Flossing under a bridge with tooth about to erupt in a few years

[shawnmcc]

I was wondering how to floss under a bridge molar attached to crowns with a molar about to erupt under it in a few years. It is pressing against the bridge the adult molar.

 

[shawnmcc]

I found out that I can put the tooth brush bristles under the molar but not floss. Will that be good enough cleaning till the new ones come in these bridges unbelievably 30 years old I don't really know how they lasted this long and before now I only did normal brushing.