Bacteria can get inside your tooth from tooth decay, a chipped or damaged tooth or filling, or gum infections which extend all the way to the root in a tooth. If the root of your tooth has become infected by bacteria you may experience spontaneous sharp or piercing pain or throbbing (especially when lying down), pain when biting or chewing, extreme sensitivity to hot or cold, persistent bad breath and discolouration from tooth decay. The pain associated with a root canal is caused by a build-up of pressure within the tooth. This pain can be controlled through the use of antibiotics before your treatment. Combining this method with current techniques and anesthetics means modern root canal therapy can be completely painless.