Tooth decay is full of bad bacteria, which are producing acid. This acid will dissolve the tooth structure, resulting in a cavity, a hole inside your tooth. If bacteria invade your tooth pulp, you’ll need a root canal treatment. This procedure removes inflamed nerves, blood vessels and connective tissues from inside your tooth. Next, your dentist will clean the inside tooth surfaces, then fill those spaces with a root filling material. In most cases, you’ll also need a crown to protect and strengthen your tooth.