As per Anderson and D'Alonzo classification the most dangerous type of odontoid fracture is
Anderson and D'Alonzo classification for odontoid fracture 
Type I : Avulsion of tip .
Type II : Fracture at junction of odontoid process and axis.
Type III : Fracture through the body of axis.
Treatment according to classification 
Type I : Conservatively
Type II : Most dangerous type, treated with screw fixation
Type III : Conservatively
Type I
Type II
Type III
Type IV