The reconstruction of a severely atrophic left posterior mandible using inlay magnesium-substituted hydroxyapatite grafting is described. Three months after reconstruction, a bone specimen was retrieved, and two dental implants were placed. A mean vertical bone gain of 4.9 mm was measured at the time of implant placement, and no problems were recorded at delivery of the provisional and definitive prostheses 4 and 8 months after implant placement, respectively. Histologic analysis revealed residual grafted material infiltrated by newly formed bone. In this clinical case, Mg-hydroxyapatite was demonstrated to be an effective grafting material for reconstruction of the posterior mandible using the inlay technique.