It is a disease caused by pulp necrosis (death of nerve), causing the invasion of bacteria from the canal to the bone causing inflammation and infection in the tissues surrounding the root.
Decay or deep fillings that cause the death of nerve
History of trauma on the tooth
Deficient root canal treatments or contaminated
It may be chronic or acute
It is usually painless, although there may be sensitiveness when biting or touching the tooth. In some cases, it may appear a sinus tract (exit point pus) Radio graphically a dark area around the root (apical lesion) is observed.
Constant sharp pain that may be accompanied by inflammation.
Undoubtedly the best prevention is brushing the teeth and mouth, because that way the plaque is removed, without biofilm, decay do not appear.
Use dental floss to clean the areas where brushing usually fails, ie between the teeth. Eating a balanced diet without abusing of sugar consumption and try to do it with meals rather than between them.