Recent patent filings hint that Dyson is working on a toothbrush with a built-in water flosser, according to an article by Gizmodo.
In the article, author Andrew Liszewski cited a patent filed by Dyson that describes a "dental cleaning appliance" that has a built-in refillable reservoir for "storing a working fluid" that can be delivered to the "oral cavity of a user" while they're brushing. The patent also references "interproximal cleaning" suggesting in-between teeth cleaning.