Rates of dentine mineralization in permanent human teeth

Previous experimental studies have estimated linear rates of dentine formation in modern humans to be close to 4μm day⁻¹. In this study a method similar to that first adopted by Kawasaki, Tanaka and Ishikawa⁵ was used to estimate linear rates of dentine mineralization over a period of 1200 days in both the cusps and cervical regions of several permanent tooth types. All teeth were from the same individual. Rates in the cusps of teeth with the tallest crowns were estimated to be between 5 μm day⁻¹ and 6 μm day⁻¹. This is higher than previous estimates in permanent tooth crowns, although rates in the cusp of a first permanent molar, where cusps were less tall and cuspal dentine therefore less thick, were close to previous estimates of 4 μm day⁻¹. Despite this variation in cuspal rates, mineralization rates were linear in all cusps studied over a long period of time. Rates in the cervical region, either close to the enamel dentine junction or to the cement dentine junction, were estimated to be between 1.3 μm day⁻¹ and 1.5 μm day¹¹, much slower than reported previously. Rates in the mid-portion of the dentine, in both the lateral part of the crown and in the cervical one-third of the root, rose steadily to match rates in the cuspal region, but then slowed towards the pulp chamber. These data extend the findings of previous studies on permanent human dentine. They demonstrate a wide range of mineralization rates in permanent dentine and provide a more secure basis for judging different rates in different locations of different human tooth types.     

Reflections on Le Quebec d'en Haut et le Quebec d'en bas

At the beginning of the 20th century Quebec stretched beyond its current boundaries. Indeed, it was commonplace to speak of Quebec d'en haut (upper) and Quebec d'en bas (lower). A common destiny seemed to disintegrate a third of the way through the century only to be rekindled in recent times.     

‘Angelic Spirits of ‘68’: Memories of 60s’ Radicalism in Responses to the 2010–11 UK Student Protests

The winter of 2010–11 saw a significant upsurge of student protest in Britain. This paper analyses the numerous references to 60s’ radicalism which circulated in responses to the protests, with a focus on left-wing media. Drawing on performativity theory, the paper traces the highly polarised divisions between affirmations and repudiations of ‘1968’ in responses to the protests. This polarisation, I argue, reflects an absence of a clear-cut collective memory of the British radical 60s. More broadly, the paper sheds light on the hitherto under-explored mechanisms through which memories of ‘1968’ shape the discursive and affective landscape of contemporary radical politics.