Age Variation of Formation Stages for Ten Permanent Teeth

Differences in the development among children of the same chronologic age have led to the concept of physiologic age as a means to define progress toward completeness of development or maturity in the individual child. Thus, physiologic age or its frequently used synonyms, biologic and developmental age, are measures for describing the status of an individual child, whereas chronologic or calendric age convey only a rough approximation of this status because of the range in development observed for any given age. Physiologic age is estimated by the maturation of one or more tissue systems, and it is best expressed in terms of each system studied. Maturation is scaled by the occurrence of one or the sequence of multiple events that are irreversible. The dentition is one of the four systems used. The other three developmental indicators refer to bone development, secondary sex characters, and stature or weight. Dental age can be determined by the emergence and by the formation of the teeth. Tooth formation is superior to tooth emergence for assessing dental maturation, because the majority of the teeth can be studied at each examination. In contrast, emergence is only a specific phase of short duration in the continuous process of eruption, rarely observed for more than one or two teeth at a time, if at all. Emergence is also influenced markedly by environmental factors such as loss of deciduous predecessors and the lack of space in the dental arch, explaining some part of the variation in root length at emergence." 2 Dental maturation is of particular significance for the timing of growth changes of the dentition in the living3 and for aging skeletal specimens when only jaws remain.4 Nevertheless, inferences of somatic maturation from either tooth formation or tooth emergence should be made with caution, because the relation of dental development and somatic development, as estimated from bone formation in the handwrist region and the appearance of secondary sex characteristics, is not, as yet, fully explored.5 In general, a low-to-medium degree of association exists for all maturity indicators, but during the adolescent growth phase, the measures of somatic development are more highly correlated.6 The purpose of the present study is to provide norms of the formation of ten permanent teeth, namely, the maxillary incisors and all eight mandibular teeth. The