A modified mercury dilatometer is described where any change in the volume of the sample is registered every 0.5 s as a change of the mercury height in the capillary, which is measured electronically instead of by the naked eye. The device is relatively low in cost and enables measurements to be made on samples regardless of their shape or size. Four different light-curing dental materials - Amelogen (Ultradent Dental Products, South Jordan, UT, USA), Z250 (3M/ESPE, Minneapolis, MN, USA), Permaflo (Ultradent) and Filtec flow (3M/ESPE) - were initially tested. From the results it was concluded that with this modified dilatometer reproducible measurements, with a measurement error (residual standard deviation) of less than 0.027% and an average coefficient of variation of less than 1.22%, could be obtained. Thus, the instrument is particularly suitable for the study of light-curing dental resins.

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This field study included the whole population of children aged 10–15 years (77 from a 0.19 mg/L F area; 89 from a 3.00 mg/L F area), with similar nutritional, dietary habits and similar ethnic and socioeconomic status. The fluoride concentration in the drinking water, the bone mineral content, the bone density and the degree of dental fluorosis were determined. The left radius was measured for bone width, bone mineral content, and bone mineral density. The mean fluorosis score was 1.3 in the low fluoride area and 3,6 in the high fluoride area. More than half the children in the low fluoride area had no fluorosis (scores 0 and 1) while only 5% in the high fluoride area had none. Severe fluorosis (30%) was only observed in the high fluoride area. The Wilcoxon Rank Sum Test indicated that fluorosis levels differed significantly (p < 0.05) between the two areas. No relationships were found between dental fluorosis and bone width or between fluorosis and bone mineral density in the two areas (Spearment Rank correlations). A significant increase in bone width was found with age but no differences amongst and boys and girls. A significant positive correlation was found in the high fluoride area between bone mineral density over age. In the 12-13 and 13-14 year age groups in the high fluoride area, girls had higher bone mineral densities. However, a significant negative correlation (p<0.02) was found for the low fluoride area (0.19 mg/L F) over age.

The palatal rugae in rats are contained in two of three zones of morpho-differentiation and develop around the time of palatal closure. Previous studies in humans and pigs have been based on crown-rump lengths but now controlled breeding in rats has allowed exact timing to be established. Twenty-nine female DB IX rats were fertilized and sacrificed in a controlled procedure and foetuses processed for light microscopy and SEM. Serial sagittal sections were made and stained with haematoxylin and eosin and Verhoef's stains. At day 13 the palate was open and no rugae were visible. At day 14 the palatal shelves had started to migrate medially and the ante-molar rugae appeared. At day 15 the palatal shelves were touching and the inter-molar rugae became visible, and at day 16 fusion was all but complete and the definitive rugal pattern established. The development and differentiation is more advanced than in humans and it is concluded that the rugae probably have a role to play in the oral function of animals whereas in humans they are becoming attenuated and the development timetable is retarded because of redundancy.

The purpose of this study was to evaluate the efficacy of two different 10% carbamide peroxide bleaching products just after treatment and after a 6-month follow-up period. Methods. Two 10% carbamide peroxide products (Opalescence PF and Nite White ACP) were applied nightly for 14 days, according to the manufacturers' instructions. The color of teeth 11 and 21 of thirty-four subjects having A2 or darker teeth were measured with a spectrophotometer (L ∗; a ∗; b ∗) before treatment, just after treatment (14 days) and after 6 months. Results and Conclusions. Both products produced significant whitening of teeth with total color change (ΔE ab ∗) of approximately 5.20 units. There was a significant improvement in all 3 color coordinates (L*, a*, and b ∗) for up to 6 months postbleaching (P < .05). Nite White showed a higher degree of relapse (27%) than Opalescence (18%) over the 6-month period. It is suggested that rebleaching after 6 months is not necessary.