Synergistic interaction between wavelength of light and concentration of H2O2 in bactericidal activity of photolysis of H2O2.

The present study aimed to evaluate the interaction between wavelength of light in the range of ultra violet A-visible and concentration of H2O2 in the reaction of photolysis of H2O2 from the point of view of hydroxyl radical (·OH) generation and the bactericidal activity. Light emitting diodes (LEDs) emitting the light at wavelengths of 365, 385, 400 and 465 nm were used at an irradiance of 1000 mW/cm(2). H2O2 was used at the final concentrations of 0, 250, 500, and 1000 mM. Quantitative analysis of ·OH generated by the LED irradiation of H2O2 were performed using an electron spin resonance-spin trapping technique. In a bactericidal assay, a bacterial suspension of Staphylococcus aureus prepared in sterile physiological saline was irradiated with the LEDs. The bactericidal activity of each test condition was evaluated by viable counts. When H2O2 was irradiated with the LEDs, ·OH was generated and bacteria were killed dependently on the concentration of H2O2 and the wavelength of LED. The two-way analysis of variance revealed that the wavelength, the H2O2 concentration and their interaction significantly affected the yield of ·OH and the bactericidal activity of the photolysis of H2O2. Therefore, it is suggested that bactericidal activity of photolysis of H2O2 could be enhanced by controlling the wavelength and the concentration of H2O2, which may contributes to shortening the treatment time and/or to reducing the concentration of H2O2.

In vitro bactericidal activity of photo-irradiated oxydol products via hydroxyl radical generation.

The oxidative power of hydroxyl radicals has been applied to disinfection systems for the purpose of oral hygiene by utilizing blue light-induced photolysis of hydrogen peroxide (H2O2) in our laboratory. In the present study, the bactericidal potential of blue light-irradiated oxydol products via hydroxyl radical generation was compared with that of 3% (w/v) H2O2. Eleven commercially available oxydol products were used in the present study. Even though a few of the products that contained ethanol, a hydroxyl radical scavenger, as an additive showed slightly lower hydroxyl radical yield as compared with 3% (w/v) H2O2, the blue-light irradiation of each oxydol product for 3 min showed similar or superior bactericidal activity against Staphylococcus aureus to that of 3% (w/v) H2O2. The results strongly suggest that any of the oxydol products tested in the present study can be used as a source of hydroxyl radicals for the disinfection technique developed in our laboratory.

Novel denture-cleaning system based on hydroxyl radical disinfection.

The purpose of this study was to evaluate a new denture-cleaning device using hydroxyl radicals generated from photolysis of hydrogen peroxide (H2O2). Electron spin resonance analysis demonstrated that the yield of hydroxyl radicals increased with the concentration of H2O2 and light irradiation time. Staphylococcus aureus, Pseudomonas aeruginosa, and methicillin-resistant S aureus were killed within 10 minutes with a > 5-log reduction when treated with photolysis of 500 mM H2O2; Candida albicans was killed within 30 minutes with a > 4-log reduction with photolysis of 1,000 mM H2O2. The clinical test demonstrated that the device could effectively reduce microorganisms in denture plaque by approximately 7-log order within 20 minutes.

In vitro and in vivo anti-Staphylococcus aureus activities of a new disinfection system utilizing photolysis of hydrogen peroxide.

The present study aimed to evaluate in vitro and in vivo antibacterial activity of hydroxyl radical generation system by photolysis of H(2)O(2), which is a new disinfection system for the treatment of oral infection diseases such as periodontitis developed in our laboratory. Firstly, generation of the hydroxyl radical by the photolysis of H(2)O(2) in which 1 mol l(-1) H(2)O(2) was irradiated with a dual wavelength-light emitting diode (LED) at wavelengths of 400 and 465 nm was confirmed by applying an electron spin resonance-spin trapping technique. Secondly, the bactericidal effect of the system was examined under a similar condition in which Staphylococcus aureus suspended in 1 mol l(-1) H(2)O(2) was irradiated with LED light, resulting in substantial reduction of the colony forming unit (CFU) of the bacteria within a short time as 2 min. Finally, in vivo antibacterial effect of the photolysis of H(2)O(2) on a rat model of S. aureus infection was evaluated by a culture study. Since a significant reduction of recovered CFU of S. aureus was obtained, it is expected that in vitro antibacterial effect attributable to hydroxyl radicals generated by photolysis of H(2)O(2) could be well reflected in in vivo superficial bacterial infection.

Topical treatment of oral cavity and wounded skin with a new disinfection system utilizing photolysis of hydrogen peroxide in rats.

The present study aimed to evaluate the acute locally injurious property of hydroxyl radical generation system by photolysis of H(2)O(2), which is a new disinfection system for the treatment of periodontitis developed in our laboratory. Firstly, generation of the hydroxyl radical by a test device utilizing the photolysis of H(2)O(2) was confirmed by applying an electron spin resonance (ESR)-spin trapping technique. Secondly, the bactericidal effect of the device was examined under a simulant condition in which Staphylococcus aureus suspended in 1 M H(2)O(2) was irradiated with laser light emitted from the test device, resulting in substantial reduction of the colony forming unit of the bacteria within a short time as 2 min. Finally, acute topical effect of the disinfection system on rat oral mucosa and wounded skin was evaluated by histological examination. No abnormal findings were observed in the buccal mucosal region treated three times with 1 M H(2)O(2) and irradiation. Similarly, no abnormal findings were observed during the healing of skin treated with 1 M H(2)O(2) and irradiation immediately after wounding. Since topical treatment with the novel disinfection technique utilizing the photolysis of H(2)O(2) had no detrimental effect on the oral mucosa and the healing of full thickness skin wounds in rats, it is expected that the acute locally injurious property of the disinfection technique is low.

Synergistic effect of thermal energy on bactericidal action of photolysis of H2O2 in relation to acceleration of hydroxyl radical generation.

The purpose of the present study is to evaluate the effect of thermal energy on the yield of and the bactericidal action of hydroxyl radical generated by photolysis of H(2)O(2). Different concentrations of H(2)O(2) (250, 500, 750, and 1,000 mM) were irradiated with light-emitting diodes (LEDs) at a wavelength of 400 ± 20 nm at 25°C to generate hydroxyl radical. The 500 mM H(2)O(2) was irradiated with the LEDs at different temperatures (25, 35, 45, and 55°C). Electron spin resonance spin trapping analysis showed that the yield of hydroxyl radicals increased with the temperature, as well as the concentration of H(2)O(2). Streptococcus mutans and Enterococcus faecalis were used in the bactericidal assay. The LED-light irradiation of the bacterial suspensions in 500 mM H(2)O(2) at 25°C could hardly kill the bacteria within 3 min, while the bactericidal effect was markedly enhanced with the temperature rise. For instance, a temperature increase to 55°C resulted in >99.999% reduction of viable counts of both bacterial species only within 1 min. The photolysis of 500 mM H(2)O(2) at 55°C could reduce the viable counts of bacteria more efficiently than did the photolysis of 1,000 mM H(2)O(2) at 25°C, although the yields of hydroxyl radical were almost the same under the both conditions. These findings suggest that the thermal energy accelerates the generation of hydroxyl radical by photolysis of H(2)O(2), which in turn results in a synergistic bactericidal effect of hydroxyl radical and thermal energy.

[What prosthodontic therapy should we select for periodontally compromised patients? Part 1: Review of the literature focusing on implant therapy for periodontally compromised patients].

PURPOSE: From a large number of experimental and clinical studies, it has been suggested that dental implant therapy has good prognosis for totally and partially edentulous patients. However, it is unclear whether we can use the implants for periodontally compromised patients. The aim of the present study was is to consider scientific evidence on implant treatment for periodontitis-susceptible subjects with partially edentulous dentate. STUDY SELECTION: Clinical studies that documented survival rates or success rates of implant therapy for periodontally compromised patients were selected and reviewed. RESULTS: Most of the 22 reports that were reviewed suggested good survival or success rate of implant therapy in short-term or medium-term clinical results. CONCLUSION: Although there were only a few long-term follow up studies, it was indicated that individuals who had susceptibility to periodontal disease can be treated successfully with the implants. In all reports, treatment for infection was done before implants installation, and the importance of regular maintenance after the installation has been emphasized. From this literature review, it was advocated that periodontally compromised patients could be treated successfully with the implants. However, implant therapy should be reconsidered if oral infection cannot be satisfactorily controlled.

[What prosthodontic therapy should we select for periodontally compromised patients? Part 2: Review of the literature focusing on conventional prosthodontic therapy for periodontally compromised patients and clinical implication (RPD vs FPD vs implant)].

PURPOSE: To review the clinical literature on fixed partial denture (FPD) and removable partial denture (RPD)treatment for periodontally compromised patients with partial dentate. In addition, prosthodontic management in periodontitis-susceptible subjects was evaluated from the results of Part 1 and Part 2. STUDY SELECTION: Clinical studies that documented survival rates of FPD in periodontally compromised patients were selected and reviewed. RESULTS: There was no RPD study that fulfilled the criteria of this review paper. On the other hand, 8 reports that were reviewed in this study showed good survival rate of FPD in long-term clinical results. CONCLUSION: Since the number of reports on RPD is very few, it was difficult to evaluate the RPD treatment for periodontally compromised patients. From the results of some long-term follow-up retrospective studies, however, it was suggested that FPD of high-risk design showed excellent results. Regarding management in periodontits- susceptible subjects, it should be discussed whether positive prosthodontic treatment is necessary. Strict plaque control by both doctors and patients before/after treatment is indispensable for prosthodontic management in periodontally compromised patients.

Grindability of dental magnetic alloys.

In this study, the grindability of cast magnetic alloys (Fe-Pt-Nb magnetic alloy and magnetic stainless steel) was evaluated and compared with that of conventional dental casting alloys (Ag-Pd-Au alloy, Type 4 gold alloy, and cobalt-chromium alloy). Grindability was evaluated in terms of grinding rate (i.e., volume of metal removed per minute) and grinding ratio (i.e., volume ratio of metal removed compared to wheel material lost). Solution treated Fe-Pt-Nb magnetic alloy had a significantly higher grinding rate than the aged one at a grinding speed of 750-1500 m x min(-1). At 500 m x min(-1), there were no significant differences in grinding rate between solution treated and aged Fe-Pt-Nb magnetic alloys. At a lower speed of 500 m x min(-1) or 750 m x min(-1), it was found that the grinding rates of aged Fe-Pt-Nb magnetic alloy and stainless steel were higher than those of conventional casting alloys.