Diurnal rhythm in British Antarctic personnel.

Introduction: The diurnal rhythm of saliva cortisol and its association to adaptation, performance and health were examined in personnel over-wintering at two British Antarctic stations.

Methods: In total, 55 healthy individuals (49 males, 6 females) participated in the study. Cortisol in saliva was sampled on 3 consecutive days (at awakening, 15 and 45 min after waking, at 15.

The flexural properties of endodontic post materials.

Objectives: To measure the flexural strengths and moduli of endodontic post materials and to assess the effect on the calculated flexural properties of varying the diameter/length (D/L) ratio of three-point bend test samples.

Methods: Three-point bend testing of samples of 2mm diameter metal and fiber-reinforced composite (FRC) rods was carried out and the mechanical properties calculated at support widths of 16 mm, 32 mm and 64 mm. Weibull analysis was performed on the strength data.

The effect of clinically relevant thermocycling on the flexural properties of endodontic post materials.

Objectives: It is suggested that fibre-reinforced composite (FRC) posts have lower elastic moduli than metal posts and this will reduce the incidence of root fracture. However, the mechanical properties may be altered in the oral environment. The aims of this study were to determine the effect on the flexural properties of FRC and metal post materials produced by: (1) a thermocycling regime which was clinically relevant and representative of that which would occur during 1 year in the mouth and (2) storage for 1 year at body temperature.

Adhesive luting of all-ceramic restorations--the impact of cementation variables and short-term water storage on the strength of a feldspathic dental ceramic.

Purpose: To investigate the impact of resin cement luting variables and short-term water storage on the strength of an adhesively luted all-ceramic restorative material. An understanding of the strengthening mechanisms will result in optimisation of operative techniques and materials selection criteria.

Materials And Methods: The "fit" surfaces of 480 disk-shaped feldspathic porcelain specimens were alumina air abraded to introduce a clinically relevant surface texture and consistent surface defect population.

The mechanical properties of nanofilled resin-based composites: the impact of dry and wet cyclic pre-loading on bi-axial flexure strength.

Objectives: To determine the influence of nano-sized filler particles and agglomerates of nanoparticles ('nanoclusters') in resin-based composite (RBC) materials on the bi-axial flexure strength (BFS) following cyclic pre-loading and storage in a 'dry' or 'wet' environment.

Method: Seven commercially available RBC restoratives, Heliomolar (Ivoclar Vivadent, Schaan, Liechtenstein), Z100 MP Restorative, Filtek Z250, Filtek Supreme (3M ESPE, St. Paul, MN, USA) in Body (FSB) and Translucent (FST) shades, Grandio and Grandio Flow (VOCO, Cuxhaven, Germany), containing differing filler particle types and morphologies were investigated.

The mechanical properties of nanofilled resin-based composites: characterizing discrete filler particles and agglomerates using a micromanipulation technique.

Objective: To assess the mechanical properties of discrete filler particles representative of several inorganic fillers in modern dental resin-based composites (RBCs) and to assess the validity of a novel micromanipulation technique.

Method: RBCs with microhybrid (Filtek Z250), 'nanohybrid' (Grandio) and 'nanofilled' (Filtek Supreme), filler particle morphologies were investigated. Filler particles were provided by the manufacturer or separated from the unpolymerized resin using a dissolution technique.

Microstructure and composition of biosynthetically synthesised hydroxyapatite.

Biosynthetic hydroxyapatite (HA) manufactured utilising the bacterium Serratia sp. NCIMB40259 was characterised using X-ray diffraction (XRD), Fourier transform infra-red spectroscopy (FTIR), energy dispersive X-ray analysis (EDX) scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron diffraction (ED). SEM/EDX showed that the non-sintered material consisted mainly of calcium-deficient HA (CDHA) with a Ca/P ratio of 1.

Cure width potential for MOD resin composite molar restorations.

Objectives: To investigate the capability of modern light-curing units exhibiting differences in emission spectra and light source exit window dimensions, for "one-shot" full-width curing of extensive (molar MOD) resin composite restorations.

Method: Specimens of Tetric (TT), Tetric Ceram HB (TC), Tetric Evoceram (TE) and Tetric Ceram Bleach (TB) resin composites containing varying ratios of Lucirin (TPO) and/or camphorquinone (CQ) photoinitiators were packed into a bar-shaped mould (12 mm length x 2 mm width x 2 mm thickness). Each product was irradiated using a halogen (Optilux 401; QTH), a conventional LED (LEDemetron; LED) and two so-called "third generation" oval-footprint LED light-curing units (LCUs) of the same model.

Polyhydroxybutyrate accumulation by a Serratia sp.

A strain of Serratia sp. showed intracellular electron-transparent inclusion bodies when incubated in the presence of citrate and glycerol 2-phosphate without nitrogen source following pre-growth under carbon-limitation in continuous culture. About 1.

Psychological selection of Antarctic personnel: the "SOAP" instrument.

Introduction: The potential advantage of including a psychological test battery in the selection process for service in the Antarctic was examined in 348 applicants for employment in Antarctica with the British Antarctic Survey (BAS).

Methods: Applicants were screened with the Selection of Antarctic Personnel battery (SOAP) consisting of nine well-known psychological instruments. The SOAP scores were not revealed to the BAS selection panel members, who based the selection on operational criteria, interview, and a general medical examination.

Resin strengthening of dental ceramics- the impact of surface texture and silane.

Objectives: To examine the effect of porcelain surface texture achieved utilising three clinically relevant surface preparation methods prior to silane and unfilled resin application on the flexure strength of a low fusing feldspathic porcelain.

Materials And Methods: Five hundred and forty dentine disc-shaped specimens (15.0mm diameter and 0.

The impact of modifying alumina air abrasion parameters on the fracture strength of a porcelain laminate restorative material.

Objectives: The modification of the "fit" surface of porcelain laminate veneer restorations in order to improve adhesion prior to cementation is often indiscriminate. As a consequence, the surface flaw distribution which is implicated in the probability of failure of the restoration is likely to be dramatically modified. The purpose of the current study was to examine the impact of different air abrasion surface treatments on the bi-axial flexure strength and surface roughness of a porcelain restorative material.

Micromechanical versus chemical bonding between CoCr alloys and methacrylate resins.

Introduction: As adhesive systems for bonding to metals have developed in dentistry, considerable importance is attached to the preparation of the metal alloy for both mechanical and chemical bonding. Different grit sizes when sandblasting Cobalt Chromium (CoCr) will provide a different three-dimensional surface for bonding. Previous reports have shown that 4-Methacryloyloxyethyl trimellitic anhydride (4-Meta) resins offer high bond strengths to CoCr alloy, with various surface preparations providing varying bond strengths.

The impact of hydrofluoric acid surface treatments on the performance of a porcelain laminate restorative material.

Objectives: Hydrofluoric (HF) acid etching increases the bond strength between composite resin and porcelain surfaces and has been advocated as a pre-cementation technique for ceramic restorations. The internal surface flaw distribution which is implicated in the premature failure of ceramic restorations is modified by the etching process and little agreement exists amongst researchers as to the appropriate etching regime. The purpose of the current study was to examine the impact of HF acid concentration and etching time on the performance of a low fusing feldspathic porcelain.

A novel non line-of-sight method for coating hydroxyapatite onto the surfaces of support materials by biomineralization.

A novel method is described for the non line-of-sight coating of hydroxyapatite onto polyurethane reticulated foam and titanium discs. This utilises a biofilm of Serratia sp. NCIMB 40259 which, when challenged with a solution containing calcium chloride and phosphatase substrate, manufactures biofilm-bound material identified as hydroxyapatite by X-ray powder diffraction analysis.

Psychopathy, treatment change, and recidivism in high-risk, high-need sexual offenders.

The present study investigated 154 consecutive admissions to the Regional Treatment Center (Ontario) Sex Offender Treatment Program with reference to psychopathy and outcome. Ratings of treatment behavior, as well as clinical judgments as to whether risk was reduced, were coded based on treatment reports. With reference to Psychopathy Checklist-revised (PCL-R) scores, survival analyses indicated that high scorers recidivated at significantly higher rates than low scorers.

The effect of core:dentin thickness ratio on the bi-axial flexure strength and fracture mode and origin of bilayered dental ceramic composites.

Objectives: The aim of the current study was to assess the effect of core:dentin thickness ratio on the flexure strength, fracture mode and origin of bilayered dental ceramic composite disc specimens.

Methods: Sets of 30 bilayered composite discs with core:dentin thickness ratio of 2:1, 1:1 and 1:2 were tested in bi-axial flexure with both the reinforcing core and veneering dentin loaded in tension. Mean flexure strengths, standard deviations and associated Weibull Moduli (m) were determined.

Influence of Different Techniques of Laboratory Construction on the Fracture Resistance of Fiber-Reinforced Composite (FRC) Bridges.

The aim of the current investigation is to evaluate optimal pontic and retainer fiber positions for Polyethylene fiber-reinforced composite (FRC) restorations. In series I notch disc specimens were used to mimic loading cuspal regions of pontics. Four groups (n=15/group; codes A to D) were prepared from Artglass composite.

Bacterial biosynthesis of a calcium phosphate bone-substitute material.

A species of Serratia bacteria produces nano-crystalline hydroxyapatite (HA) crystals by use of a cell-bound phosphatase enzyme, located both periplasmically and within extracellular polymeric materials. The enzyme functions in resting cells by cleaving glycerol-2-phosphate (G-2-P) to liberate free phosphate ions which combine with calcium in solution to produce a cell-bound calcium phosphate material. Bacteria grown as a biofilm on polyurethane reticulated foam cubes were challenged with calcium and G-2-P in a bioreactor to produce a 3-D porous bone-substitute material.

Fracture resistance of fiber-reinforced composite crown restorations.

Purpose: To evaluate the laboratory fracture resistance of teeth restored with crowns constructed in one of these materials (BelleGlass HP with and without fiber reinforcement.

Methods: 40 sound maxillary premolar teeth were chosen and were allocated to four groups of 10 teeth, with the mean size of any group varying by less than 2.5% from other test groups.

The influence of interfacial surface roughness on bilayered ceramic specimen performance.

Objectives: The aim of the current study was to assess the influence of interfacial surface roughness on the performance of bilayered ceramic composite disc-shaped specimens.

Methods: Specific surface flaw distributions were introduced to a series of standard aluminous core porcelain disc specimens (12 mm diameter, 1.7 mm thickness) prior to bilayering with dentin porcelain.

The reliability in flexural strength testing of a novel dental composite.

Objectives: To investigate the reliability of bi-axial flexure and three-point flexure testing of an experimental, low-shrink oxirane-based dental composite, EXL596 compared with two conventional methacrylate based restoratives, Z250 and Z100.

Methods: Specimens (n=20) of a novel oxirane-based composite and two commercially available methacrylate based composites were fabricated for flexural testing to evaluate mean bi-axial flexure strengths, three-point flexure strengths and the associated Weibull moduli (m) following 24 h immersion in a lightproof waterbath maintained at 37+/-1 degrees C.

Results: Mean bi-axial flexure strengths and the associated m of EXL596, Z250 and Z100 were 168+/-11 MPa (m=16.

A palladium-free gallium-based alloy: analysis of composition and microstructure.

Objectives: To study the microstructure of a palladium-free gallium-based alloy (Galloy) before and after mixing to identify the metallic phases produced by the setting reaction and assess the quantitative elemental analysis of the phases present.

Methods: The Galloy powder was analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM) and the particle size distribution was determined using a high resolution particle size analyzer. Cylindrical test specimens were mechanically condensed in accordance with ISO 1559: 1986 for XRD, energy dispersive spectroscopy (EDS) and SEM analyses of the set alloy.