The Complete Deciduous Dentition
The deciduous dentition is complete after all second deciduous molars have attained occlusion, usually at around 2.5 years of age. Both dental arches are about half-round in shape. Diastemata are usually present between all teeth and particularly in the anterior region. More than sufficient space is available for a harmonious alignment of the deciduous teeth in both dental arches (Fig. 3-1). In the anterior and posterior regions, the teeth are oriented almost perpendicularly to the occlusal plane (an imaginary plane through the incisal edges of the central incisors and the distal cusps of the last molars). This orientation holds true for the mesiodistal as well as the buccolingual direction. The mandibular teeth occlude slightly lingually with the maxillary ones. The first and second deciduous molars make contact over a large area and function as grinding units in chewing. In occlusion, the mesial surface of the mandibular first deciduous molar is positioned anteriorly to that of the maxillary one; the same holds true for the two opposing second deciduous molars.
The variation in mesiodistal crown dimension of the mandibular second deciduous molar is considerable. In situations with a relatively large mesiodistal crown dimension of a mandibular second molar and otherwise normal circumstances, no mesial step generally is present at the distal surfaces of the opposing second deciduous molars (terminal plane), as is illustrated in Figure 3-1D. The terminal plane of the deciduous dentition will be flush.
Little changes take place in the deciduous dentition from age 2.5 to about age 5. This applies to the position of the individual teeth as well as to the sagittal and transverse relation between the two dental arches. The absence of obvious changes in the position of the deciduous teeth cannot be considered as a sign of arrest in the process of the development of the dentition as a whole. Superiorly and lingually to the deciduous teeth, the formatio/>