Non-contact Laser Profilometry Research Articles

Pilot clinical study to evaluate the efficacy of a professionally delivered high fluoride varnish on erosive tooth wear in an in-situ model

ObjectivesThe aim for this pilot study was to investigate the effect of a sodium fluoride varnish on step height measured by a profilometer from human enamel worn by healthy volunteers with a novel in situ/ex vivo erosion design. MethodHealthy volunteers aged 18–70 years wore a palatal splint containing 8 human enamel samples and underwent two 3-day treatment periods for 6 h a day with a varnish containing sodium fluoride at 22,600 ppm and the control with the same ingredients but without fluoride. Each splint contained 4 polished and 4 unpolished samples. The interventions were applied to the surface of the enamel samples in randomised order, removed after 6 h, then immersed ex-vivo in 1 %, pH 2.7 citric acid for 2 min, repeated 4 times a day, over 2 days. Measurements of enamel were assessed blindly by microhardness on day 2 and by non-contact laser profilometry on day 3 for the two treatments. Results24 volunteers, 2 males and 22 females aged 27–54 years, were screened and recruited. The delta microhardness, from polished samples removed at the end of day 2, for the control and fluoride treatment was 95.7 (22.9) kgf/mm2 and 123.7 (28.9) kgf/mm2, respectively (p < .005). The mean (SD) step height for the control polished enamel surfaces was 3.67 (2.07) µm and for the fluoride varnish was 1.79 (1.01) µm (p < .0005). The control unpolished enamel surfaces had a mean 2.09 (1.53) µm and the fluoride varnish was 2.11 (1.53) µm but no statistical difference was detected. ConclusionsThe results from this pilot study, utilizing an in-situ model where enamel was exposed to acid over the course of 2 days, demonstrated that a high fluoride varnish containing sodium fluoride at 22,600 ppm prevented erosive wear compared to a control on the polished enamel surfaces. Clinical significanceIntra-oral study demonstrated that a high fluoride varnish containing sodium fluoride at 22,600 ppm reduced erosive tooth wear.

Evaluation of the surface damage of dental implants caused by different surgical protocols: an in vitro study

The implant surface must withstand high insertion torque during implant insertion. The aim of this study was to investigate the damage to implant surfaces caused by two different insertion protocols in vitro. Fifteen titanium implants per group were inserted in standardized polyurethane foam models, group 1 according to a non-threaded surgical protocol and group 2 according to a threaded surgical protocol. Before and after insertion, the surfaces were visualized by scanning electron microscopy (SEM) and non-contact laser profilometry. Different surface area parameters were evaluated and maximum torque during insertion was determined. SEM detected topographical changes such as deposition of the test block and smoothening of the surface in the region of the thread crests in both groups. The laser profilometry analysis revealed significant changes in the surface topography of the implants in both groups, but no differences between the groups. Insertion torque was significantly decreased in the threaded group. Both types of surgical intervention resulted in surface damage. Less damage was detected to the thread crests with the use of a thread cutter, and most of the surface was not visibly affected by the surgical protocol at the microscopic level. The surgical protocol seems to have a minor influence on preservation of the implant surface.

A Novel Delivery System for the Controlled Release~of Antimicrobial Peptides: Citropin 1.1 and Temporin A.

Antimicrobial peptides (AMPs) are prospective therapeutic options for treating multiple-strain infections. However, clinical and commercial development of AMPs has some limitations due to their limited stability, low bioavailability, and potential hemotoxicity. The purpose of this study was to develop new polymeric carriers as highly controlled release devices for amphibian peptides citropin 1.1 (CIT) and temporin A (TEMP). The release rate of the active pharmaceutical ingredients (APIs) was strongly dependent on the API characteristics and the matrix microstructure. In the current work, we investigated the effect of the polymer microstructure on in vitro release kinetics of AMPs. Non-contact laser profilometry, scanning electron microscopy (SEM), and differential scanning calorimetry (DSC) were used to determine the structural changes during matrix degradation. Moreover, geno- and cytotoxicity of the synthesized new carriers were evaluated. The in vitro release study of AMPs from the obtained non-toxic matrices shows that peptides were released with near-zero-order kinetics. The peptide “burst release” effect was not observed. New devices have reached the therapeutic concentration of AMPs within 24 h and maintained it for 28 days. Hence, our results suggest that these polymeric devices could be potentially used as therapeutic options for the treatment of local infections.

Flexible hybrid coatings with efficient antioxidation properties

Abstract In this work, the feasibility of a transparent sol gel coating on polyamide-polyethylene (PA/PE) substrate with antioxidant properties as active food packaging was investigated. Stable water-based silicon alkoxide formulations, containing lipophilic vitamin E as natural antioxidant, were obtained adding ascorbic acid as catalyst. Comparative blank sols were prepared without antioxidant guest molecules. The sol formulations of tetraethyl orthosilicate and a mixture of alcoxysilane containing organic moieties as phenyl and methyl group were stable and easy to process via dip coating on Polyamide/Polyethylene substrates. Organic functionalities were essential to incorporate the lipophilic guests and to achieve an optimal adhesion on the polymeric substrate. The presence of stable coating was evaluated through Electron Microscopy and Optical Emission Spectroscopy analyses, while the surface roughness and optical absorption were measured by noncontact laser profilometry and by UV/vis spectra. The loaded antioxidant amount was estimated right after the coating deposition by spectroscopic UV measurements in ethanol, as its subsequent release within 14 days. The estimated antioxidant release was 10% and 40% of the loaded amount for the hydrochloric-sol and the ascorbic acid catalysed sol, respectively. The antioxidant efficacy of coatings was evaluated through the Ferric Reducing Antioxidant Power (FRAP) assay showing a significant difference in antioxidant efficacy between the vitamin E containing sols and their blank ones. Those results were confirmed by FRAP analysis even four months after the deposition.

Solid-particle erosion behavior of cast alloys used in the mining industry

The erosive-wear response of five commercial ferrous-based cast alloys used for crushing was examined in this study. The microstructures of the alloys were modified to elucidate the effect of microstructural features on wear. Erosion tests were conducted using aluminum oxide particles (90–125 μm) at 70 m/s and a normal impact angle (90°). The worn surfaces were characterized by scanning electron microscopy and 3D non-contact laser profilometry. It is found that (i) a pearlitic structure exhibiting a greater plastic deformation than both bainitic and martensitic structures shows the greatest resistance to erosive wear at normal impact and (ii) the fracture characteristics of carbide and graphite particles plays an important role in determining the erosion wear behavior of the cast alloy matrices.

Determination of the crushing strength of intact tablets using Raman spectroscopy

In the present study, the Raman spectroscopy technique was used as a non-invasive, rapid analytical method for measuring the crushing strength of tablets. The compressed tablets were individually detected, using Raman spectroscopy, and the respective crushing strength values were measured, using a tablet hardness tester as a reference method. The tablets were compressed from a granule mass containing theophylline anhydrate as an active substance. For measuring the crushing strength of the tablets, Raman spectra were recorded from the tablets. Partial least squares (PLS) regression models were constructed to obtain information from the spectra. The correlation between measured and predicted crushing strength values for the tablets was shown to be very favorable. With Raman spectroscopy, shifting of the baseline was observed as the crushing strengths of tablets (and the smoothness of the tablet surface) were increased. Consequently, correlation between the crushing strength data on the present tablets and Raman spectra was observed. Multiple scanning electron (SEM) and non-contact laser profilometry (LP) micrographs from the surfaces of the tablets were taken to describe the surfaces and applied as supportive information for the proposed spectroscopy approach. In conclusion, Raman spectroscopy is a promising alternative for established off-line/at-line tablet-testing methods for some tablet formulations.

The application of non-contact laser profilometry to the determination of permanent structural changes induced by compaction of pellets

Pellets of different mechanical properties were produced by extrusion and spheronisation process based on various composition (microcrystalline cellulose (MCC), lactose, glyceryl monostearate (GMS), water, ethanol and glycerol). Six hundred milligrams of these pellets were compacted at two different pressures (86.7 and 130MPa) to form flat-faced tablets and stored for 48h in ambient temperature and humidity after which their permanent structural change (plastic deformation) was investigated in terms of surface roughness parameters of both faces of the tablets, using a non-contact laser profilometer. The results were compared with the deformability values obtained from the force/displacement curve as well as the phase angle values obtained from the dynamic scan of a dynamic mechanical analyser. The increase in deformability of the pellets with the increase in porosity, increase in the contents of GMS, lactose or ethanol in the formulations and increase in compaction pressure was illustrated by the reduction of the surface roughness parameters. Analysis of variance identified the significant difference in the mean rugosity values of the tablets from the various formulations, tablet faces and compaction pressures. The deformability values obtained were reasonably comparable to those plasticity values obtained in terms of phase angle from the dynamic scan of the DMA and the force/displacement curves. The laser profilometry technique in conjunction with scanning electro-microscopy (SEM) demonstrated the low and broad based wavelike structure of the pellets after compaction rather than spiky sharp protrusions. This confirms the capability of determining the plastic deformability of the pellets from the surface roughness parameters obtained from non-contact laser profilometry.

3D Measurements on Extrusion Marks in Plastic Bags

The surface of different types of garbage bags was scanned using non-contact laser profilometry. Manufacturing defects known from visual inspection of the bags (fish eyes, arrowheads, and surface scratches) appear as differences in the height profile. Extrusion lines could only be detected in low-density polyethylene bags. Their correlation length is a couple of centimeters, whereas visually they continue over meters. This can be used to link together the end of one garbage bag with the beginning of the subsequent bag. Extrusion lines are of the order of 0.1 microm for high-density polyethylene garbage bags.

Shape Evolution and Stress Development during Latex−Silica Film Formation

The shape evolution and stress development of composite films of deformable acrylic latices and rigid silica spheres were studied using noncontact laser profilometry and a controlled environment st...

Use of Ti-coated replicas to investigate the effects on fibroblast shape of surfaces with varying roughness and constant chemical composition.

A two-stage replica technique with a subsequent titanium (Ti)-coating treatment was used to faithfully replicate topographies of polished, acid-etched, machined-like, finely blasted, coarsely blasted, coarsely blasted and acid-etched, and Ti plasma-sprayed Ti surfaces. The replicas were used to study the influence of different rough surface topographies on the response of human fibroblasts in vitro under conditions of constant surface chemistry for all surfaces. The surface topographies of the replicas were characterized using non-contact laser profilometry, scanning electron microscopy (SEM), and stereo-SEM, whereas surface chemistry was examined using X-ray photoelectron spectroscopy. Fibroblasts were trypsinized and plated onto the Ti-coated epoxy-resin replica surfaces for 24 h and observed with SEM. Fluorescein-5-thiosemicarbazide was used to stain the cell components including cell membrane, and the stained cells were optically sectioned using epifluorescent microscopy. The optical sections were computationally reconstructed to obtain three-dimensional images and cell volume and cell thickness determined. The different surface topographies were found to alter cell thickness and cell morphology. However, cell volume as computed from three-dimensional reconstructions was not affected by surface features. The results suggest that cells distort themselves to accommodate to rough surfaces but their volume is not significantly altered.

The influence of formulation variables on the properties of pellets containing a self-emulsifying mixture

A method of converting self-emulsifying drug delivery systems to a pellet form has been studied. Formulations with varied relative quantities of an oil/surfactant mixture, water, microcrystalline cellulose (MCC), and lactose were chosen in a statistical design after preliminary ranging experiments. Pellets were produced by extrusion/spheronization. The characteristics of the pellets were studied by sieving, disintegration testing, diametral compression, image analysis, non-contact laser profilometry, and scanning electron microscopy. The effects of the formulation variables on pellet properties were evaluated by analysis of variance. It was possible to relate the formulation variables to all the quantified pellet properties except the shape. The relative quantities of oil/surfactant and water had an effect on the amount of liquid and oil/surfactant that could be incorporated into the powder, extrusion force, median diameter, size spread, disintegration time, tensile strength, and surface roughness. The relative quantities of lactose and MCC had an effect on the amount of liquid and oil/surfactant that could be incorporated into the powder, tensile strength, and roughness only. Water was an essential element of the formulations. The maximum quantity of the specific oil/surfactant combination studied that can be incorporated was 42% of the dry pellet weight. © 2001 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 90:987–995, 2001

The Influence of Powder Properties and Tabletting Conditions on the Surface Roughness of Tablets

Tablets of five different compression formulations were investigated for their surface roughness using scanning electron microscopy and non-contact laser profilometry. It was found that the composition of a formulation not only influenced the tabletting properties of the powder mixtures, but also the surface properties of the final product. The addition of larger quantities of very brittle materials such as dibasic calcium phosphate dihydrate increased the surface roughness of tablets. An increase in tabletting pressure reduced the tablet surface roughness. Tablets were found to have smoother edges than faces, presumably due to the comparatively higher shear stress at the die walls and a polishing effect during tablet ejection. The assessment of surface roughness in three dimensions appeared more powerful than a simple line profile measurement.

The effect of compression force on surface structure, crushing strength, friability and disintegration time of erythromycin acistrate tablets

The surface roughness of erythromycin acistrate tablets was studied by non-contact laser profilometry. Seven roughness parameters and 3D fractal dimension were examined. The mechanical properties (including crushing strength, friability and disintegration time) were determined, and SEM data were taken from the tablets. According to the results, the crushing strength and the disintegration time of the tablets increased with increasing compression force. At higher compression forces the crushing strength reached a constant level. The friability of the tablets behaved quite unexpectedly and minimum friability was observed at a compression force of 14 kN. Except for fractal dimension, the roughness parameters behaved very much in the same way as the friability of the tablets. The SEM data supported the friability and surface roughness data of the tablets.

Influence of stress intensity and crack speed on fracture surface topography: mirror to mist to macroscopic bifurcation

The development of roughness on the fracture surfaces of a brittle, glassy, epoxy resin from the mirror-to-mist transition to macroscopic bifurcation has been investigated using optical microscopy, scanning electron microscopy (SEM) and contact and non-contact laser profilometry. Most of the observations were made on specimens fractured in edge-notched tension. In a series of tests the initial crack length was varied to obtain fracture surfaces formed by accelerating and decelerating cracks without macroscopic bifurcation (specimen A) and by cracks which accelerated continuously to macroscopic bifurcation (specimen B). Some observations were made on specimens tested in compact tension to study changes in fracture surface topography associated with crack arrest in stick-slip fracture. There was a close correlation between the topographical detail revealed by the different techniques. In specimen A the roughness increased progressively from the mirror-to-mist transition and reached a maximum before decreasing as the crack decelerated. The topographical features revealed by optical microscopy and SEM were the same for accelerating and decelerating cracks at the same roughness value. In specimen B the roughness increased continuously to macroscopic bifurcation. There was a close similarity between the topographical features at all levels of roughness. A simple model for the basic step involved in roughness formation is presented which involves an element of the crack tip tilting out of the plane of the main crack before stopping (micro-bifurcation). The scale of micro-bifurcation ranged from 3 μm in the early stages of mist, when the crack velocity was close to 10% of the shear wave velocity, to the full width of the specimen (6 mm) at macroscopic bifurcation. The micro-bifurcation process develops from crack surface undulations and does not involve micro-crack nucleating ahead of the main crack. It is concluded that the relationships between crack velocity and dynamic stress intensity, and the value of the limiting crack velocity, must be interpreted in terms of micro-mechanical processes at the crack tip which are strongly dependent on specific material characteristics.

Influence of stress intensity and crack speed on fracture surface topography: mirror to mist transition

The transition from very smooth “mirror” crack growth to the early stages of roughening associated with “mist” has been investigated using a range of surface topography techniques. The fracture mechanics properties of the brittle, glassy and isotropic epoxy resin used in this work were characterized using compact tension (CT) and double torsion (DT) tests (K Ic=0.65 MN m−3/2). In the DT test, the mist to mirror transition occurred over a large section of the test sample and this facilitated examination by optical microscopy, scanning electron microscopy, atomic force microscopy and non-contact laser profilometry. Measurements on Wallner lines and river lines were used to map the crack velocities and directions over the fracture surface. The transition from mist to mirror, for a decelerating crack, occurred at a crack velocity, v c=0.1 v t, where v t is the shear wave velocity. There was a sharp change in roughness at the transition but no discontinuity in the crack deceleration behaviour. Two main topographical features were observed at the transition: firstly, undulations in the mirror region which decreased in amplitude away from the transition for a decelerating crack and, by implication, vice versa; secondly, a progressive decrease in river line density (for a decelerating crack). Detailed atomic force microscope profilometry was used to determine the surface topography associated with these features. The results provide an insight into the development of crack instabilities under dynamic conditions and a basis for interpreting the progressive development of roughness up to macroscopic bifurcation.