What is the core material of choice for a premolar which has broken to the gum line with a post placed?

Our suggestion is to use a low-viscosity core material that will adapt well around the post, as well as make up the bulk of the core. First, use a dual-cured bonding agent (Futurabond DC, VOCO America, Inc.) in the post space. Then, inject a dual-cured core material such as Luxacore Z Dual (DMG America), cement the post and light cure. Finally, continue to build the bulk of the core material with the same product, so that the post space and core are all filled by one material.