Matrix metalloproteinases (MMP's) are a family of zinc-and calcium-dependent proteases, related to the function and structure of tissues because they act mainly on the degradation of protein components of the extracellular matrix (ECM), including dentinal and bone matrices. Studies show, in different animal and human models, a high and predominant expression of MMPs 2 and 9 both in periapical lesions and in intracanal exudates of teeth with acute periapical abscesses, in periapical granulomas and cysts and in crevicular gingival fluid of teeth with chronic periapical lesions, and also, during the progression of pulp and periapical diseases, they play an important role in the immune and inflammatory response of the host promoting the degradation of the extracellular matrix, degradation of the pulp tissue and periapical inflammation. Epigallocatechin-3-gallate (EGCG), an extract derived from green tea, has been extensively studied in the health field due to its beneficial properties, such as the ability to inhibit the proteolytic activity of matrix metalloproteinases (MMPs) in several systemic diseases and even in periodontal disease. However, the action of EGCG on the expression and distribution of these matrix metalloproteinases, when used as a intracanal dressing in endodontics, has not yet been evaluated. The hypothesis of this work is that EGCG is capable of reducing the expression of MMP-2 and MMP-9 when used as a intracanal dressing in the endodontic treatment of teeth of dogs with periapical lesions. The aim of this study is to evaluate the effect of applying an EGCG-based paste as a intracanal dressing in the expression of MMP-2 and MMP-9 in teeth of dogs with experimentally induced periapical lesions. A total of 70 roots of dog premolars with complete rhizogenesis and experimentally induced periapical lesions, were randomly divided into 5 groups submitted to different clinical conditions and treatments: 1) Healthy teeth; 2) Teeth with untreated periapical lesion; 3) Teeth treated endodontically in a single session; 4) Teeth treated endodontically in two sessions: paste based on EGCG (Composition: EGCG powder, zinc oxide and polyethylene glycol 400); 5) Teeth treated endodontically in two sessions: paste based on calcium hydroxide -Calen® (Composition: powdered calcium hydroxide, zinc oxide and polyethylene glycol 400). At 120 days after root canal filling, the animals were euthanized and the specimens were processed histotechnically and stained with HE and immunofluorescence so that it was possible to observe the expression of MMPs 2 and 9. Tissue disorganization, inflammatory infiltrate and expression of MMPs 2 and 9 were classified into scores ranging from 1 to 4 (absent, mild, moderate and severe). The results were subjected to statistical analysis using the Kruskal-Wallis test and Dunn's post test (95% confidence). It was observed that endodontic treatment in a single session resulted in persistent tissue disorganization, inflammatory response, did not provide repair of the cementum, alveolar bone and...