Meta-analyses allow to combine results systematically and to obtain more precise quantitative results on the efficacy of a therapy. For the clinician, the comparison of two therapy modalities is particularly of interest. Several meta-analyses exist in the field of periodontal regenerative procedures. The problem is that the results are difficult to interpret for the clinician. It is only the clinical effect that can indicate the superiority of a certain treatment modality, e.g. remaining periodontal pockets. The aim of the present systematic review was the re-evaluation of studies of existing meta-analyses and to determine the probability of remaining periodontal pockets of more than 3 respectively 5 mm after active therapy. The probability of remaining periodontal pockets over 3 respectively 5 mm was significantly higher after periodontal flap procedure without regenerative procedures, compared to guided tissue regeneration (GTR) or the use of enamel matrix derivatives. Moreover, the probability of remaining pockets over 3 mm was with GTR on average 57% and with the use of enamel maxtrix derivatives 74%. Using the cut-off value of 5 mm this probability was reduced to 8 and 17%, respectively. A new clinical attachment that was less than 50% of the original level was to be expected in 29% (GTR) and 15% using enamel matrix derivatives. This statistical interpretation permits not only the clinician, but also the patient to compare the efficacy of the different treatment modalities using the probability of primary clinical effect outcomes.