Treatment planning for the placement of an implant in a site with a thin crestal ridge should address the probability that a buccal dehiscence will result. The aim of the present investigation was to perform guided bone regeneration (GBR) around implants with buccal dehiscences and evaluate the outcomes of using autogenous bone grafts harvested from three different intraoral sites. Forty-six Osseotite implants, 4 mm in diameter, were placed in thin crestal ridges, resulting in an uncovered implant surface from the buccal aspect. The lengths of the buccal dehiscences ranged from 3 to 7 mm as measured from the implant cervix to the most apical extent of the uncovered threads. A standard GBR technique was carried out to augment the bone defect around the buccal implant surface immediately after implant placement. The cases were divided into three groups according to receipt of an autogenous bone graft from the ramus, tuberosity, or mandibular symphysis. In all cases, e-PTFE membranes were used to cover the grafted areas. Grafted sites were exposed after 6 months, membranes were removed, and residual distance between the implant cervix and most uncovered thread was recorded. All grafting materials were able to produce a certain degree of bone regeneration. In terms of bone change level, the three groups were not equal. The mandibular symphysis group exhibited the highest mean bone growth level, followed by the ramus group. The tuberosity produced the poorest result. Mandibular and ramus autogenous bone grafts represent the best choice in materials for GBR procedures around implants, while tuberosity bone grafts can be used as an alternative.