Guided Tissue Remineralization of Resin-Bonded Acid-Etched Dentin

Contemporary biomineralization strategies incorporate non-classical crystallization pathways of fluidic amorphous nanoprecursors and mesoscopic transformation. Using two functional biomimetic molecules, we previously regenerated mineralized dentin from acid-etched dentin using the Guided Tissue Remineralization (GTR) approach, with definitive intrafibrillar remineralization of type-I collagen. Degradation of denuded collagen within dentin adhesive resin-infiltrated dentin is a pertinent problem in dentin bonding. Here, we show that GTR provides a means of salvaging these degrading bonds by remineralizing resin-dentin interfaces. The GTR medium consists of a Portland cement/simulated body fluid that includes polyacrylic acid and polyvinylphosphonic acid biomimetic analogs for amorphous calcium phosphate dimension regulation and collagen targeting. Both interfibrillar and intrafibrillar apatites became readily discernible within the adhesive-bonded dentin after 2-4 months. Amorphous nanoprecursors created by GTR also penetrated the adhesive resin matrix to create nanocomposites. We anticipate GTR to be the starting point for more sophisticated strategies in extending the longevity of resin-dentin bonds

Dentin: A Dynamic Substrate - A Review

The structure of dentin is unusual in that the number and size of its tubules changes as one moves from the periphery toward the pulp chamber. Near the pulp, the tubules are very close together and the water con tent of this deep dentin is high. Near the enamel, the tubules are far apart, occupying less than 1% of the surface area. When enamel or dentin is cut, the surface becomes covered by an adherent layer of cutting debris called the smear layer. Its composition presumably reflects the composition of the underlying dentin. It is only about 1 μm thick but its presence modifies the function of the dentin a great deal. It lowers dentin permeability and therefore can be regarded as protective. However, it masks the underlying dentin and hence interferes with attempts to bond dental materials directly to dentin. If it is removed, the dentin becomes much more permeable and fluid shifts across the open tubules can cause sensitivity in vivo. As smear layers are very acid-labile, they often dissolve in oral fluids. Several attempts have been made to replace smear layers with acid resistant structures that accomplish the same function. Smear layer structure is being studied by using both scanning electron microscopy as well as electronic particle sizing equipment. The close adaptation of dental materials to smear layers and to underlying dentin is currently an area of very active research. Removal of smear layers increases adaptation and bonding strength but may increase the incidence of pulpal inflammation if the bonding is not uniform or permanent. The dynamics of dentin are just beginning to be understood

The environmental spending needs of Scotland’s local authorities

Scottish citizens benefit from 19% more public spending per head than English citizens. The ‘Barnett formula’ is slowly reducing the gap, but very little is known about the countries’ relative needs and hence about how far the present gap is defensible: the aim of this paper is to throw some light on the countries’ relative needs. We begin with the complex formulae that the Westminster government uses to assess the spending needs of English local authorities, and we use these English formulae to assess the needs of Scottish local authorities for three major blocks of local services. These formulae suggest that Scotland needs 6.4% more per head than England for environmental, protective and cultural services, 8.1% more for highway maintenance, and between 24.3% and 35.3% more for fire services. We also combine these results with those of two other papers concerned with local education and social services to show that these English formulae put Scotland’s per capita needs for local government services as a whole at about 6% above England’s. However, we then compare the relative needs of Scottish local authorities as assessed by the English formulae with their relative needs as assessed by the Scottish needs formulae that are currently used by Holyrood, and we find major differences. This suggests either that at least one country uses seriously flawed formulae to assess needs, or that the two countries have different conceptions of need

Scotland’s social services spending needs: an English view

Scottish citizens enjoy 25% more spending per head on public services than English citizens, but almost nothing is known about the countries’ relative needs and hence about how far this gap is defensible. We explore their spending needs for local authority services, which cover over half the spending concerned. We first compare needs for local personal social services. To do so, we take the complex formulae with which the Westminster government assesses the needs of English local authorities, and we use these formulae to assess the needs of Scottish local authorities. The formulae suggest that Scotland needs 15.3% more per head than England. We then combine these results with those of two earlier papers that explore other local services to show that the English formulae put Scotland’s per capita needs for local authority services as a whole at about 6% above England’s. However, we also compare the relative needs of Scottish local authorities as assessed by the English formulae with their relative needs as assessed by the Scottish needs formulae currently used by Holyrood, and we find major differences. This suggests either that at least one country assesses needs with seriously flawed formulae, or that the two countries have different conceptions of need

A Distributional Analysis of the Warblers of the West Indies. (Volumes I and II).

Wood-warblers (Aves:Emberizidae:Parulinae) are a conspicuous and perhaps declining component of the avifauna of North America and the Neotropics. The West Indies are home to 16 permanent resident species and have been included in the ranges of 40 migrant species. On the basis of specimens in the world\u27s museums and published literature, I report the known status, seasonality, and natural history of warblers in the Virgin Islands (1 permanent resident; 29 migrants), the Western Caribbean (2;28), the Lesser Antilles (5;26), the Bahamas (5;38), Bermuda (0;38), Puerto Rico (3;30), Jamaica (2;32), Hispaniola (4;31), and Cuba (4;35). I grouped the migrants into nine categories: (1) two species are strictly accidental, (2) five are accidental but not entirely unusual, (3) seven winter and generally migrate on the mainland but appear infrequently in the West Indies, (4) two winter in South America but migrate exclusively through the West Indies, (5) seven are typically mainland birds that are regular in small numbers in the West Indies, (6) two are uncommon species for which the West Indies constitute important winter range, (7) two are rare species that winter exclusively in the region, (8) seven winter commonly both in the West Indies and the Neotropical mainland, and 9) six are common and largely or exclusively West Indian in winter. Within groups, there is variation in distribution, seasonality, and habitats and resources utilized. Because each species is unique, management recommendations cannot be applied to the group as a whole. Most migrant species use generalized and often disturbed habitats and are not necessarily suffering from widespread human-induced habitat degradation. Resident warblers, including nine species, subspecies, or populations that are potentially threatened, tend to require undisturbed habitat. Management should concern maintenance or enhancement of habitat for these populations

Intelligence and action agents: 185 years of state security

Tijdens de Tweede Wereldoorlog voelden talrijke Belgische burgers, mannen en vrouwen, van alle leeftijden en beroepsklassen, verontwaardigd door de bezetting van hun vaderland, zich geroepen om ‘iets’ te doen. Zij zouden uitgroeien tot een zeer bijzondere vorm van het Verzet. In totaal 18.716 erkende IAA – Inlichtingen en Actie Agenten, in 129 IAD – Inlichtingen en Actie Diensten, actief in het bezette België. Zij werden aangestuurd door de Veiligheid van de Staat in ballingschap te Londen, in samenwerking met de Britse diensten MI.6, MI.9 en SOE. Zij waren actief in: politieke, economische en militaire spionage; sabotage; psychologische oorlogsvoering; propaganda; ontsnappingslijnen; meteorologische inlichtingen; ondersteuning van gedwongen werkweigeraars; ... Minstens 4.000 van hen werden gearresteerd en 1.815 vermoord (neergeschoten, onthoofd, omgekomen in concentratiekampen ...). Dit boek brengt hun verhaal en geeft deze onbekende helden na 70 jaar een naam

Capacidade de união de resinas adesivas à dentina afetada e infectada por cárie

Hybridized dentin permits dental treatments that were previously impossible with conventional techniques, opening new frontiers in modern adhesive dentistry. We have investigated the adhesive property of current bonding systems to caries-infected dentin by a microtensile bond strength test (µTBS) and transmission electron microscopy (TEM), and suggested that bonding resin could infiltrate into caries-infected dentin partially to embed carious bacteria within hybrid layers. We have named this concept of caries control as modified sealed restoration (MSR). On the other hand, Kuraray Medical Inc. (Tokyo, Japan) has developed an antibacterial adhesive system (ABF, now marketed in USA as Protect Bond). So as to evaluate the effectiveness of ABF on root caries control, we have examine the microtensile bond strengths (µTBS) of ABF to normal versus carious root dentin and the interfacial morphology by a scanning electron microscopy (SEM). ABF could form the hybrid-like structures by infiltrating into the surfaces of the root carious dentin, and the mean value of µTBS of ABF to root carious dentin was 23.0 MPa. These results suggested that MSR combined with ABF might be an advantageous minimal invasive therapy for root caries.As técnicas adesivas permitiram inovações nos tratamentos restauradores da atualidade. Este estudo investigou a qualidade de união de diferentes sistemas adesivos ao substrato dentinário afetado e infectado por cárie, através de testes de microtração e microscopia eletrônica de transmissão e varredura (MET). Os resultados sugerem que a resina adesiva pôde infiltrar na dentina infectada e envolver as bactérias na camada híbrida. Esse conceito de controle da cárie foi denominado de "Restauração-Selante Modificada" (RSM). Por outro lado, a empresa Kuraray Med. Inc .(Japão) desenvolveu um sistema adesivo com propriedades anti-bacterianas (ABF), o qual é comercializado nos EUA como Protect Bond. Para avaliar a efetividade do sistema ABF sobre cáries radiculares, empregou-se testes de resistência adesiva e análise por microscopia eletrônica. O sistema ABF foi capaz de formar uma estrutura interfacial semelhante à camada híbrida, através da infiltração na superfície da dentina cariada radicular e os valores de resistência de união foram em média de 23 MPa. Os achados sugerem que a combinação da técnica RSM com o sistema ABF parece ser uma alternativa para o emprego da terapia de mínima invasão em cáries radiculares

Proteolytic activity and degradation of bovine versus human dentin matrices

Non-human teeth have been commonly used in research as replacements for human teeth, and potential dissimilarities between the dental tissues should be considered when interpreting the outcomes. Objective: To compare the proteolytic activity and degradation rate of bovine and human dentin matrices. Methodology: Dentin beam specimens were obtained from human molars (n=30) and bovine incisors (n=30). The beams were weighed hydrated and after complete dehydration to obtain the mineralized wet and dry masses. Then, the beams were demineralized in 10 wt% phosphoric acid. Next, 15 beams from each substrate were randomly selected and again dehydrated and weighed to obtain the initial demineralized dry mass (DM). Then, the beams were stored in saliva-like buffer solution (SLBS) for 7, 14 and 21 days. SLBS was used to evaluate hydroxyproline (HYP) release after each storage period. The remaining beams of each substrate (n=15) were tested for initial MMP activity using a colorimetric assay and then also stored in SLBS. DM and MMP activity were reassessed after 7, 14 and 21 days of incubation. The data were subjected to two-way ANOVA tests with repeated measures complemented by Bonferroni’s tests. Unpaired two-tailed t-tests were also used (p<0.05). Results: Similar water and inorganic fractions were found in human and bovine dentin, while human dentin had a higher protein content. The most intense proteolytic activity and matrix deterioration occurred short after dentin was demineralized. Both substrates exhibited a sharp reduction in MMP activity after seven days of incubation. Although human dentin had higher MMP activity levels, greater HYP release and DM loss after seven days than bovine dentin, after 14 and 21 days, the outcomes were not statistically different. Conclusion: Bovine dentin is a suitable substrate for long-term studies involving the degradation of dentin matrices

Hydration interactions: aqueous solvent effects in electric double layers

A model for ionic solutions with an attractive short-range pair interaction between the ions is presented. The short-range interaction is accounted for by adding a quadratic non-local term to the Poisson-Boltzmann free energy. The model is used to study solvent effects in a planar electric double layer. The counter-ion density is found to increase near the charged surface, as compared with the Poisson-Boltzmann theory, and to decrease at larger distances. The ion density profile is studied analytically in the case where the ion distribution near the plate is dominated only by counter-ions. Further away from the plate the density distribution can be described using a Poisson-Boltzmann theory with an effective surface charge that is smaller than the actual one.Comment: 11 Figures in 13 files + LaTex file. 20 pages. Accepted to Phys. Rev. E. Corrected typos and reference

Studying bubble-particle interactions by zeta potential distribution analysis

Over a decade ago, Xu and Masliyah pioneered an approach to characterize the interactions between particles in dynamic environments of multicomponent systems by measuring zeta potential distributions of individual components and their mixtures. Using a Zetaphoremeter, the measured zeta potential distributions of individual components and their mixtures were used to determine the conditions of preferential attachment in multicomponent particle suspensions. The technique has been applied to study the attachment of nano-sized silica and alumina particles to sub-micron size bubbles in solutions with and without the addition of surface active agents (SDS, DAH and DF250). The degree of attachment between gas bubbles and particles is shown to be a function of the interaction energy governed by the dispersion, electrostatic double layer and hydrophobic forces. Under certain chemical conditions, the attachment of nano-particles to sub-micron size bubbles is shown to be enhanced by in-situ gas nucleation induced by hydrodynamic cavitation for the weakly interacting systems, where mixing of the two individual components results in negligible attachment. Preferential interaction in complex tertiary particle systems demonstrated strong attachment between micron-sized alumina and gas bubbles, with little attachment between micron-sized alumina and silica, possibly due to instability of the aggregates in the shear flow environment