Jae Jun Ryu

Effects of anodized titanium with Arg-Gly-Asp (RGD) peptide immobilized via chemical grafting or physical adsorption on bone cell adhesion and differentiation

PURPOSE This study examined the effects of the immobilization of Arg-Gly-Asp (RGD) peptide (CAAALLLKERGDSK) on anodized titanium (Ti) via chemical grafting or physical adsorption methods on cell adhesion and osteoblast differentiation. MATERIALS AND METHODS The RGD peptide was immobilized on the anodized Ti surface by means of physical adsorption or chemical grafting. The chemical composition of each RGD-immobilized Ti substrate was examined by x-ray photoelectron spectroscopy. The level of cell proliferation was investigated via tetrazolium (XTT) assay. Alkaline phosphatase activity and calcium deposition were evaluated by alizarin red S staining, and mRNA expression of the differentiated osteoblast marker genes was analyzed by reverse-transcriptase polymerase chain reaction. RESULTS Cell adhesion was enhanced on the RGD-immobilized Ti substrates compared to the anodized Ti surfaces. In addition, significantly increased cell spreading and proliferation were observed with the cells grown on the RGD-immobilized Ti (P < .05). Furthermore, the osteoblasts on the RGD-immobilized Ti showed significant increases in the integrin ?1 and type I collagen levels and small increases in osteonectin and osteocalcin levels (P < .05). Interestingly, the chemical grafting method resulted in significantly greater effects on adhesion and differentiation than the physical adsorption method (P < .05). CONCLUSION RGD-immobilized Ti substrates might be effective in improving the osseointegration of dental implants. In particular, the chemical grafting method of RGD immobilization is more favorable and is expected to provide positive outcomes with future animal and clinical studies.

Laser Modulation of Heat and Capsaicin Receptor TRPV1 Leads to Thermal Antinociception

Er,Cr:YSGG lasers are used clinically in dentistry. The advantages of laser therapy include minimal thermal damage and the alleviation of pain. This study examined whether the Er,Cr:YSGG laser has in vivo and in vitro antinociceptive effects in itself. In capsaicin-evoked acute licking/shaking tests and Hargreaves tests, laser irradiation with an aerated water spray suppressed nociceptive behavior in mice. Laser irradiation attenuated TRPV1 activation by capsaicin in Ca2+ imaging experiments with TRPV1-overexpressing cells and cultured trigeminal neurons. Therefore, the laser-induced behavioral changes are probably due to the loss of TRPV1 activity. TRPV4 activity was also attenuated, but limited mechanical antinociception by the laser was observed. The laser failed to alter the other receptor functions, which indicates that the antinociceptive effect of the laser is dependent on TRPV1. These results suggest that the Er,Cr:YSGG laser has analgesic effects via TRPV1 inhibition. Such mechanistic approaches may help define the laser-sensitive pain modality and increase its beneficial uses.

Influence of Transmucosal Designs of Dental Implant on Tissue Regeneration in Beagle Dogs

This study was conducted to evaluate the influence of concave machined and concave microgrooved profiles of the transmucosal portion of implants on early peri-implant tissue regeneration. We assessed implants with 3 different transmucosal profiles: the bevel group that had only a bevel in the transmucosal part, bioseal group and bioseal/groove group that had a micro-groove in the S-shaped portion of the implant. A total of 36 implants (12 of each type) were placed in the edentulous mandibular ridges of 6 beagle dogs. We used radiographs to investigate the mesio-distal change of the marginal bone. Bucco-lingual bone resorption and soft tissue reactions were evaluated histologically. Radiographic and histological analysis did not show any difference in mesio-distal or bucco-lingual marginal bone resorption among any of the 3 groups (p > 0.05). The bioseal and bioseal/groove groups had more rigid connective tissue attachment than that in the bevel group. However, the bevel group had significantly long junctional epithelium attachment and the bioseal and bioseal/groove groups had long connective tissue attachment (p < 0.05). Implants with S-shaped concavity of the transmucosal portion resulted in a firmer connective tissue barrier, and thus, a better soft tissue regeneration, than implants with straight bevel.