“…Most previous studies investigating the different effects of degree of FI on tooth loss had concluded that a gradient effect exists increasing from degree I to II and then to III (Dannewitz et al., ; Graetz et al., ; Johansson, Johansson, & Ravald, ; McGuire & Nunn, ; Salvi et al., ). A meta‐analysis of this association concluded that RR of tooth loss was approximately 1.67 for degree II versus I, 1.83 for III versus II and 3.13 for degree III versus I (Nibali et al., ). In the present study, the breakdown of extraction by FI was 1.4%, 7.9%, 12.8% and 8.1%, respectively, for molars with no FI, degree I, degree II and degree III FI during SPT.…”