PFM Crown Dark Margin — ORE Part 1 MCQ

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EasyProsthodonticsPFM Crown Dark MarginORE Part 1

A 55-year-old patient has a metal-ceramic crown supporting an upper anterior bridge. At review, the gingival margin has receded and a dark line is visible at the cervical edge of the crown. What is the most likely explanation?

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Correct answer: D — The metal crown margin has become exposed

Explanation lettering: E = shown as A · D = shown as B · A = shown as D · B = shown as E

A is correct. Metal-ceramic (PFM) crowns contain a metal coping and may have a metal cervical margin. Gingival recession moves the soft-tissue margin apically and can expose this metal edge, producing a characteristic dark line at the crown margin, especially in the upper anterior aesthetic zone. Long-term clinical follow-up of metal-ceramic crowns reports supragingival margins resulting from gingival recession. Marginal caries may cause breakdown, soft tooth tissue or radiographic change, rather than a uniform line revealed by recession. Chlorhexidine causes extrinsic surface staining, typically more diffuse than a line at a crown edge. Amalgam tattoo and melanotic macule are pigmented lesions within the mucosa and would not coincide precisely with the cervical crown margin.

Reference: Walton TR. Twenty-year follow-up of metal-ceramic single crowns: a retrospective study. International Journal of Prosthodontics. 2008. https://pubmed.ncbi.nlm.nih.gov/18717088/