Adhesive properties of metals on oxide substrates, such as MgO, critically depend on the effective covalent character of metal-oxygen. In ionic solids the anisotropy among directional Compton profiles was shown to be strongly dependent upon the iono-covalent character of cohesive interactions. A systematic study of momentum density was thus undertaken for MgO, both experimental and theoretical. Reliable DCPs were obtained at ESRF, anisotropies being in fair agreement with Hartree-Fock calculations. In order to refine coupling parameters among valence orbitals, a three-dimensional (3D) reconstruction of momentum density is necessary. Various approaches are considered besides spherical harmonics reconstruction, we propose a simple and efficient Gaussian fit of DCPs, followed by an extrapolation to the 3D momentum density. Preliminary results are discussed.