Explore the vast range of titles available.

The formation of materials with negative thermal expansion (NTE) based on a phase transition-type mechanism (NTE-II) in 50 T–x (temperature–composition) RF[sub.3]-R’F[sub.3] (R = La-Lu) systems out of 105 possible is predicted. The components of these systems are “mother” RF[sub.3] compounds (R = Pm, Sm, Eu, and Gd) with polymorphic transformations (PolTrs), which occur during heating between the main structural types of RF[sub.3]: β-(β-YF[sub.3]) → t-(mineral tysonite LaF[sub.3]). The PolTr is characterized by a density anomaly: the formula volume (V[sub.form]) of the low-temperature modification (Vβ-) is higher than that of the high-temperature modification (Vt-) by a giant value (up to 4.7%). In RF[sub.3]-R’F[sub.3] systems, isomorphic substitutions chemically modify RF[sub.3] by forming R[sub.1−x]R’[sub.x]F[sub.3]solid solutions (ss) based on both modifications. A two-phase composite (β-ss + t-ss) is a two-component NTE-II material with adjustable parameters. The prospects of using the material are estimated using the parameter of the average volume change (ΔV/V[sub.av]). The V[sub.av] at a fixed gross composition of a system is determined by the β-ss and t-ss decay (synthesis) curves and the temperature T. The regulation of ΔV/V[sub.av] is achieved by changing T within a “window ΔT”. The available ΔT values are determined using phase diagrams. A chemical classification (ChCl) translates the search for NTE-II materials from 15 RF[sub.3] into an array of 105 RF[sub.3]-R’F[sub.3] systems. Phase diagrams are divided into 10 types of systems (TypeSs), in four of which NTE-II materials are formed. The tables of the systems that comprise these TypeSs are presented. The position of T[sub.trans] of the PolTr on the T scale for a short quasi-system (QS) “from PmF[sub.3] to TbF[sub.3]” determines the interval of the ΔT[sub.trans] offset achievable in the RF[sub.3]-R’F[sub.3] systems: from −148 to 1186 ± 10 °C. NTE-II fluoride materials exceed known NTE-II materials by almost three times in this parameter. Equilibrium in RF[sub.3]-R’F[sub.3] systems is established quickly. The number of qualitatively different two-component fluoride materials with the giant NTE-II can be increased by more than ten times compared to RF[sub.3] with NTE-II.

The addition of tin to mouth rinses is, at least in vitro, a promising strategy for symptomatic therapy of dental erosion. The aim of this study was to evaluate the in situ efficacy of an experimental tin-containing fluoride solution on erosive tissue loss in human enamel and dentine. The study was a three-cell (7 days each) crossover design involving eight healthy participants. Samples were mounted on buccal shields of mandibular mouth appliances, which were worn for 24 h except during meals and drinks. Specimens were demineralised extraorally with 0.05 M citric acid (pH 2.3) for 6 × 5 min daily and were treated with test solutions intraorally once per day for 30 s after the first demineralisation. Three solutions were used: placebo (negative control), a commercially available tin- and fluoride-containing (SnF 2 ) mouth rinse (positive control, 409 ppm Sn 2+ , 250 ppm F − , pH 4.2) and an experimental solution (pH 4.5) containing 1,900 ppm Sn 2+ (SnCl 2 ) and 1,000 ppm F − (AmF/NaF). Tissue loss (micrometre) was determined profilometrically. In enamel, tissue loss was 54.8 ± 8.6 in the placebo, 24.5 ± 14.4 in the positive control and 9.7 ± 4.1 in the experimental solution group. The respective values for dentine were 48.5 ± 13.0 in the placebo, 32.8 ± 9.6 in the positive control and 26.2 ± 6.7 in the experimental solution group. The experimental solution was notably effective for enamel but was less effective for dentine. The positive control solution was less effective than the experimental solution; its effects for enamel and dentine were similar.

This study aimed to evaluate the influence of the use of remineralizing agents on the tensile bond strength. The study sample consisted of 80 recently extracted molars, which were randomly divided into four experimental groups (n = 20): groups FG1 and FG30, in which fluoride varnish was used, and groups RG1 and RG30, in which Recaldent tooth mousse was used. The mesiobuccal surfaces served as experimental, and distobuccal as control (n = 80). Brackets were bonded to both surfaces and were submitted to a tension test at different time intervals (T1 and T30). Tensile bond strength (TBS) and the amount of adhesive remnant (ARI) were assessed. A statistically significantly lower mean of TBS compared to the control group was found only in the FG1 group ( p  < 0.001), and no significant difference was found between the other groups. The FG1 group showed significantly higher ARI scores ( p  < 0.001) compared to the control group. No significant difference was found between the other groups. In conclusion, bonding brackets one day after applying fluoride varnish significantly reduced the TBS, but after 30 days it was set back to an optimal value. The use of Recaldent before orthodontic treatment had no adverse effect.

Casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) slows the progression of caries and remineralizes enamel subsurface lesions. The aim of this study was to determine the ability of CPP-ACP to increase the incorporation of fluoride into plaque and to promote enamel remineralization in situ. Randomized, double-blind, cross-over studies involved mouthrinses and dentifrices containing CPP-ACP and fluoride. The mouthrinses were used for 60 sec, three times/day for 5 days, and supragingival plaque was collected and analyzed for F. The dentifrices were rinsed as a water slurry for 60 sec four times/day for 14 days in an in situ model. The addition of 2% CPP-ACP to the 450-ppm-F mouthrinse significantly increased the incorporation of fluoride into plaque. The dentifrice containing 2% CPP-ACP produced a level of remineralization similar to that achieved with a dentifrice containing 2800 ppm F. The dentifrice containing 2% CPP-ACP plus 1100 ppm F was superior to all other formulations.

A new modification of PbF(IO[sub.3]) has been obtained as single crystals from hydrothermal synthesis, alongside the known centrosymmetric, Pb(IO[sub.3])[sub.2], as a second phase. Measured with the Kurtz-Perry SHG method, the new crystals are phase-matchable for YAG:Nd laser radiation and demonstrate strong SHG output. According to an X-ray diffraction analysis conducted on a single crystal at low temperature, the new crystals appear monoclinic, of space group Pn, as opposed to the known orthorhombic modification of the PbF(IO[sub.3]), of space group Iba2. The new crystals were also measured at room temperature, showing an orthorhombic disordered variant of the new phase (space group C2ma, standard Abm2). This variant presents an \"average structure\" with the mirror plane in the group. The low-temperature X-ray single-crystal experiment allowed us to find the correct structural model, where the mirror plane was found as a twin element in the real monoclinic Pn structure. A careful crystal chemical analysis led to a whole family of nonlinear optical crystals with a common formula, AX(IO[sub.3]), A = Bi, Ba, Pb, X = O, F, (OH), currently counting six representatives, including the well-known BiO(IO[sub.3]). All of them possess common central cationic layers similar to those known in Aurivillius-type phases, with anionic iodate layers attached above and below these layers instead of the perovskite-like, or halogens. The structure-property relationships are discussed with respect to the important role of the large cations: Pb[sup.2+], Bi[sup.3+] or Ba[sup.2+]. A number of iodates with similar structures are also analyzed.

Single-phase samples of the Ba[sub.1−x]Ce[sub.x]F[sub.2+x] solid solution (x = 0.3–0.4) were synthesized by directional crystallization in the form of single crystals and by co-precipitation from aqueous nitrate solutions using potassium fluoride as a fluorinating agent in the form of nanopowders. The cathodoluminescence of the pressed powder samples was studied in comparison with the BaF[sub.2]: Ce single crystals in 250–460 nm (2.7–5 eV) spectral range upon excitation by an electron accelerator. The cathodoluminescence spectra of the samples revealed a wide band in the range of 3.0–4.0 eV, which consists of two typical components of Ce[sup.3+] with decay time 23 ns in the case of single crystals and three decay times 27 ns, 140–170 ns, and ~600 ns in the case of pressed powders. The decay time of the short-wavelength component (27 ns) in the case of pressed powders is close to the lifetime of the excited state of the Ce[sup.3+] ion. The developed X-ray phosphors can be applied for embedding in diamonds for diamond–nanoparticle composite preparation.

Surface-fluorinated TiO.sub.2 materials with high 001 facet exposure were prepared by a simple and high-yield preparation procedure. Faceted/fluorinated samples showed a high photocatalytic performance not only in oxidation processes, tested in phenol and methyl orange degradation, but also in a reduction process as Cr(VI) photoreduction. Reaction rates for these materials greatly exceeded the ones obtained for materials prepared without fluorine addition and for commercial TiO.sub.2 Degussa (Evonik) P25 used as reference photocatalyst. A broad characterisation of the samples allowed us to estimate the percentages of different facets and the amount and form in which the fluorine is found on the surfaces. Good photocatalytic behaviour can be ascribed to both high 001 facet exposure and adsorbed fluorine on the photocatalysts surfaces.

Objectives To compare the antibacterial effect of Nanosilver Fluoride varnish (NSF) varnish, P11-4 and Sodium Fluoride (NaF) varnish against salivary Streptococcus mutans (S. mutans) and Lactobacilli . Methods 66 patients aged 10–24 years old were randomly assigned to receive single application of NSF, P11-4 or NaF varnish. Baseline unstimulated saliva samples were collected before the agents were applied and S.mutans and Lactobacilli colony forming units (CFU) were counted. After one, three and six months, microbiological samples were re-assessed. Groups were compared at each time point and changes across time were assessed. Multivariable linear regression compared the effect of P11-4 and NSF to NaF on salivary S. mutans and Lactobacilli log count at various follow up periods. Results There was a significant difference in salivary S. mutans log count after 1 month between P11-4 (B= -1.29, p  = 0.049) and NaF but not at other time points nor between NSF and NaF at any time point. The significant reduction in bacterial counts lasted up to one month in all groups, to three months after using P11-4 and NaF and returned to baseline values after six months. Conclusion In general, the antimicrobial effect of P11-4 and NSF on salivary S. mutans and Lactobacilli was not significantly different from NaF varnish. P11-4 induced greater reduction more quickly than the two other agents and NSF antibacterial effect was lost after one month. Clinical relevance NSF varnish and P11-4 have antimicrobial activity that does not significantly differ from NaF by 3 months. P11-4 has the greatest antibacterial effect after one month with sustained effect till 3 months. The antibacterial effect of NSF lasts for one month. NaF remains effective till 3 months. Trial Registration This trial was prospectively registered on the clinicaltrials.gov registry with ID: NCT04929509 on 18/6/2021.

Background Silver diamine fluoride (SDF) is a simple and non-invasive agent used to arrest early childhood caries (ECC). This study aimed to investigate potential changes to the oral microbiome in children with ECC who were treated with SDF and sodium fluoride (NaF) varnish at three different frequency regimens. Methods Forty-five children ( n  = 15 per group) with ECC were recruited from community-based dental clinics in Winnipeg, Canada into an open-label, parallel-group, randomized clinical trial testing three different treatment frequency regimens of SDF. A total of 195 carious lesions were treated with two applications of 38% SDF and 5% NaF varnish (and assessed over three study visits one month, four months, or six months apart. Dental plaque samples were collected at each visit. Sequencing of the V4-16 S rRNA and ITS1 rRNA genes were used to study the supragingival plaque microbiome. Results Microbial diversity analyses showed no significant differences in the overall microbiome after SDF treatment. However, significant changes in the abundance of specific bacteria and fungi, particularly Lactobacillus spp., Bifidobacterium spp., and Candida spp., were observed after treatment. Furthermore, overabundance of Streptococcus mutans and Candida dubliniensis at baseline was observed in children who had at least one caries lesion not arrested after one SDF application, compared to those who had 100% arrest rates. The overall arrest rates for treated carious lesions were 75.9% at the second visit and 92.8% at the third visit. Arrest rates were higher for all lesions after two applications of SDF with NaF varnish, and applications one month and four months apart had higher arrest rates (95.9% and 98.5%) than six months (81.1%) apart. Conclusions Applications of SDF with NaF varnish were an effective modality for arresting ECC, with higher arrest rates after two SDF applications. No loss of diversity but changes in the abundance of specific bacteria and fungi were observed after SDF treatment. Trial registration ClinicalTrials.gove NCT04054635 (first registered 13/08/2019).