Females have a lower incidence of hypertensive and cardiovascular disorders that may relate to differences in nitrogen oxides in the blood and saliva. Some nitrogen oxides are recycled with the help of oral bacteria to nitric oxide which is protective against vascular disorders. This study will test the hypothesis that females have different numbers and species of these nitrogen-oxide reducing bacteria.

Inclusion Criteria:

• Healthy subjects aged 18-45 who have volunteered themselves and are willing to sign the consent form

Exclusion Criteria:

1. Healthy subjects unwilling to consent
2. History of hypertension, diabetes or hypertensive on BP measurement
3. Pregnant, or any possibility that a subject may be pregnant unless in the latter case a pregnancy test is performed with a negative result
4. History of any serious illnesses, including recent infections or trauma
5. Subjects taking systemic medication (other than the oral contraceptive pill)
6. Subjects with self-reported use of mouthwash or tongue scrapes
7. Subjects with recent or current antibiotic use (within 3 months)
8. Subjects with a history, or recent treatment of (within last 3 months) of any oral condition (excluding caries), including gingivitis, periodontitis and halitosis

Community sample