MATERIALS AND METHODS: This parallel, single-blinded, randomised controlled trial (RCT) consisted of 22 periodontitis patients who had molar with advanced furcation involvement (FI). All patients followed the same inclusion criteria and were treated following the same protocol, except for radiographic evaluation (CBCT vs. periapical). This study proposed and evaluated five parameters that represent the extent and severity of furcation defects in molars teeth, including CEJ-BD (clinical attachment loss), BL-H (depth), BL-V (height), RT (root trunk), and FW (width).