A test of inter- and intra-observer error for an atlas method of combined histological data for the evaluation of enamel hypoplasia ☆ Charlotte Primeau ⁎, Sara O. Arge, Charlotte Boyer, Niels Lynnerup Laboratory of Biological Anthropology, Department of Forensic Medicine, University of Copenhagen, 2100 Copenhagen, Denmark abstract article info Article history: Received 7 October 2014 Received in revised form 17 February 2015 Accepted 21 March 2015 Available online 1 April 2015 Keywords: Ageing Dental atlas Systemic stress Archaeological populations Dental pathology This report presents the dental chart data of Reid and Dean (2006) and Holt et al. (2012), combined into a single colour atlas for estimating age-at-defect formation of enamel hypoplasia. It is suggested that this dental chart may replace the dental chart of Massler et al. (1941), as data from Reid and Dean (2006) and Holt et al. (2012) takes into account hidden cuspal enamel and as such is considered more accurate. The colour atlas was tested for inter- and intra-observer error, using 177 teeth with linear enamel hypoplasia from 30 archaeological skeletons. Results indicate that the colour atlas presented here is an easy and consistent tool for estimating age of enamel hypoplasia formation on the incisors, canines, and first molars. The significant change of this approach is the use of histological data, known to be more accurate than previously published data, combined and presented in a single coloured dental atlas facilitating the evaluation of enamel hypoplasia in the field and laboratory. © 2015 Elsevier Ltd. All rights reserved. 1. Introduction Enamel hypoplasia is a manifestation of temporary disturbance to the function of the enamel producing ameloblasts. This causes a reduc- tion of enamel thickness expressed as defects located horizontally on the tooth crown (Odgen, 2008). Enamel hypoplasia can be divided into three types of hypoplasia; furrow form (commonly termed linear), pit form and plane form (Hillson and Bond, 1997). This report examined the dental atlas by observing linear enamel hypoplasia but would be equally applicable to pit form enamel hypoplasias (EH). As enamel is generally well preserved in archaeological skeletons and tooth enamel does not remodel once formed it is a permanent marker that is readily available to study. EH is most often observed on the permanent teeth, particularly mandibular canines and maxillary central incisors (Goodman and Armelagos, 1985; Hillson and Bond, 1997; Goodman and Song, 1999). Enamel hypoplasia is a non-specific marker of system- ic stress and has generally been attributed to infectious diseases and nu- tritional deficiencies (Goodman and Rose, 1990; Hillson and Bond, 1997). For a more detailed review of the development of dental enamel see Goodman and Rose (1990) and Hillson and Bond (1997). Enamel defects caused by systemic stress will be visible in multiple teeth following the known dental schedule of chronological develop- ment, which therefore may be used to age the event. Recording the presence or absence of EH is standard practice in bioarchaeology. The estimation of age at formation of EH is desirable for the interpretation of growth disruptions in past populations during pre-adult years. The aim of this study is to present the combined chart data as published by Reid and Dean (2006) and Holt et al. (2012) illustrating their defined age cohorts by colour for the ease of usability. The combined coloured dental atlas is tested for inter- and intra-observer error to assess the consistency of estimated age from this dental atlas. The colour atlas presented is similar to that published by Massler et al. (1941). However, the dental chart published by Massler et al. (1941) was based on data from Logan and Kronfeld (1933). This data has received criticism for using a small sample size and not taking into account hidden cuspal enamel (Goodman and Song, 1999). Other mac- roscopic methods, such as that of Goodman and Rose (1990), do not take into account the non-linear growth of enamel whilst still being based on the same material as Massler et al. (1941). Microscopic methods as suggested by Hillson (1992) can be can be prohibitive due to the time required, as well as cost of specialized equipment. The coloured dental atlas presented here is suggested as a quick non- metric and categorical method that can be used for estimating the age of EH formation. 2. Material and methods The Reid and Dean (2006) publication utilised a total sample set of 678 teeth. Contained within this data set were two primary data sets: Northern European and South African. Additionally there were two sec- ondary data sets: canines from a medieval Danish population and third molars from a modern North American population. The proportional Journal of Archaeological Science: Reports 2 (2015) 384–388 ☆ Grant sponsorship: The Danish Velux Foundation. ⁎ Corresponding author at: Laboratory of Biological Anthropology, Department of Forensic Medicine, Frederik V's Vej 11, 2100 Copenhagen, Denmark. E-mail address: Charlotte.primeau@sund.ku.dk (C. Primeau). http://dx.doi.org/10.1016/j.jasrep.2015.03.007 2352-409X/© 2015 Elsevier Ltd. All rights reserved. Contents lists available at ScienceDirect Journal of Archaeological Science: Reports journal homepage: http://ees.elsevier.com/jasrep