Dog show and?

i have been just back from a dog show and my Kerry Blue terrier got 2 firsts and best in show but the judge said that his teeth are letting him down when he enters in some categories , how can I solve this as he has got yellow teeth , mostly in the top ! serious answers only, we have tried to brush them but he does'nt like it, he is 7 yrs old. and we only enter him into local dog shows.