Fillings replace tooth structure that was damaged by decay. It is called a filling because a new material fills the hole that decay left. Caught early enough, cavities can be treated easily and painlessly. However, if left untreated decay can lead to tooth pain and/or infection.
Bonding involves adhering composite resin material that is matched to the color of the tooth, to the front of the tooth. This is done to repair damage done to the teeth by decay, to alter the alignment of teeth, close gaps between the teeth, or for cosmetic purposes.
This is used to fill in narrow grooves in a tooth that cannot be adequately cleaned by brushing. In some cases, the tooth structure has fine grooves or pits which accumulate plaque, not because the person doesn't brush, but because they're too narrow to allow even one bristle into them. These will develop cavities over time. The dentist will brush on a coating that seals the grooves and pits, making it possible to brush off all the plaque and keep your teeth healthy.
X-rays are used to diagnose defects in the bone and between the teeth. X-rays are a necessary part of the diagnostic process, and not to use them could lead to undiagnosed disease. Without an X-ray of the whole tooth, and supporting bone and gum tissues, there is no real way to detect infection or pathology that requires attention.
In our office we use state-of-the-art digital radiography which allows us to take X-rays using 70-95% less radiation versus conventional X-rays.