The purpose of the present study was to compare block and particulated bone grafts for jaw augmentation in combination with immediate implant placement. Bone defects measuring 10 mm x 10 mm x 30 mm were prepared on each side of the mandible of eight minipigs. After a healing period of 3 months, the defects in four animals were augmented with iliac crest grafts as a block or particulated graft, combined with immediate implant insertion. Clinical inspection was performed after 14 days. Complete exposure of grafts and implants was discovered. The surgical procedures were altered in the fifth animal. Inspection was made after 4 days showing no alterations. However, after another 7 days, grafts and implants were exposed. Consequently, the study was discontinued and all eight animals were killed. It is concluded that an intraoral approach is not applicable for this type of experimental surgery in minipigs. This paper describes some of the presumed reasons for the failure of the study.