Table 1 Exclusion criteria

 1. Under eighteen-years-old

 2. Systemic disease (malignant tumour, alimentary tract haemorrhage, systemic infection)

 3. Pregnant or breastfeeding women

 4. Active dental caries, apical periodontitis, periodontal diseases, pericoronitis

 5. Orthotics or removable denture in the mouth

 6. Less than 24 teeth in the mouth

 7. Systematic antibiotics or immunomodulators within 3 months

 8. Oral topical administration of antibiotics or fluorine within 2 weeks