Impact of Dynamic and Static Load on Bone Around Implants: An Experimental Study in a Rat Model.

PURPOSE: This study aimed to evaluate peri-implant bone reactions to dynamic and static loads in a rat model. MATERIALS AND METHODS: Two cylindrical titanium implants were placed in the left tibia diaphysis of 39 rats, which were divided into three groups: static load for 4 weeks (S4), static load for 8 weeks (S8), and static load for 4 weeks followed by dynamic load for 4 weeks (S4D4). All implants received a mechanical lateral load. After the experiment, the implants were extracted to determine the attachment strength around the bone and implant. The new bone formation and bone-to-implant contact were measured using plain and polarized light microscopy. RESULTS: Histologic tissue analysis revealed good contact between the bone and implant, and new bone formation around all implants. The S4D4 group had the greatest attachment strength, new bone formation, and complex collagen fiber orientation in the new bone tissue, compared with the other groups. No statistically significant differences in bone-to-implant contact were observed among the three groups. CONCLUSIONS: Applying dynamic and static loads to osseointegrated implants increased the amplification of new bone. The attachment strength was significantly improved when dynamic load was used for 4 weeks, compared with when static load was used.

Development of oral and extra-oral endosseous craniofacial implants by using a mesh structure for connective tissue attachment.

Connective tissue attachment to a mesh structure incorporated on the surface of oral implants and extra-oral endosseous craniofacial implants (EOECI) was investigated. Two types of implants were prepared: TI and TI-Mesh. TI was composed of an upper and a lower component, both comprised of a titanium cylinder, which could be connected using a titanium screw. The composition of the TIMesh was similar, but the lower cylinder had a lateral groove that was covered with a titanium mesh. In animal experiments performed using rat calvaria, the lower component was first implanted and was left submerged for 3 weeks, then the upper component was mounted percutaneously. After an additional 2 weeks, each implant and the surrounding tissues were harvested and evaluated. Histological observations revealed collagen fibers originating from surrounding hypodermal tissues anchored to the mesh structures of the TI-Mesh whereas no such collagen fibers were observed around TI. Significantly greater values of the attachment strength, the thickness of the dermal tissue, the thickness of hypodermal tissue, and the attachment lengths were observed in TI-Mesh than those of TI. Thus connective tissue attachment with collagen fibers anchored to the mesh was achieved by incorporating mesh structures into the percutaneously placed implants.

Prognosis of adult patients transplanted with liver grafts < 35% of their standard liver volume.

We have previously reported that a graft volume (GV) > 30% of the recipient's standard liver volume (SLV) can meet the recipient's metabolic demands. Here we report our experience with adult-to-adult living donor liver transplantation using left side grafts < 35% of the recipient's SLV. Of 143 adult living donor liver transplants, 13 auxiliary partial orthotopic liver transplants, 8 right side grafts, and 2 retransplantation cases were excluded. The resulting 120 cases were divided into 2 groups: group S consisted of 33 patients who received liver grafts < 35% of their SLV, and group L consisted of 87 patients who received liver grafts > or = 35% of their SLV. Patient characteristics, postoperative liver function, duration of hospital stay, and recipient survival rates were compared between the 2 groups. There were no significant differences between groups in recipient or donor background characteristics. The mean GV/SLV ratio of group S was 31.8%, whereas that of group L was 42.5%. There were no significant differences in the postoperative serum total bilirubin levels, prothrombin time international normalized ratio, daily ascites volume, or duration of postoperative hospital stay between the groups. The 1- and 5-year survival rates in group S were 80.7% and 64.2%, respectively, whereas those of group L were 90.8% and 84.9%, respectively, with no significant difference between groups. In conclusion, graft size was not considered to be the only cause of so-called small-for-size graft syndrome, and left side grafting appears to be the procedure of choice for adult-to-adult living donor liver transplantation because of the lower risk to donors in comparison with right lobe grafting.