Forty patients with partially or fully edentulous atrophic jaws having less than 5 mm of residual crestal bone height and/or less than 3 mm of bone thickness , as measured on computerised tomography ( CT ) scans , were randomised into two groups according to a parallel group design , either to be augmented with autogenous onlay bone blocks ( 20 patients ; AB group ) from the mandibular ramus or the iliac crest , or with onlays blocks of spongious bone of equine origin ( 20 patients ; XB group ) .