<qa>  What is the primary treatment for infrabony defect?In each of 90 patients one infrabony defect shall be treated by regenerative techniques guided tissue regeneration GTR, enamel matrix derivative EMD. Prior to , 6, 12, and 24 months after surgery clinical measurements Plaque Index PlI, probing depth PD, vertical clinical attachment level CAL-V, Gingival Index GI and standardized radiographs are obtained. 