Podcast
Questions and Answers
What is the primary function of silver in dental amalgam?
What is the primary function of silver in dental amalgam?
Which disadvantage of dental amalgam is primarily associated with its metal color?
Which disadvantage of dental amalgam is primarily associated with its metal color?
Which element in dental amalgam serves as a scavenger during its manufacture?
Which element in dental amalgam serves as a scavenger during its manufacture?
What effect does tin have on dental amalgam?
What effect does tin have on dental amalgam?
Signup and view all the answers
What is a common reason for the declining popularity of dental amalgam?
What is a common reason for the declining popularity of dental amalgam?
Signup and view all the answers
What is a characteristic of low copper amalgam alloys?
What is a characteristic of low copper amalgam alloys?
Signup and view all the answers
Which factor does NOT favor contraction in amalgam?
Which factor does NOT favor contraction in amalgam?
Signup and view all the answers
In amalgam properties, what occurs during the initial setting phase?
In amalgam properties, what occurs during the initial setting phase?
Signup and view all the answers
What distinguishes high copper alloys from low copper alloys?
What distinguishes high copper alloys from low copper alloys?
Signup and view all the answers
What effect does longer triturating times have on amalgam?
What effect does longer triturating times have on amalgam?
Signup and view all the answers
Study Notes
Dental Amalgam Overview
- Amalgam is an alloy combining liquid mercury with solid metal particles (silver, tin, copper, sometimes zinc, palladium, indium, selenium)
- Used as a dental restoration material for over a century, due to low cost, ease of application, strength, and durability
- Concerns regarding aesthetics, environmental pollution, mercury toxicity, and the availability of composite materials have diminished its popularity
- Commonly used for posterior restorations and large foundation restorations, sometimes for cores with crowns.
Advantages of Dental Amalgam
- Reasonably easy to insert, not a sensitive technique
- Maintains anatomical form
- Provides adequate resistance to fractures (strength)
- Prevents marginal leakage over time
- Suitable for stress-bearing areas
- Relatively long service life (durability)
- Cost-effective
Disadvantages of Dental Amalgam
- Silver color does not match tooth structure
- Brittle, prone to corrosion and galvanic action
- Can exhibit marginal breakdown
- Does not retain weakened tooth structure
- Regulatory concerns regarding disposal in wastewater
Composition of Dental Amalgam
- Primarily consists of silver and tin, with smaller amounts of copper, zinc, and trace elements (gold, palladium, indium, selenium).
- Various types exist based on copper content (low copper, high copper) and zinc content: zinc containing and zinc free.
- Specific percentages of silver, tin, copper, and zinc vary by amalgam type (e.g., low copper has 70.3% silver)
Function of Amalgam Constituents
-
Silver (Ag):
- Crucial in the reaction and provides its alloy color -Reduces creep -Increases strength, setting expansion & resistance to tarnish
-
Tin (Sn):
- Controls the reaction between silver and mercury, preventing unacceptable speed and expansion -Reduces strength, hardness, resistance to tarnish and corrosion
- Copper (Cu): -Increases hardness & strength -Increases setting expansion
- Zinc (Zn): -Acts as a scavenger during manufacture -Reduces brittleness in the amalgam form -Can cause delayed expansion with moisture contamination
Classification of Amalgam Alloys
- Based on copper content (low copper, high copper) and zinc content (zinc containing, zinc-free).
- Based on the shape of the particles (lathe-cut, spherical, mixed shapes)
- Further classified as binary (e.g., silver-tin), ternary (e.g., silver-tin-copper), or quaternary (e.g., silver-tin-copper-indium) alloys based on the number of metals
Properties of Set Amalgam
- Dimensional changes are minimal after setting, with slight expansion or contraction
- Initial contraction period (first 20 minutes) occurs due to mercury dissolving in alloy particles
- Expansion occurs later, possibly from mercury reacting with silver and tin
- Factors favoring contraction include: low mercury-alloy ratio, higher condensation pressure, smaller particles and longer triturating times
- Stable dimensions usually achieve after 6–8 hours
- Delayed expansion can occur due to zinc contamination with water during trituration or condensation, spanning 3–5 days to months
Strength of Amalgam
- Good compressive strength but does not withstand high tensile/bending strength
- Cavity design crucial for minimizing tension/shear forces during service
- Factors affecting strength include: triturating (under-trituration/over-trituration), mercury content, and condensation pressure
- Initial strength gain takes time. At least 70% of its strength is gained within 8 hours post placement
- Cavity design to reduce tensile stresses, with sufficient depth in the amalgam
- Porosity weakens the material
Creep as a Factor in Amalgam
- Creep is a time-dependent permanent deformation under static or intermittent loads
- Low-copper amalgams exhibit higher creep rates linked to marginal deterioration
- High-copper amalgams exhibit lower creep rates
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
This quiz explores the characteristics, advantages, and disadvantages of dental amalgam as a restoration material. Learn about its composition, historical use, and the factors affecting its popularity. Test your knowledge on its properties and applications in dentistry.
