Admixed high copper alloy powder contains
**Core Concept**
The question pertains to the composition of admixed high copper alloy powder, a critical aspect of dental materials science. Admixed high copper alloys are used in dental casting due to their excellent corrosion resistance and high strength-to-weight ratio. These alloys typically contain a combination of metals, with copper being a key component.
**Why the Correct Answer is Right**
The correct answer is A. 9-20% copper because the American Dental Association (ADA) and other regulatory bodies specify that admixed high copper alloys used in dental casting must contain between 9% and 20% copper. This narrow range ensures that the alloy maintains its desired properties while minimizing the risk of corrosion and toxicity. The presence of copper within this range also facilitates the formation of a protective oxide layer, which enhances the alloy's durability and resistance to degradation.
**Why Each Wrong Option is Incorrect**
**Option B:** This option is incorrect because it extends the upper limit of copper content to 20%, which is still within the acceptable range but does not accurately represent the minimum acceptable copper content for admixed high copper alloys.
**Option C:** This option is incorrect because it includes a copper content range of 9-30%, which exceeds the upper limit specified by regulatory bodies and could compromise the alloy's properties and safety.
**Option D:** This option is incorrect because it includes a copper content range of 13-30%, which also exceeds the upper limit specified by regulatory bodies and could compromise the alloy's properties and safety.
**Clinical Pearl / High-Yield Fact**
When working with dental alloys, it's essential to remember that the composition and properties of these materials can significantly impact the success and longevity of dental restorations. Admixed high copper alloys are a popular choice due to their excellent corrosion resistance and high strength-to-weight ratio, but it's crucial to ensure that the alloy meets the specified composition requirements to ensure optimal performance.
**✓ Correct Answer: A. 9-20% copper**