A printhead with a printhead die, an ink manifold and heat sink substrate has a continuous sealing surface surrounding the printhead die which is formed by the ink manifold, heat sink substrate and filler material disposed therebetween. The filler material acts as caulking to eliminate gaps around the printhead die, particularly between the ink manifold and heat sink substrate, and to provide a smooth surface for abutment with a capping member. A fluid-tight seal is obtained between the capping member and the continuous sealing surface on the printhead, thus preventing the drying out of ink in the nozzles through evaporation of volatile ink components. In some priming nozzle configurations, the leaktight seal also facilitates priming of the printhead.