Fig. 3

Pathological and molecular studies. A Histological study between the erythematous border and deepithelialization demonstrating inflammatory reaction with lymphocytes and collagen fibres (HE, left × 100 and right × 300); B Histological study in the central portion of the lesion with necrotizing inflammation and accumulation of colonies of gram-positive bacteria (arrow); C Gram stain histology demonstrating positivities for gram-positive bacteria with coccoid-shaped colonies (GS, × 100); D Oral microbiota profiling. Upper graph: alpha diversity (Gini-Simpson index) throughout transplantation and follow-up. Bottom graph: with relative abundance (RA) of the genus Actinomyces. DB dental biofilm, GCF gingival crevicular fluid, OM oral mucosa (HE hematoxylin and eosin, GS gram-staining, NGS next-generation sequencing)