Why should you fill cavities in baby teeth? Why You Should Have Baby Teeth Filled Cavities result from tooth decay, which can be both the result of genetics or of poor dental hygiene. The more porous a tooth is, the more likely it is to succumb to tooth decay. ... For some children, so-called baby teeth can last until they are 12 or 13. Tooth decay is an infection. Should decayed baby teeth be pulled? Sometimes Extraction Is Necessary However, sometimes your dentist will have no choice but to pull the baby tooth early. If the decay is so advanced it's causing gum issues or pain for your child, extraction becomes the best option.