Decontamination methods to restore the biocompatibility of contaminated titanium surfaces

PURPOSE: The reaction of cells to a titanium implant depends on the surface characteristics of the implant which are affected by decontamination. The aim of this study was to evaluate the cytocompatibility of titanium disks treated with various decontamination methods, using salivary bacterial contamination with dental pellicle formation as an in vitro model. METHODS: Sand-blasted and acid-etched (SA) titanium disks were used. Three control groups (pristine SA disks [SA group]; salivary pellicle-coated SA disks [pellicle group]; and biofilm-coated, untreated SA disks [NT group]) were not subjected to any decontamination treatments. Decontamination of the biofilm-coated disks was performed by 14 methods, including ultrasonic instruments, rotating instruments, an air-powder abrasive system, a laser, and chemical agents. MG63 cells were cultured in the presence of the treated disks. Cell proliferation assays were performed on days 2 and 5 of cell culture, and cell morphology was analyzed by immunofluorescence and scanning electron microscopy (SEM). A vascular endothelial growth factor (VEGF) assay was performed on day 5 of culture. RESULTS: The cell proliferation assay revealed that all decontaminated disks, except for the 2 groups treated using a plastic tip, showed significantly less cell proliferation than the SA group. The immunofluorescence and SEM analyses revealed that most groups showed comparable cell density, with the exception of the NT group, in which the cell density was lower and bacterial residue was observed. Furthermore, the cells grown with tetracycline-treated titanium disks showed significantly lower VEGF production than those in the SA group. CONCLUSIONS: None of the decontamination methods resulted in cytocompatibility similar to that of pristine SA titanium. However, many methods caused improvement in the biocompatibility of the titanium disks in comparison with the biofilm-coated, untreated titanium disks. This suggests that decontamination is indispensable for the treatment of peri-implantitis, even if the original biocompatibility cannot be restored.

Establishment of a dental license regulation authority is required in Korea: results of the Delphi technique / 보건의료교육평가

PURPOSE: In addition to dental education, a system for the evaluation and management of dental licensing and certification is required to meet the growing societal demand for more competent dentists. In this study, the Delphi technique was used to gather opinions from a variety of professionals on the problems of and remedies for the dental license management system in Korea. METHODS: Delphi surveys were conducted from April 2016 to October 2016 in South Korea. A variety of dental professionals were included and categorized into 3 groups according to their expertise as follows: the basic dentistry group, the clinical dentistry group, and the policy group. The Delphi technique was conducted in 3 rounds of e-mail surveys, each with different questions that probed with increasing depth on the dental license management system. In each successive round, the responses were categorized, scored on a Likert scale, and statistically analyzed. RESULTS: After categorizing the results of the first survey and ranking the results of the second survey using the Delphi technique, regulation by a licensing authority was found to be the most critical issue. This was followed by the license renewal system, continuing education, a tiered licensure system, improvement of foreign license approval, and utilization of retirees, in decreasing order of importance. The third Delphi survey showed a similar ranking, with regulation by a licensing authority being the major concern. Opinions regarding the dental license management system were provided as open-ended responses. The responses of the 3 groups showed statistically significant differences in the scores for the issue of regulation by a licensing authority. After re-grouping into the dentistry group and the policy group, the issue received a significantly higher score in the dentistry group. CONCLUSION: The quality of dental treatment should be managed to protect patients and dental professionals. For this purpose, the establishment of an independent license regulation authority along with legislative changes is required.

Comparison of digital models generated from three-dimensional optical scanner and cone beam computed tomography

PURPOSE: The objective of this study was to compare the accuracy of digital models from 3 dimentional (3D) optical scanner and cone beam computed tomography (CBCT). MATERIALS AND METHODS: We obtained digital models from 11 pairs of stone casts using a 3D optical scanner and a CBCT, and compared the accuracy of the models. RESULTS: The error range of average positive distance was 0.059 - 0.117 mm and negative distance was 0.066 - 0.146 mm. Statistically (P < 0.05), average positive distance was larger than 70 µm and shorter than 100 µm, and that of negative distance was larger than 100 µm and shorter than 120 µm. CONCLUSION: We concluded that the accuracy of digital models generated from CBCT is not appropriate to make final prostheses. However, it may be acceptable for provisional restorations and orthodontic diagnoses with respect to the accuracy of the digitalization.

Prevention of Biofilm Infections

Biofilms are well-organized, complex microbial communities that are often highly resistant to antimicrobial agents and host defenses. Biofilms are often formed on the surfaces of surgical implants and indwelling catheters. Being extremely resistant to removal, biofilms, once formed, cause numerous complications and often result in persistent infections that require long-term hospitalization for treatment. Until now, preventive measures employing prophylactic antimicrobials that prohibit or restrict biofilm formation have been the only feasible, effective options available, with the constant concomitant threat of antimicrobial resistance. However, the development of chemical agents that specifically act upon the virulence of biofilms, rather than destroying the microorganisms or suppressing their growth, is a promising new approach. Such agents are highly desirable in that they might allow clinicians to prevent the development of antimicrobial resistance. Effective suppression of biofilm formation would dramatically change the way to treat infectious disease. In this literature review, the types of infections associated with biofilms and relevant therapeutic options that have been approved, in use, or under development to treat biofilm infections are discussed, along with novel approaches to biofilm control that may be applicable to the development of future anti-biofilm agents.

Fc gammaR genetic polymorphisms of periodontal disease in Korean population / 대한치주과학회지

No abstract available.

The Role of Immune Response in Periodontal Disease

The periodontal diseases are infections caused by bacteria in oral biofilm, a gelatinous mat commonly called dental plaque, which is a complex microbial community that forms and adhere to tooth surfaces. Host immune-pathogen interaction in periodontal disease appears to be a complex process, which is regulated not only by the acquired immunity to deal with ever-growing and -invading microorganisms in periodontal pockets, but also by genetic and/or environmental factors. However, our understanding of the pathogenesis in human periodontal diseases is limited by the lack of specific and sensitive tools or models to study the complex microbial challenges and their interactions with the host's immune system. Recent advances in cellular and molecular biology research have demonstrated the importance of the acquired immune system in fighting the virulent periodontal pathogens and in protecting the host from developing further devastating conditions in periodontal infections. The use of genetic knockout and immunodeficient mouse strains has shown that the acquired immune response, in particular, CD4+ T-cells plays a pivotal role in controlling the ongoing infection, the immune/inflammatory responses, and the subsequent host's tissue destruction.

High levels of soluble herpes virus entry mediator in sera of patients with allergic and autoimmune diseases

Herpes virus entry mediator (HVEM) is a newly discovered member of the tumor necrosis factor receptor (TNFR) superfamily that has a role in herpes simplex virus entry, in T cell activation and in tumor immunity. We generated mAb against HVEM and detected soluble HVEM (SHVEM) in the sera of patients with various autoimmune diseases. HVEM was constitutively expressed on CD4(+)and CD8(+)T cells, CD19(+)B cells, CD14(+)monocytes, neutrophils and dendritic cells. In three-way MLR, mAb 122 and 139 were agonists and mAb 108 had blocking activity. An ELISA was developed to detect sHVEM in patient sera. sHVEM levels were elevated in sera of patients with allergic asthma, atopic dermatitis and rheumatoid arthritis. The mAbs discussed here may be useful for studies of the role of HVEM in immune responses. Detection of soluble HVEM might have diagnostic and prognostic value in certain immunological disorders.

Constitutive expression of 4-1BB on T cells enhances CD4+ T cell responses

4-1BB, a transmembrane molecule, member of the tumor necrosis factor receptor superfamily, is an important costimulatory molecule in the immune response, plays a key role in the clonal expansion and survival of CD8(+)T cells. In this study, we investigated 4-1BB regulation of CD4(+)T cell responses using 4-1BB transgenic (TG) mice that constitutively expressed 4-1BB on mature T cells. We first showed that CD4(+)T cells of 4-1BB TG mice had more sustained proliferative capacity in response to TCR/4-1BB stimulation in vitro compared to WT mice. Secondly, 4-1BB TG mice exhibited a more elevated contact hypersensitivity (CHS) response mediated by CD4+ Th1 cells due to more vigorous expansion of and apoptotic inhibition of CD4(+)T cells. Finally, CD4(+)T cells of 4-1BB TG mice had a heightened capacity for T cell priming. Overall, our results demonstrate the involvement of 4-1BB in CD4(+)Th1 cell responses by regulating the clonal expansion and survival of CD4(+)T cells as seen in CD8(+)T cells.

Osteoprotegerin is present on the membrane of osteoclasts isolated from mouse long bones

Osteoprotegerin (OPG), a member of the tumor necrosis factor receptor superfamily, is known to inhibit osteoclastogenesis by acting as a soluble decoy receptor for the receptor activator of NF-kB ligand (RANKL). We report the presence of OPG on the membrane of osteoclasts and the possibility of the direct action of OPG on them. Highly pure osteoclast precursors were isolated from mouse long bones and induced to differentiate into mature osteoclasts by M-CSF and soluble RANKL (sRANKL). The presence of OPG on the membrane of these cells was confirmed by western blotting and immunostaining. Furthermore, sRANKL was found to be bound to the OPG on the osteoclast precursors. These results suggest that OPG might have a new role during the differentiation of osteoclasts beyond its role as a soluble decoy receptor. The mechanism of the existence of OPG on osteoclast precursors remains to be found.

Development of bone regenerating material using bone morphogenetic protein(rhBMP-2) and bioresorbable polymer

Effect of Subinhibitory Concentrations of Antibiotics on Cell Surface Properties of Streptococcus gordonii and Staphylococcus aureus

Antibiotics were reported to be able to alter bacterial surface properties in subinhibitory concentrations (sub-MICs). The effects of sub-MICs of certain antibiotics on a bacterial surface property such as hemagglutination, as well as on the cell morphology were studied using Streptococcus gordonii and Staphylococcus aureus. The effect of sub-M1Cs of antibiotics on the binding of these bacteria to immobilized fibrinogen were also investigated. The MICs of antibiotics were determined by culturing S. gordonii and S. aureus in media supplemented with serially diluted drug solutions, and one-half the MIC was used as the sub-MIC of the drugs, unless stated otherwise. Sub-MICs of antibiotics did not affect bacterial agglutination of erythrocytes. Microscopic observation of S. gordonii grown at sub-MIC concentration of 0.02 ug/ml of amoxicillin revealed cell enlargement of 1.6 times those grown without the drug. When grown in the sub-MIC amount of 0.08 ug/ml of cefazolin, most S. gordonii cells were enlarged and elongated into rod-shape, resulting in 3 times the size of the cells grown without the antibiotic. The data from the fibrinogen-binding experiments showed that the binding of S. gordonii to immobilized fibrinogen was increased with all the B-lactam drugs tested; the binding of S. aureus to immobilized fibrinogen, on the other hand, was decreased with the same drugs. The results show that low concentrations of certain B-lactam antibiotics are able to cause alterations in cellular morphology of S. gordonii and affect the binding of S. gordonii and S. aureus to immobilized fibrinogen.