DESIGN: Prospective, single-blind, randomised controlled trial with an allocation ratio of 1:1 over a 12-week follow-up.

SETTING: Government Orthodontic Unit, Raub Dental Clinic, Raub, Pahang, Ministry of Health, Malaysia.

PARTICIPANTS: A total of 40 patients aged 13-25 years undergoing orthodontic treatment with fixed appliances.

METHODS: The 40 patients were recruited and randomly allocated to a control (n = 20) or trial group (n = 20). Participants in the trial group received weekly oral hygiene reminders via the WhatsApp application for 12 weeks, while the control group did not receive any reminders. The primary outcome was oral hygiene, which was measured by the single-blinded examiner using the Orthodontic Plaque Index (OPI) at three orthodontic check-ups: baseline (T0); 6-week follow-up (T1); and 12-week follow-up (T2).

RESULTS: The mean age was 17 years, and 80% were female patients. At the end of the 12-week follow-up, improvements in OPI scores were observed, regardless of the intervention. At T2, the median OPI score for the trial group (n = 20) was 0 (interquartile range [IQR = 0) while that for the control group (n = 20) was 2 (IQR = 0). A Mann-Whitney U test revealed a statistically significant difference (P <0.05), with effect size r = 0.87 between the control and trial groups, whereby the latter witnessed marked improvement in OPI throughout the visits. No harms or adverse effects occurred in this trial.