Amalgam Restoration in Dentistry

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Questions and Answers

Which property of high-copper amalgam is stated in the text?

Low compressive strength

Similar compressive strength to dentin (correct)

Low tensile strength

High tensile strength

What is the primary cause of initial contraction in amalgam shortly after trituration?

Formation of hydrogen gases

Growth of crystal matrix

Zinc oxide formation

Alloy particle dissolution in mercury (correct)

What is the main consequence of delayed expansion in amalgam due to moisture contamination?

Increased porosity

Pulpal pressure pain

Decreased strength

Protrusion of restoration out of the cavity (correct)

What problem may occur due to excessive corrosion of amalgam?

Release of metallic products into the oral environment Signup and view all the answers

When does delayed expansion in amalgam typically occur?

3-5 days after insertion Signup and view all the answers

What is the reason for the growth of crystal matrix leading to expansion in amalgam?

Formation and growth around alloy particles Signup and view all the answers

What is the main purpose of using silver in dental amalgam?

Increases strength and setting expansion Signup and view all the answers

Which component of dental amalgam reduces strength, hardness, and setting expansion?

Tin Signup and view all the answers

What role does copper play in dental amalgam?

Increases compressive strength and reduces flow Signup and view all the answers

Why is the presence of zinc in dental amalgam not always essential?

It causes delayed expansion if contaminated with moisture Signup and view all the answers

Which component of dental amalgam is the only pure metal that is liquid at room temperature?

Mercury Signup and view all the answers

What property of dental amalgam determines its classification based on particle size?

Particle size Signup and view all the answers

In which of the following situations might amalgam restoration be preferred?

Class 5 lesions in nonesthetic areas with limited access Signup and view all the answers

What is a contra indication for using amalgam as a dental restoration material?

Anterior teeth requiring esthetic concern Signup and view all the answers

What is a common reason for replacement of amalgam restorations?

Tooth fracture Signup and view all the answers

Why does amalgam not adhere to the tooth structure?

Poor adaptation to cavity walls Signup and view all the answers

What can lead to poor adaptation of amalgam to cavity walls?

Shallow preparations with thin section of amalgam placement Signup and view all the answers

What might cause porosity in an amalgam filling?

Contamination during placement Signup and view all the answers

What is the copper content percentage range for high copper alloys?

6-30% Signup and view all the answers

Which type of alloy particles needs more mercury (Hg) for condensation?

Lathe-cut variety Signup and view all the answers

What is the dominant form of amalgam particles in the admixed powder alloy mentioned?

Lathe-cut Signup and view all the answers

Which type of alloy results in the formation of gamma-two phase, leading to corrosion?

Low copper alloys Signup and view all the answers

Which type of amalgam has properties including less marginal breakdown and less susceptibility to corrosion?

High copper alloys Signup and view all the answers

Why do spherical type alloy particles require less mercury (Hg) for condensation?

They have a smooth surface Signup and view all the answers

What is the primary cause of marginal fracture of enamel or amalgam?

Delayed expansion causing high points in amalgam filling Signup and view all the answers

What can cause 'Amalgam Blues' as mentioned in the text?

Continuous leakage around filling Signup and view all the answers

Why is it important to avoid roundening the line angles during restoration?

To prevent marginal fracture of enamel or amalgam Signup and view all the answers

What is a possible consequence of bonding amalgam restoration with enamel and dentine?

Possible improvement in restoration durability Signup and view all the answers

Which factor may result in periodontitis or fracture of the filling or tooth after an amalgam filling?

Delayed expansion in zinc containing alloys Signup and view all the answers

How does inadequate pulp protection relate to post restorative pain according to the text?

It may give rise to pulpal hyperemia leading to pain Signup and view all the answers

Study Notes

Classification of Amalgam Alloys

Based on copper content:
- Low copper alloy (less than 6%)
- High copper alloy (more than 6-30%)
Based on zinc content:
- Zinc-containing (more than 0.01%)
- Non-zinc-containing (less than 0.01%)

Particle Size and Shape

Micro-cut: less than 10 microns
Fine-cut: 10-30 microns
Coarse-cut: greater than 30 microns
Lathe-cut (irregular shape)
Spherical type (smooth surface)
Admixed powder alloy (2/3 lathe-cut, 1/3 spherical)

Composition of Amalgam Alloys

Low copper alloys: Ag 63-70%, Sn 26-28%, Cu 2-6%, Zn 0-2%
High copper alloys: Ag 69%, Sn 17%, Cu 13%, Zn 1%

Properties of High Copper Alloys

Less marginal breakdown
Less susceptible to corrosion
Moderate to large restoration
Can be used for cuspal restorations
Suitable for teeth that act as abutments for removable devices
Suitable for Class 5 lesions in non-aesthetic areas

Contraindications of Amalgam

Anterior teeth where esthetics is a prime concern
Small to moderate classes I and II restorations that can be well isolated
Patients with a history of allergy to mercury or other amalgam components

Clinical Performance of Amalgam Restoration

Amalgam does not adhere to tooth structure
Failures of dental amalgam occur due to:
- Tooth fracture
- Recurrent caries
- Amalgam fracture
- Marginal breakdown

Reasons for Replacement of Amalgam

Recurrent caries due to contamination and poor condensation
Amalgam fracture due to shallow preparation and sharp internal line angles
Marginal breakdown due to incorrect cavosurface angle and delayed expansion

Post-Restorative Pain

Causes of post-restorative pain:
- High points in amalgam filling
- Delayed expansion in zinc-containing alloys
- Inadequate pulp protection
- Continuous leakage around filling
- Bonded amalgam restorations

Bonded Amalgam

Used to bond amalgam restoration to enamel and dentine
Reduces microleakage and post-operative sensitivity

History of Amalgam

Dentists used silver coins in filling and mixing with mercury
Amalgam has been the most used restorative material for over 175 years

Composition of Amalgam

Amalgam alloy (silver-tin alloy with varying amounts of copper and zinc)
Mercury (activates reaction and is the only pure metal liquid at room temperature)

Properties of Amalgam

Compressive strength of high-copper amalgam: 380-550 MPa
Tensile strength of high-copper amalgam: low
Dimensional changes:
- Initial contraction: small amount of contraction in the first half hour
- Expansion: due to formation and growth of the crystal matrix
- Delayed expansion: occurs 3-5 days after insertion and continues for months due to moisture contamination
Corrosion: disintegration of the outer surface leading to increased porosity, loss of strength, and release of metallic products

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Description

Explore the history and composition of dental amalgam, a common restorative material used by dentists for over 175 years. Learn about the process of mixing amalgam alloy with mercury to create fillings for defective teeth.