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- Andersson, R. M., et al.
(författare)
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Characterization of probe binding and comparison of its influence on fluorescence lifetime of two pH-sensitive benzo c xanthene dyes using intensity-modulated multiple-wavelength scanning technique
- 2000
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Ingår i: Analytical Biochemistry. - : Elsevier BV. - 0003-2697 .- 1096-0309. ; 283:1, s. 104-110
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Tidskriftsartikel (refereegranskat)abstract
- Quantitative pH imaging using the carboxy semi-naphthofluorescein dyes SNAFL-1 and SNAFL-2 can be performed by measurement of intensity ratios or fluorescence lifetimes. However, there is a controversy as to whether the latter method has the practical advantage of a straightforward pH calibration in buffers compared to a cumbersome and time-consuming procedure in cells. In this study we have undertaken a systematic study of the potential factors influencing the fluorescence lifetime of the probes at different pH using confocal microscopy. In vitro results demonstrate that factors such as lipid and protein concentrations have a substantial influence on pH measurements based on fluorescence lifetime. The pH could be overestimated by more than 2 pH units. Studies in permeabilized COS-7 cells demonstrate the same trends as observed in the in vitro studies.
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- Carlsson, Kjell, et al.
(författare)
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Confocal pH imaging of microscopic specimens using fluorescence lifetimes and phase fluorometry : influence of parameter choice on system performance
- 2000
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Ingår i: Journal of Microscopy. - : Wiley. - 0022-2720 .- 1365-2818. ; 199, s. 106-114
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the performance of confocal pH imaging when using phase fluorometry and fluorophores with pH-dependent lifetimes. In these experiments, the specimen is illuminated by a laser beam, whose intensity is sinusoidally modulated. The lifetime-dependent phase shift in the fluorescent signal is detected by a lock-in amplifier, and converted into a pH value through a calibration procedure. A theoretical investigation is made of how the different system parameters will influence the results concerning sensitivity and noise. Experiments carried out with the fluorophore SNAFL-2 support these theoretical predictions. It is found that, under realistic experimental conditions, we can expect a pH change of 0.1 units to be easily detected in an 8-bit digital image. However, the pixel-to-pixel root mean square noise is often of the order of one pH unit. This comparatively high level of noise has its origin in photon quantum noise. pH measurements on living cells show a systematic deviation from expected values. This discrepancy appears to be the result of fluorophore interaction with various cell constituents, and is the subject of further investigation.
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| 7. |
- Malmqvist, S., et al.
(författare)
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Using 445 nm and 970 nm lasers on dental implants-an in vitro study on change in temperature and surface alterations
- 2019
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Ingår i: Materials. - : MDPI AG. - 1996-1944. ; 12:23
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to evaluate the safety of using a 445 nm laser on dental implants by comparing it with a laser with 970 nm wavelength. Two models, a pig mandible and glass ionomer cement, were used to evaluate the temperature increase in dental implants during laser irradiation with both wavelengths. Temperature was measured every second at four different places on the dental implants. Different power settings, effects of water cooling, distance of the laser fibre to the dental implant and continuous comparison to a pulsed laser beam were tested. Surface alterations on titanium discs after laser irradiation for 4 min at 2.0 W, were analysed in a scanning electron microscope (SEM). The maximum temperature and time to reach each of the thresholds were comparable between the 445 nm and 970 nm lasers. Neither the 445 nm nor the 970 nm wavelength showed any signs of surface alterations on the titanium discs. Using a 445 nm laser on dental implants is as safe as using a 970 nm laser, in terms of temperature increase and surface alterations. Applying a generous amount of cooling water and irradiating in short intervals is important when using lasers on dental implants.
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| 8. |
- Tellefsen, G., et al.
(författare)
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The role of the toothbrush in the abrasion process
- 2011
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Ingår i: International Journal of Dental Hygiene. - : Wiley. - 1601-5029 .- 1601-5037. ; 9:4, s. 284-290
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Tidskriftsartikel (refereegranskat)abstract
- Aim: To evaluate the relative abrasivity of different toothbrushes both qualitatively and quantitatively. Materials and Methods: Acrylic plates were exposed to brushing in a brushing machine with ten different toothbrushes with water alone and with a toothpaste. The results were evaluated using a profilometer after one and 6 h of brushing (corresponding to 2000 and 12 000 double strokes, respectively). A surface roughness value (Ra-value) and also a volume loss value were calculated from the profilometer measurements. These values were then compared to each other. Results: The results showed that brushing with water alone caused less abrasion than when a toothpaste was added. Six-hour brushing with water caused less abrasion than 1 h with a toothpaste. The number of filaments or filament diameter influenced the results in various ways. When brushing with water, the harder toothbrush (Jordan Medium) caused more abrasion (higher Ra-value), but when adding the toothpaste, the softer toothbrush (Jordan soft) caused more abrasion after 12 000 double strokes. Conclusion: Besides supporting the fact that a toothpaste is needed to create a significant abrasion, this study also showed that a softer toothbrush can cause as much and in some cases more abrasion than harder ones. When conducting abrasivity studies, it is important to look at both the quantitative and qualitative aspect of abrasivity.
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