Rom J Morphol Embryol 2018, 59(3):811–817 ISSN (print) 1220–0522 ISSN (online) 2066–8279 ORIGINAL PAPER Histological and immunohistochemical study on the apical granuloma ALEXANDRA CARINA BĂNICĂ 1) , SANDA MIHAELA POPESCU 2) , VERONICA MERCUŢ 1) , CRISTINA JANA BUSUIOC 3) , ANCA GABRIELA GHEORGHE 4) , DIANA-MARIA TRAŞCĂ 5) , ANCA DANIELA BRĂILA 6) , ALINA IREN MORARU 7) 1) Department of Prosthetic Dentistry, Faculty of Dental Medicine, University of Medicine and Pharmacy of Craiova, Romania 2) Department of Prosthetics and Oral Rehabilitation, Faculty of Dental Medicine, University of Medicine and Pharmacy of Craiova, Romania 3) Research Center for Microscopic Morphology and Immunology, University of Medicine and Pharmacy of Craiova, Romania 4) Department of Endodontics, Faculty of Dental Medicine, University of Medicine and Pharmacy of Craiova, Romania 5) Department of Medical Specialties, University of Medicine and Pharmacy of Craiova, Romania 6) Department of Obstetrics and Gynecology, University of Medicine and Pharmacy of Craiova, Romania 7) Department of Odontology, Faculty of Dental Medicine, University of Medicine and Pharmacy of Craiova, Romania Abstract Introduction: Periapical granuloma is one of the most frequent periodontal pathology and belongs to the group named as apical periodontitis. Materials and Methods: Out of 78 of diagnosed granulomas, we selected samples that we analyzed histologically and immunohistochemically. Results: The histopathological aspect has been dominated by the presence of mononuclear cells of the lymphocyte and plasma cells type, showing the chronic aspect of the apical lesion. Also, we noticed that in the apical granuloma macrophages occur most often. This density of macrophages explains cellular and tissular disruption that occur in apical region of the tooth under the influence of bacterial flora that reached this area, as they have the role to phagocyte pathogens and cell and tissue residues that result from bacterial aggression. The reaction of the plasma cells, determined by their number, has been always associated with the age of the granulomas, and it is more intense in old, neglected granulomas, compared to recent granulomas. Conclusions: The number and type of immunity cells varies in the apical granuloma accordingly to the age of granuloma. Keywords: apical granuloma, histopathological exam, immunohistochemistry, immune response.  Introduction Chronic periapical lesions represent a frequent complication related either to a badly done endodontic treatment as well as to a not treated or badly treated cavity that complicates with pulpal and then periodontal pathology. Often, they pass as chronic disease with little to no perspective of conservative treatment [1–3]. Periapical lesions are classified depending on their histological structure, radiological dimension and clinical manifestations, such as periapical granuloma, periapical condensation, radicular cysts and others [4, 5]. The periapical granuloma has a complex structure, resulting of proliferative processes as well degenerative and infiltrative manifestations. There are described four areas between the dental root and the alveolar bone: first is an area of necrosis and even infection; second, there is a layer of contamination, where the first reactions of defense occur, with vasodilatation and inflammatory exudate; third, the area of irritation, where cellular multi- plication occurs; fourth, the area of stimulation where the toxins determine a reaction from osteoblasts [6]. Clinicians are still making efforts to create a treatment that can be effective and heal these kinds of lesions [7], but in order to achieve that multiple studies of the complex structure in different stages of development of the granuloma must be undertaken still. This is the purpose of our study, to determine the status of various lesions, correlating the histological, immunohistochemical (IHC) founding with clinical and radiological data.  Materials and Methods The study involved 78 cases of periapical granuloma, diagnosed as such considering the clinical and radiological assessment. The patients were selected from private practices during one year. Of the 78 periapical granulomas, 32 were a complication of an untreated complicated caries and the rest have been complication of an endodontic treatment that was not correctly made. The age of the patients was between 26 and 57 years old. In all cases, the treatment was tooth extraction and cleaning the socket with a curette, removing all damaged tissue. All samples were fixed in 10% formalin, for 48–72 hours. For the histological study, the fragments were embedded in paraffin and colored with the Hematoxylin–Eosin (HE) and Goldner– Szekely (GS) trichrome stainings. For the IHC study, from the biological material embedded in paraffin, we made serial sections that were collected on slides covered with poly-L-lysine and dried in a thermostat at 37 0 C, for 24 hours. After that, we deparaffinized and hydrated the sections. The exposure of the antigens of interest was R J M E Romanian Journal of Morphology & Embryology http://www.rjme.ro/