Fig. 1

The responses of parents’ oral health knowledge. Item 1: It is normal for gums to bleed while brushing teeth; Item 2: Bacteria is one of the causes of gingivitis; Item 3: Brushing teeth does not help prevent gingivitis; Item 4: Bacteria causes dental caries; Item 5: Eating dessert is associated with increased dental caries risk; Item 6: Fluoride does not help to protect teeth; Item 7: Pit and fissure sealing can prevent caries; Item 8: Oral diseases will cause some certain systemic diseases; Item 9: Dental plaque is the main cause of caries and gingivitis. The response ‘wrong’ of item 1, 3, and 6 is the correct response, while the response ‘right’ of other items is the correct response. The response ‘right’, ‘don’t know’ and ‘wrong’ was scored 1, 0, and 0 respectively