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The aims of this work were to assess dental age using the Demirjian system and to evaluate the discrepancy between chronological and dental age among children residing in Western Australia. Forty panoramic radiographs of 5- to 11-year-old children taken at the paediatric clinic of a dental hospital in Western Australia were selected. The developmental stage of each left permanent mandibular tooth excluding the third molar was assessed by three trained examiners. Estimated dental age using the Demirjian system was compared with the chronological age of each child. The accuracy of the Demirjian system in this group of children was 42.5%. The difference between chronological age and dental age was significant (t = 4.066, df = 39, p < 0.001). Dental age estimation for Caucasian children had greater accuracy (χ2 = 5.013, df = 1, p = 0.025). Gender and orthodontic concerns were not related to the accuracy of the Demirjian system (p ≥ 0.481). The discrepancy between chronological and dental age using the Demirji...

The safety impact of differential speed limits (DSL) with a truck lane restriction was investigated on a 17 mile long elevated freeway segment over the Atchafalaya Basin in Louisiana that has been a subject of concern for the past decade due to sporadically occurring fatal crashes involving large trucks. Three before and after (B-A) methods were used in the current study: A naive B-A method, the improved B-A method, and the comparison group B-A method. The last two methods estimate the safety difference of a highway facility between, with, and without an intended treatment while taking into account other variables that may affect safety. Although all three methods show the reduction in truck and total crashes with DSL implementation, the naive method clearly underestimates the magnitude of the reductions in this case. Lack of traffic composition information makes the results from the comparison group B-A method less reliable than that by the improved B-A method. Based on the improved B-A method, that is m...