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The State of the Deciduous Dentition of a Chimpanzee Fetus (Pan troglodytes)

To date, little is known about the morphogenetic pathways involved in the establishment of the definitive morphology of primate teeth. This is especially true of man's nearest living relatives, the anthropoid apes. In a recent paper, Oka and Kraus (Arch Oral Biol 14:639-659, 1969) included a description of the morphology and extent of calcification of the first permanent molars in a term chimpanzee fetus. To our knowledge, this is the only account thus far published dealing with the morphogenetic aspect of chimpanzee dental development. In the present paper, the developing dentition of a male chimpanzee fetus (Pan troglodytes) with an approximate gestational age of 160 days is described and compared with similar developmental stages in other primate species. The gestation period in chimpanzees is approximately 225 days (RIOPELLE, Z Morphol Anthropol 53:53-61, 1963). The tooth buds were removed by gross dissection and stained with alizarin red S to determine which regions had undergone calcification. The specimen possessed all of its deciduous teeth and first permanent molars as distinct morphologic entities. Although all of the deciduous teeth were in various stages of calcification, the first permanent molars had not as yet begun to calcify. The central deciduous incisors were the furthest along in development, with approximately half of the future crown calcified. The lateral deciduous incisors had an irregular incisive border composed of several mamelons. Also, the contour of the lingual surface of these teeth varied from being essentially flat (second deciduous incisor) to being markedly concave (first deciduous incisor). The deciduous canines had only the tip of their respective crowns calcified. The maxillary first deciduous molar was bicuspid with two separate, mesiodistally elongated regions of calcification-one associated with the lingual cusp and another associated