Objective: To evaluate the effectiveness of the WhiteTeeth mobile app, a theory-based mobile health (mHealth) program for promoting oral hygiene in adolescent orthodontic patients.

Methods: In this parallel randomized controlled trial, the data of 132 adolescents were collected during three orthodontic check-ups: at baseline (T0), at 6-week follow-up (T1) and at 12-week follow-up (T2). The intervention group was given access to the WhiteTeeth app in addition to usual care (n = 67). The control group received usual care only (n = 65). The oral hygiene outcomes were the presence and the amount of dental plaque (Al-Anezi and Harradine plaque index), and the total number of sites with gingival bleeding (Bleeding on Marginal Probing Index). Oral health behaviour and its psychosocial factors were measured through a digital questionnaire. We performed linear mixed-model analyses to determine the intervention effects.

Results: At 6-week follow-up, the intervention led to a significant decrease in gingival bleeding (B = −3.74; 95% CI −6.84 to −0.65) and an increase in the use of fluoride mouth rinse (B = 1.93; 95% CI 0.36 to 3.50). At 12-week follow-up, dental plaque accumulation (B = −11.32; 95% CI −20.57 to −2.07) and the number of sites covered with plaque (B = −6.77; 95% CI −11.67 to −1.87) had been reduced significantly more in the intervention group than in the control group.

Conclusions: The results show that adolescents with fixed orthodontic appliances can be helped to improve their oral hygiene when usual care is combined with a mobile app that provides oral health education and automatic coaching. Netherlands Trial Registry Identifier: NTR6206: 20 February 2017.