There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

Oxidative stress generated by an imbalance between reactive oxygen species (ROS) and antioxidants contributes to the pathogenesis of arthritis, cancer, cardiovascular, liver and respiratory diseases. Proinflammatory cytokines and growth factors stimulate ROS production as signaling mediators. Antioxidants such as N-acetylcysteine (NAC) have been used as tools for investigating the role of ROS in numerous biological and pathological processes. NAC inhibits activation of c-Jun N-terminal kinase, p38 MAP kinase and redox-sensitive activating protein-1 and nuclear factor kappa B transcription factor activities regulating expression of numerous genes. NAC can also prevent apoptosis and promote cell survival by activating extracellular signal-regulated kinase pathway, a concept useful for treating certain degenerative diseases. NAC directly modifies the activity of several proteins by its reducing activity. Despite its nonspecificity, ability to modify DNA and multiple molecular modes of action, NAC has therapeutic value for reducing endothelial dysfunction, inflammation, fibrosis, invasion, cartilage erosion, acetaminophen detoxification and transplant prolongation.

Molecular mechanisms of N-acetylcysteine actions.

Gram-positive bacteria possess a myriad of acid resistance systems that can help them to overcome the challenge posed by different acidic environments. In this review the most common mechanisms are described: i.e., the use of proton pumps, the protection or repair of macromolecules, cell membrane changes, production of alkali, induction of pathways by transcriptional regulators, alteration of metabolism, and the role of cell density and cell signaling. We also discuss the reponses of Listeria monocytogenes, Rhodococcus, Mycobacterium, Clostridium perfringens, Staphylococcus aureus, Bacillus cereus, oral streptococci, and lactic acid bacteria to acidic environments and outline ways in which this knowledge has been or may be used to either aid or prevent bacterial survival in low-pH environments.

Surviving the Acid Test: Responses of Gram-Positive Bacteria to Low pH

Geigy Scientific Tables

Hydrogen peroxide (H2O2) is a powerful oxidising agent. It gives rise to agents known to be effective bleaching agents. The mechanisms of bleaching involve the degradation of the extracellular matrix and oxidation of chromophores located within enamel and dentin. However, H2O2 produces also local undesirable effects on tooth structures and oral mucosa. In clinical conditions, the daily low-level doses used to produce tooth whitening never generate general acute and sub-acute toxic effects. Genotoxicity and carcinogenicity only occur at concentrations that are never reached during dental treatments. Some transient adverse effects have been reported on the oral mucosa and the digestive tract if the product is swallowed. Local effects may occur on the oral mucosa and dental tissues during whitening, namely, pulp sensitivity, cervical resorption, release of selected components of dental restorative materials, and alteration of the enamel surface. Most of the local effects are dependent of the technique and concentration of the product so far used, but as the results of bleaching obtained are not stable, repeated treatments add to the adverse effects. The informed decision to administer or not and the control of bleaching effects should stand in the hand of dental surgeons and certainly not as it appears at present, as cosmetics sold without any restriction despite the potential health hazards of peroxides.

Undesirable and adverse effects of tooth-whitening products: a review.

The aims of this present study were (1) to assess the antimicrobial effect of ozone from a novel ozone–generating device (Heolozone, USA) [0.052% (v/v) in air delivered at a rate of 13.33 ml·s–1

Antimicrobial Effect of a Novel Ozone– Generating Device on Micro–Organisms Associated with Primary Root Carious Lesions in vitro

This study compared the ability of two sodium fluoride dentifrices, one containing 5,000 ppm fluoride (Prevident 5000 Plus) and the other 1,100 ppm fluoride (Winterfresh Gel), to reverse primary root caries lesions (PRCLs). A total of 201 subjects with at least one PRCL each entered the study and were randomly allocated to use one of the dentifrices. After 6 months, 186 subjects were included in statistical analyses. At baseline and after 3 and 6 months, the lesions were clinically assessed and their electrical resistance measured using an electrical caries monitor. After 3 months, 39 (38.2%) of the 102 subjects in the 5,000 ppm F- group and 9 (10.7%) of 84 subjects using the 1,100 ppm F- dentifrice, had one or more PRCLs which had hardened (p = 0.005). Between baseline and 3 months, the log10 mean +/- SD resistance values of lesions for subjects in the 1,100 ppm F- group had decreased by 0.06+/-0.55, whereas those in the 5,000 ppm F- group had increased by 0.40+/-0.64 (p<0.001). After 6 months, 58 (56.9%) of the subjects in the 5,000 ppm F- group and 24 (28.6%) in the 1,100 ppm F- group had one or more PRCLs that had become hard (p = 0.002). Between baseline and 6 months, the log10 mean +/- SD resistance values of lesions for subjects in the 1,100 ppm F- group decreased by 0.004+/-0.70, whereas in the 5,000 ppm F- group, they increased by 0.56+/-0.76 (p<0.001). After 3 and 6 months, the distance from the apical border of the root caries lesions to the gingival margin increased significantly in the 5,000 ppm F- group when compared with the 1,100 ppm F- group. The plaque index in the 5,000 ppm F- group was also significantly reduced when compared with the 1,100 ppm F- group. The colour of the lesions remained unchanged. It was concluded that the dentifrice containing 5,000 ppm F- was significantly better at remineralising PRCLs than the one containing 1,100 ppm F-.

Reversal of primary root caries using dentifrices containing 5,000 and 1,100 ppm fluoride.

PURPOSE To assess the effect of ozone on the microbial flora and clinical severity of primary root caries. METHODS 26 patients with 70 primary root carious lesions (PRCLs) were entered. Each PRCL was classified in terms of color, cavitation, size, hardness, distance from the gingival margin and severity. Overlying plaque was then removed and each lesion dried. A biopsy was taken from half of each PRCL using a sterile excavator. Subsequently, the remaining lesions were exposed to ozone gas for a period of either 10 seconds (n = 35) or 20 seconds (n = 35) and a further biopsy was taken. RESULTS Using a paired Student t-test, a significant (P < 0.001) difference (mean +/- SE) in total micro-organisms was observed in the ozone-treated samples after either a 10 seconds (log10 4.35 +/- 0.49) or 20 seconds (log10 0.46 +/- 0.26) ozone application compared with the control samples (log10 7.00 +/- 0.24) and (log10 6.00 +/- 0.21) respectively. Using Pearson's correlation tests, there were significant correlations for the reduction in total micro-organisms after 10 seconds of ozone application with cavitation, size, distance from gingival margin and severity of PRCLs (P < 0.05). In conclusion, ozone application either for 10 or 20 seconds dramatically reduced most of the micro-organisms in PRCLs without any side effects recorded at recall intervals between 3 and 5.5 months. Out of the 65 PRCLs reviewed, 33 lesions had become hard, 27 lesions reversed to severity index 1 from severity index 2, and five lesions remained the same following ozone application for a period of either 10 or 20 seconds.

Effect of ozone on the oral microbiota and clinical severity of primary root caries.

Nanoparticles (NPs) are insoluble particles smaller than 100 nm in size. In order to prevent microbial adhesion or enamel demineralization in orthodontic therapy, two broad strategies have been used. These are incorporating certain NPs into orthodontic adhesives/cements or acrylic resins (nanofillers, silver, TiO2, SiO2, hydroxyapatite, fluorapatite, fluorohydroxyapatite) and coating surfaces of orthodontic appliances with NPs (i.e. coating bracket surfaces with a thin film of nitrogen-doped TiO2). Although the use of NPs in orthodontics can offer new possibilities, previous studies investigated the antimicrobial or physical characteristic over a short time span, i.e. 24 hours to a few weeks, and the limitations of in vitro studies should be recognized. Information on the long-term performance of orthodontic material using nanotechnology is lacking and necessitates further investigation and so do possible safety issues (toxicity), which can be related to the NP sizes.

Edward Lynch

Papers

Undesirable and adverse effects of tooth-whitening products: a review.

Antimicrobial Effect of a Novel Ozone– Generating Device on Micro–Organisms Associated with Primary Root Carious Lesions in vitro

Reversal of primary root caries using dentifrices containing 5,000 and 1,100 ppm fluoride.

Effect of ozone on the oral microbiota and clinical severity of primary root caries.

Nanoparticles in orthodontics, a review of antimicrobial and anti-caries applications.