Neural correlates of top‐down modulation of haptic shape versus roughness perception

Exploring an object's shape by touch also renders information about its surface roughness. It has been suggested that shape and roughness are processed distinctly in the brain, a result based on comparing brain activation when exploring objects that differed in one of these features. To investigate the neural mechanisms of top‐down control on haptic perception of shape and roughness, we presented the same multidimensional objects but varied the relevance of each feature. Specifically, participants explored two objects that varied in shape (oblongness of cuboids) and surface roughness. They either had to compare the shape or the roughness in an alternative‐forced‐choice‐task. Moreover, we examined whether the activation strength of the identified brain regions as measured by functional magnetic resonance imaging (fMRI) can predict the behavioral performance in the haptic discrimination task. We observed a widespread network of activation for shape and roughness perception comprising bilateral precentral and postcentral gyrus, cerebellum, and insula. Task‐relevance of the object's shape increased activation in the right supramarginal gyrus (SMG/BA 40) and the right precentral gyrus (PreCG/BA 44) suggesting that activation in these areas does not merely reflect stimulus‐driven processes, such as exploring shape, but also entails top‐down controlled processes driven by task‐relevance. Moreover, the strength of the SMG/PreCG activation predicted individual performance in the shape but not in the roughness discrimination task. No activation was found for the reversed contrast (roughness > shape). We conclude that macrogeometric properties, such as shape, can be modulated by top‐down mechanisms whereas roughness, a microgeometric feature, seems to be processed automatically.     

Application of disaccharides alone and in combination,for the improvement of stability and particle properties of spray-freeze dried IgG

Purpose: Spray-freeze drying (SFD) is a recently applied method to develop pharmaceutical powders. This study aimed to analyze the competence of Trehalose, Mannitol, Lactose, and Sorbitol instability and aerosolization of Immunoglobulin G (IgG) via SFD.

Methods: Induced soluble aggregates were quantified at 0 and 3?months, and 45?°C using size-exclusion chromatography. Conformation and thermogravimetric assessments were done by Fourier transform infrared spectroscopy and differential scanning calorimetry. Laser light scattering was performed to determine the particle sizes. Aerodynamic features were characterized by twin stage impinger and scanning electron microscopy.

Results: Although sugars/polyols preferably stabilized IgG following the process, storage stabilization was achieved in Trehalose, Trehalose-Lactose, Lactose, and Trehalose-Mannitol-based powders with soluble aggregates <5%. The conformation of antibody was preserved with β sheet content from 66.28% to 76.37%. Particle sizes ranged from 5.23 to 8.12?µm. Mannitol exhibited the best aerodynamic behavior, fine particle fraction (FPF: 70%) but high degree of protein aggregation during storage.

Conclusions: SFD could favorably stabilize antibody using Trehalose and its combination with Lactose and Mannitol, and also, Lactose alone. Sorbitol disturbed IgG powder recovery. Incorporation of other types of excipient is required for efficient respiratory delivery of IgG molecules.     

Nanotubes in the human respiratory tract – Deposition modeling

Deposition of inhaled single-wall carbon nanotubes (SWCNT) and multi-wall carbon nanotubes (MWCNT) in the respiratory tract was theoretically investigated for various age groups (infants, children, adolescents, and adults). Additionally, possible effects of the inhalative flow rate on nanotube deposition were simulated for adult lungs. Theoretical computations were based on the aerodynamic diameter concept and the assumption of particles being randomly transported through a stochastic (close-to-realistic) lung structure. Deposition of nanotubes was calculated by application of well validated empirical deposition formulae, thereby considering Browian motion, inertial impaction, interception, and sedimentation as main deposition mechanisms acting on the particles. Results of the simulations clearly show that for a given inhalation scenario (sitting breathing) total, bronchial, and acinar nanotube deposition increase with subject's age, whereas extrathoracic deposition is characterized by a decrease from younger to older subjects. According to the data provided by the model, MWCNT, whose aerodynamic diameters exceed those of SWCNT by one order of magnitude, are deposited in specific respiratory compartments to a lower extent than SWCNT. A change of the physical state from sitting to heavy work results in a common decline of bronchial and extrathoracic deposition of nanotubes. Total deposition is slightly increased for SWCNT and moderately decreased for MWCNT, whereas acinar deposition is significantly increased for SWCNT and decreased for MWCNT. Based on the results of this contribution it may be concluded that SWCNT bear a higher potential as health hazards than MWCNT, because they are accumulated in sensitive lung regions with higher doses than MWCNT.     

The Effect of Brushing on Surface Roughness of Denture Lining Materials

PURPOSE: The purpose of this study was to test the effect of brushing on surface roughness of two resilient liners (Luci Sof and Sofreliner) compared with an acrylic resin (QC 20). MATERIALS AND METHODS: Twenty specimens of each material were prepared (25 mm x 14 mm x 3 mm). Ten specimens served as controls and were stored in distilled water and not brushed. The remaining ten specimens were subjected to mechanical brushing, using an MSEt plus machine to simulate brushing at a rate of 5.0 strokes per second (30,000 cycles). Surface roughness measurements were recorded before and after brushing. Random samples were analyzed using scanning electron microscope. Data collected were analyzed by a two-way analysis of variance using material and treatment as variables, followed by Tukey's test (alpha= 0.05). RESULTS: Initial surface roughness of materials indicated that QC 20 was the smoothest (0.13 microm), and Luci Sof the roughest (0.68 mum). Sofreliner had an intermediate value (0.31 microm). All materials were significantly different. Mechanical brushing significantly increased surface roughness in all the materials. Although there was no statistical difference between QC 20 and Luci Sof after mechanical brushing (0.88 and 1.00 microm, respectively), both differed significantly from Sofreliner (7.74 microm). CONCLUSION: The two resilient liners and the acrylic resin became rougher, to a greater or lesser extent, when subjected to mechanical brushing.     

Surface characteristics of aesthetic restorative materials - an SEM study

To determine the degree of surface roughness of glass-ionomer cements (GICs) and polyacid-modified resin composite (PAMRC) after polishing and immersion in various foodstuffs. Three tooth-coloured restorative materials were used: a PAMRC (F2000), a conventional glass-ionomer cement (CGIC) (Fuji IX) and a resin-modified glass-ionomer cements (RM-GIC) (Fuji II LC). Disk-shaped specimens were prepared and tested with either a plastics matrix finish or after polishing with wet silicon carbide papers up to 2000-grit. All specimens were immersed in 37 degrees C-distilled water for 1 week, followed by three different foodstuffs (red wine, coffee or tea) for a further 2 weeks. Replicas of specimens were prepared by taking polyvinyl siloxane impressions, casting in epoxy resin, gold sputter-coating and examining using a Field-Emission Scanning Electron Microscope. The polished and matrix finish specimens of F2000 showed many microcracks at low magnification, and eroded surfaces with missing and protruding particles at high magnification in the polished specimens. The surface-polished specimens of Fuji II LC were considerably rougher than the matrix-finish specimens, with large voids and protruding filler particles. The effects of foodstuffs on Fuji II LC and F2000 were not noticeable. The CGIC became noticeably rougher after exposure to coffee and tea. All specimens had the smoothest surface when they were cured against a plastics matrix strip, and all materials had a rougher surface after polishing. None of the foodstuffs produced a perceptible increase in roughness on RM-GIC and PAMRC surfaces, whereas coffee and tea markedly increased the surface roughness of Fuji IX.     

Influence of surface roughness on streptococcal adhesion forces to composite resins

Objective

To determine streptococcal adhesion forces with composite resins with different surface roughness.

Methods

Polishing and grinding were applied to obtain smooth (roughness 20 nm), moderately rough (150 nm) and rough (350 nm) surfaces of two orthodontic, light-cured composites. Adhesion forces between Streptococcus sanguinis and Streptococcus mutans and the composite surfaces were measured using atomic force microscopy in absence or presence of a salivary conditioning film. Initial adhesion forces were measured as well adhesion after 120 s of contact, as longer contact times are known to result in stronger adhesion forces (“bond-strengthening”). Surface roughness in absence and presence of salivary conditioning films were compared using ANOVA, while adhesion forces were subjected to a Weibull analysis.

Results

Initial adhesion forces in absence of a salivary conditioning film amounted between −0.7 and −0.9 nN for smooth composite resins and increased between −1.0 and −2.0 nN for the roughest surfaces. Streptococcal adhesion forces after bond-strengthening were significantly stronger than upon initial contact, irrespective of the composite type. Salivary conditioning films significantly decreased the surface roughness of the composites, as well as the streptococcal adhesion forces. Yet, also in the presence of a conditioning film, rougher composite surfaces exerted stronger adhesion forces, irrespective of composite type or bacterial strain.

Conclusion

Streptococcal adhesion forces to orthodontic composite resins increase with increasing roughness of the composite surfaces. Composite surface roughness less affects adhesion forces with S. mutans than with S. sanguinis.     

The mucosal attachment to titanium implants with different surface characteristics: an experimental study in dogs

BACKGROUND: Findings from in vitro studies have indicated that the orientation and proliferation of cells on titanium surfaces may be influenced by the topography of the surface on which they are grown. It may be argued, therefore, that differences may occur in the mucosal attachment to titanium implants with different surface roughness. AIM: The present experiment was performed to study the composition of the soft tissue barrier that formed to implants prepared with well-defined smooth or rough surfaces. MATERIAL AND METHODS: Five beagle dogs were used. Four implants made of c.p. titanium were placed in the right edentulous mandibular premolar region. After 3 months, two different types of abutments were connected: one experimental (OA) with a dual, thermal acid-etched surface ('Osseotite'), and one regular (RA) abutment with a 'turned' surface. At the end of a 6-month period during which proper plaque control had been maintained, biopsies including the implant and the surrounding soft and hard tissues were obtained, decalcified and processed for light and electron microscopy. A confocal He-Ne laser profilometer was used to study the surface topography of the abutments. RESULTS: The attachment between the peri-implant mucosa and titanium abutments with either a turned (RA; 'smooth') or acid-etched (OA; 'rough') surface was similar from both a quantitative and a qualitative aspect. The attachment comprised a barrier epithelium and a zone of connective tissue attachment of similar dimension at RA and OA. It was further observed that the 'inner' zone of the connective tissue attachment at both types of abutment was composed of about 30-33% fibroblasts and 63-66% collagen. CONCLUSION: It was demonstrated that the soft tissue attachment that formed to implants made of c.p. titanium was not influenced by the roughness of the titanium surface.