Patient presenting to the dental clinic with gingivitis and fulfilling the inclusion criteria will be included in the study after taking informed consent. Participants will be divided into three groups. Each group will be instructed to apply metronidazole gel, chlorhexidine gel or combination of metronidazole and chlorhexidine gel on the marginal gingiva. Measurement for the gingival index will be taken at baseline, at 2 weeks and at 4 weeks interval

Training of the examiner:

Participating investigators(Resident and supervisor) will be trained and calibrated on the development of the trial, case selection, measurement techniques, sample collection, data compilation sheets and their precise role in the study. In order to evaluate the intra-examiner reliability, five subjects not involved in the study will be evaluated twice by each investigator for the measurements at the interval of one week.

Methodology:

On the first visit after clinical examination, the specially designed baseline study proforma will be filled-in. The bleeding sites, probing depth and the gingival index score will be calculated.

Group A subjects will be instructed to apply a standard 0.2 % Chlorhexidine gel (clinica gel) on the marginal gingiva for the next 14 days, twice a day for 30 minutes, after morning and evening tooth brushing.

Group B subjects will be instructed to apply 0.8 % Metronidazole gel (anaerobic gel) twice daily for 30 minutes after morning and evening tooth brushing for two weeks.

Group C subjects will be instructed to apply 0.2 % Chlorhexidine gel (clinica gel) on the marginal gingiva after morning tooth brushing for 30 minutes and 0.8 % metronidazole gel (anaerobic gel) after evening tooth brushing for 30 minutes for two weeks. Subjects in these groups will receive the detailed and precise instruction and demonstrations on the diurnal alternate application of the two gels.

The application of the topical gels will be halted after 2 weeks and second clinical examination will be carried out for bleeding sites, probing depth and the gingival index score. Scaling & polishing of teeth in all three groups and oral hygiene instructions will be reinforced. Subjects will be recalled at 4 week for evaluation of gingival and oral hygiene indices. The reading will be recorded in the study proforma.

Randomization, blinding and treatment allocation:

Subjects will be assigned to one of the three study groups using a computer generated randomization list. The recruitment of the patients will be performed by one investigator. All the measurements at the baseline and follow ups will be performed by the second investigator. Patient, the operator (until the gel will be handed over by the dental assistant), the investigator who is taking the measurement and the statistician will be blinded about the intervention groups. This will be ensured by giving codes to the intervention groups only known to the principal investigator who is not involved in the measurement and interaction with the patient.

Inclusion Criteria:

• Patients having 20 or more healthy teeth
• Systematically healthy patient with no co-morbid
• Subjects with clinically confirmed gingivitis having positive bleeding gums on probing in every sextant
• Subjects having teeth without any clinical attachment loss

Exclusion criteria:

• Subjects with clinical attachment loss of greater than 2 mm on two sites
• Pregnant or lactating females
• Subjects with removal or fixed dental prosthesis
• History of surgical or nonsurgical periodontal therapy in the last 6 months
• Use of antibiotic in the last 30 days
• Habit of smoking or use of smokeless tobacco
• Allergic to Metronidazole or Chlorhexidine
• Presence of any craniofacial syndrome patients
• Patients on medications that have effects on gingival conditions (such as Nifedipine, Cyclosporine and Phenytoin etc.

Subjects will be assigned to one of the three study groups using a computer generated randomization list. The recruitment of the patients will be performed by one investigator. All the measurements at the baseline and follow ups will be performed by the second investigator. Patient, the care provider, the investigator who is taking the measurement and the statistician will be blinded about the intervention groups. This will be ensured by giving codes to the intervention groups only known to the principal investigator who is not involved in the measurement and interaction with the patient.