Seung-Ho Ohk

Anti-cariogenic effects of erythritol on growth and adhesion of Streptococcus mutans

Erythritol is one of the most widely used low calorie sugar substitutes and has known inhibitory effects on the growth of Streptococcus mutans. However, the mechanism underlying this inhibition is poorly understood. Expression profiles of the glucosyltransferase (GTF) and fructosyltransferase (FTF) genes in S. mutans were evaluated in the presence of erythritol and other sweeteners. Adhesion of S. mutans to different carbohydrates was also determined across a range of concentrations. Erythritol significantly (p<0.05) inhibited adherence of S. mutans under multiple conditions, compared with sucrose. Erythritol significantly (p<0.05) inhibited expressions of gtfB, gtfC, gtfD, and ftf in the presence of various carbohydrates compared with sucrose. These findings were consistent with an anti-cariogenic effect of erythritol on S. mutans, and suggested mechanisms by which erythritol inhibits formation of dental caries.

Sterilization effects of a TiO2 photocatalytic film against aStreptococcus mutans culture

Streptococcus mutans is one of the more significant pathogens involved in the development of dental caries in humans. The purpose of this research was to design a TiO2-coated dental instrument and to determine the bactericidal effects of the instrument onS. mutants. TiO2 photocatalytic films were prepared by the low-pressure metal-organic chemical vapor deposition (LPMOCVD) method using titanium tetraisopropoxide (TTIP) as precursor. The photocatalytic reaction was carried out on a TiO2-coated pyrex petri dish with an ultraviolet (UV) light emitting diode (LED) illuminator or a fluorescent lamp light source. Our data indicates that the relative survival ratio ofS. mutans when plated onto TiO2 photocatalytic films and under exposure to UV-A light for 15 min was 0.01%. In addition, a fluorescent lamp light source also had bactericidal effects on theS. mutans plated TiO2 photocatalytic films. These results indicate that TiO2-coated dental materials or devices may be useful in dental treatments for the prevention of carious or enamel demineralization.

Plasma treated high-density polyethylene (HDPE) medpor implant immobilized with rhBMP-2 for improving the bone regeneration

We investigate the bone generation capacity of recombinant human bone morphogenetic protein-2 (rhBMP-2) immobilized Medpor surface through acrylic acid plasma-polymerization. Plasma-polymerization was carried out at a 20 W at an acrylic acid flow rate of 7 sccm for 5 min. The plasma-polymerized Medpor surface showed hydrophilic properties and possessed a high density of carboxyl groups. The rhBMP-2 was immobilized with covalently attached carboxyl groups using 1-ethyl-3-(3- dimethylaminopropyl) carbodiimide and N-hydroxysuccinimide. Carboxyl groups and rhBMP-2 immobilization on the Medpor surface were identified by Fourier transform infrared spectroscopy. The activity of Medpor with rhBMP-2 immobilized was examined using an alkaline phosphatase assay on MC3T3-E1 cultured Medpor. These results showed that the rhBMP-2 immobilized Medpor increased the level of MC3T3-E1 cell differentiation. These results demonstrated that plasma surface modification has the potential to immobilize rhBMP-2 on polymer implant such as Medpor and can be used for the binding of bioactive nanomolecules in bone tissue engineering.

Evaluation of osseointegration ability of porous polyethylene implant (medpor) treated with chitosan

Purpose. We suggest a successful and simple Medpor treated way with chitosan and evaluate more improved osseointegration ability of it than the orignal. Materials and Methods. Medpor was punched into circular shape and dipped into the chitosan gel solution. The Medpor plates soaked with chitosan were identified by the SEM images. We evaluated the growth rate of MC3T3-E1 cell using Von Kossa staining and MTT assay as in vitro experiment. And we implanted both Medpor plates into skull of domestic rabbits for in vivo experiment. We evaluated the osseointegration result with an optical microscope in postoperative 3 weeks and 6 weeks histologically. Results. The in vitro MC3T3-E1 cell growth rate on Medpor soaking with chitosan was faster than the original one in both Von Kossa staining and MTT assay. In animal test, Medpor soaking with chitosan shows more pronounced new bone than original Medpor too. Conclusion. Medpor soaking with chitosan was a successful modification. It is believed that the upgraded osseointegration ability of Medpor soaking with chitosan gives many benefits to clinicians using a Medpor implant for oral and maxillofacial reconstruction surgery.