Just a quick post to show people the general principle of a filling. Bacteria enter a small entry point but may eat away a significant amount of tooth on the inside. Your toothbrushing keeps the surface of the tooth looking and feeling solid. This is a case I did today which is a comparatively small cavity. See how much tooth can be damaged by a small hole causing no pain or symptoms whatsoever. That is why we say to have 6 month checks and cleans at the dentist. This tooth actually has two fillings. Which of the two do you think will be better for the tooth?
As always, remember dental decay is a progressive disease. Early damage is reversible, moderate needs a filling, severe needs a crown with or without root canal treatment, and extensive decay means an extraction. Prevention and early detection rules!