Birch, W.J.; (2012) Incremental growth of deciduous tooth enamel. Doctoral thesis , UCL (University College London).

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Abstract

Deciduous tooth formation begins before birth and ends after birth. This makes it more difficult to construct a continuous developmental chronology for deciduous teeth than for permanent teeth. The discovery of the neonatal line in enamel and confirmation that it marks birth, allowed the expansion of deciduous dental chronologies, which until this time had been largely based on qualitative descriptions. The aim of this study was to use the daily incremental record in deciduous enamel to document rates of enamel formation and to use these data to produce regression equations that describe the average rates of deciduous enamel formation for each tooth type. These formulae can then be applied to all deciduous teeth even when daily increments are not visible, in order to estimate crown formation times and other events during crown development, as well as to determine the age at death where enamel formation has ceased prior to completion. In permanent teeth, rates of enamel formation vary between 2.5μm per day at the EDJ to 6.5μm per day at the enamel surface. Seventy deciduous ground sections were examined and it was established that the daily rates in deciduous enamel varied less, with regional weighted means for all tooth types ranging from 2.85μm per day at the EDJ to 3.40μm per day at the enamel surface with extreme outliers of 2.07 to 4.97μm per day. The average daily incremental growth rate of enamel in deciduous teeth was calculated for each tooth type, the weighted mean of the apposition rate over both aspects (labial/buccal and lingual) and over all three regions (cervical, lateral and occlusal) for all tooth types was 3.23μm per day. A key finding of this study was that there is a marked reduction in the enamel formation rate in the zone immediately following the neonatal line or following other accentuated striae assumed to be associated with stressful events. A catch-up phase usually followed these events, during which the previous rates recovered. These data provide clear evidence of enamel hypoplasia associated with both the birth process and other events that cause stress in perinatal life.

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