Flossing is an obvious way to disrupt pathogenic bacterial colonies by abrasion. I think irrigation is much better, as it reaches deep pockets below gums. But it doesn't replace flossing entirely.
Those two, coupled with regular brushing of teeth, gum and tongue, plus oral probiotics should keep issues at bay.
In particular, my experience with probiotics is that tartar calculus fell apart within a few months. I have never had a cavity.
Sadly most dentists don't place too much emphasis on these as it goes against their business model: drill, fill and bill.
