BACKGROUND The aim of this study was to compare the clinical outcome of a novel biphasic calcium composite (BCC) biomaterial versus autogenous bone spongiosa (ABS) or open flap debridement (OFD) for the treatment of intrabony periodontal defects. METHODS Forty-five subjects with at least one intrabony defect with a probing depth (PD) >or=7 mm and a vertical radiographic bone loss >or=3 mm were enrolled in the study. Subjects were randomly assigned to treatment with BCC (n = 15), ABS (n = 15), or OFD (n = 15). Clinical parameters were recorded at baseline and 12 months after surgery and included the plaque index, gingival index, PD, clinical attachment level (CAL), and gingival recession. RESULTS In all treatment groups, significant PD reductions and CAL gains occurred during the study period (P <0.0001). At 12 months, patients treated with BCC exhibited a mean PD reduction of 3.6 +/- 0.7 mm and a mean CAL gain of 3.0 +/- 0.8 mm compared to baseline. Corresponding values for patients treated with ABS were 3.4 +/- 0.8 mm and 2.9 +/- 0.9 mm, whereas OFD sites produced values of 2.8 +/- 0.8 mm and 1.6 +/- 0.7 mm. Compared to OFD, the additional CAL gain was significantly greater in patients treated with BCC (P = 0.002) and ABS (P = 0.001). The additional PD reduction was significant for the BCC group (P = 0.011) and borderline significant for the ABS group (P = 0.059). There were no significant differences of PD and CAL changes between BCC and ABS groups. CONCLUSIONS The clinical benefits of BCC were equivalent to ABS and superior to OFD alone. BCC may be an appropriate alternative to conventional graft materials.