Complete filling of canal space

* The technological properties of the materials are important for them to fulfil this function. Flow and the ability to wet dentin and gutta-percha surfaces are important, and the method of filling should not introduce air or otherwise create voids in the mass of the final filling.
* Too high radiopacity may mask an inadequately fill by a material; too low radiopacity might suggest no filling material is there when in reality it is well filled.
* In some materials, the radiopaque components may separate from other constituents making assessments of the degree of fill very difficult.