Introduction to Amalgam Restorations
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Questions and Answers

What is dental amalgam primarily composed of?

  • Gold and platinum
  • Tin and lead
  • Composite resin and glass ionomer
  • Silver-tin-copper alloy and mercury (correct)

What is a disadvantage of using dental amalgam for restorations?

  • Low long-term clinical success
  • Non-esthetic appearance (correct)
  • High wear resistance
  • Reduced strength

In which of the following scenarios is dental amalgam typically indicated?

  • Small cavities in lower incisors
  • Large cavities in posterior teeth (correct)
  • Restorations for mercury-sensitive patients
  • Esthetic restoration in anterior teeth

Which property of dental amalgam is characterized by its long-term clinical results?

<p>Excellent wear resistance (C)</p> Signup and view all the answers

What classification of dental amalgam typically requires less condensation?

<p>Spherical alloy (A)</p> Signup and view all the answers

Which of the following is NOT a contraindication for using dental amalgam?

<p>Large cavities (A)</p> Signup and view all the answers

Which characteristic of dental amalgam is primarily related to its setting reaction?

<p>Formation of a stable phase (C)</p> Signup and view all the answers

Which dental amalgam classification is known for easier carving but may lead to improper proximal contacts?

<p>Lathe-cut alloy (B)</p> Signup and view all the answers

What is a significant consequence of excessive corrosion in dental amalgam?

<p>Loss of strength (D)</p> Signup and view all the answers

How do high copper alloys compare to low copper alloys in terms of creep and flow?

<p>Less creep and flow (C)</p> Signup and view all the answers

Which property of high copper alloys contributes to their dimensional stability?

<p>Low dimensional changes (C)</p> Signup and view all the answers

Which of the following statements regarding tarnish and corrosion in amalgam is correct?

<p>High copper alloys have better corrosion resistance. (C)</p> Signup and view all the answers

In terms of tensile strength, how do low copper alloys compare to high copper alloys?

<p>Low copper alloys exhibit the lowest tensile strength. (D)</p> Signup and view all the answers

What effect does the presence of $ ext{γ}2$ in low copper amalgam have on creep?

<p>Increases the creep (D)</p> Signup and view all the answers

Which dimensional change occurs first when mercury is combined with amalgam alloy?

<p>Initial contraction (A)</p> Signup and view all the answers

How does under-trituration affect amalgam?

<p>Leads to amalgam expansion (A)</p> Signup and view all the answers

What is the coefficient of thermal expansion for low copper amalgam at 37 ℃?

<p>19.7 $ ext{μm/cm}$ (B)</p> Signup and view all the answers

What can happen if zinc-containing alloy is contaminated with moisture during manipulation?

<p>Gradual expansion of amalgam over time (B)</p> Signup and view all the answers

What is a common visual sign of tarnish on dental amalgam?

<p>Surface appearing dull (C)</p> Signup and view all the answers

What is the primary consequence of high mercury content in amalgam?

<p>Increases expansion of the restoration (A)</p> Signup and view all the answers

What can occur due to delayed expansion in zinc-containing amalgam?

<p>Post operative sensitivity (D)</p> Signup and view all the answers

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

<p>300-500 MPa (D)</p> Signup and view all the answers

Which type of amalgam has the lowest tensile strength?

<p>Low copper amalgam (D)</p> Signup and view all the answers

How much strength does amalgam lose when the temperature rises to 60°C in the mouth?

<p>50% (A)</p> Signup and view all the answers

Which factor affects the strength of amalgam by altering the trituration process?

<p>Amalgamator speed (A)</p> Signup and view all the answers

What is the modulus of elasticity range for amalgam?

<p>20-50 GPa (D)</p> Signup and view all the answers

What can lead to amalgam flowing beyond the margin during setting?

<p>Creep (D)</p> Signup and view all the answers

Which amalgam type exhibits the highest early tensile strength?

<p>High copper amalgam (C)</p> Signup and view all the answers

Low mercury content in amalgam may result in which issue?

<p>Rough and pitted surface (D)</p> Signup and view all the answers

What characterizes a low copper alloy?

<p>Less than 6% Cu (B)</p> Signup and view all the answers

Which component in dental amalgam contributes to an increase in strength and tarnish resistance?

<p>Copper (Cu) (D)</p> Signup and view all the answers

Which phase in the low copper amalgam setting reaction is the weakest?

<p>Gamma 2 (D)</p> Signup and view all the answers

What role does zinc play in dental amalgam?

<p>Prevents oxidization of other metals (B)</p> Signup and view all the answers

In high copper amalgam, what is the product formed when Ag-Cu reacts with SnHg?

<p>AgHg + CuSn (D)</p> Signup and view all the answers

What is the primary property measured by compressive strength in dental amalgam?

<p>Ability to withstand force toward an object (A)</p> Signup and view all the answers

Which of the following is true regarding high copper amalgam versus low copper amalgam?

<p>High copper amalgam has additional phases such as Ag-Cu. (D)</p> Signup and view all the answers

What effect does tin (Sn) have on the properties of dental amalgam?

<p>Increases flow and creep, decreases strength (B)</p> Signup and view all the answers

Flashcards

Dental Amalgam Restoration

A metallic restorative material made of a silver-tin-copper alloy mixed with mercury. It's used to fill cavities and restore tooth function.

Amalgam Advantages

Easy to use, strong, resists wear, and has a good track record.

Amalgam Disadvantages

Not aesthetic, less conservative (removes more tooth structure), not insulating, and more difficult tooth preparation.

Amalgam Indications

Posterior teeth, large cavities, areas with limited moisture control, and core buildup for crowns.

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Amalgam Contraindications

Anterior teeth (esthetic areas), mercury sensitivity, small cavities.

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Amalgam Composition

Silver-tin-copper alloy mixed with mercury.

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Amalgam Classification (particle shape)

Amalgam fillings are categorized based on the shape of the particles like spherical, lathe-cut, and admix.

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Amalgam Classification (Use)

Amalgam type determines where in the mouth it's best placed (i.e for large or small cavities, anterior or posterior areas).

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Low copper amalgam setting reaction

The chemical reaction of silver-tin with mercury to form different phases including silver-tin, silver-mercury, and tin-mercury.

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High copper amalgam setting reaction

The chemical reaction between silver-tin, silver-copper and mercury, forming silver-tin, silver-mercury, tin-mercury, and silver-copper phases.

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Dental amalgam properties

Amalgam's characteristics like compressive strength, tensile strength, and resistance to corrosion and tarnish.

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Low copper alloy

An alloy with less than 6% copper content.

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High copper alloy

An alloy with more than 12% copper content.

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Zinc containing alloy

An alloy with more than 0.01% zinc content.

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Zinc free alloy

An alloy with 0.01% or less zinc content.

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Compressive strength

A material's ability to withstand pressure applied against it.

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Amalgam Compressive Strength

Amalgam's ability to resist crushing forces; typically 300-500 MPa after 7 days, varying by type.

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Amalgam Tensile Strength

Amalgam's resistance to pulling forces; relatively low, 48-60 MPa after 7 days, varying by amalgam type.

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Amalgam Modulus of Elasticity

Measure of amalgam's stiffness; 20-50 GPa, stiffer with higher copper content.

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Amalgam Creep & Flow

Amalgam's time-dependent deformation under static force; Flow happens during setting, Creep after.

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Temperature Effect on Amalgam Strength

Amalgam loses strength with increasing temperature; up to 50% loss in the mouth.

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Mercury Content and Amalgam Strength

High mercury decreases strength; low mercury can produce undesirable surface texture.

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Trituration and Amalgam Strength

Mixing method (trituration) affects strength; wrong mixing causes problems even in high/low copper amalgam.

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Condensation and Amalgam Strength

Amalgam packing method (condensation) impacts strength; different alloy types require different condensation techniques.

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Amalgam Corrosion

A process where the amalgam surface degrades due to chemical or electrochemical reactions with the environment. This leads to a weakened surface, increased porosity, reduced marginal integrity (sealing between the filling and tooth), loss of strength, and potentially harmful metal release.

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Amalgam Self-Sealing?

Amalgam does not self-seal. The material itself cannot fill and seal microscopic gaps that form at the restoration margin. This lack of self-sealing can lead to recurrent decay.

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High Copper vs. Low Copper: Strength

High copper amalgams have significantly higher compressive strength than low copper amalgams. This means they can withstand more pressure and are less likely to break.

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High Copper vs. Low Copper: Tarnish & Corrosion

High copper amalgams are more resistant to tarnish and corrosion compared to low copper amalgams. This means they maintain a cleaner surface and last longer.

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Corrosion Outcomes

Corrosion of amalgam can lead to multiple problems: increased porosity, weakened margins, reduced strength, and release of metal ions into the mouth. These issues can affect the filling's lifespan and even impact oral health.

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Amalgam Creep

The tendency of amalgam to deform slowly over time under pressure, like a slowly spreading blob of toothpaste. It can weaken the restoration and cause gaps around the filling.

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High Copper vs. Low Copper Amalgam Creep

High copper amalgam has lower creep than low copper amalgam. This is because high copper amalgam has less of the 𝛾2 phase, which makes amalgam prone to creep.

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Amalgam Manipulation on Creep

Proper condensation pressure and trituration time during manipulation reduce creep in high copper amalgam.

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Amalgam Dimensional Changes

Amalgam can expand or contract due to temperature changes or chemical reactions. This change in size can affect the fit and strength of the filling.

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Amalgam Dimensional Change Mechanism

When mercury combines with amalgam alloy, it undergoes three dimensional changes: initial contraction, expansion, and limited delayed contraction.

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Delayed Expansion

If zinc-containing amalgam is contaminated with moisture, it can lead to gradual expansion of the amalgam days after setting. This can cause problems like sensitivity, occlusal interference, and gaps around the filling.

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Mercury Content vs. Expansion

High mercury content makes the amalgam more likely to expand.

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Trituration and Condensation effects on Amalgam

Under-trituration leads to amalgam expansion, while over-trituration causes amalgam contraction. Similarly, less condensation pressure leads to expansion.

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Study Notes

Introduction to Amalgam Restorations

  • Amalgam is a metallic restorative material composed of silver-tin-copper alloy and mercury
  • The unset mixture is pressed (condensed) into a cavity and contoured to restore tooth form and function
  • It's used as a direct filling material due to its mechanical properties, low cost, and easy placement

Lecture Objectives

  • Define dental amalgam restoration
  • List advantages, disadvantages, indications, and contraindications of amalgam restoration
  • Identify amalgam classifications
  • Identify amalgam composition
  • Explain the amalgam setting reaction
  • Describe amalgam properties

Advantages

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

Disadvantages

  • Non-esthetic
  • Less conservative (more tooth structure removal)
  • Non-insulating
  • More difficult tooth preparation
  • Environmental concern

Indications

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

Contraindications

  • Esthetic areas (anterior teeth)
  • Mercury-sensitive patients
  • Small cavities
  • If composite restoration offers a better, more conservative restoration

Amalgam Classification

  • Classification based on particle shape (spherical, lathe-cut, admix)
  • Classification based on copper content (low copper, high copper)
  • Classification based on zinc content (zinc-containing, zinc-free)

Amalgam Composition

  • Silver (Ag): Increases strength, resists tarnish and corrosion
  • Tin (Sn): Decreases strength, increases flow and creep
  • Copper (Cu): Increases strength, resists tarnish and corrosion
  • Zinc (Zn): Prevents oxidization of other metals, increases strength and creep resistance

Amalgam Setting Reaction

  • Low copper amalgam (conventional): AgSn + Hg → AgSn + AgHg + SnHg
  • High copper amalgam: AgSn + Ag-Cu + Hg → AgSg + AgHg + SnHg + Ag-Cu

Amalgam Properties

  • Compressive strength: The ability to withstand force toward an object; higher in high-copper amalgam. (300 - 500 MPa)
  • Tensile strength: The ability to withstand force lateral to an object; lower in low-copper amalgam compared to high-copper (48-60 MPa)
  • Modulus of elasticity: Measurement of material stiffness. (20-50 GPa)
  • Creep & Flow: Time-dependent plastic deformation under static load; higher in low-copper amalgam
  • Dimensional changes: Changes in shape and dimensions under heat or chemical reaction; greatest in low-copper amalgam (19.7 µm/cm)
  • Tarnish & Corrosion: Discoloration or chemical/electrochemical process of metal dissolution due to environmental attack; can lead to porosity, loss of strength, and releasing metal products.

Factors Affecting Amalgam Strength

  • Temperature: Significant strength loss with increased temperature
  • Mercury content: Higher mercury content leads to decreased strength; lower mercury levels can produce a rough surface
  • Trituration: Under- or over-trituration affects strength regardless of copper content
  • Condensation: Type of alloy determines condensation pressure requirements for optimal compressive strength

Factors Affecting Amalgam Creep

  • Amalgam composition: Presence of zinc in low-copper amalgam increases creep
  • Amalgam manipulation: Proper condensation and trituration time reduces creep in high-copper amalgam

Factors Affecting Amalgam Dimensional Changes

  • Mercury content: High mercury content leads to high expansion
  • Trituration: Under-trituration causes expansion, while over-trituration causes contraction
  • Condensation: Lower condensation pressure leads to expansion

Additional Information

  • Amalgam may have self-sealing ability; filling the gap between tooth/restoration over time—likely due to creep and corrosion products
  • Amalgam restorations can corrode in the oral environment. This corrosion can trigger galvanic action, leading to ion release.

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Related Documents

Amalgam Part 1 PDF

Description

This quiz covers the essential aspects of dental amalgam restorations, including their composition, properties, advantages, and disadvantages. Learners will explore indications for use and the setting reaction involved in the restoration process. Understand the critical balance between practicality and aesthetics in dental care with amalgam.

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