Efficacy and Safety Evaluation of a Chlorine Dioxide Solution.

In this study, a chlorine dioxide solution (UC-1) composed of chlorine dioxide was produced using an electrolytic method and subsequently purified using a membrane. UC-1 was determined to contain 2000 ppm of gaseous chlorine dioxide in water. The efficacy and safety of UC-1 were evaluated. The antimicrobial activity was more than 98.2% reduction when UC-1 concentrations were 5 and 20 ppm for bacteria and fungi, respectively. The half maximal inhibitory concentrations (IC50) of H1N1, influenza virus B/TW/71718/04, and EV71 were 84.65 ± 0.64, 95.91 ± 11.61, and 46.39 ± 1.97 ppm, respectively. A 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) test revealed that the cell viability of mouse lung fibroblast L929 cells was 93.7% at a 200 ppm UC-1 concentration that is over that anticipated in routine use. Moreover, 50 ppm UC-1 showed no significant symptoms in a rabbit ocular irritation test. In an inhalation toxicity test, treatment with 20 ppm UC-1 for 24 h showed no abnormality and no mortality in clinical symptoms and normal functioning of the lung and other organs. A ClO2 concentration of up to 40 ppm in drinking water did not show any toxicity in a subchronic oral toxicity test. Herein, UC-1 showed favorable disinfection activity and a higher safety profile tendency than in previous reports.

Comparison of tetraacetylethylendiamine + sodium perborate and sodium hypochlorite cytotoxicity on L929 fibroblasts.

INTRODUCTION: Tetraacetylethylenediamine in association with sodium perborate (TAED+P) can be suggested for its use as an endodontic disinfectant because of its antimicrobial activity against different bacterial species when used at low concentrations. The purpose of this study was to measure the cytotoxicity of TAED+P on L929 fibroblasts and to compare it with that of sodium hypochlorite (NaOCl). METHODS: L929 fibroblasts were grown in Dulbecco Modified Eagle Medium containing 10% fetal calf serum (FCS) at 37 degrees C and 5% CO(2). At confluence, cells were split, plated in a 96-well plate, and incubated for 24 hours to allow attachment. The two disinfectants TAED+P and NaOCl were tested at various concentrations. The neutral red uptake and the 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyl tetrazolium bromide assays were used to evaluate the cell viability. The 50% inhibitory dose values for both disinfectants were calculated and statistically analyzed. The effect of both disinfectants on fibroblast viability was also determined in the presence of various concentrations of FCS. One-way analysis of variance with post hoc analysis using Tukey multiple comparison test was used for parametric data. RESULTS: Both disinfectants induced a dose-related loss of cell viability; TAED+P resulted less cytotoxic than NaOCl in all the examined experimental conditions. CONCLUSIONS: These data support the possible use of TAED+P as an endodontic irrigant. Further studies are required to analyze its antibacterial activity against endodontic pathogens.

Lack of cytotoxicity by Trustwater Ecasol™ used to maintain good quality dental unit waterline output water in keratinocyte monolayer and reconstituted human oral epithelial tissue models.

UNLABELLED: We previously showed that residual treatment of dental chair unit (DCU) supply water using the electrochemically-activated solution Trustwater Ecasol™ (2.5 ppm) provided an effective long-term solution to the problem of dental unit waterline (DUWL) biofilm resulting in DUWL output water quality consistently superior to potable water. OBJECTIVES: To investigate the cytoxicity of Ecasol using cultured keratinocyte monolayers and reconstituted human oral epithelial (RHE) tissue and to extend the study of Ecasol's effectiveness in maintaining the microbiological quality of DUWL output water. METHODS: TR146 human keratinocyte monolayers and RHE tissues were exposed to Ecasol (2.5-100 ppm) for 1h periods after removal of growth medium and washing with phosphate-buffered saline (PBS). Experiments were repeated using Ecasol that had been exposed for 30 min to 1-2mg/mL bovine serum albumin (BSA), equivalent to protein concentrations in saliva. To quantitatively determine cytotoxic effects on monolayers following Ecasol exposure, the Alamar Blue proliferation assay (assesses cell viability) and the Trypan Blue exclusion assay (assesses plasma membrane integrity), were used. Cytotoxicity effects on RHE tissues were assessed by the Alamar Blue assay and by histopathology. RESULTS: Ecasol at >5.0 ppm resulted in significant (P<0.001) cytotoxicity to keratinocyte monolayers following a 1h exposure. These effects, however, were completely negated by BSA pretreatment of Ecasol. No cytotoxicity was observed in the more complex RHE tissue at any of the Ecasol concentrations tested. In a 60-week study of 10 DCUs, tested weekly, the average density of aerobic heterotrophic bacteria in Ecasol-treated (2.5 ppm) DCU supply water was <1cfu/mL and in DUWL output water was 6.5cfu/mL. CONCLUSIONS: Ecasol present as a residual disinfectant in DUWL output water is very unlikely to have adverse effects on human oral tissues at levels effective in maintaining DUWL output water quality at better than potable standard water quality.

Effects of high-dose major components in oral disinfectants on the cell cycle and apoptosis in primary human gingival fibroblasts in vitro.

We evaluated the effects of high-dose major components in oral disinfectants on oral cells from the standpoints of the cell cycle and apoptosis. We examined the viability and cell cycle of human gingival fibroblasts (HGFs) treated with the components of dental disinfectants, benzethonium chloride (BEC), benzalkonium chloride (BAC), and povidone iodine (PVD-I) using a cell counting kit and flow cytometry. The IC(50) inhibitory concentration value in HGF cultures at 24 hours was 1.3x10(-2) mM BEC, 6.0x10(-3) mM BAC, and 2.6x10(-1) mM PVD-I. In the cell cycle analysis, propidium iodide-stained HGFs were arrested in G(0)/G(1) of the cell cycle by all three disinfectants, and in the apoptosis assay, annexin V-FITC/PI-stained HGFs that became apoptotic at 5.0x10(-2) and 1.0x10(-1) mM BEC and 5.0x10(-2) and 1.0x10(-1) mM BAC, but not in PVD-I at concentrations as high as 5.0x10(-1) mM. Our findings describe the effects of high-dose oral disinfectants, rather than clinical concentrations. Nevertheless, appreciating the effects of high-dose disinfectants absorbed into the human body is important, where they may accumulate in specific tissues and cells.

The influence of denture cleansers on the release of organic compounds from soft lining materials.

Biocompatibility constitutes the most fundamental requirement with respect to all dental materials to be applied within the oral cavity. In its environment, various toxic compounds may be released by dental materials which pose potential threats to the patient's health. Due to the fact that dentures remain in the oral cavity for a very long time, a detailed examination and verification of prosthetic materials with a view to their toxicity seems to be essential. By using very sensitive measurement techniques such as gas chromatography, one may determine which compounds are released by these materials. The aim of this paper was to determine the influence of various denture cleansers on the release of organic compounds from four soft dental materials used in prosthetics for lining dentures. These materials when placed in commonly used disinfectants (Corega Tabs, sodium hypochlorite, chlorhexidine, hydrogen peroxide), as well as in artificial saliva, produced 13 chemical compounds such as monomers (methyl methacrylate, ethyl methacrylate, dodecyl methacrylate), plasticizers (dibutyl phthalate, diethyl phthalate, tributyl acetylcitrate) and others (e.g. benzophenone). A comparison of chemical compounds released from acrylic-based materials and those released from silica-based materials demonstrated that acrylic-based materials are less resistant to disinfectants.

Reproductive outcomes among dental personnel: a review of selected exposures.

Since the late 1960s, investigators have assessed the risks associated with exposure to a variety of potentially harmful agents used in dental practice. This paper provides a brief overview of the epidemiologic literature examining the associations between occupational exposures to elemental mercury and anesthetic gases and reproductive outcomes, such as spontaneous abortion, congenital abnormalities and reduced fertility. Most of the epidemiologic evidence points to a significant relationship between exposure to nitrous oxide and both spontaneous abortion and reduced fertility. There is also evidence for an association between exposure to ethylene oxide and spontaneous abortion, but on the basis of the limited research available, this relationship does not appear to be statistically significant. At this time, evidence of a relationship between exposure to elemental mercury and spontaneous abortion, congenital abnormalities and reduced fertility is limited. Good mercury hygiene by dental personnel and the use of scavenging equipment on nitrous oxide systems and exhaust systems on ethylene oxide sterilizers may reduce the risk of adverse reproductive outcomes.

Assessment of genotoxicity of 14 chemical agents used in dental practice: ability to induce chromosome aberrations in Syrian hamster embryo cells.

To assess the genotoxicity of 14 chemical agents used as locally applied agents in dental practice, the ability of these agents to elicit chromosome aberrations was examined using Syrian hamster embryo (SHE) cells. Chromosome aberrations in SHE cells were induced by treatment with three of eight chemical agents used as endodontic medicaments, i.e. ethylenediaminetetraacetic acid (EDTA), formocresol (a mixture of formalin and tricresol), and sodium arsenite. The other five chemical agents, i.e. chloramphenicol, p-chlorophenol, p-phenolsulfonic acid, sodium hypochlorite, and tetracycline hydrochloride exhibited a negative response for chromosome aberrations. Assessment of three dyes used for disclosing dental plaque showed chromosome aberrations induced by basic fuchsin but not by acid fuchsin and erythrosine B. Three local anesthetics, lidocaine hydrochloride, prilocaine hydrochloride, and procaine hydrochloride, were negative for chromosome aberrations. Among the ten chemical agents that exhibited a negative response in the assay, p-chlorophenol, sodium hypochlorite, and erythrosine B induced chromosome aberrations in SHE cells when treated in the presence of exogenous metabolic activation. The percentages of cells with polyploidy or endoreduplication were enhanced by formocresol, sodium arsenite, p-chlorophenol, p-phenolsulfonic acid, sodium hypochlorite, erythrosine B, prilocaine hydrochloride, and procaine hydrochloride in the absence or presence of exogenous metabolic activation. Our results indicate that the chemical agents that had a positive response in the present study are potentially genotoxic to mammalian cells.

Ability of 13 chemical agents used in dental practice to induce sister-chromatid exchanges in Syrian hamster embryo cells.

To evaluate the genotoxic potential of 13 chemical agents used in dental practice, the abilities of these agents to induce sister-chromatid exchanges (SCEs) were examined using Syrian hamster embryo (SHE) cells. Statistically significant increases in the frequencies of SCEs were observed in SHE cells treated with all seven of the chemical agents used as endodontic medicaments: p-chlorophenol, m-cresol, formaldehyde, guaiacol, hydrogen peroxide, p-phenolsulfonic acid, and sodium hypochlorite (P < 0.01; Student t test). Assessment of two chemical agents that are applied to the oral mucosa as antiseptics showed that SCEs were induced by iodine (P < 0.01), but not by chlorhexidine. Of three chemical agents that are used as dyes for disclosing dental plaque, erythrosine B had no effect on SCE induction, while acid fuchsin and basic fuchsin increased the SCE frequencies in SHE cells (P < 0.01). Glutaraldehyde, which is used as a disinfectant for dental instruments and impressions, also induced SCEs (P < 0.01). Because SCE assays are used as a sensitive indicator for evaluating genetic toxicity of chemicals, the chemical agents that had a positive response in the present study are potentially genotoxic to mammalian cells.

Effect of ozone on enamel and dentin bond strength.

PURPOSE: To evaluate the influence of direct high-dose gaseous ozone application (2100 ppm) on dentin and enamel shear bond strength. MATERIALS AND METHODS: Ten bovine enamel and dentin samples per group were pretreated as follows: (I) ozone application (Healozone, KaVo) for 60 s alone or (II) with subsequent application of a fluoride- and xylitol-containing antioxidant (liquid reductant), (III) light-activated bleaching with 35% hydrogen peroxide for 5 min serving as negative control (Hi-Lite, Shofu), and (IV) untreated enamel and dentin (positive control). Specimens were bonded with a functional 3-step adhesive system (Syntac Classic, Ivoclar Vivadent) and restored with a composite (Tetric Ceram, Ivoclar Vivadent) according to the Ultradent method. After storage in water at 37 degrees C for 24 h, shear bond strength was measured using a Zwick universal testing machine. Data were analyzed using ANOVA and Scheffe's post hoc analysis. RESULTS: In concordance with the existing literature, bleaching resulted in significantly decreased bond strength (p < 0.05) on enamel specimens. No decrease in shear bond strength was detected for ozone-pretreated specimens compared to untreated controls. CONCLUSION: Despite a possible retention of surface and subsurface oxide-related substances during high-dose ozone application, shear bond strength was not impaired. Thus, adhesive restoration placement should be possible immediately after ozone application for cavity disinfection.

Ability of fourteen chemical agents used in dental practice to induce chromosome aberrations in Syrian hamster embryo cells.

To assess the genotoxicity of 14 chemical agents used in dental practice, the ability of these agents to induce chromosome aberrations was examined using Syrian hamster embryo (SHE) cells. Statistically significant increases in the frequencies of chromosome aberrations were induced in SHE cells treated with 7 of 10 chemical agents used as endodontic medicaments, that is, carbol camphor, m-cresol, eugenol, guaiacol, zinc oxide, hydrogen peroxide, and formaldehyde. The other 3 chemical agents, that is, thymol, glutaraldehyde, and iodoform, did not increase the levels of chromosome aberrations. Of the 4 chemical agents that are used as an antiseptic on the oral mucosa, chromosome aberrations were induced by iodine, but not by the other 3 antiseptics, benzalkonium chloride, benzethonium chloride, and chlorhexidine. Among the 6 chemical agents exhibiting a negative response in the assay, only thymol induced chromosome aberrations in the presence of exogenous metabolic activation. Our results indicate that chemical agents having a positive response in the present study are potentially genotoxic to mammalian cells and need to be studied further in detail.

Effects of autoclave sterilization on properties of dental rubber dam as related to its use as barrier membrane in guided tissue regeneration.

BACKGROUND AND OBJECTIVE: Dental rubber dams (RDs) were used as barrier membranes in guided tissue regeneration for the treatment of periodontal intraosseous defects with acceptable clinical results. The aim of the present study was to investigate the effects of autoclave sterilization on properties of RD as related to its use as a barrier membrane in guided tissue regeneration. METHODS: RDs were sterilized by either an autoclave, gamma irradiation, or chemical agents and then co-cultured with human gingival fibroblasts. The cell responses to sterilized RDs were investigated by inverted phase contrast microscopy, scanning electron microscopy (SEM) and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) technique. The surface alterations of the autoclaved RDs were observed under SEM. The tensile strength, tear strength and elongation at break of the autoclaved RDs were tested by a universal testing machine. RESULTS: The results from cell culture, microscopic and MTT studies showed that RDs sterilized by autoclave and gamma irradiation did not deteriorate gingival fibroblasts and provided surfaces suitable for cell attachment, whereas chemical-sterilized RDs were toxic to these cells. Ultrastructurally, surface changes from the non-autoclaved RDs, including some melted areas, small pores and folds were observed on the autoclaved RD surface. The tensile strength and tear strength of the autoclaved RDs were significantly lower than those of the non-autoclaved RDs (p = 0.042, p < 0.001, respectively). In contrast, the elongation at break of the autoclaved RDs was higher than that of the non-autoclaved RDs (p < 0.001). CONCLUSION: These results suggest that the autoclave sterilization deteriorated the physical properties of RDs even though they seemed to be compatible to the cultured human cells. Therefore, the sterilization method should be taken into consideration when RDs are utilized as barrier membranes.

PCNA-expression of cementoblasts and fibroblasts on the root surface after extraoral rinsing for decontamination.

Periodontal cells capable of proliferation were studied immunohistochemically on extracted human teeth after 2-min irrigation with saline or ozonized water and marking of Proliferating Cell Nuclear Antigen (PCNA). All specimens expressed PCNA. The labelling index (LI), i.e. the number of positive cells compared to the total number of cells, was 6.6% after irrigation with saline and 7.8% after irrigation with ozone. There was no difference in number and distribution of PCNA-positive cells from the coronal to the apical thirds of the roots. Irrigation with ozonized water showed higher labelling indices in comparison with saline, but this could not be statistically substantiated (P = 0.24). Ozonized water, not being isotonic, had no negative effect on periodontal cells remaining on the tooth surface after irrigation for 2 min.

Effects of camphorated parachlorophenol on human periodontal ligament cells in vitro.

To date, there has been very little research into the possible effects of endodontic therapy on regeneration of a lost periodontal attachment. The objective of this study was to examine the effects of the endodontic medication, camphorated parachlorophenol (CMCP), on human periodontal ligament cells in vitro. The cytotoxic effects of CMCP were evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide colorimetric assay and cell proliferation using a [3H]thymidine incorporation assay. CMCP inhibited the human periodontal ligament cells viability and proliferation in a dose-dependent manner (p < 0.05). These data indicate that the use of CMCP in a root canal could cause periodontium damage. Although this study was conducted in vitro, the findings suggest that it may not be advisable to use CMCP as an interim medication when a periodontal surgical procedure, especially an attempt at regeneration or a new attachment procedure, is being considered in tissues adjacent to the endodontically involved tooth.