Spaced Primary Dentition plays a critical role in the eruption of permanent teeth and the establishment of ideal occlusion. These deciduous spaces are a prerequisite to compensate for the discrepancy between the tooth sizes of primary and permanent dentitions and play a critical role in the later eruption of permanent teeth and the establishment of occlusion. Additionally, a lack of these spaces in deciduous dentition may result in disproportionate jaw and tooth sizes. Spacing in the primary dentition can be subdivided into two types: PRIMATE SPACE and DEVELOPMENTAL SPACE. Primate spaces are located between the lateral incisors and canines in the upper arch, and between the first molars and canines in the lower arch, whereas developmental spacing (also called Interdental Spacing) is found between the incisors in both the upper and lower arches. Notably, closed dentition without primate or interdental spaces can increase the risk of proximal dental caries. The absence of spacing in the primary dentition may increase the necessity of orthodontic treatment. Spaced dentition has been shown to be more common in males than in females. Coincidentally, crowded permanent dentition occurs more frequently in girls, and malocclusion and the demand for orthodontic treatment are higher in girls than in boys. In short, spaced deciduous dentition is necessary for the development of permanent dentition and normal occlusion (see Fig.).
Figure. Upper and lower occlusal views of Primary Dentition. (a) The upper dentition with space. (b) The lower dentition with space. (c) The upper dentition without space. (d) The lower dentition without space.