Go off it's food
Have runny eyes
Have a dirty bum
If your rabbit does have dental problems, speak to a vet, it may need it's teeth trimmed or rasped.
Unlike human teeth, rabbit teeth keep on growing throughout their life. Consequently, rabbits need to spend lots of time chewing to wear down their teeth.
If rabbits do not wear down their teeth they will grow too long and turn spiky and then they will dig into their cheeks and tongue, causing painful ulcers.