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Background/Purpose: Mutans streptococci (MS) and lactobacilli (LB) are associated with dental caries, but the acquisition of these organisms in young children with early childhood caries (ECC) and severe early childhood caries (S-ECC) has only been partly described. The purpose of this study was to evaluate the salivary MS and LB levels of preschool children with ECC and S-ECC, and the correlation of MS, LB levels with caries severity. Materials and methods: The study population was comprised of children from 3 to 6 years of age who visited the Pediatric Dental clinic of TCVGH. Oral examinations were performed, and whole unstimulated salivary samples were collected for buffer capacity, MS and LB counts by using commercially available diagnostic kits (CRT bacteria kit). The participants were divided into mild (dmft 9) groups; the salivary microbiological tests and buffer capacity were compared. Results: A total of 72 children with a mean age of 4.5 years participated in this study. The salivary test showed that the higher the salivary MS level the more severe the caries status in children (P = 0.001). There was also a tendency toward a higher salivary LB level in children with more severe caries, but the difference was not significant (P = 0.088). There was no significant correlation between buffer capacity and caries status. Conclusion: The salivary MS level in preschool children was significantly correlated with the severity of early childhood caries. Keywords: Early childhood caries, Severe-early childhood caries, Mutans streptococci, Lactobacilli, Preschool children

Background: The purpose of this study was to evaluate the change in intraoral cariogenic bacteria density after probiotic use in patients with orthodontic treatment, and to compare the impact of probiotics in patients with various caries risk status. Methods: Patients that planned to receive orthodontic treatment were recruited according to this study’s inclusion/exclusion criteria. A probiotic prescription (Lactobacteria 3 mg, Glycobacteria 2 mg) was started one month after the initial orthodontic treatment. Saliva sampling and cultures using a CRT kit (caries risk test) were performed at three time points (T0, T1, T2). Mutans streptococci (MS) and Lactobacilli (LB) density were evaluated and scored using the interpretation chart in the CRT kit to evaluate the change in bacteria density at three time points, to define the high and low caries risk prior to orthodontic treatment, and to evaluate if there were differences in probiotics between the high and low caries risk groups. Results: Thirty-three orthodontic patients were enrolled, twenty-two classified as high caries risk and eleven as low caries risk. After undergoing treatment for one month, the densities of MS and LB increased significantly (p = 0.011, p = 0.001); probiotics for one month decreased the density of MS and LB, but the differences were statistically nonsignificant (p = 0.109, p = 0.109). Patients classified as low risk of caries demonstrated an increase in MS and LB density one month after orthodontic treatment (p = 0.024, p = 0.001), probiotic use did not result in a significant reduction in bacteria density (p = 1000, p = 0.933). In patients with high caries risk, there were no statistically significant changes in MS count between the three time points (p = 0.127); a significant change in LB density occurred at T0–T1 (p = 0.011) only. Conclusions: Supplemental use of probiotic oral tablets during orthodontic treatment aimed at reducing cariogenic bacteria count in saliva did not achieve significant differences, regardless of patients’ risk status for caries.

This study determines the effect of Cu and S content on the structural, luminescence and electrical properties of sol–gel Zn1−xCuxSy films. The dependence of acceptors [interstitial sulfur (Si)] and donors [sulfur vacancy (VS)] on the film composition allows the hole concentration of Zn1−xCuxSy samples to be tuned. It is found that an increased Cu/Zn molar ratio leads to a reduced probability of the formation of VS, which increases the hole concentration. An increase in Cu/Zn and S/Zn molar ratios leads to a significantly increased probability of the formation of Si and a reduced probability of the formation of VS, which significantly increases the hole concentration. Clearly, compensation effects limit the hole concentration of Zn1−xCuxSy samples. The results show that Si is the origin of the p-type conductivity. It is also shown that a suitable choice of composition increases acceptor-like defect formation in Zn1−xCuxSy.

The photoluminescent and electrical properties of N-doped ZnO films fabricated by rf magnetron sputtering under various gas-flow ratios of O 2 /N 2 were examined in this study. The dependence of conduction type on the gas-flow rate of O 2 /N 2 was found. The authors identified a direct correlation between the defect spectral feature and conduction type of N-doped ZnO samples and provided a physical model for producing p-type ZnO. According to these observed results, the authors suggested that p-type conversion of N-doped ZnO may be due to a combined effect of the increased acceptor (substitutional nitrogen in oxygen site, zinc vacancy and interstitial oxygen) density and the decreased donor (oxygen vacancy) density. In addition, synthesis of p-type N-doped ZnO was repeated, suggesting that p-type ZnO can be fabricated with excellent reproducibility by rf magnetron sputtering a ZnO target doped with nitrogen.

We report fabrication of nanostructured Bi2−xSbxTe3 using hydrothermal method followed by cold-pressing and evacuated-and-encapsulated sintering techniques. To obtain lower resistivity, the reaction temperature in the hydrothermal synthesis is investigated, and the effects on the ZT values of Bi2−xSbxTe3 are reported. Both the x = 1.52 and 1.55 samples hydrothermally synthesized at 160°C show lower resistivity than the x = 1.55 sample hydrothermally synthesized at 140°C. However, the power factor is lower for the samples synthesized at 160°C due to the accompanying smaller thermopower. All three samples exhibit remarkably low thermal conductivity of around 0.41 W m−1 K−1 at room temperature. The peak ZT value occurs at 270 K for all three samples, being ZT = 1.75, 1.29, and 1.17 for x = 1.55 (synthesized at 140°C), 1.55 (synthesized at 160°C), and 1.52 (synthesized at 160°C), respectively.

We report fabrication of compacted Bi0.5Sb1.5Te3 nanoplatelets using hydrothermal methods followed by cold pressing and sintering in an evacuated ampoule at various temperature of 300–380 °C. The compacted Bi0.5Sb1.5Te3 sintered at 340 °C has the highest power factor of 11.6 μW/cm·K2 and its thermal conductivity is 0.37 W/m·K at 295 K, which is very low as compared to the typical value of 1 W/m·K. The resulting dimensionless figure of merit ZT is 0.93 at 295 K.

Nanoplatelets of Bi2-xSbxTe3 with nominal composition of x = 1.5 are synthesized using hydrothermal methods. The resulting powders are cold pressed and sintered in an evacuated and encapsulated ampoule at 340°C. Scanning electron microscope atomic force microscope, and transmission electron microscope are used to observe the microstructure of nanoplatelets and consolidated Bi0.5Sb1.5Te3. The consolidated Bi0.5Sb1.5Te3 is in fact nanostructured bulk. The power factor and thermal conductivity are 11.6 μW/cm-K2 and 0.37 W/m K at 295 K, respectively. The small thermal conductivity could be largely attributed to its nanostructured nature of the consolidated bulk. The resulting dimensionless figure of merit ZT is 0.93 at 295 K.

High ZT values of nanostructured Bi2−xSbxTe3 for energy conversion are fabricated by hydrothermal methods followed by cold-pressing and sintering in an evacuated and encapsulated ampoule. We show that the sample with a nominal composition of x = 1.55 exhibits a dimensionless figure of merit ZT = 1.65 at 290 K and 1.75 at 270 K with significant 60–70% improvement of that of the commercial state-of-the-art Bi2Te3 materials around room temperature. The significant ZT improvement arises from the much-reduced thermal conductivity. The low thermal conductivity is mainly due to the increased phonon scattering in the nanostructured materials.