More than 25 molecular species of collagen have been found in the various animal tissues. Three polypeptides of Type I collagen subunits with molecular weight of 100 kDa (two alpha 1 subunit and one alpha 2 subunit) are intertwined each other to form a triple helical structure. Type I collagen have been used for the purpose of various application in medical devices such as cell culture scaffold, matrices for drug delivery systems. Cross-linking of collagen subunits is important to reinforce mechanical strength of collagen gel in such application. I overview the various different methods and strategies for cross-linking collagen gels those has been reported in the literature and discuss the advantage and disadvantage of those methods, especially those in radiation-based methods in this review article.

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The effects of green tea polyphenol, epigallocatechin-3-O-gallate (EGCG), on tooth preservation of guinea pig incisors were investigated.
Carefully extracted and pulpectomized teeth of the guinea pigs (200-300g, 4 weeks) were irrigated with saline. After rinsing in phosphate buffer saline containing 100U/mL of penicillin and 100 mg/mL of streptomycin, the teeth were transferred to Dulbecco's Modified Eagle's Medium (DMEM) containing 10 v/v% of fetal calf serum and different concentration of EGCg, followed by incubation at 4°C for one week. Then, the teeth were recovered and put on a culture dish with DMEM. Time until cell migration of EGCG treated teeth was shorter than that of untreated teeth.
The periodontal ligament cells viability preserved with 250 mg/mL EGCG at 4°C was higher than that without EGCG. These results suggested that EGCG could be useful as a cell protective agent at low temperature preservation.

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The relationship between mechanical stress and cell differentiation is as yet unexplained. We applied mechanical reciprocating motions to mouse ES-D3 cells with a stressing mechanism. The amount of osteocalcin, which is a marker of the bone differentiation and myocardial pulse rate, was measured upon the differentiation of embryoid bodies (EBs) through three-dimensional culture in a collagen gel matrix. The mechanical stress did not have an effect on the differentiation of EBs in to myocardium. However, the amount of osteocalcin in the group to which mechanical stress was applied for 4 hours was about half of that in the control group.
It is expected that stem cells are involved in oral tissue differentiation caused by external forces based on analysis using embryonic stem cells.

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Thin carbonate apatite was deposited onto titanium using a molecular precursor method, which is a novel technique. The molecular precursor solution was prepared by the addition of dibutylammonium diphosphate salt to an ethanol solution of Ca-EDTA complex at a Ca/P ratio=1.67. The molecular precursor solution was applied to titanium and fired at different temperatures at 600°C for 2 hr using a furnace under ordinary atmospheric conditions. The coated surface was bombarded with argon ions for 5, 10, and 15 minutes. Crack formation on the coated surface was increased according to the prolongation of argon ion etching time. The presence of carbonate group inside the coatings was detected by Fourier transform infrared reflection-absorption spectroscopy. Carbonate group was present after 15 min etching. It is concluded that carbonate group was trapped inside the coated CA film when used with molecular precursor method.

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The toxic interaction between amitriptyline and fluconazole was studied in chick embryos. Chick embryos have been widely used in pharmacologic and toxicologic experiments for evaluating drug action. Fertilized eggs of White Leghorns were incubated and investigated. Amitriptyline with and without fluconazole was injected into the air sac of a fertilized egg on the 16 th day of incubation. Electrocardiograms were recorded 0 to 60 min after the injection. Changes in heart rate were expressed as mean-percent changes of the drug-treated groups to the matched control. After each drug injection alone, the heart rate was not different compared with control. However, the heart rate was significantly decreased by combination with amitriptyline and fluconazole. In addition, arrhythmia was produced by amitriptyline with fluconazole. These findings indicate that the interaction between amitriptyline and fluconazole has a marked influence on the heart rate in chick embryos.

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Present study aimed to quantify the amounts of adsorbed fibronectin on hexame-thyldisiloxane (HMDSO)-coated titanium. HMDSO coating was performed by plasma polymerization and amounts of fibronectin were quantified by the ninhydrin reaction. Plasma-polymerized HMDSO coatings were firmly attached to the titanium. The fibronectin was adsorbed onto HMDSO-coated titanium surface for 24 hr. After the NaOH hydrolysis and ninhydrin reaction of adsorbed fibronectin, the amount of adsorbed fibronectin was determined by the absorbance at 570 nm using a spectrophotometer. X-ray photoelectron spectroscopy and Fourier transform reflection-absorption spectroscopy identified the adsorption of fibronectin onto the HMDSO-coating. HMDSO-coated titanium showed significantly greater amount of adsorbed fibronectin compared with uncoated titanium. HMDSO-coating by plasma polymerization will have a potential for surface modification of titanium implant materials.

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The purpose of this study is to investigate the morphological differences of human dentin after two types of acidic conditioning: etching reagent and self-etching primer using an AFM. The 6 upper first premolars were used in this study. The specimens were divided into three groups: group 1, No-pretreatment; group 2, Etching treatment with 10% citric acid-3% ferric chloride solution in Super-bond C&B system; group 3, an etching treatment with a self-etching primer, ED primer II, in Panavia Fluoro cement. These specimens were divided into the crown and root dentin and were observed in situ using an AFM. In the no-pretreatment specimen, the diameters of dentinal tubules in both the surface and middle layers of the crown dentin were narrower than in the deep layer of crown dentin. The diameters of dentinal tubules in the root dentin were narrower than that of crown dentin. Furthermore, the peritubular dentin was observed more clearly in the root dentin as compared with the crown dentin. After etching with a 10-3 solution of Super-bond C&B, the peritubular dentin was removed in both the crown and root dentin. The diameters of dentinal tubules were wider than that of no-pretreatment dentin. After ED primer II treatment, the peritubular dentin was removed in the crown dentin, but remained in the root dentin. It was concluded that differences in the dentin region after two types of acidic conditioning were influenced the arrangement of collagen fibers, the amount of collagen, and different sets of matrix proteins in the dentin.

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Statins, cholesterol-lowering drugs, have been recently reported to activate the promoter of the bone morphogenic protein-2 (BMP-2) gene, and stimulate bone formation. In this study, we investigated whether statins promote the mineralization of a subclonal cell line with low differentiation/mineralization potential derived from a murine pro-osteoblastic cell line, MC3T3-E1. Two subclonal cell lines, a nonmineralizing subclone (subclone N) and a mineralizing subclone (subclone M) after growth in the presence of ascorbic acid, were used in this study. Mineralization was detected by von Kossa staining 14 days after the addition of ascorbic acid with or without mevastatin. Total RNA was extracted from the cultured cells 3 days after stimulation, and the mRNA expression level of osteoblast-related molecules was measured using real-time quantitative RT-PCR. Only subclone M formed a miner-alized matrix by stimulation of ascorbic acid alone. When mevastatin was added to the ascorbic acid-containing medium, not only subclone M but also subclone N formed a mineralized matrix. The mRNA expression levels of BMP-2 and osteocalcin in subclone N were significantly lower than those in subclone M. When mevastatin was added, both the mRNA levels in subclone N significantly increased, and there was no significant difference between the two subclones. These results demonstrate that statins promote mineralization in nonmineralizing osteoblasts through the induction of BMP-2 and osteocalcin. Hence, statins could be very useful for the promotion of osteoblast differentiation and mineralization in regenerative bone.

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