Measurement of alveolar bone density Dental X-ray films were taken and alveolar bone density at the root of the first mandibular premolar measured, as described elsewhere [9], using an originally designed image editing software (No. PCT/jp2004/010815). A line was drawn at the apex of the root, parallel to the boundary of the cement–enamel junction. Another line was drawn halfway between the cement–enamel junction and the apex

of the root. Lines were then drawn perpendicular to those lines at the mesial and distal spaces of the first premolar. The X-ray film density in the area of the resulting rectangles was measured by first dividing the area into pixels with sides 1/1,524 cm

in length. The brightness selleck kinase inhibitor in each pixel was then compared with a scale consisting of 256 steps of brightness (Fig. 1). XAV-939 Fig. 1 Geometry of alveolar bone measurement. a Aluminum step wedge for calibration. b Calibration of density between standard aluminum wedge and maximum/minimum density. c Defining the area of interest for the alveolar bone density In order to align and standardize the brightness and contrast among the X-ray pictures for comparison of the results of measurement among X-ray pictures taken on different occasions, an X-ray picture taken for a normal, healthy person (i.e., a 23-year-old woman having 100% bone mineral density in the example being described) was used as a reference. A histogram

hist[x] of a color bar on the reference picture was normalized according to Eq. 1. Then, the normalized histogram hist[x] is substituted in Eqs. 2 and 3 to thereby calculate the brightness mean value, mean, and the standard deviation, SD, which are referred to as the reference mean value, RefMean, and the reference deviation, RefSD, respectively. Similarly, for each of the pictures to be corrected, the histogram hist[x] of its color bar is normalized and the brightness mean value and the SD for that picture calculated. Mean, the PLEKHM2 mean value of the brightness thus calculated, and SD, standard deviation, RefMean, the reference mean value, and RefSD, the reference deviation, are substituted in Eq. 4 to Z-IETD-FMK price correct the respective pictures with respect to their brightness and contrast and to obtain corrected brightness value Y′(i,j) for each picture. $$ \rm hist \left[ x \right] = \frac\rm Num \left[ x \right]\rm TotalNum $$ (1)where x (0 ≤ x ≤ 255) is gradation, Num[x] is the number of pixels for the gradation x in the color bar, and TotalNum is the total number of pixels of the color bar.