Inhibition of tooth demineralization caused by Streptococcus mutans biofilm via antimicrobial treatment using hydrogen peroxide photolysis

OBJECTIVES

An antimicrobial technique utilizing hydroxyl radicals generated by the photolysis of 3% H₂O₂ has been developed recently. The present study aimed to evaluate the effect of H₂O₂ photolysis treatment on tooth demineralization caused by Streptococcus mutans biofilm.

MATERIALS AND METHODS

To induce tooth demineralization, S. mutans biofilm was allowed to form on the maxillary first molars collected from Wistar rats via 24-h culturing. The samples were immersed in 3% H₂O₂ and irradiated with 365-nm LED (H₂O₂ photolysis treatment). Viable bacterial counts in the biofilm were evaluated immediately after treatment and after an additional 30-h culturing by colony counting. The acidogenicity of the biofilm, re-established 30 h after treatment, was assessed by measuring the pH. The effect of H₂O₂ photolysis treatment on tooth demineralization was assessed by measuring the depth of the radiolucent layer in micro-CT images.

RESULTS

H₂O₂ photolysis significantly reduced viable bacterial counts in the biofilm to 3.7 log colony forming units (CFU)/sample, while the untreated group had 7.9 log CFU/sample. The pH of the biofilm re-established after treatment (6.6) was higher than that of the untreated group (5.3). In line with the pH measurement, the treatment group had a significantly lower depth of radiolucent layer in dentin than the untreated group.

CONCLUSIONS

H₂O₂ photolysis treatment was effective not only in killing the biofilm-forming S. mutans but also in lowering the acidogenicity of the biofilm. Thus, this technique could inhibit tooth demineralization.

CLINICAL RELEVANCE

H₂O₂ photolysis can be applicable as a new dental caries treatment.

Hormesis: wound healing and fibroblasts

Hormetic dose responses are reported here to occur commonly in the dermal wound healing process, with the particular focus on cell viability, proliferation, migration and collagen deposition of human and murine fibroblasts with in vitro studies. Hormetic responses were induced by a wide range of substances, including endogenous agents, pharmaceutical preparations, plant-derived extracts including many well-known dietary supplements, as well as physical stressor agents such as low-level laser treatments. Detailed mechanistic studies have identified common signaling pathways and their cross-pathway communications that mediate the hormetic dose responses. These findings complement and extend a similar comprehensive assessment concerning the occurrence of hormetic dose responses in keratinocytes. These findings demonstrate the generality of the hormetic dose response for key wound healing endpoints, suggesting that the hormesis concept has a fundamental role in wound healing, with respect to guiding strategies for experimental evaluation as well as therapeutic applications.

Oral bacterial decontamination using an innovative prototype for photocatalytic disinfection

OBJECTIVES

The aim of this study was to evaluate the effectiveness of a prototype photocatalytic device for bacterial decontaminations of the oral cavity.

METHODS

Sixty-four subjects (18-65) were selected and randomly assigned to eight groups (n = 8), according to oral disinfection protocol: (G1): distilled water (control); (G2): 1.5% hydrogen peroxide (HP); (G3): 3.0% HP; (G4): 0.12% chlorhexidine (CHX); (G5): Germinator; (G6): 1.5% HP + Germinator; (G7): 3.0%HP + Germinator; (G8): 0.12% CHX + Germinator. Stimulated saliva was collected before and after a 3-min mouthwash and/or Germinator application. The patients were kept relaxed and retained saliva 5-10 min, spitting out into the tube for 3 min. The percentage bacterial reduction was checked by counting the colony-forming units (CFUs) after culturing on blood agar plates. Data were subjected to one-way ANOVA followed by Tukey's post hoc test (α = 5%) for statistical significance.

RESULTS

The highest bacterial reduction was observed in groups 3 (3.0% HP), 6 (1.5% HP + Germinator), and 7 (3.0% + Germinator), with no statistically significant difference between them (p > 0.05). Groups 6 (1.5% HP + Germinator) and 8 (0.12% CHX + Germinator) showed higher bacterial reduction than groups 2 (1.5% HP) and 4 (0.12% CHX) (p < 0.05). Finally, group 5 (Germinator) showed higher bacterial reduction than control group (DW) and group 4 (0.12% CHX) (p < 0.05).

CONCLUSIONS

The photocatalytic disinfection was effective against oral bacteria and improved the antimicrobial action of 1.5% HP and 0.12%.

CLINICAL SIGNIFICANCE

The photocatalytic disinfection can be an alternative protocol to provide the oral decontamination.

Hydrogen Peroxide: Its Use in an Extensive Acute Wound to Promote Wound Granulation and Infection Control - Is it Better Than Normal Saline?

Background: Hydrogen peroxide (H₂O₂) is used as a topical antiseptic in contaminated wounds caused by road traffic accidents. It kills bacteria by producing oxidation through local, nascent, free oxygen radicals. It also removes dirt from the wound due to its frothing action. H₂O₂ is synthesized by various cells as an active biochemical agent that affects cell biological behavior through complex chemical reactions. H₂O₂ has also been used as a wound cleaning agent, removing debris, preventing infection, and causing hemostasis due to its exothermic reaction with blood. Despite its widespread use, there is scanty literature on its use to promote granulation tissue formation. Objective: In the orthopaedics literature, studies on H₂O₂ use are very limited and its potential is underestimated. In the present study, we would like to report our protocol of use of H₂O₂ for its tremendous potential for stimulating granulation and early wound healing. Material and Methods: A total of 53 patients with large acute extensive lower limb contaminated wounds reported to the emergency department have been included with and without lower limb fracture. In group A (43 patients) wound management was done using 7% H₂O₂ and group B (10 patients) was treated by only saline dressing as a control group. Results: In the present study, daily dressing by 7% H₂O₂ solution and provide solution gives excellent results compared to the Saline group. Granulation tissue appeared much earlier with a mean SD 6.3 ± 6.8 days in the hydrogen peroxide group as compared to the Saline group where granulation tissue appeared in 9.3 ± 8.4 days. Conclusion: Spontaneous wound healing is a controlled balance between destructive and healing processes. It is mandatory to remove damaged tissue to promote healing by secondary intention and minimize infection. The dynamic effect of H₂O₂ promotes faster healing, stimulates granulation, and minimizes infection by oxidative stress.

Antisense yycG modulates the susceptibility of Staphylococcus aureus to hydrogen peroxide via the sarA

Background

The infectious pathogen Staphylococcus aureus (S. aureus) is primarily associated with osteomyelitis. Hydrogen peroxide drainage is an effective antimicrobial treatment that has been adopted to combat S. aureus infections. Previous investigations have indicated that the antisense RNA (asRNA) strategy negatively modulates S. aureus YycFG TCS, and it significantly disrupts biofilm formation. However, the effects of the antisense yycG RNA (ASyycG) strategy on the susceptibility of biofilm-producing S. aureus to hydrogen peroxide and the mechanisms underlying this effect have not been elucidated to date.

Results

Overexpression of ASyycG inhibited the transcription of biofilm formation-related genes, including sarA and icaA. Additionally, the CFU counts and the live bacterial ratios of ASyycG biofilm-producing S. aureus treated with H₂O₂ were notably reduced across the groups. Notably, the predicted promoter regions of the sarA and icaA genes were directly regulated by YycF.

Conclusions

ASyycG was observed to sensitize biofilm-producing S. aureus to H₂O₂ intervention synergistically via the sarA and thus may represent a supplementary strategy for managing osteomyelitis. However, future in-depth studies should attempt to replicate our findings in animal models, such as the rat osteomyelitis model.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-021-02218-x.

Clinical Evaluation of Diode (980 nm) Laser-Assisted Nonsurgical Periodontal Pocket Therapy: A Randomized Comparative Clinical Trial and Bacteriological Study

Background: Mechanical debridement is the gold standard in the periodontitis therapy. However, it is suggested that adjunctive use of lasers can result in a more effective treatment outcome. Objective: Evaluate the efficiency of diode laser-assisted nonsurgical therapy of periodontitis as adjunctive to scaling and root planing (SRP). Methods: One hundred sixty vertical bone defects [pocket depth (PD) at baseline ≥6 mm] had been randomly allocated to receive SRP alone (group C) or SRP coupled to a diode laser (980 nm) protocol (group C+L): SRP, irrigation with hydrogen peroxide solution (3%), de-epithelization of the internal and external gingiva followed by blood stabilization, and coagulation by laser beam were made. Beam parameters: 10 μsec/pulse duration, 10 kHz, pick power of 10 W, average power of 1 W, and fiber diameter of 400 μm. Plaque index (PI), bleeding on probing, gingival recession (GR), clinical attachment level (CAL), and PD were measured at baseline, at 6 weeks, 12 weeks, 18 weeks, 6 months, and 12 months. Microbiological data were collected randomly from 26 pockets from both groups at baseline, 6 weeks, 12 weeks, and 6 months after treatment. Results: At all periods of follow-up, there was a significant difference between both groups in all clinical parameters except in GR. In group C+L, 76% of pockets had PD ≤3 mm after 12 months of follow-up and an average of PD = 1.77 ± 0.46 mm, while 56% of pockets in group control (C) had an average of PD = 5.00 ± 0.83 mm after 12 months of follow-up. Total bacteria count in group C + L was significantly lower compared to group C only at 12 weeks and 6 months of follow-up. Furthermore, there was high significant decrease in the number of Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Tannerella forsythia, and Prevotella intermedia at all the follow-up periods. Conclusions: As adjunctive to SRP, diode laser-assisted nonsurgical therapy of periodontitis has significantly improved clinical parameters of PI and POB and has significantly reduced the clinical attachment loss (CAL) and PD compared to the control group after 1 year of follow-up. A significant reduction in periodontal pathogens has been observed in group C + L only at 12 weeks and 6 months of follow-up.

Oral mucosal irritation potential of antimicrobial chemotherapy involving hydrogen peroxide photolysis with high-power laser irradiation for the treatment of periodontitis

In the present study, we assessed the oral mucosal irritation potential of antimicrobial chemotherapy involving hydrogen peroxide (H₂O₂) photolysis with a 405-nm laser device at an output power of ≥100 mW in hamsters. Twenty-four cheek pouches from 12 male Syrian hamsters received 7-min treatment with pure water (PW), 3% H₂O₂, laser irradiation of PW at 100 mW, laser irradiation of 3% H₂O₂ at 100 mW, laser irradiation of PW at 200 mW, or laser irradiation of 3% H₂O₂ at 200 mW (n = 4 each). The diameter of the irradiation area was set at 3 mm; accordingly, the calculated irradiances (optical power densities) of the 100- and 200-mW laser lights were approximately 1400 and 2800 mW/cm², respectively. In addition, 12 cheek pouches from six animals received laser irradiation of 3% H₂O₂ at 100 mW for 1, 3, or 5 min (n = 4 each). Each treatment was repeated three times at 1-h intervals. Macroscopic and histological changes were evaluated 24 h after the last treatment. In addition, in vitro bactericidal activity of the treatment against periodontal pathogens was evaluated. We found that 405-nm laser irradiation of 3% H₂O₂ caused moderate to severe oral mucosal irritation when performed at powers of 100 and 200 mW for ≥3 min, while the same treatment performed at 100 mW for 1 min resulted in mild irritation. Moreover, 1-min H₂O₂ photolysis at 100 mW caused a >4-log decrease in viable bacterial counts. These findings suggest that 1-min H₂O₂ photolysis, which can effectively kill periodontal pathogens, may be acceptable when a 405-nm laser device is used at 100 mW. However, use of the laser at a lower power would be preferable for the prevention of unnecessary oral mucosal irritation.

Long-term antimicrobial assessment of orthodontic brackets coated with nitrogen-doped titanium dioxide against Streptococcus mutans

Background

The antimicrobial properties of orthodontic wire and brackets with nitrogen-doped titanium dioxide (N-doped TiO2) coating have been studied in the past. However, the evaluation period had been short and limited to 30 days. The aim of the present study was to extend the evaluation period (up to 90 days) of assessing the long-term antimicrobial effects of stainless steel orthodontic brackets coated with nitrogen-doped titanium dioxide (N-doped TiO2).

Methods

A total of 40 stainless steel pre-adjusted premolar brackets were equally divided into two groups; namely the control group (n=20, uncoated brackets) and the experimental group (n=20, coated brackets). RF magnetron sputtering was used to apply a thin film of TiO2 on the bracket surface. The crystalline structure of the thin film was assessed using X-ray diffraction. The antimicrobial property of the brackets against Streptococcus mutans (S. mutans) was evaluated using the survival rate by colony-forming units (CFU) at four intervals: 24 hours (T0), 30 days (T1), 60 days (T2), and 90 days (T3). 2-way ANOVA Repeated Measures was used to compare the effects between the groups over the time.

Results

There was no significant interaction between group and time (p = 0.568). The orthodontic brackets coated with the N-doped TiO2 thin film showed a significant CFU reduction (37.71 ± 5.21, 37.81 ± 5.03, 37.98 ± 5.37, and 37.74 ± 5.21 at T0, T1, T2, and T3, respectively) compared to the uncoated brackets (400.91 ± 14.67, 401.58 ± 14.01, 400.31 ± 14.68, and 402.04 ± 13.98 at T0, T1, T2, and T3, respectively) through visible light (p < 0.001).

Conclusion

N-doped TiO2 coated orthodontic brackets showed strong antimicrobial property against S. mutans over a period of 90 days, which is effective in preventing enamel decalcification during orthodontic therapy.

Adjunctive antimicrobial chemotherapy based on hydrogen peroxide photolysis for non-surgical treatment of moderate to severe periodontitis: a randomized controlled trial

Treatment of severe periodontitis with non-surgical therapy remains challenging in dentistry. The present study aimed to evaluate the clinical efficacy of hydrogen peroxide (H₂O₂) photolysis-based antimicrobial chemotherapy adjunctively performed with root debridement (RD) for moderate to severe periodontitis. A randomized controlled trial was conducted that included 53 patients with 142 test teeth. The test teeth were randomly assigned to one of three treatment groups: Group 1, RD + H₂O₂ photolysis; Group 2, RD followed by administration of a local drug delivery system (minocycline chloride gel); or Group 3, RD alone. Clinical and microbiological examination were performed for up to 12 weeks following treatment. Probing pocket depth (PPD) and bleeding on probing (BoP) were improved after each treatment session. At 12 weeks, Group 1 had achieved significantly lower PPDs than the other groups, though there were no significant differences in BoP between Group 1 and the other groups. Counts of Porphyromonas gingivalis, a known periodontal pathogen, in Group 1 were significantly lower than those in Group 3, and were comparable to those in Group 2. Therefore, it is suggested that H₂O₂ photolysis treatment can be used as a novel adjunctive antimicrobial chemotherapy for non-surgical periodontal treatment.

Antimicrobial Intervention by Photoirradiation of Grape Pomace Extracts via Hydroxyl Radical Generation

The annual production of grape worldwide amounts to almost 70 million tons, and around 80% is used for winemaking. The two major wastes from winemaking process, pomace and lees account for 20 and 7% of the grapes, respectively. They have been expected as a valuable resource to be recycled because they are rich in polyphenols. Polyphenols possess prooxidatve activity as well as antioxidative one just like a two sides of a coin. A typical example of the prooxidative activity is antibacterial activity of catechins. The activity is exerted through oxidation of phenolic hydroxyl moiety coulpled with reduction of dissolved oxygen leading to hydrogen peroxide (H₂O₂) generation. In addition, once the oxidation of phenolic hydroxyl moiety is augmented by photoirradiation, highly reactive hydroxyl radical (·OH) is generated. Accordingly, there have been several reports showing that photoirardiation of polyphenols exerts bactericidal activity via ·OH generation. This review focuses mainly on antimicrobial intervention by photoirradiation of grape pomace extract in relation to ·OH generation analyzed by an electron spin resonance-spin trapping method.

Antimicrobial effect of titanium dioxide after ultraviolet irradiation against periodontal pathogen

We focused on the antimicrobial effects of titanium dioxide (TiO2) after stopping ultraviolet (UV) irradiation as an adjunctive treatment for peri-implantitis in this study. The aim was to determine the continuous photocatalytic effects of TiO2 after UV irradiation and its antimicrobial activity against periodontal pathogen. The continuous photocatalytic effects of TiO2 after UV irradiation were determined by electron spin resonance (ESR) spectroscopy using TiO2 particles of various sizes with various UV irradiation times. In addition, antimicrobial activity against Porphyromonas gingivalis was investigated by quantitation of colony-forming units (CFUs). The results showed that the ESR signal ratio for the UV-irradiated TiO2 was significantly higher than that of the non-irradiated TiO2. UV-irradiated TiO2 significantly reduced the number of P. gingivalis when compared with non-irradiated controls. These results suggest that TiO2 has a continuous photocatalytic effect even after stopping UV irradiation and that it showed antimicrobial activity against periodontal pathogen.

Efficacy and safety of a therapeutic apparatus using hydrogen peroxide photolysis to treat dental and periodontal infectious diseases

The present study aimed to evaluate the acute locally injurious property of our most current hydroxyl radical generation system by hydrogen peroxide (H₂O₂) photolysis. This system, which releases 3% H₂O₂ with a 405-nm laser, was developed in our laboratory for the treatment of dental and periodontal infectious diseases. First, the hydroxyl radical yield generated by H₂O₂ photolysis was examined by applying an electron spin resonance-spin trapping technique. Second, the bactericidal effect of the device was examined under a simulant condition in which Streptococcus mutans, a pathogenic bacterial species that causes caries, was irrigated with running 3% H₂O₂ concomitantly with laser irradiation. Finally, the acute topical effect of the model apparatus on rat palatal mucosa was evaluated by histological examination. We found that the hydroxyl radical yield was dependent upon laser output power. The bacterial count was substantially reduced within as little as 3 min. No abnormal findings were observed in the palatal mucosa, even when rats received three treatments of 3% H₂O₂ with laser irradiation at an output power of 40 mW. These results suggest that our apparatus has the ability to kill bacteria via hydroxyl radical generation and is safe to use at the lesion site of dental and periodontal infectious diseases.

Hydrogen Peroxide: A Potential Wound Therapeutic Target?

Hydrogen peroxide (H2O2) is a topical antiseptic used in wound cleaning which kills pathogens through oxidation burst and local oxygen production. H2O2 has been reported to be a reactive biochemical molecule synthesized by various cells that influences biological behavior through multiple mechanisms: alterations of membrane potential, generation of new molecules, and changing intracellular redox balance, which results in activation or inactivation of different signaling transduction pathways. Contrary to the traditional viewpoint that H2O2 probably impairs tissue through its high oxidative property, a proper level of H2O2 is considered an important requirement for normal wound healing. Although the present clinical use of H2O2 is still limited to the elimination of microbial contamination and sometimes hemostasis, better understanding towards the sterilization ability and cell behavior regulatory function of H2O2 within wounds will enhance the potential to exogenously augment and manipulate healing.

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.

Acceleration of proliferative response of mouse fibroblasts by short-time pretreatment with polyphenols

Under the hypothesis that photo-irradiated proanthocyanidin could accelerate wound healing through reactive oxygen species (ROS) formation, we examined the effect of proanthocyanidin on 3T3-L1 mouse fibroblasts with or without photo-irradiation. As a result, irrespective of presence or absence of photo-irradiation, only 1 min exposure of the cells to proanthocyanidin resulted in accelerated proliferation of the cells in a concentration-dependent manner. Similarly to proanthocyanidin, 1 min pretreatment with catechin, caffeic acid, and chlorogenic acid accelerated the proliferative response, but gallic acid, epicatechin gallate, epigallocatechin, and epigallocatechin gallate failed. If incorporated active ingredient such as proanthocyanidin for such a short time as 1 min accelerates the proliferation response, a bioassay was conducted by utilizing antioxidant potential of proanthocyanidin. That is, intracellular oxidation of 2',7'-dichlorodihydrofluorescin induced by H2O2 was significantly inhibited when the cells were pretreated with proanthocyanidin for 1 min, suggesting that incorporated proanthocyanidin into the cells exerted antioxidant effect. This was also supported by a liquid chromatography/mass spectrometry analysis in which incorporation of proanthocyanidin components such as catechin monomers and dimers into the cells within 1 min was confirmed. These results suggest that active polyphenolic compounds such as proanthocyanidin, catechin, caffeic acid, and chlorogenic acid incorporated into the cells in such a short time as 1 min could accelerate the proliferative response of the cells.

Bactericidal effect of hydroxyl radicals generated from a low concentration hydrogen peroxide with ultrasound in endodontic treatment

One approach to enhance the disinfection of root canals in endodontic treatment is ultrasonic irrigation with sodium hypochlorite. Reactive oxygen species, such as hydroxyl radical, are generated by biological defense systems to kill invading bacteria. Ultrasonic irrigation with hydrogen peroxide may be a promising option to increase hydroxyl radical generation. We examined the bactericidal effects of hydroxyl radical generated from low concentration hydrogen peroxide with ultrasound in vitro. An ultrasonic tip was submerged in 0.5 or 1.0 M hydrogen peroxide in a microfuge tube. hydrogen peroxide was irradiated with the ultrasound, the tip of which was maintained centered in the tube to mimic ultrasonic irrigation. Hydroxyl radical generation was assessed by electron spin resonance spectroscopy. Subsequently, Enterococcus faecalis suspension in hydrogen peroxide was prepared and irradiated as described above. Bactericidal effects were assessed by viable counting. Electron spin resonance measurements showed that hydroxyl radical generation increased significantly in a time- and dose-dependent manner (two-way analysis of variance and Tukey's test, p<0.05). Moreover, the bactericidal effects of hydrogen peroxide against Enterococcus faecalis were enhanced by ultrasonic irradiation in a time- and dose-dependent manner. These results suggest that ultrasonic irrigation in the presence of low concentration hydrogen peroxide can serve as a disinfection strategy in endodontic treatment.

Antimicrobial strategies centered around reactive oxygen species--bactericidal antibiotics, photodynamic therapy, and beyond

Reactive oxygen species (ROS) can attack a diverse range of targets to exert antimicrobial activity, which accounts for their versatility in mediating host defense against a broad range of pathogens. Most ROS are formed by the partial reduction in molecular oxygen. Four major ROS are recognized comprising superoxide (O2•-), hydrogen peroxide (H2O2), hydroxyl radical (•OH), and singlet oxygen ((1)O2), but they display very different kinetics and levels of activity. The effects of O2•- and H2O2 are less acute than those of •OH and (1)O2, because the former are much less reactive and can be detoxified by endogenous antioxidants (both enzymatic and nonenzymatic) that are induced by oxidative stress. In contrast, no enzyme can detoxify •OH or (1)O2, making them extremely toxic and acutely lethal. The present review will highlight the various methods of ROS formation and their mechanism of action. Antioxidant defenses against ROS in microbial cells and the use of ROS by antimicrobial host defense systems are covered. Antimicrobial approaches primarily utilizing ROS comprise both bactericidal antibiotics and nonpharmacological methods such as photodynamic therapy, titanium dioxide photocatalysis, cold plasma, and medicinal honey. A brief final section covers reactive nitrogen species and related therapeutics, such as acidified nitrite and nitric oxide-releasing nanoparticles.

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.

Topical treatment of the buccal mucosa and wounded skin in rats with a triamcinolone acetonide-loaded hydrogel prepared using an electron beam

In this study, a triamcinolone acetonide-loaded hydrogel was prepared by electron beam irradiation and evaluated for use as a buccal mucoadhesive drug delivery system. A poloxamer was modified to have vinyl end groups for preparation of the hydrogel via an irradiation cross-linking reaction. Carbopol was introduced to improve the mucoadhesive properties of the hydrogel. The in vitro release of triamcinolone acetonide from the hydrogel was examined at 37 °C. To investigate the topical therapeutic effect of triamcinolone acetonide on wounded rat skin and buccal mucosa, the appearance and histological changes were evaluated for 15 days after treatment with saline, triamcinolone acetonide solution, triamcinolone acetonide hydrogel, and blank hydrogel, respectively. Triamcinolone acetonide was released constantly from the gel formulation at 37 °C and reach 100% at about 48 h. After 15 days, in the skin of the group treated with the triamcinolone acetonide-loaded hydrogel, the wound was almost completely free of crust and a number of skin appendages, including hair follicles, had formed at the margins of the tissue. Moreover, the inflammatory response in the buccal mucosa was milder than that in the other groups, and the wound surface was completely covered with regenerating, hyperkeratotic, thickened epithelial cells. Our results indicate that the triamcinolone-acetonide hydrogel showed sustained drug release behavior, while causing no significant histopathological changes in buccal and skin tissues. Therefore, this hydrogel system may be a powerful means of drug delivery for buccal administration with controlled release and no tissue irritation.

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.