Radiographic study of relative bone density of the retromolar region in pixels and aluminum equivalent milimeters

Abstract

The objective of this research was to compare the relative bone density of the retromolar region, in pixels and aluminum equivalent milimeters. It was used an aluminum stepwedge to measure the gray levels in this region; this stepwedge was formed by 16 degrees with 0,3mm between each one. Five human dried mandibles were used, which were technicaly radiographied on the region previously mentioned, using Agfa film, 0,5 seconds of time of exposition and focal distance of 25cm. These radiographics were processed by the time and temperature method, and later digitalized with 300 dpi. The digital images were measured by the histogram resource of the Image Tool software, version 3.0 (UTHSCSA,USA). Initially the mandibles were manipulated using the bright and contrast automatic change function called stretch. Then areas of 32X32 pixels were selected for the measures in bone regions, avoiding those excessively radiopaque or radiolucent, as well as anathomic strutures, so that no alterations interfere in the levels of bone density. For the images of the aluminum stepwedge, areas of 20X50 pixels were measured using the same histogram resourse. Using the Student-t test, similar values were shown between the retromolar bone region density and the degree number 16 of the aluminum’s scale (p>0,05). It was conclude that the density of aluminum’s scale, used in the research is similar to the relative bone density of analised regions, showing that it can be used as an unit of referencial measure in the analysis of mandible gray levels.