LAUSR

BACKGROUND Current periodontal treatment involves instrumentation using hand and/or ultrasonic instruments, which are used either alone or in combination based on patient and clinician preference, with comparable clinical outcomes. This study sought to investigate early and later changes in the subgingival biofilm following periodontal treatment; to identify whether these changes were associated with treatment outcomes; and to investigate whether the biofilm responded differently to hand compared with ultrasonic instruments. METHODS This was a secondary-outcome analysis of a randomised controlled trial. Thirty-eight periodontitis patients received full-mouth subgingival instrumentation using hand (n = 20) or ultrasonic instrumentation (n = 18). Subgingival plaque was sampled at baseline and 1, 7 and 90 days following treatment. Bacterial DNA was analysed using 16S rRNA sequencing. Periodontal clinical parameters were evaluated before and after treatment. RESULTS Biofilm composition was comparable in both (hand and ultrasonics) treatment groups at all timepoints (all genus and species; p[adjusted]>0.05). Large-scale changes were observed within-groups across timepoints. At days 1 and 7, taxonomic diversity and dysbiosis were reduced, with an increase in health-associated genera including Streptococcus and Rothia equating to 30-40% of the relative abundance. When reassessed at day 90 a subset of samples reformed a microbiome more comparable with baseline, which was independent of instrumentation choice and residual disease. CONCLUSIONS Hand and ultrasonic instruments induced comparable impacts on the subgingival plaque microbiome. There were marked early changes in the subgingival biofilm composition, although there was limited evidence that community shifts associated with treatment outcomes. This article is protected by copyright. All rights reserved.