Aim Comparing the efficacy of photoablative and photodynamic diode laser in adjunct to scaling -root planing (SRP) and SRP alone for the treatment of chronic periodontitis. Materials and Methods Twenty-six patients were studied. Maxillary left or right quadrants were randomly assigned to sham-laser treatment similar to+similar to SRP or laser similar to+similar to SRP. This consisted of photoablative intra/extra-pocket de-epithelization with diode laser (lambda=810nm), followed by single SRP and multiple photodynamic treatments (once weekly, 410 applications, mean +/- SD: 3.7 +/- 2.4) using diode laser (lambda=635nm) and 0.3% methylene blue as photosensitizer. The patients were monitored at days 0 and 365 by clinical assessment (probing depth, PD; clinical attachment level, CAL; bleeding on probing, BOP) and at days 0, 15, 30, 45, 60, 75, 90, 365 by cytofluorescence analysis of gingival exfoliative samples taken in proximity of the teeth to be treated (polymorphonuclear leukocytes, PMN; red blood cells, RBC; damaged epithelial cells, DEC; bacteria). Results At day 365, compared with the control quadrants, the laser + SRP therapy yielded a significant (p similar to<similar to 0.001) reduction in PD (-1.9mm), CAL (-1.7 mm) and BOP (-33.2% bleeding sites), as well as in bacterial contamination especially spirochetes and PMN and RBC shedding in the gingival samples (p < 0.001). Conclusions Diode laser treatment (photoablation followed by multiple photodynamic cycles) adjunctive to conventional SRP improves healing in chronic periodontitis patients.