Project Summary/Abstract One in 60 U.S. children has autism and many are at high risk for poor oral health – a problem that could be addressed in part through improved toothbrushing. Technologies like mobile health apps are an ideal platform to deliver toothbrushing interventions, but few app-based interventions have focused on teens with autism and the work to date has critical limitations. Our team developed an interactive toothbrushing training app called Brush Up, which incorporates concepts from Video Self Modeling. The app helps users develop toothbrushing skills through repeated self-observation and interactions with a cartoon exemplar that reinforces correct brushing. A front-facing (“selfie”) camera on the mobile device displays the child’s face and teeth. Children brush in tandem with the cartoon exemplar. We tested the app with typically developing children ages 5 to 6 years and found significant improvements in toothbrushing duration after only one week of app use. We then piloted the same app in individuals with autism ages 4 to 22 years. Caregivers of teens with autism were particularly enthusiastic about the app and recommended ways to make the app more autism-friendly by including features that account for sensory sensitivities common in autism. We further identified missing app features that if included would increase the odds of long-term behavior change. In this 6-year UG3/UH3 grant, we have 2 Aims: (1) Pilot the app-based intervention; and (2) Conduct a Stage II efficacy trial. During the 2- year UG3 phase, we will use the Discover, Design+Build, and Test Framework to modify our existing app to make it autism-friendly, develop a control app with only a digital mirror and timer, pilot the intervention with 40 adolescents with autism ages 10 to 17 years (Waisman score ≥21), and make necessary adjustments. In the 4-year UH3 phase, we will recruit 270 adolescents with autism, randomize participants to 1 of 2 arms, and compare outcomes. The trial will last 3 months. The primary outcome is toothbrushing distribution, defined as the mean proportion of tooth surfaces brushed during the last month of the 3-month intervention and measured in each arm by the respective app. Secondary outcomes are toothbrushing duration and frequency. We hypothesize adolescents in the experimental arm will exhibit better toothbrushing distribution, duration, and frequency than those in the control arm. App data will be collected continuously during the 3-month trial and up to 3-months post-trial. Survey data will be collected at baseline, 2 weeks, 1 months, 2 months, and 3 months to assess mediators (e.g., self-efficacy) and exploratory outcomes (e.g., habit formation, quality of life). Post-trial surveys will assess long-term change and interviews with 60 participants from the 2 arms will identify ways to further improve the intervention. If found to be efficacious, our findings could address an unresolved problem that affects over 1.2 million U.S. child...