In vitro wear resistance of conventional and milled denture teeth

The study compared the wear resistance of conventional and milled double-cross-linked (DCL) polymethyl methacrylate resin (PMMA) and nano-composite infused resin denture teeth (NC). DCL PMMA and NC conventional denture teeth, and teeth milled from a DCL PMMA resin disc (DCL-CAM) and from a nano-composite and nano-ceramic infused resin disc (NC-CAM) underwent chewing simulation. The vertical changes after each 50,000 cycles up to 250,000 cycles and volumetric changes after 250,000 cycles were quantified using the Geomagic software. The wear of the conventional and milled denture teeth approximated a linear progression between 50,000 to 250,000 cycles. The conventional NC teeth wore the most by 3.4 times vertically and 12.3 times volumetrically than the milled NC-CAM, which wore the least. The wear resistance between the conventional and milled DCL PMMA teeth was not statistically different. Regarding wear resistance, the milled denture teeth (DCL-CAM and NC-CAM) are acceptable alternatives to the conventional denture teeth.Master of Scienc

Expression of surface markers on the human monocytic leukaemia cell line, THP-1, as indicators for the sensitizing potential of chemicals

Background: Evaluation of skin sensitization potential is an important part of the safety assessment of cosmetic ingredients and topical drugs. Recently, evaluation of changes in surface marker expression induced in dendritic cells (DC) or DC surrogate cell lines following exposure to chemicals represents one approach for in vitro test methods. Objective: The study aimed to test the change of expression patterns of surface markers on THP-1 cells by chemicals as a predictive in vitro method for contact sensitization. Methods: We investigated the expression of CD54, CD86, CD83, CD80, and CD40 after a 1-day exposure to sensitizers (1-chloro-2,4-dinitrobenzene; 2,4-dinitrofluorobenzene; benzocaine; 5-chloro-2-methyl-4-isothiazolin-3-one; hexyl cinnamic aldehyde; eugenol; nickel sulfate hexahydrate; potassium dichromate; cobalt sulfate; 2-mercaptobenzothiazole; and ammonium tetrachloroplatinate) and non-sensitizers (sodium lauryl sulfate, benzalkonium chloride, lactic acid, salicylic acid, isopropanol, and dimethyl sulphoxide). The test concentrations were 0.1 X, 0.5 X, and 1 X of the 50% inhibitory concentration, and the relative fluorescence intensity was used as an expression indicator. Result and Conclusion: By evaluating the expression patterns of CD54, CD86, and CD40, we could classify the chemicals as sensitizers or non-sensitizers, but CD80 and CD83 showed non-specific patterns of expression. These data suggest that the THP-1 cells are good model for screening contact sensitizers and CD40 could be a useful marker complementary to CD54 and CD86.Rasaiyaah J, 2007, BRIT J HAEMATOL, V138, P281, DOI 10.1111/j.1365-2141.2007.06622.xPython F, 2007, TOXICOL APPL PHARM, V220, P113, DOI 10.1016/j.taap.2006.12.026Bocchietto E, 2007, INT J IMMUNOPATH PH, V20, P259Sakaguchi H, 2007, ARCH DERMATOL RES, V298, P427, DOI 10.1007/s00403-006-0714-9Ciabattini A, 2006, CLIN VACCINE IMMUNOL, V13, P1037, DOI 10.1128/CVI.00110-06Sakaguchi H, 2006, TOXICOL IN VITRO, V20, P774, DOI 10.1016/j.tiv.2005.10.014Azam P, 2006, TOXICOL APPL PHARM, V212, P14, DOI 10.1016/j.taap.2005.06.018Berges C, 2005, BIOCHEM BIOPH RES CO, V333, P896, DOI 10.1016/j.bbrc.2005.05.171Cao WP, 2005, BIOCHEM J, V385, P85, DOI 10.1042/BJ20040741Gerberick GF, 2004, TOXICOL SCI, V81, P332, DOI 10.1093/toxsci/kfh213Galdiero M, 2004, MICROBIOLOGICA, V27, P309Rustemeyer T, 2003, EXP DERMATOL, V12, P682Yoshida Y, 2003, TOXICOL IN VITRO, V17, P221, DOI 10.1016/S0887-2333(03)00006-7Ashikaga T, 2002, TOXICOL IN VITRO, V16, P711Hulette BC, 2002, TOXICOL APPL PHARM, V182, P226, DOI 10.1006/taap.2002.9447Cumberbatch M, 2000, CLIN EXP DERMATOL, V25, P413Coutant KD, 1999, TOXICOL SCI, V52, P189*NAT TOX PROGR, 1999, NIH PUBLAiba S, 1997, EUR J IMMUNOL, V27, P3031Krasteva M, 1996, CLIN EXP ALLERGY, V26, P563BASKETTER DA, 1994, FOOD CHEM TOXICOL, V32, P543MOULON C, 1993, IMMUNOLOGY, V80, P373ENK AH, 1992, P NATL ACAD SCI USA, V89, P1398

Hybrid skin chips for toxicological evaluation of chemical drugs and cosmetic compounds

Development of drugs and cosmetics for topical application require safety tests in skin models. However, current skin models, such as skin cell sheets and artificial tissue-engineered skin, do not allow sophisticated toxicological evaluations (e.g., sensory irritation, hepatotoxicity). Animal models are prohibited worldwide for testing cosmetics. Therefore, reliable human skin models that recapitulate physiological events in skin tissue need to be established under in vitro settings. In this study, hybrid human skin models that enable delicate toxicological evaluations of drugs and cosmetic compounds are demonstrated. To recapitulate skin cornification, keratinocytes in the top layer of a vertical microfluidic chip were cultured at the air-liquid interface. For the skin-nerve hybrid model, differentiated neural stem cells in 3D collagen were positioned adjacent to and right below the skin layer. This model enables real-time quantitative skin sensitization analysis following chemical treatments by detecting alterations in neuronal activity in combination with a calcium imaging technique. For the skin-liver model, hepatic cells derived from pluripotent stem cells were cultured in 3D collagen distant from the skin layer. Potential hepatotoxicity of cutaneously applied chemicals in this model can be evaluated by quantification of glutathione and reactive oxygen species. Our study suggests that 3D hybrid skin chips would provide useful human skin models in pharmaceutical and cosmetic industries.11Nscopu

Biocompatibility Evaluation of Dental Luting Cements Using Cytokine Released from Human Oral Fibroblasts and Keratinocytes

Dental luting cements are commonly used in dentistry for cementation of prosthetic restoration. Many previous studies focused on the measurement of the cell viability as the method of cytotoxicity evaluation during biocompatibility study for the material. In this study, the biocompatibility of various dental luting cements were evaluated using the new method of cytokine release measurement in order to better simulate inflammatory reactions in animal or clinical model using two different oral cells; immortalized human gingival fibroblast and immortalized human oral keratinocytes. Cells were exposed to extractions of various commercially available dental luting cements for different durations. Cytokines of IL-1α and IL-8 were measured from the supernatants of the cells and the results were then compared to the conventional MTT viability test. The result from the conventional cell viability study showed a relatively simple and straight forward indication that only one of the dental luting cements tested in this study was cytotoxic with increasing duration of exposure for both cells. Meanwhile, the result from the cytokine measurement study was much more complex at the time point they were measured, type of cells used for the study and the type of cytokines measured, all of which influenced the interpretation of the results. Hence, the better understanding of the cytokine release would be required for the application in biocompatibility evaluation

Comparative study of the ocular irritation potential of various alkyl polyglucoside surfactants

In the present work, we assessed the relationship between alkyl carbon chain length and ocular irritation potentials using the hen's egg test-chorioallantoic membrane (HET-CAM) and bovine corneal opacity and permeability (BCOP) assays using 5 commercial alkyl polyglucoside surfactants with different compositions of alkyl chain lengths (C6-C16). With HET-CAM, there was a good correlation between the proportion of C(10) alkyl polyglucoside and the eye irritation potential Q score (r(2) = 0.912, p = .011). There were no significant differences between the proportion of C(10) alkyl polyglucoside and corneal opacity in BCOP assays; however, there was a relatively high positive correlation between the proportion of C(10) alkyl carbon chain lengths and corneal permeability (r(2) = 0.736, p = .063)..N

Clinical and Microbiological Efficacy of Pyrophosphate Containing Toothpaste: A Double-Blinded Placebo-Controlled Randomized Clinical Trial

(1) Background: Dental calculus works as a niche wherein pathogenic bacteria proliferate in the oral cavity. Previous studies revealed the anticalculus activity of pyrophosphates, however there was no clinical study that evaluated microbiome changes associated with calculus inhibition. Therefore, the aim of this randomized clinical trial was to evaluate the calculus inhibition of pyrophosphate-containing toothpaste and its effect on oral microbiome changes. (2) Methods: Eighty subjects with a calculus index ≥2 on the lingual of the mandibular anterior tooth were randomly allocated to the test group that pyrophosphate-containing toothpaste was given to or the placebo control group. Full mouth debridement and standardized tooth brushing instruction were given before the allocation. Plaque index, gingival index, calculus index, probing depth, and bleeding on probing were measured at the baseline, and at 4, 8 and 12 weeks. Genomic DNA was extracted from the plaque samples collected at the baseline and at 12 weeks, and 16S ribosomal RNA gene amplicon sequencing was applied for microbiome analysis. (3) Results: None of the clinical parameters showed significant differences by visits or groups, except the plaque index of the test group, which reduced significantly between 4 and 12 weeks. A significant difference of microbiome between the baseline and 12 weeks was observed in the test group. Between baseline and 12 weeks, the proportion of Spirochetes decreased in the control group, and the proportions of Proteobacteria, Fusobacteria and Spirochetes in the phylum level and the proportions of Haemophilus, Fusobacterium and Capnocytophaga in the genus level decreased in the test group. In the test group, as plaque index decreased, Streptococcus increased, and Fusobacterium and Haemophilus parainfluenza decreased. (4) Conclusion: The use of pyrophosphate-containing toothpaste effectively inhibited the dysbiosis of the oral microbiome and the proliferation of pathogenic species in periodontal disease. Clinically, plaque formation in the pyrophosphate-containing toothpaste group was effectively decreased, however there was no significant change in calculus deposition