6 Operative Dentistry I: Amalgam Restoration

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary characteristic of low copper amalgam in comparison to high copper amalgam?

It requires less mercury content.

It has the lowest compressive strength. (correct)

It has higher compressive strength.

It exhibits greater tensile strength.

What happens to the strength of amalgam when the temperature increases from root temperature to mouth temperature?

Strength increases by 15%.

Strength decreases by 50%.

Strength remains unchanged.

Strength decreases by 15%. (correct)

Which factor is most likely to decrease the strength of amalgam by up to 50%?

High mercury content. (correct)

Lower temperature exposure.

Increased trituration time.

Low condensation pressure.

What is the range of tensile strength for amalgam after 7 days?

48-60 MPa Signup and view all the answers

What is the modulus of elasticity for amalgam compared to dentin?

Amalgam is less stiff than dentin. Signup and view all the answers

What effect does under-trituration or over-trituration have on amalgam?

Decreases the strength of the amalgam. Signup and view all the answers

Which type of amalgam has the lowest creep characteristics?

High copper amalgam. Signup and view all the answers

What is the primary concern associated with high mercury content in amalgam?

Decreased strength. Signup and view all the answers

What percentage of copper defines a high copper alloy?

More than 12% Signup and view all the answers

What is the main benefit of adding zinc to a dental amalgam?

Prevent oxidization of other metals in the alloy Signup and view all the answers

In the low copper amalgam setting reaction, what compound represents the weakest phase?

Gamma 2 Signup and view all the answers

What is dental amalgam primarily composed of?

Silver, tin, copper alloy, and mercury Signup and view all the answers

Which property of dental amalgam is defined by its ability to withstand forces applied toward it?

Compressive strength Signup and view all the answers

Which of the following is NOT an advantage of dental amalgam restoration?

Aesthetic appeal Signup and view all the answers

What is a primary contraindication for the use of dental amalgam?

Mercury-sensitive patients Signup and view all the answers

What is the primary consequence of adding copper to dental amalgam?

Increase in tarnish resistance Signup and view all the answers

Which classification of dental amalgam requires less condensation during use?

Spherical alloy Signup and view all the answers

Which component in dental amalgam is known to enhance flow and creep?

Tin (Sn) Signup and view all the answers

In which situation is dental amalgam most appropriately used?

Core build up for crowns Signup and view all the answers

How long does it take for dental amalgam to reach its specified compressive strength range of 300-500 Mpa?

After 7 days Signup and view all the answers

What is a disadvantage of dental amalgam regarding tooth preparation?

More difficult tooth preparation Signup and view all the answers

What characterizes a zinc containing alloy in dental materials?

More than 0.01% Zn Signup and view all the answers

Which type of dental amalgam is typically used for larger cavities?

Lathe-cut alloy Signup and view all the answers

What is the classification of dental amalgam based on particle shape?

Spherical, lathe-cut, and admix Signup and view all the answers

What effect does the presence of $ ext{γ}_2$ in low copper amalgam have on creep?

Increases the creep Signup and view all the answers

Which factor can lead to an increase in amalgam expansion during the setting process?

High mercury content Signup and view all the answers

How long does the initial contraction of amalgam occur after mixing?

20 minutes Signup and view all the answers

What is the main consequence of delayed expansion in zinc-containing alloys due to moisture contamination?

Post-operative sensitivity Signup and view all the answers

What happens if amalgam is under-triturated?

It will expand Signup and view all the answers

What is tarnish in relation to dental amalgam?

Discoloration due to chemical reaction Signup and view all the answers

If amalgam experiences high coefficients of thermal expansion, what might be a significant dimensional change threshold?

20 $ ext{μm/cm}$ Signup and view all the answers

What effect does proper condensation pressure have on high copper amalgam?

Decreases the creep Signup and view all the answers

Study Notes

Operative Dentistry I: Amalgam Restoration and Manipulation I

Lecture Objectives:
- Define dental amalgam restoration
- List advantages, disadvantages, indications, and contraindications of amalgam restoration
- Identify dental amalgam classifications
- Identify dental amalgam composition
- Explain dental amalgam setting reaction
- Describe dental amalgam properties

Introduction to Dental Amalgam

Definition: A metallic restorative material composed of a mixture of silver-tin-copper alloy and mercury.
Application: The unset mixture is pressed (condensed) into a prepared tooth cavity and contoured to restore the tooth's form and function.

Advantages of Amalgam Restoration

Ease of use
High strength
Excellent wear resistance
Favorable long-term clinical research results
Low cost

Disadvantages of Amalgam Restoration

Non-aesthetic
Less conservative (more tooth removal during preparation)
Non-insulating
More difficult tooth preparation
Environmental concern

Indications for Amalgam Restoration

Posterior teeth restorations
Large cavities
Areas with limited moisture control
Core build-up for crowns

Contraindications for Amalgam Restoration

Aesthetic areas (anterior teeth)
Mercury-sensitive patients
Small cavities
If composite restoration offers better conservative restoration

Amalgam Classification

Based on particle shape:
- Spherical alloy: Requires less condensation, easy carving, improper proximal contact, used in class I cavities
- Lathe-cut alloy: Requires more condensation, difficult carving, proper proximal contact, used in class II cavities
- Admix alloy: Combines advantages of spherical and lathe-cut alloys
Based on copper content:
- Low copper alloy: Less than 6% copper
- High copper alloy: More than 12% copper
Based on zinc content:
- Zinc-containing alloy: More than 0.01% zinc
- Zinc-free alloy: 0.01% or less zinc

Amalgam Composition

Silver (Ag): Increases strength and expansion, increases tarnish and corrosion resistance
Tin (Sn): Decreases strength and expansion, increases flow and creep
Copper (Cu): Increases strength, increases tarnish and corrosion resistance
Zinc (Zn): Prevents oxidation of other metals, increases strength and creep resistance
Components: Alloy powder particles and mercury form the matrix and unreacted alloy particles, forming the reacted layer

Amalgam Setting Reaction

Low copper (conventional): AgSn + Hg → AgSn + AgHg + SnHg
High copper: AgSn + Ag-Cu + Hg → AgSg + AgHg + SnHg + Ag-Cu
- formation of gamma1 (strongest), gamma2 (weakest) and phases

Dental Amalgam Properties

Compressive Strength: Ability to withstand force loaded towards an object. Amalgam has high compressive strength (300-500 MPa after 7 days), influenced by amalgam type
Tensile Strength: Resistance to lateral force (stretching). Amalgam has low tensile strength (48-60 MPa after 7 days), influenced by amalgam type.
Modulus of Elasticity: Measurement of material stiffness. Amalgam (20-50 GPa) compared with dentin (15-20 GPa), composite (17-22 Gpa), and enamel (50-80 GPa)
Creep & Flow: Time-dependent plastic deformation under static load. Flow measured during setting, creep after. Creep leads to flow at the margin. High copper amalgam has lower creep than low copper amalgam
Dimensional Changes: Property of a material to change shape and dimensions under heat or chemical reaction. Amalgam has high dimensional changes and high coefficient of thermal expansion. Highest in low copper amalgam (19.7 µm/cm).
Tarnish & Corrosion: Process of surface discoloration (tarnish) or metal dissolution (corrosion) in the oral environment. Tarnish can progress to corrosion; causes mechanical failure. Excessive corrosion increases porosity, reduces marginal integrity, and lowers strength
Factors Affecting Amalgam Creep: Amalgam composition(presence of gamma phase in low copper), manipulation(condensation pressure and trituration time), which reduce creep in high copper amalgam

Factors Affecting Amalgam Dimensional Changes

Mercury Content: High mercury content leads to high expansion
Trituration: Under-trituration leads to expansion, over-trituration leads to contraction
Condensation: Less condensation pressure leads to expansion

References:

Sturdevant Art and Science of Operative Dentistry (Chapter 13 "Introduction to Amalgam Restorations," Chapter, 18 "Biomaterials")

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

This quiz explores the fundamental aspects of dental amalgam restoration, including its definition, advantages, disadvantages, and classifications. Participants will assess their understanding of amalgam properties and its setting reaction. Perfect for students of Operative Dentistry I.