Oral hygiene is a crucial factor in oral health, especially in children. To increase the awareness of oral care behaviour among children, oral care motivation plays a critical role in daily dental practices. Therefore, this cross-sectional study was conducted to investigate the current oral hygiene status and evaluate the association between oral care motivation and oral hygiene index in 7-9-year-old children at Primary School in Hanoi, Vietnam.

Clinical examinations were performed on 200 randomly selected children to assess the Simplified Oral Hygiene Index (OHI-S). Face-to-face interviews were applied to record students' intrinsic and extrinsic motivation for oral care through a questionnaire, which consisted of questions regarding demographic characteristics and oral care motivation. Data were analyzed using STATA 15.0 software and a p-value < 0.05 was statistically significant.

The mean OHI-S score was 2.48 ± 0.72. Good and fair oral hygiene were observed in 7.5% and 66% of participants, respectively. Students' motivation for dental care was predominantly extrinsic, with a mean score of 15.87 ± 1.322. Higher motivation in dental care is statistically significantly associated with oral hygiene index score (Coef=-0.27).

These results indicate that students with intrinsic motivation exhibit better oral hygiene practices. Consequently, strengthening oral health educational programs in primary schools based on intrinsic motivation could be helped improve the oral hygiene status and oral care behaviours of children.