Background and objective(s): Periodontitis is initiated by a dysbiotic host-microbe relationship. Standard periodontal treatment involves oral hygiene education, mechanical debridement and periodic follow-ups with the aims of pocket closure and maintaining a symbiotic microbial community. Nonetheless, this therapy alone may fail due to the limitations of mechanical instrumentation. The use of antimicrobial in combination to subgingival debridement has been proposed for initial and recurrent periodontitis to enhance the effectiveness of mechanical instrumentation. Antimicrobial peptide (AMP) comprised of a wide range of peptide, was found naturally in various life forms or manufactured as a synthetic compound. This study was conducted to evaluate the use of AMP as an adjunct to non-surgical periodontal treatment in terms of clinical and microbiological outcomes. Hypothesis • There are changes in clinical periodontal parameters and subgingival microbial profile following treatment with locally delivered synthetic AMP.

study design: This was a split-mouth randomised pilot study of a 3-months follow-up. Sample size calculation: The sample size was calculated using G\*Power software version 3.1.9.4 (Franz Faul, Universitat Kiel, Germany). Estimation of sample size was based on the mean and standard deviation of CAL between the test and control group of previous publication (Singh et al., 2018). Four samples in each group (test and control) were required to achieve 80% power at a significant level of 5%. Randomisation: The random allocation sequence was generated by another person who was not directly involved in the study using a Research Randomizer tools (https://www.randomizer.org/). Periodontal sites of each patient were randomised at a split mouth level (left or right halves of the dentition) to one of the two treatment groups. Allocated treatments were inserted into an opaque envelop. Treatment allocation was concealed from the clinician and only revealed once subgingival debridement was completed. intervention: At baseline, clinical measurement was recorded and target sites (sites with PPD ≥6mm) were identified. subgingival plaque were collected at target sites. The same clinician performed full mouth scaling and subgingival debridement, coupled with standardised oral hygiene instruction for all subjects. Upon the completion of treatment, second clinician applied the treatments according to the randomisation. * Test group: Subgingival instrumentation followed by Antimcrobial peptide gel (AMP) application in all target sites. * Control group: Subgingival instrumentation and normal saline irrigation in all target sites. Test and control intervention will be repeated for another 2 applications at an interval of 3 days. Subjects were re-examined and plaque sampling will be repeated at 6 weeks and 12 weeks. statistical analysis: Clinical parameters were reported as mean and standard deviation. P-value \<0.05 was considered statistically significant. intergroup and intragroup comparison of mean bleeding score, pocket depth, clinical attachment level will be conducted using SPSS software. For the metagenomic data, alpha and beta diversity were computed using QIIME 2. The difference in the relative abundance of individual genus over time will be analysed.