Retract G-code Instruction for Mendel90 (no replies)

Hi!
I am developing a software for a University Project similar to PronterFace. I need some help because I can´t do "Retract" with my printer to avoid the drooling, the printer doesn´t stop extruding material in all the process.

I try with M227, M101 and M103 (reprap Wiki) and M207 and M209 from Marlin documentation.
I have a Mendel90 with Marlin 1.0.0 RC.

Thank you.