The gum disease is an inflammation of the gum caused mainly by the biofilm (dental plaque).
You can detect it by the bleeding of the gums during the brushing, the change of colour (red patches), the change of appearance, or the presence of swelling, and sensitivity at the level of the gums.
The gum disease is caused by a bad hygiene, a systemic disease, hormonal changes (e.g.: puberty, pregnancy, menopause, etc.), or the side-effect of a drug, etc.