part 3 Flashcards
What is Dispersalloy?
A new alloy system that is a mixture of bigger particle sizes and very fine particle sizes
Dispersalloy is a type of dental amalgam used in restorations.
What is the composition of Dispersalloy compared to conventional amalgam?
Dispersalloy has 70% silver, 16% tin, <1% copper, and <2% zinc
Conventional amalgam typically has different proportions of these metals.
What is the recommended mercury content in an amalgam restoration?
50% of the alloy should be mercury
If the alloy is 65%, mercury should be 35% or less.
What role does silver play in amalgam?
Contributes to compressive strength, setting expansion, and resistance to tarnish
Silver also decreases flow and creep.
What is the effect of tin in amalgam?
Has a strong affinity to mercury, improves plasticity, increases setting time, and causes characteristic contraction
Tin is responsible for tarnish and corrosion.
What is a notable characteristic of copper in amalgam?
Difficult to unite with mercury, tarnishes readily, and increases expansion
Copper also decreases the setting time.
What is the major advantage of copper in amalgam?
Increases the strength and hardness of the material
This is crucial for the durability of dental restorations.
What is the function of zinc in amalgam?
Acts as a scavenger for oxides and sulfides, inhibits oxidation, and contributes to amalgamation
Zinc can also cause delayed expansion after 3-5 days.
What are the ADA specifications for mercury?
ADA specification #6 includes standards for packing, labeling, and purity
This ensures safe and effective use in dental applications.
What are the three types of labels for dental mercury?
- U.S.P. (US Pharmacopeia)
- A.C.S. (American Chemical Society)
- Analytical Grade
These labels indicate the quality and suitability of mercury for dental use.
What happens if there is too little mercury in amalgam?
Results in a grainy, weak, easily tarnished, and corroded amalgam
Proper mercury content is critical for the integrity of the restoration.
What are the consequences of too much mercury in amalgam?
Causes excessive expansion and weakened amalgam
This can compromise the restoration’s effectiveness.
What is one of the mercury hygiene measures?
Store mercury in unbreakable tightly sealed containers
This prevents spills and contamination.
Fill in the blank: Mercury should be confined to an easily cleaned _______.
tray
This helps in managing spills effectively.
What is recommended for cavity surfaces when working with mercury?
Coat cavity surfaces with cavity varnishes or base
This can help protect the tooth structure.
