  Twists of contact structures in dimension 3 and higher are studied in this
paper from a viewpoint of contact round surgery. Three kinds of new
modifications of contact structures which are higher-dimensional
generalizations of the $3$-dimensional Lutz twists are introduced. One of the
operations makes a contact manifold overtwisted in any dimension. Another one
makes it weakly symplectically non-fillable. And the other one makes it
strongly symplectically non-fillable. In other words, they make the overtwisted
disc, the bordered Legendrian open books, and the Giroux domains, respectively.
The first two modifications can be realized by sequences of contact round
surgeries. The first operation can be applied anywhere of any contact manifold
easily. Further, a version of the first operation keeps the homotopy classes of
contact structures as almost contact structures, and the other version
contributes to the Euler classes of contact structures.
