Data sourcesThe Cochrane Oral Health Group specialist trials, Medline and Embase databases were searched. The Journal of Clinical Periodontal Research and the Journal of Clinical Periodontology were hand searched.Study selectionRandomised controlled trials involving an intervention of surgical flap or periodontal pocket surgery including simplified, modified, access, Widman, or papilla preservation and disease or intrabony/intraosseous defect were included. Two authors screened and selected the studies.Data extraction and synthesisData extraction and risk of bias assessment were conducted by two authors. Primary outcomes were tooth survival, clinical attachment gain, probing depth reduction and gingival recession increase. Weighted means and forest plots were calculated and meta-analysis performed.ResultsThirty-one studies were included for data analysis. Twelve months after conservative surgery, tooth survival was 98%, clinical attachment loss gain 1.65 mm (95% CI 1.37-1.94), probing depth reduction 2.8 mm (CI 2.43-3.18) and gingival recession increase 1.26 mm (CI 0.94-1.49). Longer follow up showed similar results. There was insignificant evidence to suggest that clinical bone increased with this surgery.ConclusionsThe treatment of intrabony defect with conservative surgery is associated with high tooth retention and improvement of periodontal clinical parameters. Clinical performance may vary according to the type of surgical flap used.