Fifteen patients with bilateral atrophic mandibles ( 5 mm to 7 mm bone height above the mandibular canal ) and 15 patients with bilateral atrophic maxillae ( 4 mm to 6 mm bone height below the maxillary sinus ) , and bone thickness of at least 8 mm , were randomised according to a split-mouth design to receive one to three 5-mm short implants or at least 10-mm long implants in augmented bone .