Comparison of observer reliability in assessing alveolar bone changes fromcolor-coded with subtraction radiographs

Objectives: To assess intra- and interobserver agreement on marginal change s in periodontal bone from color-coded compared with subtraction radiograph s. Methods: Sequential radiographs from patients undergoing periodontal treatm ent were acquired using direct digital intra-oral radiography. Fifty-one pa irs of color-coded and subtraction radiographs were produced and evaluated twice by six dentists for changes in marginal bone. Intra- and interobserve r agreement were calculated. Results: Intra-observer agreement was significantly higher for the color-co ded radiographs (P < 0.05). Interobserver agreement was significantly highe r for color-coded radiographs at the second (P < 0.001) but not the first ( P = 0.34) evaluation. Conclusions: Color coding of radiographic differences by means of image add ition may be a feasible alternative to the subtraction technique for evalua ting periodontal bone changes.