Effect of repeated adjunctive antimicrobial photodynamic therapy on subgingival periodontal pathogens in the treatment of chronic periodontitis

The aim of this study was to compare the effect of subgingival ultrasonic scaling followed by repeated (three times) antimicrobial photodynamic therapy (PDT), ultrasonic scaling alone (US), and scaling and root planing with hand instruments (SRP) for initial periodontal treatment. Twenty-seven non-smoking systemically healthy chronic periodontitis patients were included. Residual pockets ≥4 mm deep and bleeding on probing were debrided either with SRP, US alone, or US followed by a single episode of PDT during supportive periodontal treatment. Probing pocket depth (PPD), bleeding on probing (BOP), and clinical attachment level (CAL) were monitored over 12 months. The presence of five periodontal pathogens in the pockets was determined by a commercially available micro-IDent test. Intergroup and intragroup statistical analysis was performed. All three treatments resulted in a significant clinical improvement. Additional application of PDT to US failed to result in further improvement in terms of PPD reduction and CAL gain. However, it resulted in a higher reduction of BOP at 3 and 12 months comparing to US alone or SRP (PDT from 25 to 13 and to 9 %, US from 23 to 16 and to 12 %, and SRP from 17 to 10 and to 9 %, respectively). PDT reduced the proportion of positive sites after 6 months for Treponema denticola (TD) significantly more effectively than US or SRP (p < 0.0001). Additionally, PDT resulted in a greater reduction of Aggregatibacter actinomycetemcomitans (AA), Tannerella forsythia (TF), and TD in medium pockets (4–6 mm) (p < 0.02) and of TD in deep pockets (>6 mm) compared to mechanical debridement alone (p < 0.05).