Son doesn't brush his teeth for long enough so to combat this we bought a kids teeth brushing timer with a character from a cartoon he likes. When I brush his teeth we use it and there's no complaints.
On the few times husband actually remembers to brush sons teeth without me asking if he has, he does it for about 30 seconds. The other day I said "that was really quick" and reminded him we had the timer to encourage brushing for a decent length of time.
Today he's over enthusiastically sarcastically bouncing around the house upstairs "come on let's go brush your teeth for a very long time so make sure they're gleaming!!!!"
Surely he should be encouraging good dental hygiene??