Does he have incisor problems? I've had 3 buns with mallocluded front teeth and none were very keen on hay until I had them removed.
Since two of them have molar problems too, it's important for me to get them to eat hay, or as you said, they'll have more molar problems.
After Mary developed his first spur, he was needing dentals every month or two, so I had a good think about his diet and made some dramatic changes.
Firstly, he got timothy hay as his main hay, rather than meadow hay. I used to get it from the chinchilla2shop site, but now buy from Bunnybasics as it's cheaper (but looks exactly the same). Nowadays they also get meadow hay - I get my boss to order me in several different types at work if I think they look good quality, and switch around to give them a change, and they seem pretty keen on several of the ones I get so I'd rather they eat that if they like it. They also occasionally get seed hay from chinchillas2shop as they love it (but it's been out of stock for ages until now)
He only got the bare minimum of pellets - and only because he's an indoor bun needing the vitamins, and he's always been on the small side so I've not wanted to cut pellets out completely. I switched to Science Selective rather than Excel because of the higher fibre content and the shape of them - they seem more like the bun would have to grind them than just bite into them (probably a load of rubbish but he loves them and it's been good for my buns with sensitive tummies/fussy eating habits!)
I also started giving chopped hay in a bowl daily. I alternate between a few different kinds so they don't get bored, but I feed any/all of the following:
Readigrass (not all the time as it seems a bit rich for one of my buns)
JustGrass (like Readigrass but apparently better quality/higher fibre - available from chinchillas2shop)
Timothy chop (from Bunnybasics)
High fibre grass chop (Bunnybasics again)
Combomix (chinchillas2shop)
And now all my buns have had their vaccs I try to get them out on the grass as often as possible, so they eat that and wear their teeth down.
They also usually get a lot of green leafy veg - haven't recently because I've been ill for the last month or so and it's just drained all the energy out of me, and they seem fine without it (and have the grass as a replacement). When they had veg it was things that they'd have to grind down, like carrot tops, curly kale, green cabbage, etc. in pieces as large as they can manage (considering they're 3 dwarf/mini breeds with small mouths and no front teeth!)
This diet really seems to work - Mary's not had a dental since March last year and is still going strong (though going to the vet this afternoon for a routine checkup) and Squishy hasn't needed a dental at all for his molars (and I've had him about 6-8 months - he's always been on this diet as I was aware he may get molar problems, having had malloclussion for genetic reasons like Mary rather than a trauma to the teeth like Rex did)