Chronic periodontitis is one of the most frequent and severe diseases involving the tooth. Untreated, they can lead to tooth loss. Our study involved 67 patients with chronic marginal periodontitis who underwent tooth extraction, of which 29 had moderate periodontal lesions and 38 severe periodontal lesions. The microscopic study of the dental pulp revealed significant changes in all patients. In patients with moderate periodontitis the pulp tissue was found to be the site of an enhanced process of collagenous fibrosis associated with a moderate inflammatory infiltrate, dystrophic mineralization, reduced blood vascularization and arteriolosclerosis. The dental pulp of patients with severe periodontitis showed an abundant chronic inflammatory infiltrate associated with pulpal necrosis, vascular congestion, microhemorrhages, dentin demineralization and odontoblast impairment.