This is a randomized, single blind, parallel-arm, multi-center, non-inferior clinical trial. 174 patients are recruited in total, and they are treated by Guided Tissue Regeneration (GTR). The patients are split in to two groups evenly: 87 in the experimental group and 87 in the control group.

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;