Interproximal contact hypoplasia in primary teeth: A new enamel defect with anthropological and clinical relevance

This study reports the prevalence, distribution, and expression of enamel defects in a sample of primary teeth (n = 225) from a prehistoric site in western India (1400-700 BC). Five enamel surfaces of individual, isolated primary teeth were observed for surface defects using a binocular stereomicroscope with variable power of magnification (8-20x). Standards for evaluating dental enamel defects (DDE) recommended by the Fédération Dentaire International (FDI) were employed. Details of defect expression were also recorded, including size, shape, and surface of tooth crown affected. Hypoplastic enamel defects were observed in 28% of teeth, but the distribution and expression of defects was not random. More than 50% of canine teeth had hypoplastic defects (HD); incisors and molar teeth exhibited far fewer HD. The buccal surface of canines was the most commonly affected crown surface. Areas of missing enamel were also common on the mesial and distal surfaces of canines and incisors and on the mesial surface of molar teeth. The high frequency of enamel defects found on interproximal crown surfaces warrants a label, and the name interproximal contact hypoplasia (IPCH) is proposed. Linear enamel hypoplasia (LEH) was absent from this primary dental sample. IPCH is more frequent in mandibular than in maxillary teeth, but no side preference was detected. In canine teeth, buccal hypoplasias (localized hypoplasia of primary canines; LHPC) were not positively correlated with interproximal hypoplastic defects. The etiology of IPCH may involve mesial compaction of developing teeth due to slow longitudinal growth of the jaws. Episodic bone remodeling results in ephemeral fenestrae in the mesial and distal walls of the dental crypt permitting tooth-tooth contact and disruption of amelogenesis. IPCH prevalence decreases across the subsistence transition from sedentary Early Jorwe agriculturalists to seminomadic Late Jorwe hunters and foragers, but the difference is not statistically significant. This may be due to underrepresentation of mandibular teeth in the sample. Am. J. Hum. Biol. 11:718-734, 1999. Copyright 1999 Wiley-Liss, Inc.