Hyaline ring granuloma of the mouth-A foreign-body reaction that dentists should be aware of: Critical review of literature and histochemical/immunohistochemical study of a new case.

Hyaline ring granuloma (HRG) is a rare and atypical foreign-body granulomatous chronic inflammatory condition. Our aim was to make a critical review of the literature cases and also to illustrate histochemical and immunohistochemical findings of a new case. A modified PICO strategy was used. Inclusion criteria were met by case reports and case series with a histologically confirmed diagnosis of HRG, necessarily in mouth or maxillary bones. Exclusion criteria were no access to the full-text paper. The search was done up to 2019, totalizing 231 selected cases in 54 papers. The new case was analyzed through PAS, Azan-Mallory's trichrome, and CD34 and CD68 reactions. HRG is found mainly in the mandible of men, edentulous and prosthesis users, between 51 and 60 years of age, with 0.5-120 months of duration, usually causing edema and pain or discomfort. Endogenous and exogenous theories may be complementary in HRG. Eosinophilic areas could represent particles of vegetal origin, while the hyaline material could be the result of collagen degradation. Considering the material is not always present or even is ring-shaped, we suggest the change from "hyaline ring granuloma" to "granuloma induced by vegetal inoculation."