Quantitative digital subtraction radiography for assessment of bone density changes following periodontal guided tissue regeneration

Objectives. The quantitative assessment of alveolar bone density changes in periodontal defects following guided tissue regeneration (GTR). Methods. Twelve patients with 30 intrabony lesions and 16 furcation defects took part. Standardized radiographic and clinical examinations were carried out immediately before and then 5 and 13 months after surgery. Intra-oral radiographs were evaluated by means of digital subtraction radiography (DSR). Within the subtraction images, a window ('experimental region') was defined covering the visible density changes in the defect area. Background noise was measured by using a similarly sized window ('control region') located in an area not affected by GTR. Bone density changes were quantitatively evaluated by calculation of the mean, standard deviation and maximum and minimum values of the grey-level histogram within these windows. Results. DSR revealed significant bone density gain after GTR in intrabony and furcation defects. While a continuous increase was observed over the 13 month period in intrabony defects, changes in furcation defects occurred mostly in the 5-13 month period. Clinically, a distinct vertical and horizontal attachment gain was found. The correlation coefficients between changes in radiographic density and clinical parameters were low, indicating a difference in the information obtained by the two diagnostic methods. Conclusion. Quantitative DSR is a valuable, non-invasive, objective method to obtain information on density changes in intrabony and furcation defects treated by GTR. However, a full assessment of soft and hard tissue changes requires both clinical evaluation and DSR.