Childhood neoplasias have become increasingly important in recent years in the ambit of paediatric medicine. This phenomenon has been accompanied by a spectacular improvement in the treatment of childhood cancer, long-term survival rates reaching 90% in the case of some tumours. A corollary of this success is the obligation to provide new and improved medical assistance both as regards the possible prevention of any alterations and, if possible, the avoidance of complications derived from the neoplasm itself and its treatment. Among possible secondary effects are oral manifestations of a chronic or acute nature, which may cause great discomfort, act as foci of systemic infections or have long-term after effects, all of which will depend on the exact moment of the child s development that treatment is undertaken. The incidence and severity of most oral complications is associated with pre-existent factors, such as caries, gingivitis or generally poor hygiene, which strongly affect the beginning, increase and persistence of the same. It is to be decried that a problem in the buccal cavity is allowed to develop, which a simple preventative measure, simple hygiene or dental conservation treatment could prevent or reduce.