The Potential Allergic Role of Mast Cells to Orthodontic Appliance in Orthodontic-Induced Gingival Enlargement.

BACKGROUND: Gingival mast cells (MCs) are strategically scattered throughout connective tissue and adhere to the endothelium to convert local impulses into systemic signals and attract additional immune effector cells. Numerous mediators, such as histamine, cytokines, and proteases, modulate these interaction pathways. OBJECTIVES: The purpose of this study was to determine and compare MC count in the gingival enlargement tissue of patients receiving orthodontic treatment versus patients having plaque-induced gingival enlargement without orthodontic treatment, utilising hematoxylin and eosin (H&E) staining, toluidine blue (TB), and CD117 (c-kit) immunohistochemistry (IHC) as a specific marker for MC identification. METHODS AND MATERIALS: This study involved 30 patients who were divided into three groups: Group 1 included 10 patients with clinically healthy gingival tissue that intentionally needed crown lengthening. Group 2 included 10 cases of plaque-induced gingival enlargement in individuals without orthodontic treatment. Group 3 included 10 cases of orthodontic gingival enlargement in individuals receiving orthodontic treatment. Patients received non-surgical periodontal therapy and oral hygiene instructions. After the plaque control phase, with a Gingival Index (GI) = 0 and no Bleeding on Probing (BoP), the gingiva was surgically treated. During the surgical procedure, the excised gingival margin was collected for histological examination with H&E, TB special stain, and c-kit to count the MCs. RESULTS: The gingiva of patients in group 3 was characterised by more frequent epithelial changes (mild hyperplasia of the basal layer and spongiosis), a stronger degree of inflammation, including band-like inflammatory infiltrates and individual inflammatory cells, and a milder degree of fibrosis, compared to group 2. In addition, a significant increase in the number of MCs was observed in group 3 compared with groups 2 and 1. c-kit was a more specific marker for MCs than for TB. CONCLUSION: Orthodontic-induced gingival enlargement showed a significantly higher number of mast cells than plaque-induced gingival enlargement, and this involvement of MCs, particularly, may be associated with mast cell activation and degranulation. These findings may suggest an immunological role for MCs in the pathogenesis of orthodontically induced gingival enlargement.