After everything I have been through and all my research, I believe the reason we all get gum disease and periodontitis is bacteria or fungus which ends up in our gums. It could be coming from decay in the teeth to start with and let me tell you, you cannot take notice of a dentist if they say you have no decay, it took me 3 dentists and an oral pathologist later to find out that I DID have decay in a crowned tooth which I had for 25 years. I was told by 2 dentists and an oral pathologist that there was NO DECAY UNDER THAT CROWNED TOOTH! There was as it turned out, that bad that the tooth had to be removed.
Straight away my health got better, not 100% but much better. I am now in the process of making sure I get rid of any other decay in remaining teeth, then maybe hopefully all the parasites and bacteria and fungi will be gone and hopefully then my gums will start to heal. If you have no decay for certain in your teeth you may need to do a parasite cleanse and get rid of them in other parts of your body, if you don't they keep traveling through the bloodstream setting up home wherever they like, even the gums. Mora therapy is a good way to diagnose and treat any kind of pathogens.
I have been coconut oil pulling with oregano, clove, thyme (they say the best for fungus) neem oil is very good and tea tree oil. Swishing with baking soda and taking internally capsules of oregano, neem, and thyme essential oils. (make sure they good quality essential oils, I use doterra)
For me taking 2 extra strength garlic capsules first thing in the a.m. with 2 heaped teas. diatomaceous earth and good 1/2 teas bentonite clay helps me heaps, then again I have been diagnosed with aspergillus, (a fungus) which I have no idea how I got, then who knows it could have also come from decay. Hope this info. helps anyone with a similar problem, all this has come from many hours of research and listening to oral health summits online.