This is a split-mouth, double-blind randomized controlled trial. Computerized linear radiographic measurements were used to detect infrabony defects treated with open flap debridement (OFD) or OFD associated with enamel matrix derivative (EMD), after 24 months. Ten patients presenting 2 or more defects were selected (43 defects). An individualized film holder was used to take standardized radiographs at baseline and after 24 months. Images were digitized and used to measure the distances from the cemento-enamel junction (CEJ) to the alveolar crest (AC), CEJ to the bottom of the defect (BD) and infrabony defect angle.