Restorative & Materials · single question
What is WRONG with the patient's restoration shown?
Show answer and explanation
Correct answer: A. Corrosion of the amalgam restoration
Corrosion (A) of the amalgam restoration. The image shows darkened, tarnished amalgam restorations. Amalgam corrosion occurs through:
• Tarnish: surface discoloration from sulfide/oxide layer formation (superficial, no structural damage).
• Corrosion: electrochemical reaction between amalgam phases and oral environment → structural degradation, expansion, margin breakdown, microleakage.
• Clinically: corrosion products (tin oxides) can marginally SEAL the margins initially (beneficial short-term) but long-term corrosion weakens the restoration.
• Recurrent caries (B): would appear as radiolucency under/around the restoration on X-ray. Clinically may show softening at margins — would require X-ray to distinguish.
• The dark, tarnished appearance without obvious caries = corrosion.
• Modern high-copper amalgams are much more corrosion-resistant than older low-copper amalgams.
• Tarnish: surface discoloration from sulfide/oxide layer formation (superficial, no structural damage).
• Corrosion: electrochemical reaction between amalgam phases and oral environment → structural degradation, expansion, margin breakdown, microleakage.
• Clinically: corrosion products (tin oxides) can marginally SEAL the margins initially (beneficial short-term) but long-term corrosion weakens the restoration.
• Recurrent caries (B): would appear as radiolucency under/around the restoration on X-ray. Clinically may show softening at margins — would require X-ray to distinguish.
• The dark, tarnished appearance without obvious caries = corrosion.
• Modern high-copper amalgams are much more corrosion-resistant than older low-copper amalgams.
Practice Restorative & Materials questions Restorative & Materials study notes