Polynomials over division rings

We consider properties of polynomials with coefficients in division rings. A theorem on the decomposition of a polynomial with coefficients in an arbitrary division ring is obtained. It is shown that if a non-central element is not a root of a polynomial over an arbitrary division ring, then the conjugacy class of this element contains infinitely many elements that are not roots of this polynomial. The paper also contains estimates for the number of different conjugacy classes of spherical roots for some types of polynomials over quaternion division algebras.