The aim of this study was to compare the accuracy of the Demirjian method and the Demirjian method as revised by Willems for age estimation based on orthopantomograms from central southern Chinese Han population aged 8-16 years. Discrepancies between chronological and estimated ages were statistically evaluated by analyzing 1249 orthopantomograms from 603 girls and 646 boys. Using the Demirjian method, the mean age estimates underestimated chronological age by 0.03 years (p = 0.48) for girls and overestimated it by 0.03 years (p = 0.59) for boys; these differences with respect to chronological age were not statistically significant. In contrast, the Willems method underestimated chronological age by 0.54 years (p < 0.01) for girls and 0.44 years (p < 0.01) for boys; these differences with respect to chronological age were statistically significant. Compared to the Demirjian method, the overall mean absolute error generated using the Willems method was slightly higher (0.85 and 0.86 years, respectively). Since the Demirjian method was more accurate, we highly recommend that it should be applied when estimating dental age in the Chinese Han population. Further modifications of these two methods for populations from other regions and additional studies of other age groups are warranted.

Background: To compare different anti-caries agents on microhardness and micromorphology of irradiated permanent dentin in vitro, and try to find the most effective agent to prevent radiation-dentin-destruction. Methods: A total of 120 dentin samples were prepared from 60 human teeth and randomly divided into 8 groups (n = 15), [ (1)] blank control [2]; irradiation control [3]; irradiation+ fluoride [4]; irradiation+ casein phosphate polypeptideamorphous calcium phosphate (CPP-ACP) [5]; irradiation+ CPP-ACP+ fluoride [6]; irradiation+ infiltration resin [7]; irradiation+ infiltration resin+ fluoride [8]; irradiation+ infiltration resin+ CPP-ACP. Seven samples of each groups were chosen randomly for microhardness test and eight for scanning electron microscope observation. Results: A decrease of microhardness (P < 0.05) and an obvious morphological change were presented on dentin surface after radiotherapy. After applications of anti-caries agents, the morphological destructions were effectively restored. The infiltration resin plus fluoride group (56.00 ± 4.02 Kg/mm 2 ), infiltration resin plus CPP-ACP group (56.05 ± 3.69 Kg/mm 2 ), infiltration resin group (54.70 ± 4.42Kg/mm 2 ) and CPP-ACP plus fluoride group (53.84 ± 6.23Kg/mm 2 ) had the highest dentin microhardness value after radiotherapy, and no statistically significant difference were found between them. Conclusions:Infiltration resin, CPP-ACP, fluoride and their pairwise combination can effectively prevent radiation-dentindestruction. Among them, infiltration resin with CPP-ACP, infiltration resin with fluoride, CPP-ACP with fluoride, and infiltration resin have the most protective effects on irradiation-dentin-destructions.

The purpose of this study is to provide a forensic reference data about estimating chronologic age by evaluating the third molar mineralization of Han in central southern China. The mineralization degree of third molars was assessed by Demirjian's classification with modification for 2519 digital orthopantomograms (1190 males, 1329 females; age 8-23 years). The mean ages of the initial mineralization and the crown completion of third molars were around 9.66 and 13.88 years old in males and 9.52 and 14.09 years old in females. The minimum ages of apical closure were around 16 years in both sexes. Twenty-eight at stage C and stage G and 38 and 48 at stage F occurred earlier in males than in females. There was no significant difference between maxillary and mandibular teeth in males and females except that stage C in males. Two formulas were devised to estimate age based on mineralization stages and sexes. In Hunan Province, the person will probably be over age 14, when a third molar reaches the stage G. The results of the study could provide reference for age estimation in forensic cases and clinical dentistry.

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To explore the effects of infiltration resin, casein phosphate polypeptide-amorphous calcium phosphate (CPP-ACP) and fluoride on microhardness and micromorphology of irradiated enamel. Sixty human permanent teeth were mesiodistally sectioned, yielding 120 enamel samples, which randomly divided into 8 groups: G1:

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