The Periotest values of mandibular implants, registered before and after loading by overdentures, were compared. Thirty edentulous patients with 60 Bonefit ITI implants were selected with an average age of 69 years. The Periotest values were measured 1) after a healing period of 3 months and 2) after the overdentures had been worn for a period of 12 months. Periodontal parameters were recorded at both examinations. Furthermore, 17 biopsies of mandibular bone taken from the implant sites during implant surgery were analyzed to assess the bone density. The histomorphometric evaluation was done using a point count method. At the end of the healing period, all registered Periotest values were negative, ranging from -1 to -8 with an average of 4.08. One year later, all measurements showed negative values again, ranging from -2 to -8 with an average of 4.97. The difference was statistically significant. Seventeen biopsies of mandibular bone were evaluated to determine the density. The range of bone density was from 22.4% and 90.9%. There was no correlation found between bone density and Periotest values. However, a significant correlation could be observed between mandibular atrophy and bone density.