The analysis of cytotoxicity of an experimental preparation used for the reduction of dentin hypersensitivity.

BACKGROUND: The problem of effective treatment of dentin hypersensitivity is still valid and not fully resolved. OBJECTIVES: The aim of the study was to evaluate the potential toxicity against body tissues of an experimental preparation which is supposed to reduce dentin hypersensitivity and to compare it to a commercial formulation Seal & Protect (Dentsply) by means of measuring the activity of mitochondrial dehydrogenases (the MTT assay). MATERIAL AND METHODS: The study used an original protective formulation which is supposed to eliminate hypersensitivity of dentin. A commercial preparation Seal & Protect (Dentsply) was used as the comparative material. Cytotoxic activity of the tested preparations (experimental and commercial) on murine lymphocyte cells CCL-1™ (NCTC clone 929) was determined in indirect contact with the use of the MTT test that measured the activity of the mitochondrial dehydrogenase enzyme. RESULTS: A comparison of the results obtained in the MTT assay for the commercial preparation Seal & Protect (Dentsply) and the experimental formulation indicates that an experimental formulation has considerably lower cytotoxicity before polymerization, when compared to the commercial formulation, regardless of its dilution. However, after the polymerization of the commercial formulation was completed, its parameters improved significantly, especially for higher dilution values (1 : 10 and 1 : 15). Results for the experimental formulation are higher, particularly for the dilution value of 1 : 5. The overall summary of the results obtained from the MTT assay for the commercial preparation Seal & Protect (Dentsply) and the experimental formulation indicates that the experimental formulation had a significantly lower cytotoxicity before polymerization in comparison with the commercial formulation, regardless of dilution. CONCLUSIONS: Estimating the biocompatibility of a given material is not simple, and measurement methods are rapidly evolving, as more and more is known about the interaction between dental materials and oral tissues, and also as a result of improvements in testing techniques.

Concept of experimental preparation for treating dentin hypersensitivity.

BACKGROUND: Dentinal hypersensitivity (DH) is a diagnostic and therapeutic problem that is now appearing more frequently in modern dentistry. The aim of this work was to elaborate formulation of a new, original desensitizing preparation with prolonged action based on the knowledge of similar commercializations and to compare their performance in vitro. METHODOLOGY: The analyses were performed with the aid of NMR spectroscopy. The experimental and commercial preparations were examined in vitro after thermocycling on human teeth by optical microscopy. The presence of the material on tooth tissue, its ability to penetrate into the tooth structure and its layer thickness were subjected to statistical analysis. RESULTS: A detailed knowledge on composition of commercial material was achieved from spectroscopic measurements. A new adhesive monomer was synthesized and incorporated into an experimental desensitizing formulation. The new monomer appeared to have comparable performance to the commercial one when regarding the affinity to tooth tissue and resistance to thermocycling. CONCLUSIONS: The experimental formulation comprising a new adhesive monomer seems to be promising and could be applied in dental practice providing that biocompatibility is satisfactory.

Natural and Controlled Demineralization for Study Purposes in Minimally Invasive Dentistry.

Artificially induced demineralization of enamel is frequently used during laboratory tests, particularly in minimally invasive dentistry. The aim of this study was to analyze demineralization techniques of hard tooth tissue applicable in the research of materials in minimally invasive dentistry. The most important factor taken into consideration when designing a method is to make a model as closely similar to the natural environment of the human oral cavity as it is possible. In vitro models allow us to maintain stability and control over the environment and guarantee repeatability of the results. There are main models to produce dental caries outside of the body. The first model is chemical and it uses acids. It is simplified and reflects the actual environment of the oral cavity to a lesser degree. The second model is biological and it is more accurate as it uses microorganisms which build the dental plaque. Among in vitro protocols are also used pH-cycling models. Based on the available literature, it was found that bovine teeth and human teeth with demineralization diagnosed while still inside the oral cavity are the most frequently used kind of specimens in research conducted with use of the chemical model. Not a single case of use of the biological and pH-cycling models were found in the available literature related to the research of infiltrants in minimally invasive dentistry.

High resolution proton nuclear magnetic resonance (1H NMR) spectroscopy of surviving C6 glioma cells after X-ray irradiation.

PURPOSE: To study biochemical response of living model of glioma to X-rays irradiation using high resolution proton nuclear magnetic resonance (1H NMR) spectroscopy. MATERIAL AND METHODS: Rat glioma C6 cells were irradiated with 3.8 Gy (D0, the 37% clonogenic survival dose) of X-rays from a teletherapy unit at the dose rate 8.8 Gy/min. After irradiation the cells were incubated at 37°C/5%CO2/95%O2 for various period of incubation (24, 48, 72 and 96 hours) in the fresh medium. The high resolution 1H NMR spectra of the agarose-cell mixtures (2 x 10(7) cells/ml) were acquired using a Varian Inova-300 multinuclear pulsed NMR spectrometer operating at the 1H resonance frequency of 300 MHz. The mean spectra were obtained as the averages of six independent measurements. RESULTS: The statistically significant increase in the CH2/CH3 lipid signals ratio in the C6 cells after irradiation with 3.8 Gy dose and incubation for 24-96 h was observed. CONCLUSIONS: Our method of the sample preparation enables the metabolic effects of irradiation to be observed in viable cells, which can effectively support the identification of the spectroscopic changes in vivo. Application of the gel suspensions in the NMR studies has advantages over the usual liquid suspensions in terms of improved reproducibility of the data and cell viability, with no net loss of the spectral quality.

Impact of heating method on the flocculation process using thermosensitive polymer.

The impact of suspension heating method on the flocculation process using thermosensitive polymer is reported in this paper. In experiments a model suspension of chalk in RO water (purified by Reverse Osmosis) was destabilized using a copolymer of N-isopropylacrylamide (NIPAM) and cationic diallyldimethyl ammonium chloride (DADMAC). The measurements were made using a laboratory setup consisting of a mixing tank with four baffles, Rushton turbine, laser particle sizer Analysette 22 by Fritsch and a system of pump and thermostating devices. Two different modes of heating were used. In the first case the temperature of the system was gently raised above the Lower Critical Solution Temperature (LCST) using an electrical heater placed inside the tank, while in the second case the system temperature was rapidly raised by an injection of hot water directly into the tank. It was proven that heating method as well as the polymer concentration was crucial to the shape and size of created flocs.

Electrospray ionization tandem mass spectrometric characterization of the new functional oligo(ether-ester)s structure.

The oligomeric products obtained by the polymerization of monomethacrylates of oligoethylene glycols possessing up to four oxyethylene units were examined by electrospray ionization mass spectrometry (ESI-MS). The oligomerization initiated by sodium and potassium hydrides proceeded via Michael-type addition of hydroxyl groups to carbon-carbon double bonds. Extended reaction time caused gelation, especially in the case of the more reactive potassium hydride. This study was focused on the structural assignments of the oligomeric products by use of ion trap multistage mass spectrometry (ESI-MS(2)). Precise structural characterization of the individual oligomers was based on fragmentation data.

Experimental dental bio-adhesives for direct restorations: the influence of PMnEDM homologs structure on bond strength.

OBJECTIVES: The purpose of this study was to evaluate the effect of PMnEDM dental monomer homologs chemical structure on shear bond strength between polymer-based composite and alloy. METHODS: Four light-cured experimental universal dental bio-adhesives (group codes: A (PMDM), B (PM2EDM), C (PM3EDM), D (PM4EDM)) were preliminarily evaluated with respect to sensitivity to ambient light, curing time, depth of cure, and uncured film thickness according to standardized procedures. Appropriate tests were performed to measure shear bond strength (SBS) of polymer-based composite to cobalt-based alloy with the use of the adhesives investigated. Variability of results was evaluated by use of the coefficient of variation (CV). Results were estimated with the aid of one-way analysis of variance (ANOVA), performed on the logarithmic values, with alpha=0.05 significance level. RESULTS: All materials passed the requirements according to physicochemical properties. Except for formulation D, all results estimating SBS were positive with respect to standardized requirements. The uppermost mean SBS was achieved for the A adhesive (11.45 MPa) and appeared to be significantly different compared to D one (5.07 MPa) (p=0.0495). Also the B adhesive, having slightly lower mean SBS value (10.50 MPa) exhibited a significant difference in respect to D one (p=0.0455). The means for other trial pairs did not differ statistically. SIGNIFICANCE: The materials here studied might be considered to have a practical use in dental clinics, especially the formulations B and C.

Preparation and surface properties of low-density gels synthesized using prepolymerized silica precursors.

Properties of silica xerogels and aerogels synthesized using a number of prepolymerized silica precursors were probed by 29Si magic-angle spinning (MAS) NMR spectroscopy, the small-angle X-ray scattering (SAXS) method, the nitrogen adsorption method, and transmission electron microscopy (TEM) to show that xerogels with attractive textural properties can easily be prepared using this type of precursors and the conventional one-step, base procedure. Pore sizes and overall pore volumes in these materials can be notably larger than those in the corresponding materials synthesized using tetraethoxysilane. This positive effect stems from the stronger structure of the polymeric network due to a higher degree of silica condensation on one side and a larger thickness of polymeric chains on the other. The thorough investigations of the fine silica structure demonstrate, however, that the relationship between the microstructure of the silica precursor and the micro- and macrostructures of dry gels is complex and the use of more condensed precursors favors, but does not necessarily ensure, more porous dry materials, under the same reaction conditions. Ethyl silicate 40 may be recommended as a low-cost precursor suitable for applications in this situation.