Evaluation of the results of periodontal treatment by means of digital subtraction of radiographic images.

UNLABELLED This article presents general principles and a sample case of application of digital subtraction of x-rays for objective evaluation of results of treatment in dentistry. PURPOSE Evaluation of the results of surgical periodontal treatment by means of digital subtraction of radiographic images taken before and 12 month after surgery. MATERIAL AND METHODS For evaluation of the results of guided tissue regeneration treatment of deep bony defects digital periapical x-rays were taken before and 12 months after surgery. Pairs of images obtained during treatment were calibrated to equalize vertical x-ray beam angulation followed by calibration to radiological contrast and density. Next the comparison of images taken before and after treatment was performed by means of special computer software designed to subtract content of given images. RESULTS Digital subtraction showed that the radiological density in regions where surgery was performed has decreased over a period of 12 months meaning that the mineral content which is responsible for absorbing x-ray photons has increased. Some local foci of subsurface hypomineralization were found on subtractions images. These foci couldn't be detected clinically because hypomineralization was taken place within bone. CONCLUSIONS Digital subtraction of x-rays taken before and after surgery treatment is detailed and objective method of evaluating results particularly when changes of surface and subsurface bone mineralization around teeth must be examined.