A 45 year old male presents to the dental clinic with an abraded tooth. He wants gold to be filled in that tooth. On examination, it is revealed that the tooth has cervical abrasion and class V inlay is placed. What percentage of gold is present in the restoration placed?
First, I remember that dental gold is an alloy, not pure gold. Pure gold is too soft for dental use. So, the question is about the typical composition. Class V inlays are restorations for the cervical areas of teeth, often using alloys.
Wait, the options aren't provided, but the correct answer is given as 75%. Let me verify. Dental gold alloys are usually 75% gold. They're called "18-karat" gold because 18 parts out of 24 are gold, which is 75%. The remaining 25% includes other metals like silver, copper, and palladium to harden the alloy.
So, the correct answer is 75%. The other options would be incorrect because they might suggest higher or lower percentages. For example, if someone thought it was 50% or 90%, those would be wrong. The key point here is understanding that 18-karat gold is standard in dental restorations for strength and durability. That's the high-yield fact here.
**Core Concept**
Dental restorations using "gold" are typically 18-karat alloys, composed of 75% gold. Pure gold (24-karat) is too malleable for functional use in teeth, necessitating alloying with other metals like silver, copper, or palladium to enhance hardness. Class V inlays specifically address cervical (neck) areas of teeth, often requiring durable materials.
**Why the Correct Answer is Right**
The correct answer is 75% gold. Dental gold alloys used in restorations like class V inlays are standardized as 18-karat, meaning 75% gold by mass. The remaining 25% consists of base metals (e.g., silver, copper, palladium) to improve tensile strength and resistance to wear, which are critical for occlusal forces and marginal integrity in posterior teeth.
**Why Each Wrong Option is Incorrect**
**Option A:** 50% gold is incorrect. This would correspond to a 12-karat alloy, which lacks the durability required for dental restorations.
**Option B:** 90% gold (22-karat) is incorrect. Pure gold is too soft and not used clinically; higher gold content reduces alloy strength.
**Option C:** 100% gold is incorrect. Pure gold (24-karat) is reserved for aesthetic or temporary uses only due to its malleability.
**Clinical Pearl / High-Yield Fact**
Remember the "18-karat rule": 75% gold is the standard for most dental restorations. Confusion with jewelry gold (22-karat, 91.6% pure) is common, but dental alloys prioritize mechanical properties over purity. Always associate class V inlays with 18-karat gold in exams.
**Correct Answer: C. 75%**