Amalgam VS. Composite

What is the difference between composite fillings and amalgam fillings?  They are different in color, obviously one being tooth colored and the other being silver.  In addition, there are structural differences and differences in placement technique that are important to consider when you are deciding between the two.  Silver fillings tend to cost less, however, silver fillings require that a certain amount of your tooth be removed so that the silver will be strong.  This means that even if the cavity is small, the filling requires that healthy tooth structure may be removed.  A composite filling is bonded to teeth, and can remain small:  only the cavity need be removed to restore the tooth.  New advances in composite fillings are making them more similar in longevity and strength as silver fillings without having to drill so much of the tooth out.  Ask your dentist to recommend a filling material to you according to your individual needs.

"But my teeth aren't bothering me at all..."

Usually, by the time your teeth are aching, a lot of work needs to be done.  If a tooth is sensitive to temperature or sweets, but the sensitivity goes away when the cold/sweetness goes away, then this can be either a cavity in the tooth or just a normal tooth response .  If a tooth is aching, throbbing, and keeping you awake at night, you can classify it as a toothache.  Either way, sensitivity in teeth should always be evaluated by a dentist in order to rule out decay or dying teeth or infection.  As previously posted, regular visits to your dentist are not just for the purpose of cleaning your teeth, but also for the purpose of evaluating any needs.  Once evaluated, if any cavities or fractures are found by your dentist, treatment can be recommended.

Even though your teeth may not hurt, they still may have something like a cavity or fracture developing that is best to treat early.  Early treatment is usually more conservative, leaves more natural tooth structure, and is less costly.  The cost-effectiveness of prevention is much less than the cost of fixing things that are to the point of causing pain, and don't wait if you have a toothache because it won't get better on it's own:  there will always be an underlying threat of severe infection.

Perhaps one of the largest contributors to gum disease in recent years is smoking.  Smoking, like diabetes, causes the blood supply to the gum tissue to decrease, leading to lessened healing.  Remember our mouth usually heals rapidly when compared to tissue outside of our mouth.  With less blood supply, gum tissue is more easily overrun by bacteria.  Also, smoking can cause a dry mouth, which the bacteria love:  they grow more rapidly without saliva to wash them away.  Finally, smoking is one of the leading causes of oral cancer.
A crash course in the process of gum disease is as follows:  first, the bacteria build "soft houses".  This is the fuzzy feeling on our teeth that we want to brush off when we notice it.  If given enough time, the bacteria build "hard houses" otherwise known as tartar, or calculus.  This is similar to the build-up found in old plumbing.  Most of us will remove the bacteria when we feel the fuzziness, but when gum disease is present, we cannot clean deeply enough to remove all the bacteria, so they are free to keep building.  This, in turn, causes more swelling and deeper pockets, which trap more bacteria.  All of this bacteria must be cleaned out by a professional at your dentist's office.
There are resources to help you quit smoking, which will save your mouth from the nasty side effects and definitely cost less from both the cost of buying smokes and the cost of repairing the damage done.