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Aim: This was to determine the increment of caries from 12 to 18 years of age and to explore the possibility of predicting caries increment in this period based on the caries experience at age12 years. Study design: Prospective longitudinal survey. Methods: A sample of 12-year-old children (n =159) were examined in 1993 and 70% of them re-examined at 18 years of age. Bitewing radiographs were taken and a diagnostic system using five caries grades (D1-D5) was used at both ages. Children at risk were defined as those who developed manifest caries lesions (D3-5FS) on approximal surfaces during the follow-up period. Possible predictors were analysed by calculation of sensitivity, specificity, and actual proportion of the population at risk. Results: The mean caries increment (D1-5MFS) from 12 to 18 years of age was 4.2 (SD±9.1). The percentage of caries-free adolescents at 12 and 18 years of age was 10% and 1% respectively; 25% had either a reversal or no increment in caries experience while the D1-5MFS increased in 65% of the adolescents. Of the increment of manifest lesions (D3-5FS), 18% were located in incisors/canines, 40% in premolars, 26% in first molars and 16% in second molars. Premolars had the largest proportion of the approximal surfaces with manifest caries increment. The best predictors of children at risk of approximal caries increment (D3-5FS) were caries experience (D1-5FS) on the approximal surfaces of premolars and second molars at the age of 12 years. The individuals that developed four or more manifest lesions on approximal surfaces between 12 and 18 years were the easiest to predict (sensitivity + specificity = 175%). Conclusions: There was a considerable increment of manifest caries lesions from 12 to 18 years of age in all tooth groups. The best predictors for increment of manifest caries on approximal surfaces during the age period were approximal caries in premolars and second molars at the age of 12 years.

The tree lineis the upper margin of the subalpine forest where the trees become dwarfed or are absent (Howard &,Mitchell 1985). On topographic maps, the tree line divides the landscape into two uniform regions which are often referred to as ‘above’ and ‘below’ the tree line. The teminology implies a notion of the tree line as the physical manifestation of a continuous surface describing a potential tree level. The tree level exists globally, while the tree line only appears as a contour line where the tree level intersects the topography. The tree level can be thought of as a continuous but invisible surface. This surface cuts through the landscape along the tree line. The area below this surface is described as ‘below the tree line’, while areas above the surface are ‘above the tree line’.

A method for the separation and analysis of tetralin hydroperoxide and its decomposition products by high pressure liquid chromatography has been developed. Elution with a single, mixed solvent from a μ-Porasil column was employed. Constant response factors (internal standard method) over large concentration ranges and reproducible retention parameters are reported.

The article presents letters to the editor in response to the articles "Buccaneers' Breakout at Maracaibo" and "Perspectives," by Wayne Austerman in the March 2006 issue and "Circumstance Can Make for Strange Military Bedfellows" in the April 2006 issue.

The article provides tips on making a pencil line rather than a scored parallel line to an edge by reversing a marking gauge and use it that way. Set it on that position and hold a pencil against the end of the stem.