significantly less mineral content and higher water content than enamel; water content significantly impacts bonding.
Microstructure: Dentin tubules increase in size going from the outer to the inner aspects, potentially reducing bond strength in deeper sections. Dentin is considered a dynamic tissue, able to change due to aging, cavities or even restorative interventions (such as sclerotic dentin that resist etching).
Smear Layer: A layer of debris and denatured collagen forms on cut dentin surfaces. This smear layer inhibits bonding by decreasing dentin permeability by 85%, blocking access for adhesives.

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Description

This quiz explores the foundational concepts of enamel and dentin adhesion, as outlined in chapter 4 of 'Art and Science of Operative Dentistry'. Participants will learn about adhesion mechanisms, enamel bonding procedures, and current strategies for resin-dentin adhesion. Understanding these principles is essential for advancing restorative dentistry practices.