I have a cat that I got when she was just about 1 year old. She would eat only wet food. When it came time for her next yearly check up,she already had bad teeth AT 2 YEARS OLD !!!! I was shocked. Needless to say, "dry food or nothing" I said. Well I could not get her to eat dry until I took the time to mix about a tablespoon of wet in with her twice daily meal of dry food. Well she is 6 now and no more teeth problems.
Also, some dry foods will make them more thirsty so they'll drink better. The food my cats are on is for the prevention of urinary tract infections and it makes the cats thirsty (because water consumption is a way to prevent the blockages from occuring). Your vet could tell you which ones will help in this matter (drinking that is)