Evaluation of the success rate of pit and fissure sealants on first molars: 12 months follow-up study.

INTRODUCTION: Dental caries by far is the most prevalent concern of the preadolescents and adolescents in dental clinics. Despite the provision of local fluoride, the occlusal surfaces of teeth are susceptible to dental caries. Pit and fissure sealant therapy is a preventive method to decrease dental caries in permanent teeth. The present study aimed to evaluate the success of fissure sealant treatments of first molar teeth, at 3, 6 and 12 months follow-ups. MATERIALS AND METHODS: Sixty-five children were randomly selected. The subjects had already received fissure sealants in the department of public health dentistry. Demographic data, including age and gender, sealant failure and the type of failure were recorded in the relevant checklists. Feigal criteria were used to evaluate the success or failure of fissure sealant treatments. RESULTS: Overall success rate was 74.3% for 1 year. Evaluation of the failure rate showed that at the 3-month interval, 20.6% of the sealants exhibited failure (57.1% due to margin discoloration and 42.9% due to lack of margin adaptation). 28.6% of the sealants failed at the 6-month (75% due to marginal discoloration and 25% due to anatomical form) and 41.2% failed at the 12-month interval (57.1% due to marginal discoloration and 42.9% due to the lack of margin adaptation). CONCLUSION: The total failure rate of fissure sealant failures after 1 year was 27.7%. The most frequent reason for the failure of fissure sealants was marginal discoloration.

DFT study of interaction of Palladium Pdn (n = 1-6) nanoparticles with deep eutectic solvents.

In this study, we use density functional theory (DFT) calculations to investigate the stability, reactivity and interactions of Palladium Pdn (n = 1-6) nanoparticles with ChCl:U and ChCl:EG based deep eutectic solvents (DESs). We find that the DES … Pdn complexes are stabilized by two types of binding; Pdn-X anchoring bonds (X = N atom of -NH2 group in urea and [Cl]- anion) and Pdn…H-X (X = C, N and O) unconventional H-bonds. Analyses based on AIM, NBO, NCI, and EDA suggest that the anchoring bonds, which are electrostatic in nature are stronger than the unconventional H-bonds, which are van der Waals in nature. The Energy Decomposition Analysis reveals that the charge transfer plays an important role in the stability of DES…Pdn complexes. Thermochemical calculations, including enthalpy (ΔH) and free energy (ΔG), indicate that the formation of the DES…Pdn complexes is exothermic and occurs spontaneously. The binding energy (ΔEb) calculations show that the ChCl:U DES has a stronger interaction with the Pdn nanoparticles than their ChCl:EG DES counterparts. On the other hand, a similar trend for the ΔEb, ΔH and ΔG values of the complexes is observed with increasing nanoparticle size of Pdn (DES…Pd5> DES…Pd6> DES…Pd4> DES…Pd3> DES…Pd2> DES…Pd1). Our results show that the magnitude of charge transfer (ΔQ) value in the complexes follow the order observed for the ΔEb values. It is also observed that increasing the energy gap Eg values of the complexes decreases the ΔEb and ΔQ values of the complexes. The reactivity parameter calculations of the complexes show that the Eg and chemical hardness (η) values of ChCl:U…Pdn and ChCl:EG…Pdn complexes decrease with an increase in the nanoparticle size. Additionally, the global electrophilicity index (ω) values of the DES…Pdn complexes increase with an increase in the Pdn nanoparticle size, while no clear trend is seen for the chemical potential (µ) values of the complexes. The urea-based DES shows better suitability towards Pdn nanoparticles than the ethylene glycol-based DES. Overall, such DESs are potentially promising green solvents for nanoparticle synthesis and activity.

Amperometric detection of ultra trace amounts of Hg(I) at the surface boron doped diamond electrode modified with iridium oxide.

Iridium oxide (IrOx) films formed electrochemically on the surface boron doped diamond electrode by potential cycling in the range -0.2 to 1.2V from a saturated solution of alkaline iridium(III) solution. A strongly adherent deposit of iridium oxide is formed after 5-10 potential scans. The properties, stability and electrochemical behavior of iridium oxide layers were investigated by atomic force microscopy and cyclic voltammetry. The boron doped diamond (BDD) electrode modified with electrodeposition of a thin film, exhibited an excellent catalytic activity for oxidation of Hg(I) over a wide pH range. The modified electrode shows excellent analytical performance for Hg(I) amperometric detection. The detection limit, sensitivity, response time and dynamic concentration ranges are 3.2nM, 77nAmuM(-1), 100ms and 5nM-5muM. These analytical parameters compare favorably with those obtained with modern analytical techniques and recently published electrochemical methods.

Disposable amperometric sensor for neurotransmitters based on screen-printed electrodes modified with a thin iridium oxide film.

Potential cycling in the range from -0.2 to +1.2 V is used for the electrodeposition of hydrous iridium oxide films onto a screen-printed electrode from a saturated solution of alkaline iridium(III) solution. The iridium oxide redox couple shows a stable and obvious reversible redox, with the formal potential being pH dependent in the range 1-14. The properties, stability and electrochemical properties of iridium oxide films were investigated by cyclic voltammetry. A modified electrode showed excellent catalytic activity toward the oxidation of neurotransmitters (catecholamines) over a wide pH range (2-8). The electrocatalytic behavior is further exploited as a sensitive detection scheme for adrenaline and dopamine by hydrodynamic amperometry. Under the optimized conditions, the calibration curves are linear in the concentration range 0.1-70 and 0.1-15 microM for dopamine and adrenaline determination, respectively. The detection limit and sensitivity are 30 nM and 30 nA/microM for adrenaline and 15 nM and 80 nA/microM for dopamine. Finally, the analytical performance of the modified electrode was demonstrated for the elimination of interference by uric acid in catecholamines determination when present in a 1000-fold concentration excess.