Eighty-five studies were included.
Reduction in probing depth: root planing, without any adjunctive therapy, resulted in a continuous reduction up to week 8, followed by a period of stabilisation up to week 24 (from 7.5 to 4.8 mm). For CHX 2%, this reduction continued up to week 12, after which a status quo was noticed (from 7.5 to 4.2 mm). Systemic doxycycline gave a continuous reduction until week 24 (from 5.4 to 3.6 mm); however, this was only based on a single study. For systemic metronidazole application, there was a decrease in the probing depth for the first 4 weeks, then a stabilisation for weeks 8 to 12, and from week 12 to week 24 there was a renewed reduction in the probing depth (from 7.5 to 5.8 mm). For locally-applied metronidazole 1%, there was a stable situation in the first 4 weeks, after which the probing depth started to increase again.
Eradication of spirochetes: CHX 2% seemed to have a supplementary effect even up to 24 weeks after therapy, although this was only based on 2 studies. Systemic doxycycline also had an extra effect on the reduction of total amount of spirochetes, but only one study could confirm these findings. The strongest effect on eradication of spirochetes was shown by the systemic intake of metronidazole (750 mg/day), with a continuous reduction up to week 24.
For the occurrence of A. actinomycetemcomitans, supplementary effects were only seen for locally-applied minocycline and for systemic doxycyline, for which a reduction of A. actinomycetemcomitans up to 24 weeks after the start of the treatment was reported. Once again, these statements may have been based on only a very limited number of studies.
For P. gingivalis, there was a recurrence after root planing, without any additional therapy, within 4 weeks. This relapse only to occur with CHX 2% after 8 weeks (based on only 1 study), whilst for locally-applied minocycline, there appeared to be no relapse, even 24 weeks after the baseline examination (based on only 2 studies).