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THE PROCESS of tooth emergence is traditionally a source of information on the status and progress of physiologic development. Concentrating on the applied aspects of the problem, authors of the studies in the literature are publishing for the practicing dentist, orthodontist, and forensic anthropometrist. The practitioner has found this material useful within broad limits in planning treatment and as a criterion of age. However, both the practitioner and the research worker would profit from a more detailed analysis of the patterns of dental eruption.Studies of the emergence of the teeth of the Pima Indians showed that replacement of the deciduous teeth with the permanent ones is for them a process which starts later and finishes earlier than in most other populations. These materials also permitted another view of the importance of the second premolar-second molar eruption sequence. Some authors have claimed that the second premolar followed by the second molar is an advanced trait and the reverse, that is, the second molar followed by the second premolar, is a primitive or ancestral sequence. The Pima material supports the rather recent work and discussions by Garn, Koski, and Lewis' that the so-called ancestral sequence is common in at least several modern populations. In approaching these and other problems it was found that the parameters, methods, types of studies, and the available data from previous publications had to be subjected to review. TOOTH EMERGENCE PARAMETER STUDIESAs the number of studies to determine the parameters of the distribution of tooth emergence with age increase, it becomes apparent that a re-evaluation should be made of the basis of comparability of such studies. Clements, Davies-Thomas, and Pickett2'3 have taken a step in this direction in their recent study of the age and order of permanent tooth emergence in British children. They point out the necessity for both the assembly of new data and the use of modern methods of analysis. Most of the previous studies based their analyses upon the observation of Klein and associates4 that the frequencies of erupting teeth at successive ages follow the normal probability

Fourteen morphologic crown traits were observed in a sample of 1528 Pima Indians of south-central Arizona. Pima dentitions are characterized by high frequencies of shoveling, incisor winging, the hypocone, the lower canine distal accessory ridge, cusp 6, and the protostylid. They exhibit low frequencies of the metaconule and lower premolar multiple lingual cusps and moderate frequencies of the canine tubercle, Carabelli's trait, cusp 7, and lower second molars with four cusps and X groove patterns. When Pima crown trait frequencies were compared to those of 13 Southwest Indian samples, their closest affinities were to other Uto-Aztecan groups, the Papago and Hopi. The Pima are most divergent from Athapaskans and are also clearly removed from Yuman speaking groups and the Zuni. In general, the pattern of dental morphologic variation in the Southwest corresponds closely to linguistic divisions.