Subtraction radiology demonstrates crestal bone loss in experimentally induced marginal periodontitis

The potential diagnostic usefulness of subtraction radiology in dentistry was evaluated by means of an experimental model of marginal periodontitis in cynomolgus monkeys. Beam-guiding, field-limiting, intraoral radiographic instruments were modified to allow construction of appliances which yielded repeatable superimposable radiographic images during the course of a 16-week study. Marginal periodontitis was induced in monkeys by means of circumferential silk sutures tied around mandibular second molar and second premolar cementoenamel junctions, and serial radiographs were taken at weekly intervals for 16 weeks. Control subtraction masks were made from pretreatment radiographs, and bone loss was evaluated by means of elapsed-time films to give the subtraction prints. The subtraction films clearly showed increasing bone loss with time and were produced easily with size O dental films. This technique appears to have considerable potential usefulness in the evaluation of bone-density changes in experimental models of dental diseases as well as in the clinical setting.