Dr. Paul G. Byers

That is an excellent question. There are many strains of bacteria that live in the mouth. The question is really one of balance. In a healthy mouth, the bacterial counts are low. The gum are healthy because the body's natural immune system is able to keep thing in check.
When gum disease sets in, the bacteria begin to get out of balance. The immune system kicks in to do what it's "programmed" to do, i.e. dilate capillaries to deliver more blood and white blood cells to the area yo fight the infection. At this point, the bacteria can get into the blood stream and colonize elsewhere in the body, e.g. leaky or weak heart valves, prosthetic joints, etc.
Routine dental vists, cleanings, and meticulous homecare can help to prevent this from becoming an issue.

Regular flossing contributes to maintaining healthy teeth and gums by removing the bacteria and food debris that accumulates between your teeth.
Regular flossing, at least once daily, is recommended because of the short time it takes for the bacteria to "set up shop" on your teeth.
Gently slip the floss through the contacts and, making a tight "C" with the floss against the tooth, glide the floss up and down the tooth surface. Remember between every 2 teeth, there are 2 surfaces to clean. Do NOT snap the floss in as this may traumatize the gums.
Generally, it is recommended to use lightly waxed floss.

There could be several reasons. Without seeing a radiography (X-ray), it's difficult to say. Contact your general dentist, or the specialist who performed the treatment.

Getting numb for a dental procedure is not always necessary. Everybody's tolerance is different, but in my experience, small cavities can be completed without anesthetic with less discomfort that getting the shot, thereby reducing the length of time you have to be in the chair as well as not having to be numb for several hours after the procedure.
While I don't recommend it for everyone, I realize that every patient has a different tolerance. If you think you would like to try it, go for it! Just let the dentist know that if you want to get numb during the procedure, you want to raise your hand to let him know and you WANT to get numb. You might surprise yourself.

Yes. Gum disease directly affects you ability to control your diabetes and in turn your uncontrolled diabetes makes it more difficult to manage your gum disease. I recommend two things:
1) a complete oral examination to determine the extent of the gum disease and to establish a treatment plan to address the dental issues, and
2) a visit to your primary care physician to address the diabetes.
Uncontrolled diabetes will not only have oral issues, but can lead to other serious general systemic health issues.