A clinical trial is reported in which the roots of extracted mandibular teeth were replaced by dense hydroxyapatite root replica implants (Calcitite®, Calcitek Inc, San Diego, Calif) prior to the insertion of immediate complete dentures. The degree of alveolar resorption that took place was compared in a test and control group. After a follow-up period of 1 year, patients provided with root replica implants were found to have significantly higher and wider residual ridges than control patients. Schlagwörter: alveolar resorption, hydroxyapatite, ridge preservation