In vivo and in vitro irritation testing of low concentrations of hydrofluoric acid

Calcium, magnesium and aluminium ions as decontaminating agents against dermal fluoride absorption following hydrofluoric acid exposure

The fluoride ions of the industrially largely irreplaceable, locally corrosive hydrofluoric acid (HF) can scavenge cations in biological tissues, which explains their high toxic potential, and also leads to local acidification through proton release. The influence of three complexing agents, calcium (Ca²⁺) gluconate (as 2.5% Ca²⁺gel and individually (2.84%) or commercially (10%) formulated Ca²⁺solution), magnesium (Mg²⁺) gluconate (2.84%) solution and aluminium (Al³⁺) solution (Hexafluorine®, pure and diluted) on the absorption of fluoride following HF exposure (1-3 min, 100 μl, 30%/0.64 cm²) through human skin was investigated in an ex-vivo diffusion cell model. Fluoride absorption was assessed over 6-24 h and analysed with a fluoride electrode. Decreasing the contamination time reduced the fluoride absorption distinctly which was further reduced by the application of fluoride-binding decontamination agents (Ca²⁺, Mg²⁺, Al³⁺) or water alone without being significantly different. Ca²⁺ appeared slightly more effective than Mg²⁺ in reducing fluoride absorption. Moreover, the addition of pH adjusting buffer promoted the decontamination efficacy. Fluoride-binding agents can facilitate the decontamination of dermal HF exposure. However, prompt decontamination appeared to be the key to successful limitation of fluoride absorption and pushes the choice of decontamination agent almost into the background.

A Descriptive in vitro Electron Microscopic Study of Acidic Fluoride-Treated Enamel: Potential Anti-Erosion Effects

This study aimed to investigate the surface zones of acidic fluoride-treated enamel. Human teeth were each divided into three or four enamel specimens that were treated for 10 min with solutions of 0.2 and 0.4% HF (pH 3.09 and 2.94), 1.74% SnF2 (pH 2.9), 0.68% TiF4 (pH 1.6) and 0.84% NaF (pH 4.5). Untreated specimens functioned as negative controls. The microstructure and elemental composition of the surface zones were studied by scanning electron microscopy/energy-dispersive X-ray (EDX) analysis, transmission electron microscopy (TEM) and nanospot-EDX following cross-sectional preparation using focused ion beam technology. TEM/EDX analyses of NaF-treated specimens showed a 500-nm-thick closed surface film containing 20-40 at% (atomic percent) F. HF-treated specimens had a distinct surface film 200-600 nm thick (dense, not globular) containing 45-47 at% F. TiF4-treated specimens had a surface film of 200-300 nm in thickness containing 8-11 at% Ti but no detectable fluoride. SnF2-treated specimens had a modified surface enamel layer varying in thickness from 200 to 800 nm with an inhomogeneous distribution of Sn. Local spots were detected with as high as 8 at% Sn (30 wt%, weight percent). The results suggest that the reaction mechanisms of SnF2 and TiF4 solutions with dental enamel differ from those occurring after enamel exposure to acidulated NaF and HF solutions. While the HF and NaF treatments resulted in the formation of CaF2-like material as shown by EDX, no significant surface fluoridation was found for SnF2 and TiF4 solutions within the TEM/EDX detection limits. These results suggest that the erosion-protective mechanisms of these latter compounds probably relate more to the formation of hardly soluble and acid-resistant reaction surface films and less to surface fluoride incorporation.

Etching effect of acidic fluorides on human tooth enamel in vitro

OBJECTIVE

This in vitro study aimed to examine the etching effect of acidic fluoride solutions on enamel.

MATERIALS AND METHODS

24 human teeth divided into 48 enamel-specimens were partly isolated with impression material. Specimens were exposed for 10 min to 20ml of the following solutions: 1.6% TiF4, 3.9% SnF2, 0.2% HF and 1.8% citric acid (CA). The isolation was removed and 24 specimens analysed by profilometry (Δheight: exposed/isolated enamel surfaces, surface roughness parameters). For the remaining 24 specimens [Ca(2+)] in the test solutions was analysed by atomic absorption spectroscopy.

RESULTS

Median Δheights (μm) after exposure were: TiF4 0.07, SnF2 -0.03, HF -0.14 and CA -5.92. TiF4-exposed surfaces showed both deposits and etched areas and exhibited statistically significant different surface roughness parameters compared to the HF- and SnF2-exposed surfaces. Median [Ca(2+)] values (ppm): TiF4 1.88, SnF2 0.11, HF 0.10 and CA 2.17.

CONCLUSION

At the [F] tested in this study it can be concluded that SnF2- and HF solutions had negligible erosive effects on enamel. TiF4 solution resulted in an incomplete surface deposition associated with calcium dissolution suggesting that TiF4 applied as solution may not be advisable.

Multiparametric and semiquantitative scoring systems for the evaluation of mouse model histopathology--a systematic review

BACKGROUND

Histopathology has initially been and is still used to diagnose infectious, degenerative or neoplastic diseases in humans or animals. In addition to qualitative diagnoses semiquantitative scoring of a lesion`s magnitude on an ordinal scale is a commonly demanded task for histopathologists. Multiparametric, semiquantitative scoring systems for mouse models histopathology are a common approach to handle these questions and to include histopathologic information in biomedical research.

RESULTS

Inclusion criteria for scoring systems were a first description of a multiparametric, semiquantiative scoring systems which comprehensibly describe an approach to evaluate morphologic lesion. A comprehensive literature search using these criteria identified 153 originally designed semiquantitative scoring systems for the analysis of morphologic changes in mouse models covering almost all organs systems and a wide variety of disease models. Of these, colitis, experimental autoimmune encephalitis, lupus nephritis and collagen induced osteoarthritis colitis were the disease models with the largest number of different scoring systems. Closer analysis of the identified scoring systems revealed a lack of a rationale for the selection of the scoring parameters or a correlation between scoring parameter value and the magnitude of the clinical symptoms in most studies.

CONCLUSION

Although a decision for a particular scoring system is clearly dependent on the respective scientific question this review gives an overview on currently available systems and may therefore allow for a better choice for the respective project.

The chick chorioallantoic membrane imaging method as a platform to evaluate vasoactivity and assess irritancy of compounds

OBJECTIVE

To determine if the chick chorioallantoic membrane (CAM) is a potential alternative that is capable of screening test substances for vasoactivity in terms of vessel diameter changes. The CAM was also evaluated as a tool for irritancy screening.

METHODS

Visual assessment of the CAM for irritancy after the application of the test substance or solvent to its surface was made. An imaging based-in-vivo CAM model was developed by imaging CAM blood vessels in a pre-defined area using a semi-automatic image processing and analysis technique to measure blood vessel diameters. Solvents and drugs such as 70% v/v ethanol, normal saline, 5% w/v glucose monohydrate, glycerin, glucagon, N-methylpyrrolidone, nicotine, glyceryl trinitrate, glucagon, propranolol and caffeine were tested on the CAM.

KEY FINDINGS

Propranolol, nicotine and glycerin were irritants on CAM. Changes in the diameters of fine blood vessels were accurately measured by high resolution image analysis. Vasoconstriction was seen with 70% v/v ethanol while vasodilation was displayed with glucagon and caffeine. The results reflected expected trends with evidence of feedback mechanisms ensuring homeostasis.

CONCLUSION

The CAM model can be applied to assess pharmaceutical and cosmetic formulations in early development work to gain useful insights to potential irritancy and biological effects of components and formulations.

The CAM-LDPI method: a novel platform for the assessment of drug absorption

OBJECTIVES

This study aimed to explore the use of the chicken chorioallantoic membrane (CAM) with laser doppler perfusion imaging (LDPI) as a platform to assess absorption of vasoactive drugs.

METHODS

The optimal age of the CAM to be employed in the test and the indicator of vasoactivity were first established. Test substances that included common solvents and vasoactive drugs were tested on the CAM surface to determine their irritancy and blood perfusion effects.

KEY FINDINGS

Insignificant changes in blood perfusion were observed with deionized water, 0.9% w/v soldium chloride and 5% w/v glucose monohydrate, as well as theophylline and glucagon. Complex changes in blood perfusion were detected with ethanol, N-methyl-2-pyrrolidone, glycerin and propranolol. Both caffeine and glyceryl trinitrate resulted in a drop in blood perfusion.

CONCLUSIONS

It was concluded that the LDPI offers a rapid and non-invasive method to measure blood perfusion in the CAM. The latter provides a potentially useful platform in formulation studies to evaluate the effects of additives on drug absorption using caffeine or glyceryl trinitrate as model drugs.