Quantitative Laser Fluorescence Research Articles

The Potential of Self-assembling Peptides for Enhancement of In Vitro Remineralisation of White Spot Lesions as Measured by Quantitative Laser Fluorescence.

To test the remineralisation potential of a single application of self-assembling peptides or acidic fluoride solution using quantitative light-induced fluorescence (QLF) in vitro. Bovine enamel disks were prepared, and white spot lesions were created on one half of the disk with an acidic buffer solution. After demineralisation, disks were allocated into three groups of 11 specimens each. Group A served as a control group and received no treatment. Group B had a single application of fluoride, and group C was treated once with self-assembling peptides. All disks were embedded in a plastic mold (diameter 15 mm, height 9 mm) with an a-silicone, and remineralisation was initiated using a pH-cycling protocol for five days. Four experimental regions on each disk were measured prior to the start of the study (T0), after demineralisation (T1) and after the remineralisation process (T2) using QLF. After demineralisation, all areas showed a distinct loss of fluorescence, with no statistically significant difference between the groups (ΔF from -69.3 to -10.2). After remineralisation, samples of group B (treated with fluoride) showed a statistically significant fluorescence increase (ΔF from T1 to T2 15.2 ± 7.3) indicating remineralisation, whereas the samples of control group A and group C (treated with self-assembling peptides) showed no significant changes in ΔF of 1.1 ± 1.9 and 2.5 ± 1.9, respectively. Application of self-assembling peptides on demineralised bovine enamel did not lead to increased fluorescence using QLF, indicating either lack of remineralisation or irregular crystals. Increased fluorescence using QLF indicated mineral gain following a single application of a highly concentrated fluoride.

A Comparison of Different Methods for Fissure Caries Detection

Summary The aim of the study is to compare the diagnostic capabilities of three different diagnostic methods: Quantitative Laser Fluorescence (QLF) − DIAGNOdent Classic (DD), Light-Induced Fluorescence (LIF) − SoproLife daylight and blue fluorescence, and their relevance to ICDAS II system in detection of fissure caries lesions in permanent molars. Permanent molars (n = 45) are divided in two groups: 1) third molars, n = 35; 2) first and second molars, n = 10. They are examined by 2 examiners with and without magnification x5 using ICDAS II, SoproLife “day light” and “blue light” (405nm), LIF, DIAGNOdent Classic − emitting laser light on 655nm, QLF. The results are proven with histological bucco-lingual or mesio-distal sections through the body of the lesion with diamond blade rinsed with water. Photos of all occlusal surfaces of the molars are taken before and after the sections. The lowest overdiagnosis rate is found with SoproLife camera. When visual examination is applied overdiagnoses are fewer than with DD. DD is not capable to differentiate white and brown spots from a caries lesion. Soprolife is not capable to differentiate brown spots from a caries lesion. The most accurate method in this in vitro study for diagnosis of fissure caries is LIF (SoproLife) − 75.6% of the teeth are correctly diagnosed, followed by ICDAS (57.8%) and QLF (DIAGNOdent) (40%).

The erosive potential of some alcopops using bovine enamel: An in vitro study

Objectives Alcoholic soft drinks have become increasingly popular and have high concentrations of citric acid and alcohol so might have the potential to cause dental erosion. This study aimed to investigate the erosive potential of alcopops on bovine enamel in vitro. Methods Six bovine upper incisors were prepared and sectioned to give six slabs per tooth, 4 mm × 4 mm each. Each slab was covered with nail varnish, leaving an exposed window (2 mm × 2 mm). Samples were immersed in 20 ml of each of the test solutions for 20 min, 1 h, and 24 h under gentle agitation (100 rpm). Enamel surface loss was determined using Quantitative Laser Fluorescence (QLF), Non-contact Profilometry (NCP) and Transverse Microradiography (TMR). Results Enamel loss occurred with all test drinks and the positive control ( p < 0.05), and the depth of lesion correlated with pH and time. No significant difference was observed between 20 min and 1 h exposure, although both times had significantly ( p < 0.05) greater erosion when compared with baseline. Within each alcopops group significant erosion had occurred at 24 h exposure compared with the baseline and previous times. Conclusion All the tested alcopops resulted in significant enamel loss at 24 h ( p < 0.001) with direct correlation between degree of enamel loss and both pH and increasing exposure time.

Reliability of Quantitative Laser Fluorescence Analysis of Smooth Surface Lesions Adjacent to the Gingival Tissues

The aim of this study was to determine the impact of analysis patch border inclusion or exclusion on the reliability of quantitative laser fluorescence (QLF) analyses of lesions close to the gingival margin. Ninety-three lesions on the maxillary anterior teeth were imaged using a fluorescent capturing system. All the lesions were located on the gingival third of the teeth. One examiner undertook two analyses of the images 1 week apart and another examiner undertook a single analysis. Analyses were undertaken using QLF 2.00 g with four patch borders. Each border was assessed as active or inactive. QLF metrics ΔF, ΔQ and area were exported. Kappa statistics were used to measure the agreement of border inclusion between all three analyses, and intra-class correlation coefficients (ICCs) were used to determine the intra- and inter-examiner reliability of the QLF metrics. Agreement on border exclusion was poor; with intra-examiner kappa of 0.48 and inter-examiner at 0.20. However, despite the inconsistencies in border exclusions the ICCs for each QLF metric were high; intra-examiner ΔQ 0.91, ΔF 0.80 and area 0.92; inter-examiner ΔQ 0.86, ΔF 0.68, area 0.88. Lesions adjacent to the gingival margin will often require a patch analysis border to be excluded in order to ensure a satisfactory reconstruction and thus accurate analysis. The decision to include or exclude a border and, if excluded, which border to select appears to be highly variable between examiners. Nevertheless, the QLF metrics appear to be robust as demonstrated by the high ICCs noted in this study.

The Influence of Drying on Quantitative Laser Fluorescence and Optical Pathlengths in Incipient Natural Caries Lesions

Drying effects in 14 natural lesions were studied with quantitative light-induced fluorescence and optical pathlength spectroscopy. Results were compared with clinical judgments of the lesion surface and microradiographical characterizations of the lesions. Relative fluorescence and average pathlength decreased as a function of drying time with a decay time ranging from 35.5 to <1 min. Depth and mineral loss correlated with average pathlength total changes (r = –0.79/–0.60, respectively) and poorly with total fluorescence changes (r 0.3). The decay time of the drying process for the relative fluorescence correlated well with a theoretical model based on water diffusion in lesion and surface layer, but only for large decay times. Clinical judgments could not be related to the surface layer properties or the changes in the average pathlength, but were weakly related to the changes in the relative fluorescence. We conclude that (i) fluorescence effects are mostly due to the screening by the lesion of the fluorescence from the dentin and enamel-dentin junction; (ii) water evaporation in lesions conforms to the diffusion laws only in large lesions with low surface layer penetrability; (iii) the evaporation process is controlled by the surface layer only for small surface penetrabilities (≈ 0.1 vol% µm^–1).

A longitudinal laser fluorescence study of white spot lesions in orthodontic patients

Orthodontic treatment with fixed appliances increases the caries risk in young persons. The aim of this study was to apply a new caries diagnostic method, quantitative laser fluorescence, for longitudinal in vivo quantification of changes in incipient enamel lesions related to fixed orthodontic appliances. Seven young patients with active caries lesions disclosed at removal of the orthodontic brackets and bands were enrolled in the study. Caries preventive measures were intensified, including dietary advice, oral hygiene instructions, and the regular use of a fluoride dentifrice. The caries lesions were monitored with the quantitative laser fluorescence method after removal of the brackets and once a month thereafter. For each lesion, three quantities were measured: lesion area (mm 2), mean fluorescence loss (%) over the lesion, and maximum loss of fluorescence (%) in the lesion. During a 1-year follow-up period, the areas of the lesions decreased and the enamel fluorescence lost was partly regained indicating that a remineralization process had occurred. It was concluded that quantitative laser fluorescence seems suitable for in vivo monitoring of mineral changes in incipient enamel lesions, and useful for the evaluation of preventive measures in caries prone persons, such as orthodontic patients. (Am J Orthod Dentofacial Orthop 1998;113:595-602)

Inhibition of nuclear accumulation of karyophilic proteins in living cells by microinjection of the lectin wheat germ agglutinin

The lectin wheat germ agglutinin (WGA), which has been reported to inhibit nuclear protein uptake in vitro by isolated nuclei (Finlay et al. (1987) J. Cell Biol. 104, 189), also blocks, on microinjection into living cells, the migration of proteins into the cell nucleus. Radioactively labeled nuclear proteins were injected into the cytoplasm of Xenopus oocytes and their reentry into the nucleus was analyzed in the presence or absence of WGA by two-dimensional gel electrophoresis. In another set of experiments, fluorescently labeled nucleoplasmin was injected, alone or together with WGA, into the cytoplasm of rat hepatoma cells, and its nucleocytoplasmic distribution was studied by quantitative laser fluorescence microscopy. The results indicate that WGA inhibits the uptake of karyophilic proteins in general, independent of their sizes. Since the nucleocytoplasmic flux of a dextran with M r, 10,000 was not affected it can be excluded that WGA acts by a general blockade or constriction of the functional pore channel. At reduced WGA concentrations, the rate but not the final extent of nuclear protein accumulation was decreased. These findings support the concept that the O-glycosidically bound carbohydrates of certain nuclear pore complex proteins are exposed to the pore interior and that these regions are probably involved in nucleocytoplasmic translocation processes.

Sulfur chemistry in flames

Quantitative laser fluorescence measurements of the concentrations of SH, S2, SO, SO2 and OH have been made in the post flame gases of a series of 10 atmospheric pressure, stoichiometric and fuel-rich H2/O2/N2 flames, containing 0, 0.25, 0.5 or 1% mole fraction of sulfur as H2S. The present discussion characterizes the chemistry of sulfur in the fuel-rich flames and also validates this fluorescence monitoring technique. A kinetic rate analysis of all the possible interactions has established that the sulfur chemistry is controlled by 8 fast bimolecular radical reactions. S, S2, SH, H2S, SO and SO2 are all coupled by fast reactions and it is only a result of the imposition of the non-equilibrated H2/O2 flame chemistry that controls their relative proportions. Termolecular reactions, other than providing a catalytic means for recombining excess H and OH concentrations are insignificant. The establishment of the equilibration of the reaction H+SO2=SO+OH provides a new method whereby fluorescence measurements of OH along with SO and SO2 can be used to determine both H and H2 concentrations in stoichiometric flames containing sulfur. This study constitutes the first systematic application of quantitative laser fluorescence measurements to a study of chemistry in a series of flames of varying composition and temperature. It demonstrates an important and powerful new method of great sensitivity and non-perturbing nature for the detailed study of combustion processes.