Brushing teeth

My 16 month old hates brushing her teeth. She screems and pushes the toothbrush away. She will brush by herself for 5 seconds, but doesn't let us do it. Her pediatrician said it's fine to let her brush by herself once per day, but my husband or myself have to do it before bed.  We've tried brushing our teeth with her, letting her watch a YouTube video of kids brushing their teeth, during bath time, etc.