A Clinical Trial to Evaluate the Safety and Effectiveness of Resorbable Collagen Membrane - MatrixflexTM

Inclusion Criteria: 1. Aged 18 to 65 years, male or female; 2. patients were clinically diagnosed with chronic periodontitis according to the international classification of periodontal disease in 1999; 3. Only solitary lesion site requires surgical treatment and must meet the following criteria: 1. The baseline PD≥7 mm ; 2. After debridement during operation, the defect of the vertical bone at the adjacent surface ≥4mm, and at least one alveolar buccal wall can be detected; 3. The wideness of the keratinized gingiva≥2 mm; 4. Based on the X-Ray image, the dental crowns at the bottom of the bone socket should be at least 3mm; Exclusion Criteria: 1. The test tooth has open surgical debridement history within the most recent one years; 2. Known allergy to collagen of animal origin; 3. Clinical or radiographic signs of untreated acute infection at the surgical site, apical pathology, root fracture, severe root irregularities, cemental pearls, cemento-enamel projections not easily removed by odontoplasty, untreated carious lesions at the cemento-enamel junction (CEJ) or on the root surface, subgingival restorations and/or restorations with open margins at or below the CEJ;