Apparatus is provided that includes a dental implant having a lateral external surface. The implant is shaped so as to define a lumen therethrough having a lateral opening through the lateral external surface. The apparatus further includes a retaining element, and a delivery tube having a distal tube end. The retaining element is configured to assume (a) a first position in which the retaining element removably couples the distal tube end to the implant such that the delivery tube is in fluid communication with the lumen via the lateral opening, and (b) a second position in which the retaining element does not couple the distal tube end to the implant. Other embodiments are also described.