Unhealthy mouth can cause focal infection, a local infection that causes subsequent infection in other part of body.
Focal infection can carry bacteria into blood vessel trough cavities and gum inflammation that can cause Endocarditis ( Inflammation of heart valves), Atherosclerosis (Inflammation of walls of arteries), heart defect, and cardiac arrest.
Lack of oral hygiene can also increase risk of heart diseases such as coronary heart disease and Gingivitis that can cause rapid blood freezing that can lead to stroke.
Oral bacteria that find it's way into the blood vessel can also effect pregnancy. It can stimulate premature birth and infant disabilities.