European Journal of Molecular & Clinical Medicine ISSN 2515-8260 Volume 05, Issue 01, 2018 89 Effect of locally delivered 0.2% Thymoquinone gel in subjects with Grade C Periodontitis: Clinical, Immunological and Microbiological Assessment Author: Walid Elamrousy, Department of Periodontology, Faculty of Dentistry, Kafrelsheikh University, Kafrelsheikh, Egypt Email: waled_hammed@den.kfs.edu.eg Tel: +201005724781 Abstract: Objectives: To evaluate the clinical, immunological and microbiological efficacy of local application of Thymoquinone (TQ) gel in subjects with grade C periodontitis. Materials and Methods: Twenty-six individuals of both sexes aged between 24 and 37 years, diagnosed as grade C periodontitis with pocket depth ≥5 mm were selected for this study. The patients received a complete prophylaxis including scaling and root planning (SRP) followed by local intrapocket administration of placebo gel in the control group and 0.2% TQ gel in the study group sites. Probing pocket depth (PPD), relative attachment level (RAL), matrix metallo-proteniease-8 (MMP8) concentration in gingival crevicular fluid (GCF) and Aggregatibacter actinomycetecomitans (A.a) count in subgingival plaque were measured and recorded at baseline and 8 weeks postoperatively. Results: At 8 weeks evaluation period, TQ group showed a significant reduction in PPD, RAL, MMP-8 levels in GCF and A.a count in subgingival plaque samples when compared to the placebo group. Conclusion: The results showed more favorable clinical, immunological and microbiological outcomes with topically administered 0.2 % TQ gel when used as an adjunct to nonsurgical periodontal therapy in subjects with grade C periodontitis. Keywords: Thymoquinone, local drug delivery, grade C periodontitis, Nigella sativa Introduction: According to the current classification of periodontal diseases Aggressive periodontitis is named periodontitis grade C (1) . The prevalence of Aggressive periodontitis ranged from 0.3 to 4.5% of population, with the localized form being less prevalent (2) . Localized grade C periodontitis occurs mainly in teenagers with high risk of tooth loss at young age due to rapid progressive destruction of periodontal tissue and rapid alveolar bone resorption. It mainly occurs in the incisors and first permanent molars, and is generally symmetrically distributed. In addition, it can affect the adjacent teeth if not early treated properly (3) . Oral hygiene instructions and SRP are performed to reduce and eliminate the dental biofilm, and consequently, the pathogenic microbiota responsible for localized grade