The radiopacity that frequently obliterate the root apices of maxillary molars is
Maxillary sinus
Palatine bone
Zygoma and Zygomatic process of Maxilla
Orbital process of Zygomatic bone
FigureA  shows  the  inferior  border  of  the  zygomatic  process  of  the  maxilla  over the  molars.  This  structure  lies  buccal  to  the  teeth  and  appears to  move  mesially  as  the  x-ray  beam  is  oriented  more  from the  distal.  Similarly,  as  the  angulation  of  the  beam  is  increased vertically,  the  zygomatic  process  is  projected  occlusally  over the  teeth.