A double-blind randomized clinical trial was conducted for 14 days with 37 systemically healthy patients having chronic generalized gingivitis. The current study was designed to investigate the anti-inflammatory and antimicrobial efficacy of Nigella Sativa oil compared with chlorohexidine; assessing clinical parameters and gingival interleukin 6 (IL6) and interleukin 18 (IL18) levels and supra-gingival plaque analysis.

A total of 37 systemically healthy patients, aged between 20 to 40 years with chronic generalised gingivitis were recruited based on the inclusion and exclusion criteria, from the Dental Clinic at Princess Nourah bint Abdulrahman University. The sample size was based on previously reported studies conducted to assess gingival crevicular interleukin levels using mouthwashes. A study information sheet was provided to each patient and the methodology of the clinical trial was explained. Written informed consent was obtained from each participant before enrolling on the study.

A double-blind randomized clinical trial was conducted Ethical clearance was obtained from the Institutional Review Board at Princess Nourah bint Abdulrahman University (Registration number: 20-0261).

Subjects were assigned computer-generated random numbers and were blindly assigned to one of two groups; Group 1- Nigella Sativa (NS) or Group 2- Chlorohexidine (CHX) (n=20) according to the sequence of the computer-generated random numbers by an investigator not directly involved in the clinical examination and sample collection. The interventions were either N. sativa oil (Al-Hussan Food Products Factory, Riyadh, Kingdom of Saudi Arabia), which was brought from the local market in Riyadh or Chlorohexidine (Middle East Pharmaceutical Industries Ltd, Riyadh, Kingdom of Saudi Arabia). Group 1: Maintained adequate plaque control levels using mechanical methods + N.sativa oil (5ml oil + 5ml water) pulling for 3 mins twice daily in the morning and at night, and Group 2: maintained adequate plaque control levels using mechanical methods + chlorohexidine rinse twice daily 10ml in the morning and at the night.

Unified oral hygiene instructions and instructions for each intervention were provided to all participants. A 24-hour contact number was provided to each participant, to report any concerns, adverse reactions or for any further information. Participants were told that they were free to drop out at any time.

Oral prophylaxis was performed on the same day of recruitment to bring the plaque score to almost zero, and the subjects in each group were given either N.sativa oil or chlorohexidine according to the blind randomised allocation by a third person. On day zero (baseline) of the trial after scaling, and on day 15 at the end of the trial; the following clinical parameters were assessed; plaque index (PI) and gingival index (GI) and plaque samples, as well as gingival crevicular fluid (GCF) samples, were collected.

Prior to the study, two dental examiners were calibrated to measure PI and GI, to reduce inter-examiner variability.

The collected data were analyzed using Graphpad PRISM (San Deigo, USA). Non-parametric signed Rank tests and parametric t-tests were used, as well as Fisher's exact test for contingency analysis. P values were calculated and a p value below 0.05 was deemed as a significant difference.

Inclusion Criteria:

• At least 20 natural teeth
• Patients with moderate to severe gingivitis
• No tooth attachment loss

Exclusion Criteria:

• Periodontitis
• Cigarette smokers
• Antibiotic therapy (within the last 3 months)
• Systemic diseases
• Pregnant women
• Lactating women
• Current orthodontic treatment
• Using an intra-oral artificial prosthesis
• Using other chemical agents as a mouthwash

At this moment in time, there is no intention or need to make individual participant data available to other researchers.