Magister Chirurgiae Dentium - MChD / Tooth discoloration has increased the demand by patients to pursue aesthetic treatment options. Bleaching is considered a conservative approach in performing an aesthetic treatment for discolored teeth; however colour rebound and post-operative sensitivity are among the adverse effects associated with vital bleaching. In-office bleaching systems employ the use of high hydrogen peroxide concentrations. The effects of in-office bleaching agents on the degree of colour change and the gender differences in relation to bleaching outcomes are questionable. Post-operative sensitivity can be considered a bleaching side effect and the number of patients that experience it is unknown. Aim: The aim of this study was to assess the outcome of an in-office vital bleaching technique. Objectives: The objectives of this study were to evaluate the degree of colour change after vital tooth bleaching using a 35% hydrogen peroxide gel (Yotuel® Special, Biocosmetics Laboratories, Spain), using a spectrophotometer (CM-2600d Konica, Minolta) to measure the colour change at each intervention during the bleaching process, to assess the post operative sensitivity during the first week of the intervention, to evaluate the patients' perception of the colour change and to compare it to the colour change (~E) expressed in numeric values and to investigate whether gender differences exist in relation to the outcome of the bleaching procedure. Materials and Methods: The maxillary anterior teeth of 22 patients comprising of 11 males and 11 females were. bleached with a 35% hydrogen peroxide gel (Yotuel® Special, Biocosmetics Laboratories, Spain). Pre-treatment readings of the two maxillary central incisors using a spectrophotometer (CM-2600d Konica, Minolta) were obtained. Subsequent readings were obtained after scaling and polishing, before bleaching (which was used as a baseline reading), immediately after bleaching, one week and one month postoperatively. Patients were requested to complete a form regarding postoperative tooth sensitivity and their colour perception toward the bleaching treatment. Results: The quantitative effect of the bleaching material on tooth colour showed an increase in L * values and a decrease in a* and b* values, the changes were significant (p values- 0.05) except for the mean value of b* one month after bleaching which was only significant between five and ten percent.

We recently reported that embryonic stem cells-conditioned medium (ES-CM) contains antiapoptotic factors that inhibit apoptosis in the cardiac myoblast H9c2 cells. However, the mechanisms of inhibited apoptosis remain elusive. In this report, we provide evidence for the novel mechanisms involved in the inhibition of apoptosis provided by ES-CM. ES-CM from mouse ES cells was generated. Apoptosis was induced after exposure with H2O2 (400 μm) in H9c2 cells followed by the replacement with ES-CM or culture medium. H9c2 cells treated with H2O2 were exposed to ES-CM, and ES-CM plus cell survival protein phosphatidylinositol 3-kinase/Akt inhibitor, LY-294002, or extracellular signal-regulated kinase (ERK1/2) inhibitor, PD-98050. After 24 h, H9c2 cells treated with ES-CM demonstrated a significant increase in cell survival. ES-CM significantly inhibited (P < 0.05) apoptosis determined by terminal deoxynucleotidyl transferase dUTP-mediated nickend labeling staining, apoptotic ELISA, and caspase-3 activity. Importantly, enhanced cell survival and inhibited apoptosis with ES-CM was abolished with LY-294002. In contrast, PD-98050 shows no effect on ES-CM-increased cell survival. Furthermore, H2O2-induced apoptosis is associated with decreased levels of phosphorylated (p)Akt activity. Following treatment with ES-CM, we observed a decrease in apoptosis with an increase in pAkt, and the increased activity was attenuated with the Akt inhibitor, suggesting that the Akt pathway is involved in the decreased apoptosis and cell survival provided by ES-CM. In contrast, we observed no change in ES-CM-decreased apoptosis or pERK with PD-98050. In conclusion, we suggest that ES-CM inhibited apoptosis and is mediated by Akt but not the ERK pathway.

OBJECTIVE - Exercise training has been shown to restore vasodilation to nitric oxide synthase (NOS) activation in arterioles distal to coronary artery occlusion. Because reactive oxygen species are generated during NOS uncoupling and the production of vasodilator H2O2 is increased during exercise in patients with coronary disease, we proposed that H2O2 may contribute to the restoration of vasodilation in porcine coronary occlusion model. METHODS AND RESULTS - Left circumflex (LCX) coronary artery of miniature swine was progressively occluded for 8 weeks followed by exercise training (EX; 5 days/wk treadmill) or sedentary (SED) protocols for 12 weeks. Arterioles were isolated from distal LCX and nonoccluded left anterior descending (LAD) artery for in vitro study. Vasodilation to NOS activators adenosine and ionomycin was impaired in SED LCX, but not LAD, arterioles. This impairment was restored by L-arginine. NO production induced by adenosine was also reduced in SED LCX arterioles. EX had no effect on LAD arterioles but improved NO production and restored dilation of LCX arterioles. NOS blockade (L-NAME) inhibited vasodilation to NOS activators in LAD (SED & EX) arterioles but was ineffective in SED LCX arterioles. In EX LCX arterioles, vasodilation to NOS activators was slightly inhibited by L-NAME but abolished by catalase. H2O2 production was markedly increased by adenosine in EX LCX arterioles. CONCLUSIONS - This study demonstrates that endothelium-dependent NO-mediated dilation is impaired in SED LCX arterioles and that EX training restores the impaired function. It appears that H2O2, in addition to NO, contributes significantly to EX-induced restoration of endothelium-dependent dilation of coronary arterioles distal to occlusion.

In many countries of the world and in some parts of the United States milk is produced which has a high bacterial contamination. Such milk of undesirable quality is frequently delivered to factories engaged in the manufacture of cheddar cheese. This milk commonly contains large numbers of lactic acid-producing bacteria or other types of microorganisms which cause objectionable flavors and textural defects in the cheese. The improvement of the quality of milk supply under some conditions is a matter of great difficulty so that the manufacture of inferior quality milk into cheese is a problem often encountered. In the United States pasteurization of milk is used to reduce the bacterial content and give the cheese maker control over the manufacturing process. Public health officials favor pasteurization as a protection against pathogens; however, in many areas of the world pasteurization is not available. Although pasteurization of milk for cheddar cheese offers certain advantages such as destruction of pathogenic bacteria which may be present, and control of certain undesirable fermentations, experience has shown that pasteurized milk cheese develops flavor slowly and, even with extended ripening, does not have as satisfactory a flavor as good raw milk cheese. The slow ripening usually is attributed to the destruction by heat of certain essential bacteria and enzymes normally present in milk. Pasteurization, however, destroys many enzymes indigenous to milk as well as some beneficial organisms; consequently, cheese made from pasteurized milk ripens more slowly than cheese made from raw milk. For years, leading dairy technologists have been laboring assiduously but quite unsucessfully to produce cheese free from undesirable organisms yet comparable in flavor and in the rapidity of ripening to the best quality of raw milk cheese. Pursuant to these objectives a number of methods such as replenishing the enzymes in milk destroyed by pasteurization, the use of select ripening cultures, and the use of mixtures of various percentages of raw and pasteurized milk have been tried but without complete success. These objectionable features of pasteurization led to interest in another method such as the treatment of milk with edible hydrogen peroxide to control fermentation by means of its germicidal and inhibitory action. This comparative study was conducted to determine the effect of the germicidal properties of hydrogen peroxide in treating raw milk for cheddar cheese making in relation to the flora, quality, and ripening of the cheese. This study was concerned with the remedial measures which can be applied to milk to overcome some defects in the cheese. The antiseptic and germicidal properties of hydrogen peroxide are well known. A study involving the use of hydrogen peroxide and catalase has many possibilities in the dairy industry, and the practical aspects of this problem are numerous. Some phases are herewith indicated: 1. If hydrogen peroxide could be used to improve the general quality of cheddar cheese, it would be a boon to the industry and should have a value in the manufacture of cheddar cheese for shelf curing purposes, canning, processing, and for natural ripening in transparent packages. 2. It was believed that the use of hydrogen peroxide and catalase would increase the safety of raw milk cheese. (Kernsman, 1934, found that 0.1 percent of hydrogen peroxide killed E. coli, E. typhi and staphilococcus.) 3. If hydrogen peroxide could be used for destroying organisms harmful in milk and thus for preventing undesirable fermentation, yet leave intact more of the natural enzymes than is possible in accepted pasteurization procedures, the cheese treated with hydrogen peroxide and catalase might ripen faster than pasteurized-milk cheese and have a finer and more pronounced flavor. 4. If approved by public health authorities in the United States, treating milk with hydrogen peroxide would be a simple method of reducing bacterial content in small communities and rural areas. Such procedure would be very practical in preventing growth of bacteria in milk produced under unsanitary conditions. 5. If the use of hydrogen peroxide could be proved practicable, a beneficial program in most countries and especially in the Middle East where dairy equipment and pasteurizers are not readily available and where the production of unsanitary milk predominates might be established. 6. Since this process does not require special equipment it might prove economical and might become, in the future, a useful method of reducing the bacterial content of milk and preserving some of the natural characteristics of the raw milk for cheese making.

Rate limited chemical reactions can be enhanced by improving the mass transport of the suspended analyte to the catalytic (or electrocatalytic) surface. While many attempts have been made to enhance this mass transport, these approaches are limited to utilizing only two enhancement methods – increasing available catalytic surface area, and increasing the flow of analyte in solution. Flow through high aspect ratio microstructures, however, would provide additional mass transport enhancement via boundary layer confinement. Platinum functionalized carbon nanotube microarray membranes (Pt-CNT-MMs) offer enhanced mass transport via all three methods, and were fabricated for demonstration in a H2O2 sample system, for which propulsion and chemical sensing applications were investigated. Propulsion testing of Pt-CNT-MM samples demonstrated thrust typically required for MUV propulsion, while achieving high H2O2 fuel utilization. Also, the proposed approach minimizes component exposure to the environment and is comprised of a simple, static architecture relative to other micro-propulsion systems. Moreover, it was shown that additional thrust is attainable by further enhancing the introductory rate of the H2O2 fuel to the Pt-CNT-MMs, which would effectively increase the locomotive capability of this propulsion system. Pt-CNT-MMs used for chemical sensing of H2O2 likewise demonstrated favorable performance. Initial studies revealed that the molar flux achieved for a Pt-CNT-MM sample in a through-flow environment (50 [µL s-1]) was approximately a ten-fold increase over that achieved in a stirred environment (150 [rpm]). This ten-fold increase in molar flux can be attributed to both an increase in exposed electrocatalytic surface area, as well as increase in boundary layer confinement. Furthermore, comparison of sensed molar flux to calculated molar flux for through-flow conditions revealed that Pt-CNT-MMs can achieve near-complete H2O2 oxidation within the flowrate range studied. Additionally, chronoamperometric testing of a Pt-CNT-MM sample demonstrated a sensitivity toward H2O2 of 9.18 [mA mM-1 cm-2], over one hundred times that of the GluOx/Pt-SWCNT/PAA structures referenced herein (0.0724 [mA mM-1 cm-2]).1 These findings suggest that mass transport enhancement, achieved by Pt-CNT-MMs applied in through-flow environments, heightens the performance achieved in rate-limited chemical reactions. Specifically, Pt-CNT-MMs demonstrate high fuel utilization in H2O2 based propulsion applications, as well as offer a highly sensitive preliminary structures for non-invasive glucose sensing.

Ultramicroelectrodes (UMEs) are useful as probes for evaluating electroactive species in confined spaces (e.g., inside living cells) and for measuring fast electrochemical reactions. However, UME applications often require modification of the electrode surface to improve selectivity and sensitivity towards target analytes. Previous research in our group demonstrated that a simple soft nitriding method introduces surface nitrogen (N)-containing groups on carbon fiber (CF), leading to improved electroreduction of hydrogen peroxide (H2O2) on CF-UMEs. However, sensitivity for H2O2 detection using N-CF-UMEs was low compared to that for other modified UMEs. As an alternative to N-CF-UMEs, a simple strategy for preparing phosphorus (P)-doped CF-UMEs was first investigated. Since P-CF-UMEs performed similarly to N-CF-UMEs, an alternative epoxy sealing strategy for preparing CF-UMEs and doped-CF-UMEs was also developed. Compared to P-CF-UMEs and N-CF-UMEs prepared by traditional laser-assisted pipette pulling, the epoxy-sealed electrodes exhibited 20-50 times higher sensitivities and 2-3 times lower detection limits for H2O2.

Hydrogen peroxide is used in various fields, such as food preservative, bleaching, oxidizing, reducing, and chemical reaction reagents. However, inappropriate use may have harmful effects to human health or environment. A number of analytical methods have been developed for the determination of hydrogen peroxide. Herein is described the effort to develop an optical fiber chemical sensor based on the evanescence wave absorbance that can detect the presence of, and measure the concentration of, hydrogen peroxide. For the H2O2 optical fiber sensor, Nafion membrane was coated in the fiber optic. Titanium ions dispersed in a Nafion membrane can form a TiO-H2O2 complex with the H2O2 diffused into the membrane. The complex is shown to absorb light with a maximum absorption near 360 nm. The intensity of the absorbance peak is directly proportional to the concentration of H2O2. At present, this sensor has been tested for detecting H2O2 concentrations ranging from 0.03 ppm to 9 ppm in an aqueous solution at room temperature. Additionally, coating polydimethylsiloxiane (PDMS) outside the fiber optic can detect H2O2 in high concentration 300ppm and high temperature 70oC. Finally, the use of the developed optical fiber chemical sensor allows the direct determination of H2O2 in milk.

Petroleum spills cost large sums of money to remediate, which has resulted in the use of more in-situ technologies, including chemical oxidation, as cost effective alternatives to traditional methods of remediation. There are numerous case studies documenting the success of hydrogen peroxide as an in-situ oxidizer in that regulated BTEX concentrations were lowered below target cleanup levels. Little information is available; however, regarding the behavior of petroleum hydrocarbons post injection of hydrogen peroxide or what chemical derivatives may be produced as a result of the oxidation process. Laboratory protocols have been employed to yield data regarding the behavior of BTEX specifically, and all volatile gasoline constituents in general, over a period of time post injection of hydrogen peroxide. The results of the data indicate variations in petroleum compound behavior are predicated on the concentration of hydrogen peroxide, the degree of contamination, and the presence of a soil matrix.

Ultraviolet light (UV) and hydrogen peroxide (H2O2) decrease eggshell bacteria. However, when combined, the optimum amount of each and effects on hatchability are unknown. In Experiment 1, when compared to other concentrations of H2O2 and lengths of UV, the combination of 1.5% H2O2 and 8 minutes of UV yielded optimum results with a 3 log10 CFU/egg reduction in bacteria on the eggshell. In Experiment 2, exposing eggs to this optimum combination yielded a 1000 fold reduction in eggshell bacteria but only a numerical increase in hatch of set and hatch of fertile. In Experiment 3, eggs exposed to repetitive treatments of H2O2 and UV yielded a 4 log reduction in eggshell bacteria but no differences in hatchability or chick characteristics. In conclusion, the combination of H2O2 and UV proved to be effective for eggshell sanitization, especially when used repetitively, and did not alter hatchability.

DNA mismatch repair (MMR) recognizes and repairs bases incorrectly incorporated during DNA replication. Germ line mutations in two MMR genes, namely hMSH2 and hMLHl, account for approximately 98% of hereditary non-polyposis colorectal cancers. There is conflicting evidence for the role of hMLHl and hMSH2 in the transcription-coupled repair (TCR) pathway of nucleotide excision repair (NER). Here we have examined the role of these MMR genes in NER using two reporter gene assays. AdHCMVlacZ is a replication-deficient recombinant adenovirus that expresses the B-galactosidase reporter gene under the control of the human cytomegalovirus (HCMV) immediate-early promoter. We have reported a reduced host cell reactivation (HCR) for B-galactosidase expression of UVC-irradiated AdHCMVlacZ in TCRdeficient Cockayne syndrome (CS) fibroblasts compared with normal fibroblasts, indicating that HCR depends, at least in part, on TCR. In addition, we have reported that UVC-enhanced expression of the undamaged reporter gene is induced at lower UVC fluences to cells and at higher levels after low UVC fluences in TCR-deficient compared with normal human fibroblasts, suggesting that persistent damage in active genes triggers increased activity f~om the HCMV-driven reporter construct. We have examined HCR and UV-enhanced expression of the reporter gene in hMLHl-deficient HCT116 human colon adenocarcinoma cells and HCT116-chr3 cells (the MMR-proficient counterpart of HCT116) as well as hMSH2-deficient LoVo human colon adenocarcinoma cells and their hMSH2-proficient counterpart SW 480 cells. We show a greater UV -enhanced expression of the undamaged reporter gene after low UVC exposure in HCT116 compared with HCT 116-chr3 cells ;md in Lo Vo compared with SW 480 cells. We show also a reduced HCR in HCT 116 compared with HCT 116-chr3 cells and in Lo Vo compared with SW 480 cells. However, the reduction in HCR was less or absent when cells were pretreated with UVC. These results suggest that detection of an involvement of hMLHl and hMSH2 in TCR is dependent on UVC (254 nm) fluence to cells. We have also used these two reporter gene assays to examine the role of hMSH2 and hMLHl in the repair of oxidative DNA damage induced by UV A light (335-400 nm) and H20 2• UV A and H20 2 produce a number of oxidative lesions in DNA (such as 8hydroxyguanines and thymine glycols) that are repaired by the base excision repair (BER) pathway. \ve show a reduced HCR for B-galactosidase expression of UVAtreated AdHCMVlccZ in hMSH2-deficient LoVo human colon adenocarcinoma cells compared to their hMSH2-proficient counterpart SW480 cells, but not in hMLHl-deficient HCT116 human colon adenocarcinoma cells compared to the hMLHl-proficient HCT116-chr3 cells. We also show that pre-treatment of cells with UVA enhances reporter gene expression to higher levels and at lower UV A fluences in Lo Vo compared to SW480 cells but not in HCT116 compared to HCT116-chr3 cells. These results suggest an involvement of hMSH2 but not hMLHl in the repair of UVA-induced oxidative DNA damage. In contrast, no detectable differences were observed between SW480 and LoVo cells, as well as HCT116-chr3 compared to HCT116 cells, in both of the reporter gene assays that used H20 2 as the DNA damaging agent. Based on these results, these findings suggest that neither hMSH2 nor hMLHl play a significant role in the repair of oxidative damage induced by H202. / Thesis / Master of Science (MS)