A study of CdS nanoparticle surface states by potential-modulated sub-bandgap spectroscopy

The potential modulation spectrum of CdS Q-dots deposited on an optically transparent electrode has been investigated. A peak at 580 nm, that corresponded to bleaching of a sub-bandgap absorption, was observed. It was established that the peak was related to electron injection into the conduction band of the CdS Q-dots. The mechanism by which the absorption of surface states may be monitored using potential-modulated absorption spectroscopy is outlined.     

Reduction of silver complexes: towards an ever more elaborated insight in the influence of the type of ligand on the reaction rate

The present work deals with the investigation of the electrochemical reduction of silver thiosulphate (1,2-Ag(S₂O₃)₂^3?), thiocyanate (1,3-Ag(SCN)₃^2?) and 1,8-dihydroxy-3,6-dithiaoctane (1,2-Ag(DTO)₂⁺) complexes. The influence of the ligand type on the charge transfer rate is explained by the changing positions of the density distributions of electronic energy levels of the three complexes. The basics for this approach are the theories of energy band models (EBMs). An experimental methodology is developed to determine the energy density distributions. A Ti/TiO₂ substrate, obtained by galvanostatically anodising Ti, is put forward as an appropriate substrate for this investigation, and its semiconducting properties are determined. On this substrate, charge transfer (CT) controlled currents can be measured in a sufficiently large potential domain for the three systems. A method of pre-plating is optimised such that the overall semiconducting character of the substrate is kept during the monitoring of the (quasi-)stationary current/voltage diagrams. The active surface areas, necessary for the calculation of the current density/potential curves, are calculated. The positions of the energy density distributions, obtained by the derivation of the current density/voltage diagrams, of the three complexes, show that thiosulphate exhibits the smallest density of accepting energy levels in the given potential domain. For potentials above 0.5 V vs. SCE, the DTO complex has the largest density of vacant energy levels, but for lower potentials the situation is reversed.     

The use of overdentures in the management of severe hypodontia associated with microdontia: a case report

Dental anomalies may compromise both esthetics and function in the pediatric patient. The present paper reports a rare case associated with both microdontia and severe hypodontia in a 13 year-old girl. The treatment was accomplished through the use of overdentures, which also served as a bite plane to increase vertical dimension of occlusion and as a potential space maintainer.     

Cleaning efficiency of nickel-titanium GT and .04 rotary files when used in a torque-controlled rotary handpiece

This study determined if the cleaning efficiency of nickel-titanium rotary files in an endodontic electric handpiece using a no-torque control setting was superior to that obtained when using the torque-control feature. Fifty extracted human anterior teeth with straight canals were divided into two groups of 20 and two control groups of 5. Canals were instrumented with GT and .04 ProFile nickel-titanium files until a size 35 advanced to working length. Samples were sectioned and the apical 6 mm of the canal was photographed (x20) and projected onto a 3- x 4-foot grid with squares measuring 0.5 inches each. Total debris was the percentage of the number of squares containing debris versus the total number of squares. The teeth in the torque-controlled group showed an average of 24.99% debris versus 15.55% for the teeth in the no-torque group. The difference was not statistically significant; therefore, no difference can be said to exist between the two torque settings in terms of cleaning efficiency.     

Kiefergelenkbeschwerden bei juvenilen Patienten mit rheumatischen Erkrankungen

Fragestellung

Ziel der Untersuchung war es, die Häufigkeit von klinischen Kiefergelenkbeschwerden bei Kindern mit rheumatischen Erkrankungen zu erfassen und Zusammenhänge zwischen dem Stadium der rheumatischen Erkrankung und dem klinischen Bild einer Kiefergelenksymptomatik zu evaluieren.

Material und Methodik

Im Rahmen einer prospektiven Untersuchung wurden die Kiefergelenke von 48 Kindern mit einer rheumatischen Erkrankung klinisch untersucht. Folgende Parameter wurden evaluiert: Knacken, Reibegeräusche, Druckdolenzen, Dauer der rheumatischen Erkrankung sowie die Anzahl der betroffenen peripheren Gelenke. Das Stadium der rheumatischen Erkrankung wurde mit Hilfe der Steinbrocker-Klassifikation erfasst.

Ergebnisse

Insgesamt wiesen 26 Patienten (54,17%) eines oder mehrere der o. g. Kiefergelenksymptome auf. Der Chi-Quadrat-Test ergibt keine signifikanten Zusammenhänge zwischen dem Grad der Steinbrocker-Klassifikation und dem Auftreten pathologischer Befunde am Kiefergelenk. Eine erhöhte Anzahl der von der rheumatischen Erkrankung betroffenen Gelenke führt nicht zu einem signifikanten Anstieg von pathologischen Kiefergelenkbefunden. Es zeigt sich jedoch ein signifikanter Zusammenhang zwischen der Erkrankungsdauer und dem Auftreten pathologischer Kiefergelenkerscheinungen. Knack- und Reibegeräusche kommen mit zunehmender Erkrankungsdauer signifikant häufiger vor (p=0,011).

Schlussfolgerung

Kinder mit rheumatischen Erkrankungen neigen häufiger zu Kiefergelenkerkrankungen als Kinder ohne rheumatische Erkrankungen. Mit Fortdauer der rheumatischen Erkrankung steigt die Inzidenz pathologischer Kiefergelenksbefunde.     

Evaluation of pluronic polyols as carriers for grafting materials: study in rat calvaria defects

BACKGROUND: Pluronic polyols are a family of non-ionic surfactants currently used as drug carriers for antibiotic, anti-inflammatory, and anti-neoplastic agents. Therapeutic administration of non-ionic surface-active agents is known to facilitate early collagen synthesis and microcirculation, thus promoting wound healing. The purpose of this study was to determine the in vivo effects of pluronic polyols combined with either an allograft or an alloplast on the healing of critical-sized calvarial defects. METHODS: One hundred fifty (150) adult (95 to 105 days old) male Sprague-Dawley rats weighing between 375 and 425 g were randomly and evenly assigned to each of 15 separate treatment groups and anesthetized, and 8 mm calvarial critical-sized defects were created. Pluronic F-68 (F-68) or pluronic F-127 (F-127) was administered either topically or systemically and in conjuction with demineralized bone powder (DBP), tricalcium phosphate (TCP), or non-grafted controls. Pluronic polyols are easily mixed with either DBP or TCP to improve handling ease. Calvaria were harvested at 12 weeks postsurgery and evaluated histomorphometrically, by contact radiography with subsequent densitometric analysis, through energy spectrometry utilizing a scanning electron microscope, and by fluorescent microscopy. RESULTS: There was a significant difference in the percentage of bone fill among the control, TCP, and DBP only groups, P <0.05. The only significant difference within any of these groups was between the TCP control and TCP plus systemic F-127, P<0.05. CONCLUSIONS: Although there were isolated differences, the overall trend was that the pluronic polyol and the mode of administration did not result in a significant change in bone wound healing as measured by the percentage of bone fill. Pluronic polyols may be considered as carriers for osseous graft materials.     

Effect of caries disclosing agents on bond strengths of total-etch and self-etching primer dentin bonding systems to resin composite

This study examined the effect of caries disclosing dyes on composite to dentin shear bond strengths of a total etch, one-bottle and two self-etching, non-rinsing primer dental adhesives. Two caries disclosing dyes were evaluated, Seek and Snoop, with three dentin adhesives, Prime & Bond NT, Prompt L-Pop and Clearfil SE Bond. Extracted human molars stored in 0.2% sodium azide were sectioned longitudinally to expose dentin and embedded in acrylic, leaving the dentin exposed. Each dentin adhesive had three test groups (n=12); a control and one with each of the caries disclosing dyes. The control group had the dentin conditioned and the adhesive applied following the manufacturer's instructions. The caries disclosing dye groups had the dentin first treated for 10 seconds with the disclosing dye, rinsed, then the dentin adhesives were applied as in the controls. A column of Tetric Ceram was bonded after dentin adhesive placement to each specimen and light cured. Specimens were stored in room temperature water for 24 hours, thermocycled for 1,000 cycles between 5 degrees C and 55 degrees C and tested in shear until failure. Mean +/- SD shear bond values (SBV) were determined in MPa. A one-way ANOVA and Student Neuman Keuls multiple comparison test within each DBS were performed at a significance level ofp<0.05 to analyze the caries disclosing dyes input on SBV versus the controls. Surface analysis to determine the nature of the type of dentin/composite fracture/ separation was also performed. For the fracture analysis data, a Chi-Square test was performed at a significance level of p<0.05. The results of this study indicate that using the two tested caries disclosing dyes, with a total etch, one bottle and two self-etching, non-rinsing primer dental adhesives did not negatively affect the dentin-to-composite shear bond strengths of the three tested dentin bonding systems (p>0.05).     

Bone scintigraphy as an adjunct for the diagnosis of oral diseases

Bone scintigraphy is a very sensitive method for the detection of osteoblastic activity of the skeleton. The technique consists of imaging the uptake of bone-seeking radiopharmaceuticals, particularly technetium-99m labeled diphosphonates, in the mineral component of bone, which consists of hydroxyapatite crystals and calcium phosphate, as well as in the organic matrix such as collagen fibers. Plain radiographs, computed tomography, and magnetic resonance imaging are classified as structural imaging modalities, whereas bone scintigraphy is a functional method. In many cases, radionuclide imaging techniques are the only means by which early physiologic changes that are a direct result of biochemical alteration may be assessed, before significant bone mineral changes can be detected by other means. Since many oral diseases may cause metabolic changes in the oromaxillofacial complex, it would be of great value to use bone scintigraphy to evaluate more completely some conditions involving the bones in the region to formulate more appropriate treatment plans. Based upon the current literature, the authors discuss the possible applications of bone scintigraphy as a diagnostic and treatment planning adjunct for oral diseases. Bone scintigraphy has proven particularly useful in the study of malignant lesions and in the evaluation of vascularized bone grafts used for maxillofacial reconstructions.     

A case of bitten Bettongs

Australia has a unique collection of native fauna, which is often threatened by physical harm or the destruction of its habitat and conservation of endangered species is a primary concern. Investigation of the recent deaths of Bettongs in Lincoln National Park, South Australia was undertaken by the Forensic Odontology Unit, Adelaide University to determine the likely perpetrator. Feral domestic cats were deemed to be responsible, as indicated by bitemarks on the radiotransmitter collars.