No moral hazard, but there is a hazard to not brushing your teeth: cavities, and more explicitly, the financial cost of having cavities repaired. Even the best dental insurance plans in America are capped at $1500 - $3000 of benefits a year, usually less than a single root canal or crown.

But that does open the door to a very interesting question (far outside of the scope of this discussion): would people change their habits of brushing their teeth if that hazard didn't exist, e.g. your dental repairs were free? D: