UCLA

Although dental implants have become a standard treatment procedure, there is still a growing demand to enhance their osseointegration capability to address complex cases, such as host sites with bone grafts and type IV bone. This study explored the viability and effectiveness of pre-osseointegrated implants to achieve faster establishment of bone-implant integration using cell sheet technology. Cells harvested from the rat bone marrow were cultured on a poly (N-isopropylacrylamide) culture dish. Taking advantage of the ability of temperature responsive conversion of the dish from hydrophobic to hydrophilic, the layer of the grown cells was detached as a sheet. For in-vitro experiments, the cell sheet (single or double layered) was transferred to acid-etched titanium disks and examined for its capability to show cell metabolic

activity, osteoblastic phenotypes and responsiveness to an osteogenic enhancer molecule, N-acetyl cysteine (NAC). For in vivo study, the experimental titanium implants (1 mm in diameter and 2 mm in length) were coated with the cell sheet and placed into rat femurs. After 2 weeks of healing, the implants were subjected to the biomechanical push-in test to evaluate the strength of bone-implant integration. Cell sheet grown on temperature sensitive dishes showed the expected cell metabolic activity levels and osteoblastic phenotypes of cells grown on regular culture dishes. Cell sheets, created from bone marrow cells, were successfully transferred as an intact sheet, to titanium disks and showed the alkaline phosphatase (ALP) activity. Double layers of the sheets showed 2-fold greater cell metabolic activity than single layered ones. The cell sheets treated with NAC showed significantly greater ALP activity in a NAC dose-dependent manner. The cell sheet-coated implants showed a 2.2-fold greater push-in value than uncoated implants. This is the first study that has established an osteogenic cell sheet applicable to titanium implants. Transferred cell sheets to titanium surfaces are capable to show reliable osteogenic phenotypes and to accelerate the bone-titanium integration, can be enhanced by foreign molecules and show increased cell metabolic activity levels depending on the number of layers of cell sheets transferred.