The citing, under law 10.4(c), carries a low-end entry point of a four-week ban, with a top-end sanction of anywhere between 12 weeks and a year should he be found guilty.
His charge under law 10.4(a) - striking an opponent with the fist, arm... head or knee - carries a low-end entry point of a two-week ban with a top-end entry point of at least eight weeks.
Stade Francais lock Juan Cruz Guillemain faces a more serious charge under the same law after allegedly striking Grenoble's Fabien Alexandre with his head. The top-end entry point for Guillemain's citing is from 16 weeks to two years.
All three cases will be heard in Dublin on Thursday, with His Honour Judge Jeff Blackett passing judgement on O'Gara while Ireland's independent Judicial Officer Pat Barriscale will rule on both Estebanez and Guillemain.