I wouldnt feed dry food only, it lacks the moisture a cat needs and if he doesnt actually like it then I'd stick to wet food. Most dry is full of carbs which cats don't need anyway, although some brands are now cottoning on to that fact and introducing high meat/low or no carb dry, like Applaws, but I still wouldnt feed only that. Dry food doesnt clean their teeth as was previously thought either, in fact it can contribute to dental problems, but nor will wet food keep their teeth clean. You can help to keep the teeth clean by giving chunks of meat (raw or cooked) that he has to tear at, or raw chicken wings (note - RAW bones only, never cooked).