A three layer structure model of fluoridated enamel containing CaF2, Ca(OH)2 and FAp.

OBJECTIVES: The aim of this study was to develop a molecular-based structural model of human teeth after fluoridation with a commonly used amine fluoride, which is highly significant for understanding the effectiveness of topical fluoridation. METHODS: This multi method study used XPS, MAS-NMR and Raman-spectroscopy measurements in order to analyze powdered synthetic hydroxylapatite (HAp), powdered human enamel samples and human enamel pieces treated with amine fluoride (Elmex) fluid) in vitro. RESULTS: The results lead to a complete structural characterization of the fluoridation products. A three layer composition of calcium hydroxide, calcium fluoride and an apatite species was identified. SIGNIFICANCE: The top surface CaF(2) layer acts as a fluoride reservoir and covers a layer of antimicrobial effective Ca(OH)(2). Ca(OH)(2) is a well-known therapeutic agent. However, up to now Ca(OH)(2) has not been described as a reaction product after topical fluoridation. Below the Ca(OH)(2) layer an acid resistant apatite species (FAp) was detected which reached directly into the bulk enamel HAp species. The three layer composition identified helps to understand the influence of fluoride application in the pathogenic mechanisms of tooth decay. Each component in this newly suggested structure model has a specific function, which explains how topical fluoridation of enamel reduces dental caries and influences its pathogenic mechanisms.

Chemical analysis and bonding reaction of RelyX Unicem and Bifix composites--a comparative study.

OBJECTIVES: The chemical and physical properties of the dual curing luting composites RelyX Unicem (3M ESPE) and Bifix (VOCO) were analyzed with regard to their elemental composition, surface morphology and polymerization reaction. The bonding of both materials to hydroxyapatite (HAp) was studied. METHODS: The main components were analyzed by XPS and EDX. The minor components were identified with ICP-OES. Moreover, the morphology was examined by SEM and the polymerization reaction products were investigated using GPC. XPS was also applied to study the bonding mechanisms to HAp. RESULTS: The inorganic product particles consist of an Al-Si-Na-glass network, which incorporates radiopaque strontium and barium for Bifix and strontium and lanthanum for RelyX Unicem. RelyX Unicem contains about 10% fluoride and 2% Ca(OH)(2), whereas Bifix comprises 2% fluoride. After polymerization, reaction products of 10(5)-10(6)g/mol were identified with RelyX Unicem. Both products contain mono- and oligomeric compounds. The reaction with HAp generates calcium atoms with a reduced binding energy. They act as an electron acceptor and show chemical interaction between the composite and HAp. With RelyX Unicem 86% of the calcium atoms reacted, compared to 65% with Bifix. SIGNIFICANCE: The intense chemical interaction of RelyX Unicem with HAp seems to be relevant to clinical aspects and explains the mechanical product properties. After setting, a polymer was found with RelyX Unicem but only monomeric/oligomeric products were identified at the surface of Bifix.

Chemical and physical surface and bulk material characterization of white ProRoot MTA and two Portland cements.

OBJECTIVES: The chemical and physical properties of white ProRoot MTA were analyzed in the bulk and at the surface and compared with two common Portland cements types CEM1 and CEM2. METHODS: The main components were analyzed by X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray analysis (EDX), and the minor constituents were identified with inductively coupled plasma optical emission spectroscopy (ICP-OES). Moreover, the setting of the different cements was studied: the chemical composition of the surface of both powder and bound cement was investigated by XPS and the morphological changes were examined by scanning electron microscopy (SEM). RESULTS: In ProRoot MTA, the amount of gypsum is approximately half of that of the Portland cements. ProRoot MTA consists of less toxic heavy metals (Cu, Mn, Sr), less chromophores (Fe3+), and less Al-species, but contains about 2 at % Bi. In contrast to Portland cements, ProRoot MTA contains about 2 at.% Bi. In all three products, the amount of sulfur at the surface in the bound cements was 3 times higher than in the powder, indicating that in terms of the kinetics of the hardening reaction, a sulfate action mechanism prolongs the setting time. The Portland cements are composed of particles with a wide range of size, whereas ProRoot MTA showed a uniform and smaller particle size. SIGNIFICANCE: With regard to chemical and physical surface and bulk properties, ProRoot MTA cannot simply be substituted by the cheaper Portland cement. Both products are similar but not equal and exhibit marked differences.

Cytotoxic effects of novel polyoxotungstates and a platinum compound on human cancer cell lines.

The cytotoxicity of a new platinum compound Pt1 [2,9-dimethyl-4,7-diphenyl-1,10-phenanthrolinedichloroplatin(II)] and six polyoxometalates (POM1-6) on two neuroblastoma cell lines (SHEP-SF and KCN) and an Ewing's Sarcoma cell line (CADO-ES-1) was studied. Cisplatin [cis-diamminedichloroplatinum(II)] and carboplatin [cis-diammine(cyclobutanedicarboxylato)platinum(II)] were used as reference agents. Using MTT tests, the cytotoxicity (LD50: lethal doses 50%) of the compounds were measured at different concentrations. After 72 h exposure, the LD50 data for the platinum-containing substances ranged between 4.47 x 10(-6) and 1.91 x 10(-4) M. The SHEP-SF cell line displayed the highest sensitivity to cisplatin. The novel platinum agent Pt1 had a similar cytotoxic effect to the reference agent cisplatin. Both cisplatin and Pt1 were more cytotoxic than carboplatin. The POMs reduced cell viability compared to untreated cells at concentrations between 8.4 x 10(-7) and 3.47 x 10(-5) M. POM1 ([(CH3)4N]2Na6.5(NH4)2[SnII1.5(WO2(OH))0.5(WO2)2(SbW9O33)2] x 32H2O) was the most effective polyoxoanion with a mean LD50 value of 8.83 x 10(-6) M in the three cell lines tested. With CADO-ES-1 and KCN cells, POM1 was found to be more effective than the platinum compounds cisplatin, carboplatin and Pt1.