The orthograde intracanal placement of mineral trioxide aggregate (MTA ) in the treatment of root canals with an open apex is technique sensitive, primarily because of its poor handling properties. Placement of the material within the confines of the root canal is difficult. The current case series presents the results of 12 treated open apex cases, using MTA condensed by hand against an internal matrix of absorbable collagen sponge (ACS) to create an apical plug. The results of the technique are encouraging, while the success of MTA in apexification has been reiterated. Keywords: absorbable collagen sponge, apexification, apical plug, MTA, open apex