Research has shown that periodontal disease is caused by the inflammatory reaction to bacteria under the gums, so periodontal disease technically may not be contagious. However, the bacteria that cause the inflammatory reaction can be spread through saliva. This means that if one of your family members has periodontal disease, it’s a good idea to avoid contact with their saliva by not sharing eating utensils or oral health equipment. If you notice that your spouse or a family member has the warning signs of a possible periodontal problem (bleeding, red and swollen gums, or bad breath) you may want to suggest that they see the periodontist for an exam. It may help to protect the oral health of everyone in the family.

–Perio.org