In 1997, an embryonic stem cell test (EST) for in vitro embryotoxicity was developed in Germany. This test could accurately predict the embryotoxicities of unknown chemicals, as demonstrated by an international validation test. However, the metabolic factors of chemicals should be considered because their embryotoxicities cause systemic effects. In the present study, chemicals were metabolized using a culture system of rat liver hepatocytes. Then, the culture medium was used to differentiate mouse ES cells. Myocardial pulse rates were compared using Ag, Pd, Cu, and In, metal elements used in the upper structure of dental implants, depending on the presence or absence of metabolism. As a result, Ag, Pd, and In had significant effects on cell differentiation, while Cu had reduced effects due to metabolism. These results may be explained by the effects of metallothionein in the liver. Thus, metabolic factors should be considered for the embryotoxicity test.

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A strontium apataite (SrAp) thin film was coated onto a titanium substrate using radio frequency sputtering technique. To increase crystallinity of the sputtered films, the coated films were subjected to a hydrothermal treatment. The crystallinity of the films was determined using X-ray diffractometer (XRD). Cell reaction to the prepared film was evaluated by measuring the cell attachment of human osteosarcoma cell line Saos-2, alkaline phosphatase (ALP) activity and osteocalcin (OCN) expression of primary rat osteoblast. From XRD patterns, the as-sputtered SrAp film had higher crystallinity than the as-sputtered HA film. In the cell attachment measurement, the number of attached cells on the SrAp film after the hydrothermal treatment (hyd- SrAp) was higher than that of the as-sputtered SrAp film, whereas, the number of attached cells showed no significant difference between the hyd-SrAp film and the hyd-HA film (the HA film after the hydrothermal treatment). In the cell area, both of the hyd-HA film and the hyd-SrAp film, showed the same cell area as titanium. The number of vinculin on the hyd-SrAp film was larger than that of the hyd-HA film. The ALP activity for the hyd-SrAp film was higher than the sp-SrAp film, whereas, the ALP activity for the hyd- SrAp film was lower than that for the hyd-HA film. In OCN expression, the hyd-SrAp film showed the largest value in all samples. These results indicated that the hyd-SrAp film had a good cell attachment, and the osteoblast differentiation on the hyd-SrAp film was comparable to the hyd-HA film after 14 days of culture.

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Bisphosphonates are well known drugs that can inhibit bone resorption and normalize the high rate of bone turnover that characterizes osteoporosis. Recently, hydroxyapatite (HA) has been used in a bisphosphonates local delivery system to enhance peri-implant bone formation, and the results are generally encouraging. In the present study, a thin film HA coating prepared by radio frequency (RF) magnetron sputtering technique was used as a bisphosphonate carrier. The purpose of the present study is to evaluate whether a coating concentration of zoledronic acid (ZOL), a nitrogen containing bisphosphonate, can improve peri-implant bone formation and decrease bacterial adhesion. Custom made sputtered HA coated titanium cylinders with different amounts of ZOL were inserted into the femur of OVX rats. After 2 weeks healing, the animals were sacrificed and the samples were analyzed histologically and radiologically. The results indicated that the ZOL released from the sputtered HA coating stimulated peri-implant bone formation at relatively low doses (0.5 μg and 2 μg), which is even lower than previously reported using a ZOL administered plasma spray HA coating. Furthermore, the bacterial adhesion to the HA implant seemed unaffected by the application of ZOL. The results from this study demonstrate the effectiveness of a local delivery of ZOL from the sputtered HA coating in order to increase the peri-implant bone formation.

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We tried fabrication of the guided bone regeneration (GBR) membrane in which the osteoanagenesis was possible in short period by coating a hydroxyapatite (HAp) thin film on the bioabsorbable polymer sheet. Polylactic acid-glycolic acid copolymer (PLGA) was used for the membrane. The HAp thin film was prepared by using a pulsed laser deposition technique. Biocompatibility of the HAp/PLGA hybrid membrane was evaluated by cell culture experiment using osteoblast cell. Also, the clinical simulation test of HAp/PLGA membrane was carried out by using a femoral defect model of dog. In the in-vitro cell test, the HAp/PLGA membrane showed more excellent cell proliferation than the PLGA membrane. As a result of in-vivo animal test, the HAp/ PLGA membrane showed more excellent osseous conduction than the PLGA membrane. From the above results, it was proven that the HAp/PLGA membrane was very useful as the osseous conduction device in the next generation.

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