For more than 70 years calcium hydroxide has played a major role in endodontic therapy, although many of its functions are now being taken over by the recently introduced material MTA. Calcium hydroxide may be used to preserve the vital pulp if infection and bleeding are controlled; to repair root fractures, perforations, open apices and root resorptions. Endo-perio lesions are complex and the correct diagnosis is essential if treatment is to be successful. However, root canal treatment will always be the first phase in treating such lesions.