MF had it too?
so that disease must be inherited correct?
Not necessarily. Periodontal disease is just a fancy way of saying gum disease. It can be inherited, but it's fairly common even today, and is usually caused by inadequate oral hygiene. Not that the IF didn't take care of their teeth -- it's just that oral care (particularly home oral care) has come a long way since the turn of the century.
From
www.perio.org:
"The main cause of periodontal disease is bacterial plaque, a sticky, colorless film that constantly forms on your teeth.
"In the mildest form of the disease, gingivitis, the gums redden, swell and bleed easily. There is usually little or no discomfort. Gingivitis is often caused by inadequate oral hygiene. Gingivitis is reversible with professional treatment and good oral home care.
"Research proves that up to 30% of the population may be genetically susceptible to gum disease. Despite aggressive oral care habits, these people may be six times more likely to develop periodontal disease."