The research assumes that there was a correlation in people who had gum disease and heart disease because this population of people tend to not take care of their health overall. In other words, those people who do not pay attention to well-known prevention methods, like not smoking, correct diet, exercise and diabetes prevention, are also less likely to have good oral hygiene.
This paper goes on to say that the previous work showing a relation between gum disease and cardiovascular disease is "unwarranted", and that long-term trials are needed to make a final conclusion.
So, keep those pearly whites clean and pretty because a healthy smile is a pretty smile, but unfortunately, we cannot assume that it is helping your heart.
Keep on shining!