In silico evaluation of the peripheral and inner seals in complete denture master impressions using a custom-developed 3D software.

OBJECTIVES: Despite the complexity of the edentulous anatomy, little evidence exists as to what impression techniques and materials should be employed for an optimal result. The aim of this in silico study was to evaluate the trueness of peripheral and inner seals of different edentulous jaw impressions. MATERIALS AND METHODS: Twelve maxillary edentulous participants (male = 8, female = 4; age 68.5 ± 11.7 years) participated in this study. Four different impression materials and techniques, irreversible hydrocolloid (Alginate; Blueprint X-Crème, Dentsply Sirona, PA, USA), polyvinyl siloxane impression (PVS; Aquasil Ultra+ Medium, Dentsply Sirona, PA, USA), and subsequently modified with ZnOE (PVSM) and an optical impression (Optical; 3Shape A/S, Copenhagen, Denmark), were tested against a control impression: low-fusing impression compound border molding (Kerr Corp., CA, USA) followed by a ZnOE impression (ZnOE; SS White impression paste, S.S. White Group, Gloucester, England). All impressions were scanned and analyzed using a custom-built 3D comparison software analyzing the vertical and horizontal trueness. RESULTS: The vertical discrepancy (peripheral seal) of the impression surface was significantly more true for PVSM than Alginate (p = 0.001), PVS (p = 0.019), and Optical groups (p < 0.001). Where the horizontal discrepancy (inner seal) was compared, the impression surface was more true for PVSM than Alginate (p < 0.001) and Optical (p < 0.001). PVS group was also significantly more true than Optical (p = 0.015). CONCLUSION: Impression techniques and materials may significantly influence the peripheral and inner seal of an edentulous jaw impression. CLINICAL RELEVANCE: When using a polyvinylsiloxane impression material for master edentulous impressions, a selective inner seal reline with a conventional zinc oxide eugenol impression paste can improve the inner seal.

Systematic Variations of Ion Hydration in Aqueous Alkali Metal Fluoride Solutions.

Aqueous solutions of three alkali metal fluorides-NaF, KF, and CsF-have been studied by dielectric relaxation spectroscopy (DRS) over the frequency range 0.2 ≲ ν/GHz ≤ 89 at 25 °C and at concentrations 0.05 ≲ c/mol L-1 ≲ 1. The combination of these measurements with analogous literature data for RbF(aq) and M'Cl(aq) (M' = Li, Na, K, and Cs) made possible a systematic analysis of the hydration of F- and the alkali metal cations. Unlike the other halide ions, F- was found to have a well-defined hydration shell which contains ∼7 water molecules, consistent with the appearance of a "slow"-water mode at ∼10 GHz in the spectra. Limiting total effective hydration numbers (Zt0) for M'F(aq), obtained from the solvent-related modes, did not follow a simple sequence, varying in the order CsF < NaF < RbF < KF. However, it is shown that this anomalous sequence results from subtle variations in the strength of the M'+-OH2 bonding. Thus, it was established that Zib0(M'+) values, corresponding to the numbers of strongly ("irrotationally") bound (ib) water molecules around the cations, do vary with charge density in the order Li+ ≫ Na+ > K+ > Rb+ > Cs+. It was also found that Zs0(M'+), the number of moderately bound ("slow") water molecules, varied in the same order: K+ > Rb+ > Cs+. However, the presence of ib water molecules in the hydration shells of Li+ and Na+ attenuates their further interaction with surrounding water molecules such that Zs0(M'+) ≈ 0 for both ions.

Monoolein: a magic lipid?

During the last few years, there has been an extraordinary increase in publications describing the manifold applications of monoolein, one of the most important lipids in the fields of drug delivery, emulsion stabilization and protein crystallization. In this perspective we present a comprehensive review of the phase behavior of this 'magic lipid'. An account of various mesophases formed in the presence of water and a collection of formulae for the calculation of their nano-structural parameters are provided. Effects of chemical and biological molecules including lipids, detergents, salts, sugars, proteins and DNA on the classical behavior are also discussed. Physicochemical triggers such as, temperature, pressure and shearing modulate the phase behavior of monoolein self assemblies that are covered in subsequent sections. Finally the growing applications of monoolein in various fields are also reported.

Scandium sulfate complexation in aqueous solution by dielectric relaxation spectroscopy.

Ion association in aqueous solutions of scandium sulfate has been investigated at 25 degrees C and at concentrations from 0.01 to 0.8 M by broadband dielectric spectroscopy over the frequency range 0.2

Ion association and hydration in aqueous solutions of LiCl and Li2SO4 by dielectric spectroscopy.

A systematic study of the dielectric relaxation spectra of aqueous solutions of LiCl and Li2SO4 has been made at solute concentrations of 0.05 < or = c/M < or = 1.0 and 2.0, respectively, and over a wide range of frequencies (0.2 < or = nu/GHz < or = 89) at 25 degrees C. The spectra were best described by a superposition of four Debye processes, consisting of the two well-known water relaxations at ca. 8 and 0.5 ps and two ion-pair contributions at ca. 200 and 20 ps, corresponding to the presence of double-solvent-separated (2SIP) and solvent-shared (SIP) ion pairs, respectively. Consistent with spectroscopic studies, no contact ion pairs were detected over the studied concentration range. The overall ion association constants K(o)(A) obtained were in good agreement with literature data for both salts. Detailed analysis of the solvent relaxations indicated that Li+ has a significant second solvation sheath although there were differences between the effective hydration numbers obtained from LiCl and Li2SO4, which might arise from competition for the solvent from the anions.

Hydration of tetraphenylphosphonium and tetraphenylborate ions by dielectric relaxation spectroscopy.

A systematic study of the dielectric relaxation spectra of aqueous solutions of NaBPh4 and Ph4PCl has been made at solute concentrations of 0.02 < or = c/M < or = 0.82 and 0.20, respectively, and over a wide range of frequencies (0.2 < or = nu/GHz < or = 89) at 25 degrees C. The spectra were best described by a superposition of four Debye processes, consisting of a very small ion-pair contribution with an average relaxation time of about 300 ps, a "slow"-water relaxation at 17 ps, and two bulk-water relaxations at 8 ps and 0.25 ps, respectively. The slow-water process has been assigned to the presence of a sheath of water molecules surrounding BPh4- and Ph4P+, whose structure has been enhanced by its proximity to the bulky hydrophobic phenyl rings. A structure-making effect on the remaining solvent water can also be observed at low concentrations. More importantly, BPh4- and Ph4P+ show almost identical hydration characteristics, which provides indirect support for the use of the tetraphenylphosphonium tetraphenylborate reference electrolyte assumption in deriving single-ion thermodynamic properties.

Is there an anionic Hofmeister effect on water dynamics? Dielectric spectroscopy of aqueous solutions of NaBr, NaI, NaNO3, NaClO4, and NaSCN.

A systematic study of the dielectric relaxation spectra of aqueous solutions of NaBr, NaI, NaNO(3), NaClO(4), and NaSCN has been made over a wide range of frequencies (0.2 < or = nu/GHz < or = 89) and solute concentrations (0.05 < or = c/M < or = 1.5) at 25 degrees C. The spectra could be adequately described by a single Cole-Cole (CC) process, symmetrically broadened relative to that of pure water. However, similar quality fits were also obtained with a three-Debye-process (3D) model consisting of a small ion-pair contribution at lower frequencies and two solvent relaxations at higher frequencies. Assuming the ions to be solvent separated, the 3D model provided estimates of their association constants and their rate constants for formation and dissociation. The bulk water relaxation times obtained from both models showed almost no dependence on the nature of the anion. Nevertheless, there were subtle differences in the concentration dependences of the relaxation times which correlated with some, but not all, of the anion properties that are believed to be relevant for explaining the anionic Hofmeister series.

Comparison of fracture tests of denture base materials.

STATEMENT OF PROBLEM: Clinical studies have shown midline fracture to be a common problem in dentures. In order to evaluate the resistance of denture base resins against fracture, not only impact strength measurements but also fracture toughness tests should be performed. PURPOSE: The aim of this study was to determine the fracture toughness of denture base resins and to compare the results with impact strength measurements. MATERIALS AND METHODS: Seven heat-polymerized denture base resins were chosen for the study: 5 high impact (GC Luxon, Injectall IPF HI-I, Ivocap Plus, Lucitone 199, and Trevalon HI) and 2 conventional (Major Base 2 and Probase Hot). Three series of 12 specimens were used for the Charpy impact test (specimen dimensions: 80 x 10 x 4 mm, notch depth: 2 mm) and 2 Izod impact tests (specimen dimensions: 50 x 6 x 4 mm; notch depth: 1.2 mm for the first series, 3.4 mm for the second series). The maximum stress intensity factor (K(I,max)) (MPa.m(1/2)) and the work of fracture (WOF) (kJ/m2) were measured for 8 specimens in a fracture toughness test (specimen dimensions: 40 x 8 x 4; notch depth: 3.2 to 3.3 mm). A 1-way ANOVA with a post-hoc Tukey-Kramer test (alpha=.05) was used to compare the data. RESULTS: The results achieved by the different materials and the rankings varied, depending on which parameter was considered. For example, the 1.2-mm Izod impact strength of Ivocap Plus (2.49 +/- 0.24 kJ/m2) was not significantly different from GC Luxon (2.64 +/- 0.15 kJ/m2) and significantly higher than Major Base 2 (1.99 +/- 0.23 kJ/m2) and Probase Hot (1.79 +/- 0.20 kJ/m2) (P<.001). On the other hand, the Charpy impact strength of Ivocap Plus (1.47 +/- 0.16 kJ/m2) was almost half the value of GC Luxon (2.85 +/- 0.05 kJ/m2) and not significantly different from Major Base 2 (1.36 +/- 0.03 kJ/m2) and Probase Hot (1.36 +/- 0.09 kJ/m2). In the fracture toughness test, the K(I,max) values of GC Luxon (2.63 +/- 0.09 MPa.m(1/2)), Lucitone 199 (2.53 +/- 0.08 MPa.m(1/2)), Trevalon HI (2.56 +/- 0.13 MPa.m(1/2)), and Ivocap Plus (2.41 +/- 0.04 MPa.m(1/2)) were not significantly different. Among all parameters, the WOF value appeared to be the test that allowed a clear differentiation between the products, placing Probase Hot (0.27 +/- 0.03 kJ/m2) and Major Base 2 (0.38 +/- 0.03 kJ/m2) on a low level, Injectall IPF HI-I (0.63 +/- 0.17 kJ/m2) on an intermediate level, Ivocap Plus (1.12 +/- 0.06 kJ/m2) on a medium-high level, and Lucitone 199 (1.41 +/- 0.06 kJ/m2), GC Luxon (1.50 +/- 0.17 kJ/m2), and Trevalon HI (1.58 +/- 0.07 kJ/m2) on a high level. CONCLUSION: Specimen geometry and testing configuration influenced the impact strength measurements. The fracture toughness method seems to be more suitable than impact strength measurements to demonstrate the effects of resin modifications. The differences between conventional and so-called "high-impact" denture base resins are more clearly demonstrated with fracture toughness measurements.