Podcast
Questions and Answers
Which property of high-copper amalgam is stated in the text?
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?
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?
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?
What problem may occur due to excessive corrosion of amalgam?
When does delayed expansion in amalgam typically occur?
When does delayed expansion in amalgam typically occur?
What is the reason for the growth of crystal matrix leading to expansion in amalgam?
What is the reason for the growth of crystal matrix leading to expansion in amalgam?
What is the main purpose of using silver in dental amalgam?
What is the main purpose of using silver in dental amalgam?
Which component of dental amalgam reduces strength, hardness, and setting expansion?
Which component of dental amalgam reduces strength, hardness, and setting expansion?
What role does copper play in dental amalgam?
What role does copper play in dental amalgam?
Why is the presence of zinc in dental amalgam not always essential?
Why is the presence of zinc in dental amalgam not always essential?
Which component of dental amalgam is the only pure metal that is liquid at room temperature?
Which component of dental amalgam is the only pure metal that is liquid at room temperature?
What property of dental amalgam determines its classification based on particle size?
What property of dental amalgam determines its classification based on particle size?
In which of the following situations might amalgam restoration be preferred?
In which of the following situations might amalgam restoration be preferred?
What is a contra indication for using amalgam as a dental restoration material?
What is a contra indication for using amalgam as a dental restoration material?
What is a common reason for replacement of amalgam restorations?
What is a common reason for replacement of amalgam restorations?
Why does amalgam not adhere to the tooth structure?
Why does amalgam not adhere to the tooth structure?
What can lead to poor adaptation of amalgam to cavity walls?
What can lead to poor adaptation of amalgam to cavity walls?
What might cause porosity in an amalgam filling?
What might cause porosity in an amalgam filling?
What is the copper content percentage range for high copper alloys?
What is the copper content percentage range for high copper alloys?
Which type of alloy particles needs more mercury (Hg) for condensation?
Which type of alloy particles needs more mercury (Hg) for condensation?
What is the dominant form of amalgam particles in the admixed powder alloy mentioned?
What is the dominant form of amalgam particles in the admixed powder alloy mentioned?
Which type of alloy results in the formation of gamma-two phase, leading to corrosion?
Which type of alloy results in the formation of gamma-two phase, leading to corrosion?
Which type of amalgam has properties including less marginal breakdown and less susceptibility to corrosion?
Which type of amalgam has properties including less marginal breakdown and less susceptibility to corrosion?
Why do spherical type alloy particles require less mercury (Hg) for condensation?
Why do spherical type alloy particles require less mercury (Hg) for condensation?
What is the primary cause of marginal fracture of enamel or amalgam?
What is the primary cause of marginal fracture of enamel or amalgam?
What can cause 'Amalgam Blues' as mentioned in the text?
What can cause 'Amalgam Blues' as mentioned in the text?
Why is it important to avoid roundening the line angles during restoration?
Why is it important to avoid roundening the line angles during restoration?
What is a possible consequence of bonding amalgam restoration with enamel and dentine?
What is a possible consequence of bonding amalgam restoration with enamel and dentine?
Which factor may result in periodontitis or fracture of the filling or tooth after an amalgam filling?
Which factor may result in periodontitis or fracture of the filling or tooth after an amalgam filling?
How does inadequate pulp protection relate to post restorative pain according to the text?
How does inadequate pulp protection relate to post restorative pain according to the text?
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.
