Abstract: Objective To compare the efficacy of subgingival scaling and root planning (SRP) combined with Nd: YAP laser and SRP alone in the treatment of periodontitis and the influence on subgingival micro-organisms. Methods Patients met inclusion criteria with generalized periodontitis were enrolled in this randomized controlled split-mouth clinical study, one week after supragingival scaling as the baseline. The test side was treated with SRP combined with Nd:YAP laser, while the control side was treated with SRP alone. Periodontitis-affected sites from the homonymous single root teeth in a homomaxillary pair in each patient were selected for gingival crevicular fluid (GCF) and subgingival plaque sampling. The probing depth (PD) and bleeding on probing (BOP)were detected, while GCF and subgingival plaque samples were collected at baseline, 6 weeks and 12 weeks after treatment. ELISA was used to detect the concentration of interleukin-6 (IL-6) in GCF. We analyzed and compared microbial compositions of each sample by 16S rDNA high-throughput sequencing. Results Clinical indicators of the test and control sides were significantly improved compared with baseline, but there was no significant difference between the two groups. The IL-6 concentration in GCF in two groups was significantly lower than that in the baseline. Six weeks after treatment, the IL-6 concentration in the test side was significantly lower than that in the control group(P＜0.05). α-diversity analysis showed that Shannon index was higher and Simpson index was lower on the control side at both 6 weeks and 12 weeks after treatment than at baseline. Sequencing results showed that, at 6 weeks after treatment, the relative abundance of Prevotella and Saccharibacteria_incertae_incerta_sedis in the test side decreased significantly compared with the baseline(P＜0.05). The relative abundance of Treponema was lower, and the relative abundance of Capnocytophaga was higher than that of the control side(P＜0.05). There was no significant difference at 12 weeks. Conclusion Nd: YAP laser combined with SRP and SRP alone both have significant effect on treating periodontitis. There was no significant difference in clinical indicators between these two therapeutic methods. However, Nd: YAP laser may be beneficial to the reduction of GCF IL-6 concentration and the inhibition of certain periodontal pathogens in subgingival plaque in a short time.

Key words: periodontitis, scaling and root planning, Nd:YAP laser, 16S rDNA high-throughput sequencing technology