The invention concerns a novel moldable and/or flowable composition for application to a bone defect site to promote new bone growth at the site. The composition includes a therapeutic material and a carrier comprising means for achieving reverse phase characteristics. In one embodiment, the therapeutic material can be a resorbable alloplastic material and the carrier can be a poloxamer. In a specific embodiment, the resorbable alloplastic material is a biphasic material composed of hydroxyapatite and tricalcium phosphate (HA-TCP), and the carrier is poloxamer 407 (PLURONIC® F-127). The invention further includes methods for using the novel composition.