Endodontic therapy is root canal treatment. When decay affects dentine, microorganisms and toxins may reach the dental pulp (nerve fibers, blood vessels and lymphatic vessels), thus causing inflammation. Clinical symptoms: spontaneous, pulsating and spasmodic toothache, especially at nighttime, and pain caused by various irritants. However, there can be no distinct symptoms. Irreversible changes take place when inflammation spreads to the entire tissue of the pulp. So, in order to protect alveolar bone from toxins, the pulp must be removed from the tooth root canals, and endodontic specialist must prepare it for canal filling. That is what endodontic treatment is for.