Disease
The medical term for a gum infection is gingivitis and describes an infection limited to the area of the gums. Due to the infection the gums are swollen, reddened and tends to bleeding when touched (e.g. while tooth brushing). This may lead to avoidance of this areal during the cleaning process.
But it is the opposite that helps! the stains have to be removed diligently from the infected sections, because gingivitis is curable and can be improved at home by simply improving one's dental hygiene.