Evaluating sources of variation in the identification of linear hypoplastic defects of enamel: a new quantified method

Assessment and interpretation of the presence of developmental defects of enamel formation that result from childhood experiences of growth disruption, enamel hypoplasia, is a standard part of almost any systematic bioarchaeological assessment. However, different identification methods lead to different results. This study presents a new method of defect identification that offers a quantitative criterion for establishing defect presence rather than relying solely on observer judgement. It then compares this with a standard field approach to assessing enamel hypoplasia and a non-quantified microscopic approach in order to determine (a) if traditional methods of identifying enamel hypoplasia under little or no magnification offer the same information about the experience of childhood health as methods that examine dental enamel growth microscopically, and (b) the effect of using a quantified criterion to identify enamel hypoplasia. A case study using simultaneously developing teeth in one individual is presented where observations of defect presence are made both macroscopically and microscopically and with and without this novel metric method. The results demonstrate that the chosen scale of observation is a critical variable in identifying linear hypoplastic defects of enamel. Defects that occur in the more cervical regions of a tooth are ‘missed’ by methods that rely on macroscopic observation or the unaided visual judgement of the observer. This finding has considerable implications for the interpretation of reported enamel hypoplasia prevalence.