One of the most important points about tooth decay is that you don't always recognize it when it's in the early stages.
Which is exactly why it’s important to see your dentist or dental hygienist regularly for a thorough cleaning and oral exam, in addition to following a consistent oral care routine of twice-daily toothbrushing and daily flossing.
Whether decayed teeth cause a toothache depends on where they're located. A cavity in the tooth enamel doesn't cause pain. In fact, you won't notice that you have a toothache until the decay reaches the dentin, the softer mid-layer of a tooth that lies between the enamel and the pulp. Decayed teeth can be saved if they are identified while they affect only the enamel or dentin, but if they decay reaches the nerve-filled pulp at the center of a tooth, a root canal or tooth extraction may be necessary.
A root canal will preserve the tooth, but in severe cases your dentist may recommend tooth extraction instead. If you have a tooth removed due to severe decay, it's important to practice good oral hygiene and follow your dentist's instructions for keeping the gum tissue clean while you consider options for a replacement tooth or teeth. Replacing missing teeth is important for oral hygiene for several reasons, in part because you will keep the neighboring teeth from shifting and affecting your bite.