Evaluation of markers RANKL-OPG-Interleukin in crevicular gingival fluid (FGC) Total proteins were quantified by the Bradford ® system (R & D Systems Inc., Minneapolis, MN, USA) and from 50 ul of sample eluted from medieronn levels of RANKL, OPG and interleukin by ELISA (Quantikine®; R & D Systems Inc. ) following the manufacturer's protocol. The average absorbance at 492 nm with correction at 630 nm using an automated plate reader (Universal ELx800 Microplate Reader, Bio-Tek Instruments Inc., Winooski, VT, USA). The concentration of the markers in each sample was calculated using an equation of the line of 4th grade.