This case report describes the bilateral reconstruction of a severely atrophic posterior mandible in a 30-year-old woman using allograft block versus particulate grafting in the inlay technique. Three months later, four dental implants were placed and bone core biopsy specimens were taken for histologic evaluation. During implant placement, the grafted sites were stable with good clinical osseointegration. The histologic analysis showed the presence of compact bone revealing areas of demarcation between grafted bone, newly formed bone, and bone-regenerated areas. Allografts might serve as an alternative to autogenous and heterologous grafting in posterior mandible augmentation using the inlay technique.