The interstitial point defect increases the density of a solid. Frenkel defect is also a type of this defect but it do not increases the density.
Also, the mass / volume concept of density tells us that density should be same in both cases, as they are basically interstitial defect. Then what happened to a covalent solid that density increased , and why it didn't happened to ionic solid?
(Please understand that it is not a duplicate of Why Frenkel defect does not impact the density of the solid? )