Humans have two sets of teeth, hence called dipyodont. The first set is called primary dentition, because of its first arrival in the oral cavity, it is a transitory phase and it is finally replaced by a set of permanent/secondary dentition through a mixed dentition period. The role played by primary dentition is very crucial and has far reaching consequences even though they stay for a very crucial short duration of the whole human life. The primary dentition acts as a guide for the erupting permanent successors as it acts as a space maintainer for the permanent dentition. Any pathology which leads to loss of teeth or tooth structure leads to migration of adjacent tooth/teeth in the newly created space. This process leads to impingement of crucial space for the eruption of the succedaneous dentition leading to malocclusions. Space maintainer is a fixed or removable appliance designed to preserve the space created by the premature loss of a primary tooth or a group of teeth. We have discussed about factors influencing space loss after premature loss of primary teeth and various types of fixed and removable space maintainers in maintenance of arch length.