Hi Nigglynellie and all
I have had periodontal disease and for a considerable time although they didn't think to tell me until 5 or so years ago and then didn't really offer much help. Eventually I finally had a dentist who gave me good advice and I had to go to the dentist every 3 months. I brush normally with an electric tooth brush, morning and night, floss daily and use a small dental brush between my teeth. Try to buy toothpaste that is at least 15,000 ppm - some supermarkets own brand fit the bill. I have also given up smoking as this is seen as a partial cause by the dental profession. Gradually, over time my condition has improved and my teeth seem to have stabilised - lost 2 but they were pretty well filled and one had an on-going abscess. At lunch time I quite often use mouthwash, especially if I have been taking any form of sugar, although a small piece of cheese neutralises the mouth successfully (so I understand).
I do think some of it is hereditary as my father had it but smoked like a chimney and DD2 has begun to have the same problem - never smoked in her life and eats little sugar.
Apparently citrus fruit softens the enamel and teeth should not be cleaned until after 20 minutes of indulging, the same goes for soft drinks that are acidic. Hope this helps and keep on with whatever regime the hygienist has given you. Over time, hopefully it will improve