I don't know, from what I remember my company's dental plan didn't make financial sense. FWIW if insurance covered 80% these fillings would have cost me $300. So $300 plus the cost of dental insurance for the past 2.5 years, would I really have saved that much compared to $1,300 out of pocket today?
Keep in mind both of my checkup cleanings were only $60 each, I know they would have been free with insurance though.
tl;dr I gambled and lost, but not too bad. I'll get dental insurance going forward though for the free cleanings
If it was like $30+ a month then I can see how you can justify it over the 2.5 years but if it's less then you dun goofed ---