All on 4 dental appliance failure - what is the strongest appliance available?

I had the procedure done about 2years ago, I have 6 implants in the upper arch and 5 in the lower arch. All my implants are good but it’s he appliance that keeps breaking and I want the strongest available appliance available. I don’t trust my dentist I feel I was miss led and never really had a choking on material color or size.