Single or repeated antimicrobial photodynamic therapy as adjunct to ultrasonic debridement in residual periodontal pockets: clinical, microbiological, and local biological effects

This study aims to assess in residual periodontal pockets the clinical, microbiological, and local biological effects of antimicrobial photodynamic therapy (PDT), delivered after ultrasonic instrumentation either once or twice in a 1-week interval. A single center, three-arm randomized longitudinal study was carried out for 6 months. Twenty-eight systemically healthy patients on periodontal maintenance with residual pockets (pocket depth (PD) ≥5 mm, clinical attachment loss ≥2 mm, and bleeding upon probing (BOP+)) were included. Residual pockets on three teeth, separated from each other by at least two other teeth, served as study sites. After ultrasonic debridement, they were randomly assigned to either PDT delivered twice within 1 week (group A), PDT delivered only once (group B), or sham treatment without activating the laser (group C). Methylene blue was applied with a blunt irrigator tip into the pockets. Sites were irradiated with laser light at a wavelength of 670 nm using a light-diffusing tip introduced into the pocket. Initial PD was 5.9 ± 0.9, 6.3 ± 1.3, and 6.3 ± 1.5 mm in groups A, B, and C, respectively, differences being nonsignificant. PD was significantly reduced in all groups. At month 3, PD was significantly lower in groups A (2.9 ± 1.1 mm; p = 0.04) and B (2.8 ± 1.1 mm; p = 0.03) compared to group C (3.5 ± 1.2 mm). At month 6, none of the sites in group A had persisting pockets PD >4 mm and BOP+, whereas two sites in group B and four sites in group C stayed in this category. Detection frequencies of the studied microorganisms at >1,000 and >100.000 cells/ml did not change significantly from baseline to months 3 or 6 in any group. A significant overall decrease was observed from baseline to month 6 for C-reactive protein, serum amyloid A, fibrinogen, procalcitonin, and α-2 macroglobulin. When looking at the groups separately, C-reactive protein was significantly lower only if the laser had been activated twice (p < 0.05). Other differences between groups were not significant. A single or double episodes of PDT had some additional benefit over ultrasonic instrumentation alone.