 Inclusion criteria of the study were: a adult subjects with chronic periodontitis presenting b radiographic evidence alveolar bone loss at the proximal aspect of the tooth, c intrabony defect deeper than 4mm, d probing pocket depth 6 mm at the site, e unremarkable general health according to medical history and clinical judgment, f no medications taken for at least six months and no antibiotics taken for twelve months before the beginning of the study. Subjects who have quit the habit of smoking for at least one year before the beginning of the study were considered as non-smokers and, if the other included criteria were met, were included in the present sample. Exclusion criteria for the study were: a subjects with early onset or aggressive forms of periodontitis, b current smokers, c presence of significant systemic diseases i.e., cancer, AIDS, diabetes, d clinical evidence of furcation defects, e presence of apical radioleucency and f previous lack of cooperation with the maintenance program. 