This review highlights the regeneration of gingival oral epithelium and neural elements incident to dental implantation. The regeneration process of nerve fibers can be divided into the three following stages; 1) an epithelial healing stage; 2) a completion stage of epithelial regeneration; and 3) a stage of osseointegration establishment. Prior to gradient disappearance of inflammatory reaction around the epithelium, the nerve fibers begin to regenerate in the healing peri-implant epithelium. After completion of epithelial healing, the peri-implant epithelium exhibits the same neural density and terminal morphology as the intact junctional epithelium. These regenerated nerve fibers show a beaded-in-appearance, suggesting that these fibers contain neuropeptides including calcitonin gene-related peptide and substance P which have diverse functions. These findings indicate that the peri-implant epithelium share some structural and functional features with normal junctional epithelium, although these two epithelia have different origins.

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Objectives. Bone defects make up a significant clinical problem. The purpose of the present study was to evaluate the osteogenic tissue behavior in a titanium (Ti) porous scaffold with immobilization of bone morphogenetic protein (BMP) -2 in vivo.
Methods. Ti scaffold (pore size: 200-500 μm) with or without BMP-2 immobilization was implanted into a created defect of a rat femur.
Results. One week after implantation, only bone marrow cells were present around the scaffold without BMP, but new bone formation could be observed around the scaffold with BMP. Two weeks after implantation, new bone tissue had formed around the scaffold with and without BMP-2 immobilization.
Conclusions. Ti porous scaffold with BMP-2 immobilization can manufacture new bone tissue at an early stage, and can be a beneficial in the repair of bone defects.

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Objective: To compare the effects of strontium substituted hydroxyapatite of different porosities on the biological behaviors of the osteoblasts derived from rabbit bone marrow in in vitro culture.
Methods: Bone marrow was obtained from healthy rabbit,and then was cultured and induced into osteoblasts,which were compounded with Sr-HA and HA(as the positive contrast) ceramics of different porosities(50%,60% and 70%).The proliferation and differentiation of all the cultured cells were observed at different time points under inverted phase contrast microscope and scanning electron microscope(SEM) respectively. The activity of alkaline phosphatase in these osteoblasts was quantitatively detected.
Results: After cultured with Sr-HA with different porosities, the osteoblasts from rabbit bone marrow showed the biological and morphological properties similar to those of uncompounded osteoblasts. Sr-HA didn't show any adverse effects on the cell functions. In addition, Sr-HA with a porosity of 70% could facilitate the entrance of cells into the pores of the material.
Conclusion: Sr-HA is an optimal scaffold material for bone tissue engineering, which can be potentially found clinical application for bone defect repair. Because of the good connectivity of Sr-HA with a porosity of 70%, it has better effect on the growth of osteoblasts and more possibility of application as a scaffold material for bone tissue engineering than Sr-HA with other porosities.

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The synthetic pure hydroxyapatite(HA) have excellent biocompatibility and a little osseous inductivity, however, there are still some shortcomings such as the high degree of crystallibility and the quite stability of the structure. Strontium seemed to have the potential to change the biocompatibility and physicochemical characteristics of HA for implant use. Sr-HA containing 1%, 5%, 10%, 100% Sr²⁺ were synthesized by solution-reaction system. MTT assay and Flow Cytometry (FCM) method were used to test the cytotoxicity of Sr-HA bioceramic. Result shows that there's no obvious cytotoxicity of all the Sr-HA bioceramics. But the cytotoxicity increases as the Strontium concentration raising. As the FCM method shows, there's no apparent difference between the pure hydroxyapatite and all of the Sr-HA. Through this in vitro study on cytotoxicity we can come to the conclusion that the Sr-HA bioceramics have no obvious cytotoxicity and may have good biocompatibility, especially 1%, 5% Sr-HA.

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It has been reported that simvastatin, which is a cholesterol synthesis inhibitor and a therapeutic drug for hypercholesteremia, stimulates bone morphogenetic protein 2 expression in osteoblasts, suggesting potentiality of simvastatin in local bone augmentation. We prepared bovine atelo-collagen or calcium sulfate containing simvastatin and applied these materials to the rat lower incisor sockets. After 4 weeks, the bone of the extracted site was examined radiographically and histologically. Calcium sulfate containing simvastatin remarkably increased the thickness of the alveolar bone. This effect was not observed when simvastatin alone was applied or when atelo-collagen was used as a drug carrier. Although further studies are required, the present results indicate that simvastatin augments bone around tooth socket, which is carrier-dependent.

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Three-dimensional culture of the cells in vitro is expected for therapeutic purposes. We self-prepared alginate sponges by freeze-drying the mixture of 2 % (low-molecular-weight, medium-molecular-weight and high-molecular -weight) sodium alginate solutions and 0.2% calcium sulfate solution. The low-molecular-weight alginate sponge had the largest interconnected porosities with mean diameter of more than 100μm. We seeded L929 and UMR106 cells on the low-molecular-weight alginate sponge, and cultured them for 7 and 31 days. For 7 days, optical microscopy revealed that two cells became round-shaped while adhering to the sponge wall. For 31 days, scanning electron microscopy (SEM) clarified that two cells were flat elongated or round-shaped with many interconnected projections. The low-molecular-weight alginate sponge appears to be useful as a three-dimensional scaffold for cell culture in vitro.

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