Once you indicate which hand you brush with, the app invites you to use its "smart brushing analyzer," which taps artificial intelligence to map your mouth and give feedback on how long you've brushed and which spots you've missed. The E1's vibrating bristles were more comfortable than those of most electric toothbrushes I've tried, but on my first run I earned a scolding. It seems I only brushed for 79 seconds, rather than the recommended two-minute minimum, and skipped five teeth entirely. On later brushes, a pushy in-app coach painstakingly guided me through scrubbing both sides of the teeth in every corner of my mouth. The coach offers an illustrated view of your teeth, tracking each section as you brush and warning if you go astray. The biggest challenge was figuring out exactly where to prop my phone; I needed to see it clearly but not risk drooling on it (as I learned the hard way) or accidentally elbowing it into the toilet.