From the research I had to do when I had two cats with medical issues was that the dry food for teeth thing was outdated information. Just like many medical/nutritional things with humans, they learn new things everyday. That's not to say that dry food is torture for your cats, but think about it...do felines in the wild eat the kind of things that make up the bulk of dry food (even the grain-free ones)? That being said, it's a debate that can go on forever, and most pet parents who decide one between the other are just doing what they think is best.
Now..my experience: as my cats aged, they started putting on weight, having dry dander issues, skin chewing, and overall just various medical probs (mostly to do with age). I was also plagued by a purger...you know the type, scarf and barf? First, I tried switching them from regular dry to a higher quality grain-free dry (not too hard since this was just after that event where so many animals died from the pet food). I did notice some improvement in other areas, but still no weight loss. Two vets -- my regular and a vet specialist (long story), mentioned a lot of cats bulk up on dry food. So I switched them to half wet/half dry. Holy cow! Like new kitties! The bulk started slowly fading, their fur became glossy and dander-free, and the barfing stopped. And the best part...less litter box messes to clean, iykwim

. (in their case, apparently carbs=more potty).
Here's the part that may actually help you, because I had to struggle to make the transition too.
1) make a slow transition -- give them wet as a treat, then put it next to the dry, then start giving them more wet, less dry...if that means they still ignore the wet, at dinner time put the wet down first, wait and hour, then put down some dry
2) if you don't have a set dining time, make one. If you free feed dry through out the day, stop. Get earplugs for the yowling
3) you can try blending the wet with the dry all together, but in my experience this meant NO food was eaten
4) you may have to try many different types of wet before you find the one that works. Start out at Petco or Petsmart trying various ones of the small cans. Don't be too discouraged --there's a key for every lock.
5) In my case, my cats wouldn't eat the chunky type...would just lick the gravy. I always went for the "pate" type. Now and again I accidentally bought the chunky, in which case I'd mash it
6) try mixing some pumpkin with their wet. My cats thought it was a great treat, and it's really good for them. Oddly they HATED fish oil additive though.
7) remember not to use too many fish-based wet foods -- it can exacerbate urinary issues
8) all wet food is not created equal -- some are just as junky as those cheap dry foods i.e. all nasty fillers. Avoid ones with meat by-products if you can.
9) Don't worry if you can't get your cat to eat only wet. One of my cats never made the full transition, and was not eating enough, so I just made sure she got a wee bit of grain-free dry.
10) It is FALSE that you should just let them go hungry if they won't eat, with the premise that one who gets hungry enough will give in and eat. This may happen, but truly cats can go on one heck of a hunger strike before they do. And the fact is that, due to their anatomy, even a short time without food or even too little food can cause liver damage. They are not humans, nor are they dogs. Their unique system means this is an issue you shouldn't play around with. Which also means that if you notice they are not eating enough of their wet food, don't be stubborn. Give them some dry and try again later.
Best of luck to you and your feline friend.