After premature loss of deciduous teeth, the remaining teeth in the dental arch are prone to migration and thus reduce the space required to accommodate permanent teeth. The safest way to prevent future malocclusions is to install a space maintainers. Their purpose is to keep the space open until permanent teeth erupt. They can be used to reduce the severity of developmental malocclusion, the complexity of orthodontic treatment, the overall treatment, the time, but also the patient's finances. Before their application, it is necessary to take a comprehensive anamnesis, perform a detailed clinical examination, assess the available space and examine and determine the patient's oral hygiene. The need to apply a space maintainers can be greatly reduced by good preventive measures in decidous and mixed dentition.