A 38-year-old woman sought dental care for treatment of decay of tooth #37 (left mandibular second molar). At that time she had no medical or dental history of note, was not taking any medication and had no other restorations in her mouth. After intraoral examination and analysis of the periapical X-ray of the tooth in question, the tissue affected by the caries was removed and a class I cavity preparation of Black was made and filled with silver amalgam. No postoperative problems occurred.
After 19 months, the patient returned to the dental office as she suspected caries in other teeth. Intraoral examination revealed an atrophic, slightly erythematous area on the left jugal mucosa, precisely in the region of the mucosa in contact with the molar restored with silver amalgam. The right jugal mucosa had a normal appearance. When asked about the lesion, the patient informed us that she had not noticed it, although recently she had sometimes felt a strange sensation in that area when eating spicy food. She also informed us that she had not received any type of treatment since the previous visit, when the amalgam restoration was performed. When asked about any history of allergy, she had no previous history of allergic reactions. Careful examination of the lesion shows that it projects onto the silver amalgam restoration, coming into intimate contact with it during certain oral movements, making it necessary to separate the mucosa with the mirror in order to be able to see the lesion properly.

To confirm the nature of the lesion histologically, a biopsy of the lesion is taken. The pathology study of the biopsy of the lesion showed squamous epithelium with irregular acanthosis and foci of parakeratosis, with marked spongiosis and the presence of exocytosis of lymphocytic elements in the stratum corneum. The underlying stroma showed a chronic lymphocyte-like inflammatory infiltrate distributed discretely in a band, with involvement of the stratum basale. In depth, fibroconnective and adipose tissue was observed with some thin-walled vascular structures, without relevant alterations. The anatomopathological diagnosis was compatible with oral lichen planus, the histological picture observed in the mucosa being equivalent in the skin to an acute-subacute dermatitis.

Once the nature of the lesion was explained to the patient and the possibility of it disappearing by removing the silver amalgam restoration, she decided not to replace the restoration as she felt that she had no significant discomfort and did not wish to undergo the treatment again. Restorations of other teeth were made with composite resin, without any mucosal reaction.