Manipulating chiral spin transport with ferroelectric polarization.

A magnon is a collective excitation of the spin structure in a magnetic insulator and can transmit spin angular momentum with negligible dissipation. This quantum of a spin wave has always been manipulated through magnetic dipoles (that is, by breaking time-reversal symmetry). Here we report the experimental observation of chiral spin transport in multiferroic BiFeO3 and its control by reversing the ferroelectric polarization (that is, by breaking spatial inversion symmetry). The ferroelectrically controlled magnons show up to 18% modulation at room temperature. The spin torque that the magnons in BiFeO3 carry can be used to efficiently switch the magnetization of adjacent magnets, with a spin-torque efficiency comparable to the spin Hall effect in heavy metals. Utilizing such controllable magnon generation and transmission in BiFeO3, an all-oxide, energy-scalable logic is demonstrated composed of spin-orbit injection, detection and magnetoelectric control. Our observations open a new chapter of multiferroic magnons and pave another path towards low-dissipation nanoelectronics.

Problem-Based Learning - An Overview.

The main objective of Problem-Based Learning (PBL) is to develop problem-solving skills, collaborative learning skills, self-directed learning skills, communication skills, deeper learning skills, lifelong learning skills, and better retention in the students to equip them better in their professional careers. Unlike the traditional curriculum which is mainly based on didactic lectures, PBL is based on a group of students working on a problem and solving it. PBL is a promising teaching and learning tool that can be adopted in all fields, especially in Medical and Dental curricula.

Fluoride content in various types of tea used by tea stalls in Salem district - An in vitro cross sectional study.

Background: Tea leaves are natural rich source of fluoride and are known as fluorine absorbants. It is consumed on large scale in India and thus needs to be monitored for its daily fluoride consumption by customers. Tea manufacturers should mention fluoride concentrations on the packages to avoid overdose through unknown consumption by consumers. Objectives: To detect the levels of fluoride in tea at different periods of boiling and to compare the fluoride levels in various brands of tea at different periods of boiling. Methodology: A survey was conducted in 25 tea stalls of Salem on the type of tea and time of boiling black tea. The five most common brands of tea will bought for the study. The stainless-steel vessel will be used in the methodology for boiling tea. Mettur water will be used for the preparation of black tea and 1 g of tea leaves to 100 ml of hot (~95°C) deionized water (1% w/v tea infusion) and allowed the mixture to stand for 5 min in a glass beaker. After 5 min, the infusions were filtered and again left standing until they are cooled to room temperature. All fluoride measurements will be completed within 4 h of the preparation of the infusion. About 2 min and 4 min boiling will be followed. The fluoride present in each brand of tea will be calculated from black tea prepared using 2-(parasulfophenylazo)-1,8-dihydroxy-3,6-naphthalene-disulfonate (SPADNS) calorimetric method. Results: The distribution of mean score of fluoride level in tea powders available in tea shops of Salem when boiled in distilled water was (559.00 ± 112.12). The mean score of fluoride level in tea powders available in tea shops of Salem boiled in Mettur water was (689.05 ± 116.34). To test the significance of difference between the average fluoride in tea powders available in tea shops of Salem when boiled in distilled water and Mettur water, the independent t-test was used. the P value is <0.05, and hence, it is found that there is significant difference between the average fluoride in tea powders available in tea shops of Salem boiled in distilled water and Mettur water. Conclusion: Thus, the study showed tea consists of significant amount of fluoride concentration that is consumed on daily basis. The study also evaluated fluoride concentration in tea preparations using different water. The study shows necessity for regulations of mentioning fluoride concentration on tea packs.

A Cross-Sectional Study to Find the Correlation between the Level of Fluoride in Drinking Water, Dental Fluorosis and Associated Risk Factors- A Original Research.

Background: The present study was conducted to assess the relationship between drinking water fluoride (F) levels, dental fluorosis dental caries, and associated risk factors in the elderly population. Materials and Methods: A cross-sectional analytical study was conducted on 50 patients aged 25-60 years, selected by stratified random sampling from different areas with different levels of naturally occurring F in drinking water. The patients were assessed for dental fluorosis according to WHO basic survey guidelines. The overall oral health status of the patients was assessed by decayed missing filled teeth DMFT index and the bacterial count of saliva was calculated using the Caries Risk Test (CRT). Statistical analysis was done using mean, standard deviation, standard error, Z-test, Mann-Whitney U Test, and Chi-square test. Results: The results of the present study revealed that the prevalence of fluorosis was 24%. The number of patients with dental fluorosis was highest in those who consumed water with high groundwater fluoride levels irrespective of the source of drinking water. Caries prevalence in the study population was about 5.56 ± 1.95. Conclusion: There was a moderate prevalence of fluorosis in patients, and caries prevalence is high in areas below optimal F areas. Caries prevalence and mean DMFT scores were least common in patients with optimal fluoride levels in drinking water and highest in those with below optimal fluoride in drinking water.

Strain-Driven Mixed-Phase Domain Architectures and Topological Transitions in Pb1- x Srx TiO3 Thin Films.

The potential for creating hierarchical domain structures, or mixtures of energetically degenerate phases with distinct patterns that can be modified continually, in ferroelectric thin films offers a pathway to control their mesoscale structure beyond lattice-mismatch strain with a substrate. Here, it is demonstrated that varying the strontium content provides deterministic strain-driven control of hierarchical domain structures in Pb1- x Srx TiO3  solid-solution thin films wherein two types, c/a and a1 /a2 , of nanodomains can coexist. Combining phase-field simulations, epitaxial thin-film growth, detailed structural, domain, and physical-property characterization, it is observed that the system undergoes a gradual transformation (with increasing strontium content) from droplet-like a1 /a2  domains in a c/a domain matrix, to a connected-labyrinth geometry of c/a domains, to a disconnected labyrinth structure of the same, and, finally, to droplet-like c/a domains in an a1 /a2  domain matrix. A relationship between the different mixed-phase modulation patterns and its topological nature is established. Annealing the connected-labyrinth structure leads to domain coarsening forming distinctive regions of parallel c/a and a1 /a2  domain stripes, offering additional design flexibility. Finally, it is found that the connected-labyrinth domain patterns exhibit the highest dielectric permittivity.

Exploring the Pb1- x Srx HfO3 System and Potential for High Capacitive Energy Storage Density and Efficiency.

The hafnate perovskites PbHfO3 (antiferroelectric) and SrHfO3 ("potential" ferroelectric) are studied as epitaxial thin films on SrTiO3 (001) substrates with the added opportunity of observing a morphotropic phase boundary (MPB) in the Pb1- x Srx HfO3 system. The resulting (240)-oriented PbHfO3 (Pba2) films exhibited antiferroelectric switching with a saturation polarization ≈53 µC cm-2 at 1.6 MV cm-1 , weak-field dielectric constant ≈186 at 298 K, and an antiferroelectric-to-paraelectric phase transition at ≈518 K. (002)-oriented SrHfO3 films exhibited neither ferroelectric behavior nor evidence of a polar P4mm phase . Instead, the SrHfO3 films exhibited a weak-field dielectric constant ≈25 at 298 K and no signs of a structural transition to a polar phase as a function of temperature (77-623 K) and electric field (-3 to 3 MV cm-1 ). While the lack of ferroelectric order in SrHfO3 removes the potential for MPB, structural and property evolution of the Pb1- x Srx HfO3 (0 ≤ x < 1) system is explored. Strontium alloying increased the electric-breakdown strength (EB ) and decreased hysteresis loss, thus enhancing the capacitive energy storage density (Ur ) and efficiency (η). The composition, Pb0.5 Sr0.5 HfO3 produced the best combination of EB  = 5.12 ± 0.5 MV cm-1 , Ur  = 77 ± 5 J cm-3 , and η = 97 ± 2%, well out-performing PbHfO3 and other antiferroelectric oxides.

A New Route to Azadithiolato Complexes.

The reaction of [(MeC(5)H(4))(2)Ti(SH)(2)] with cyclic imines with the formula (CH(2)NR)(3) gives 2-aza-1,3-dithiolato chelate complexes [(MeC(5)H(4))(2)Ti{(SCH(2))(2)NR}] (1, R = Ph; 2, R = Me; 3, R = CH(2)Ph). These compounds demonstrate that azadithiolate ligands can exist on mononuclear metal centers. The complexes were characterized by (1)H NMR spectroscopy, ESI-mass spectrometry, and X-ray crystallography. Variable-temperature (1)H NMR studies reveal that the dithiolate ligands undergo ring inversion like other dithiatitanacyclohexanes. Treatment of [(MeC(5)H(4))(2)Ti{(SCH(2))(2)NPh}] (1) with [Fe(benzylideneacetone)(CO)(3)] afforded [Fe(2){(SCH(2))(2)NPh}(CO)(6)] in good yield.

Perception, Knowledge, and Attitude of Problem-based Learning among Dental College Students in India: A Closed-ended Questionnaire Study.

CONTEXT: Problem-based learning (PBL) is mostly a student-centered learning method, and it is a new method used in medical and dental education all over the world. In India, PBL is a part of the learning process sparingly followed. Contrary to other institutions, PBL has been introduced in dental curriculum along with the traditional curriculum very recently. AIM: The aim of this study was to evaluate the newly introduced PBL curriculum among the dental students using a closed-ended questionnaire on a five-point scale. MATERIALS AND METHODS: The questionnaire on PBL was prepared in Google Forms, comprising 22 closed-ended questions on a five-point Likert scale, ranging from strongly disagree (1) to strongly agree (5). We carried out a pilot study in 10% of the target population to check validity and feasibility. Final study was conducted in the targeted population of 185 dental students who had undergone PBL sessions. RESULTS: The responses for the questionnaire thus received from the students were compiled and analyzed using Google Forms software. Overall rating of PBL by the respondents was as follows. The majority of the student's responses were agreed with 54.6% and a significant number of students strongly agreed with PBL at 33%. CONCLUSIONS: This study shows the responses of the students on aspects of group learning, imparting content knowledge, improvement of group skills, improvement of communication skills, and carrying out self-directed learning within the Indian context of dental health education.

Manipulating magnetoelectric energy landscape in multiferroics.

Magnetoelectric coupling at room temperature in multiferroic materials, such as BiFeO3, is one of the leading candidates to develop low-power spintronics and emerging memory technologies. Although extensive research activity has been devoted recently to exploring the physical properties, especially focusing on ferroelectricity and antiferromagnetism in chemically modified BiFeO3, a concrete understanding of the magnetoelectric coupling is yet to be fulfilled. We have discovered that La substitutions at the Bi-site lead to a progressive increase in the degeneracy of the potential energy landscape of the BiFeO3 system exemplified by a rotation of the polar axis away from the 〈111〉pc towards the 〈112〉pc discretion. This is accompanied by corresponding rotation of the antiferromagnetic axis as well, thus maintaining the right-handed vectorial relationship between ferroelectric polarization, antiferromagnetic vector and the Dzyaloshinskii-Moriya vector. As a consequence, La-BiFeO3 films exhibit a magnetoelectric coupling that is distinctly different from the undoped BiFeO3 films.

Management and Disposal of Mercury and Amalgam in the Dental Clinics of South India: A Cross-Sectional Study.

CONTEXT: Dental offices are known to be one of the largest users of inorganic mercury in the preparation of amalgam-a restorative material which, if not handled and disposed through scientific methods, can pose grave threats to the biosphere. AIMS: The objective of this study was to assess and record the mercury management and disposal strategies of dental practitioners belonging to the two South Indian states, Kerala and Tamil Nadu. SUBJECTS AND METHODS: A questionnaire regarding the usage and disposal of a filling material containing mercury (amalgam) was designed and distributed online. The 150 dental practitioners partaking in this study responded anonymously. RESULTS: The results were statistically analyzed using chi-square test and the P value was evaluated. The usage of amalgam was correlated with the age of the practitioner and the nature of practice and it was found to be statistically significant. The number of fillings was correlated with the years of practice and locality of the clinic, which were found to be statistically significant. CONCLUSIONS: This study showed that mercury was widely preferred and utilized even today as a restorative material by dentists and dental specialists, despite the availability of other alternative strategies. Only a minor section of practitioners were found to be aware of the global changes in the guidelines pertaining to the handling and disposal of amalgam. We feel that Safe Mercury Amalgam Removal Technique, amalgam safety rules, and amalgam-free practice should be a part of the academic curriculum and continuing dental education.

Comparative Evaluation of Dental and Skeletal Fluorosis in an Endemic Fluorosed District, Salem, Tamil Nadu.

BACKGROUND: High levels of fluoride in the drinking water, especially ground water, results in skeletal fluorosis which involves the bone and major joints. This study was conducted to assess the prevalence of skeletal fluorosis to compare with dental fluorosis in an endemically fluorosed population in the District of Salem, Tamil Nadu. MATERIALS AND METHODS: Institutional ethical clearance was obtained. A total of 206 patients who reported to the Department of Hematology for blood investigations were the participants in this study. Age, sex, place, weight, height, dental fluorosis, and skeletal complaints were noted down. Body mass index was calculated, and statistical analysis was performed. RESULTS: Dental fluorosis was present in 63.1% and absent in 36.9% of the samples reported. Skeletal fluorosis was present in 24.8% and was absent in 75.2%. A large number of the patients had knee pain and difficulty in bending. Chi-square test was used for statistical analysis. Skeletal fluorosis and age were compared and P value was 0.00 and was significant. Dental fluorosis and skeletal fluorosis were compared and P value was found to be 0.000 and significant. DISCUSSION AND CONCLUSION: There is a need to take measures to prevent dental and skeletal fluorosis among the residents of Salem district. Calcium balance should be maintained, and fluoride intake should be minimized to reduce the symptoms. The government should provide water with low fluoride level for drinking and cooking. Once the symptoms develop, treatment largely remains symptomatic, using analgesics and physiotherapy.

The effect of fluorosis on human teeth under light microscopy: A cross-sectional study.

BACKGROUND: Fluoride is needed for the normal development of bone and teeth; in high levels, it affects developing teeth and bone. Dental fluorosis (DF) is caused by ingestion of excess fluoride mainly through drinking water. AIM: The present study aims to observe and understand the histological changes of fluorosed teeth under light microscope (LM). MATERIALS AND METHODS: Teeth which were indicated for extractions for orthodontic or periodontal problems were selected. Thirty extracted teeth were selected with varying degrees of DF based on modified Dean's fluorosis index. Ground sections of these teeth were prepared and the sections were studied under binocular LM. Photomicrographs were taken under high power objective using 15 megapixels Nikon camera. RESULTS AND CONCLUSION: Qualitative histologic changes in different grades of fluorosed teeth were evaluated in enamel, dentin, cementum and between their junctions. Fluoride interacts with enamel in both mineral phases and organic macromolecules by strong ionic and hydrogen bonds resulting in incomplete crystal growth at prism peripheries. This presents as hypomineralization of enamel and dentin, increased interglobular dentin, increased secondary curvatures and changes in cementum such as diffuse cementodentinal junction and increased thickness of Tomes' granular layer. Changes in the structure of the teeth with Dean's index below 2 and teeth with Dean's index of 2 and above were compared using Chi-square test. P value was found to be highly significant being 0.00047. Many of the features of dental fluorosis seen in the present study under light microscope are comparable to those results studied under specialized microscopes.

Medical ethics.

Mutual trust and relationship between doctors and patients is an important factor of treatment plan. Changing trends in medical field does affect this relationship. This article reviews the basic code of conduct for every medical practitioner.

A comparison of the sealing ability of various temporary restorative materials to seal the access cavity: An in vitro study.

INTRODUCTION: In multiple-appointment root canal treatment, a temporary filling material is used to seal the access cavity between visits. The primary function of this material is to prevent the contamination of the root canal system by fluids, organic debris, and bacteria from the oral cavity. MATERIAL AND METHODS: A total of fifty extracted noncarious unrestored human maxillaryanterior teeth with intact crowns and roots were selected The canals were instrumented using stepback technique and sodium hypochlorite (3%) and hydrogen peroxide (3%) were used as irrigants for each specimen alternatively. The coronal two-thirds of each canal were flared using Gates-Glidden drills up to no. 3 size and obturated with Gutta-percha using zinc oxide-eugenol (ZnOE) as sealer. The teeth were then randomly selected and divided into six groups out of which four were experimental groups and two control groups. The teeth were then immersed in 2% methylene blue dye solution for 3 days. All sealing materials and Gutta-percha were gently removed from the walls of the canal, and the entire circumference of the canal wall examined for dye penetration. RESULTS: The lowest mean leakage was in the Fermit-N group followed by Cavit-W, ZnOE, intermediate restorative materials (IRM), and positive control. CONCLUSION: Fermit-N showed better sealing ability compared to cavit, ZnOE and IRM.

A non-invasive study to estimate and compare salivary sialic acid level as tumor marker in patients with pre-cancer and oral cancer.

INTRODUCTION: Sialic acids are important terminal sugars of the carbohydrate chains of cell membrane glycoproteins and glycolipids. The progressive rise in total sialic acid (TSA) levels has been significantly associated with tumor progression and metastasis. MATERIALS AND METHODS: Samples of 2 ml of unstimulated whole saliva were collected from 20 healthy patients, and 20 cases of histopathologically confirmed oral pre-cancer patients and 20 cases of histopathologically confirmed oral squamous cell carcinoma (OSCC) patients, using the method of Navazesh. Estimation of total sialic acid was done by the histochemical method of Yao et al. RESULTS: The study revealed significantly elevated total sialic acid (TSA) levels in the saliva of oral precancer and OSCC patients, yielding a mean value of 59.75 ± 7.29 mg/dl and 204.85 ± 60.38 mg/dl, respectively, against the mean value of 21.65 ± 5.71 mg/dl of the healthy controls. Also, high total sialic acid (TSA) levels in the well-differentiated squamous cell carcinoma cases were appreciable to those of moderately differentiated ones. DISCUSSION AND CONCLUSION: The result suggests the correlation of elevated salivary TSA levels with the progression of OSCC. In conclusion, the study indicates that the glycoprotein metabolism is significantly altered in the saliva of patients, with both oral pre-cancer and OSCC.

The prevalence of dental fluorosis and its associated factors in Salem district.

CONTEXT: There are various regions in India that have high levels of fluoride in drinking water sources. Many people residing in such places suffer from dental fluorosis (DF). AIMS: To evaluate the prevalence of DF in children residing in Salem and also to find any correlation between DF and other related factors. MATERIALS AND METHODS: One school from each block of Salem (total 21 blocks) was selected for the study. A single examiner had evaluated untreated caries, lesions, and DF (for permanent anterior teeth and molars) using the Dean's fluorosis index, in all children. Water fluoride level determination at each school was done using the Tamil Nadu Water Fluoridation and Drainage Board field kit. Other factors that may have contributed to DF were assessed using a questionnaire, which was provided to each student. The data obtained were statistically analyzed using the SPSS software version 11.5. STATISTICAL ANALYSIS: Chi-square test was used for statistical analysis. RESULTS: DF was present in 56.9% of the children examined. It was mostly seen in 9 years old (72%) and male (59%) children. A positive correlation was found between the occurrence of DF and the duration of residence in a place with high water fluoride content, consumption of borewell water (64%), the parts per million of fluoride in drinking water, consumption of black tea (59%). However, no correlation was found between DF, dental caries, consumption of milk, or consumption of foods cooked in aluminum vessels. CONCLUSION: There was a correlation between DF and factors such as male gender, bore well water consumption, black tea consumption and the duration of residence in a place with high water fluoride content.

Gorlin-Goltz Syndrome: Case report and literature review.

Gorlin-Goltz syndrome (GGS) is an infrequent multisystemic disease with an autosomal dominant trait, with complete penetrance and variable expressivity, though sporadic cases have been described. This article includes a case report and an extensive review of the GGS with regard to its history, incidence, etiology, features, investigations, diagnostic criteria, keratocystic odontogenic tumor and treatment modalities.

Dental rehabilitation of a child with early childhood caries using Groper's appliance.

The mainstay of pediatric dental practice is the successful esthetic rehabilitation of a preschooler with advanced carious lesions. Loss of masticatory efficiency, compromised esthesis, mispronunciation of labiodentals sounds, and development of abnormal oral habits are compromises arising due to the loss of primary anterior teeth at an early age either due to trauma or due to caries. Parental desire is the most decisive factor for the placement of an anterior esthetic appliance. This unique case report highlights the fabrication of simple, Groper's appliance in a 5-year-old child with early childhood caries.

Surgical management of a large cleft palate in a Pierre Robin sequence: A case report and review of literature.

Pierre Robin syndrome or Pierre Robin sequence (PRS) is a congenital etiologically heterogeneous condition presenting with various malformations. Here we are reporting the surgical management of an 18-month-old female baby who was referred from Department of Pediatrics with a complaint of a large cleft palate. She was taken up for palatoplasty with consent for elective tracheostomy. After genetic evaluation, the authors conclude that the presented case was a PRS in isolation with mild cardiac anomalies and an inferiorly placed hypoplastic epiglottis. Patient should be followed up and growth modifications of the jaws should be done.

Prevalence of early childhood caries and its risk factors in 18-72 month old children in Salem, Tamil Nadu.

BACKGROUND: Early childhood caries (ECC) is one of the most common dental diseases among the preschoolers, leading to suboptimal health. A study was planned to evaluate the prevalence of ECC in preschool children in the age group between 18 and 72 months and its relationship with parent's education and socioeconomic status of the family. MATERIALS AND METHODS: This cross-sectional study was conducted among 2771 children selected randomly, in the age group 18-72 months and attending playschools and primary schools in urban, semi-urban, and rural areas of Salem, Tamil Nadu. A modified Winter et al. questionnaire and a proforma were used for collecting information on each child. The completed questionnaire and proformas were statistically analyzed and evaluated. The statistical analysis was done using Student's t-test and analysis of variance (ANOVA) to obtain mean values. RESULTS: The prevalence of ECC in Salem was 16% with a mean dfs of 5.23 ± 1. Prevalence was high among the children of low socioeconomic status group and the children of working mothers, with a mean dfs of 10.47. CONCLUSION: The prevalence of ECC was 16% in Salem, Tamil Nadu. ECC was seen more in children of working mothers, lower parental education, and lower socioeconomic groups.