[Impact of the coronavirus on Dutch oral health care and practice]. / Impact van het coronavirus op de praktijkvoering van de Nederlandse mondzorg.

Among dental hygienists and dentists in the Netherlands, the impact of the SARS-CoV-2 pandemic on oral healthcare practices from March to July 2020 was investigated. Of the 1,700 healthcare providers approached, 433 completed questionnaires could be used. The results show that the pandemic has had a profound impact on both the accessibility of oral healthcare and on care provided in oral healthcare practices. Extra attention was paid to hygiene and infection prevention: the types of personal protective equipment and the protocols and procedures were adjusted by many oral healthcare providers. The confirmed prevalence of oral healthcare providers with COVID-19 in this study was 1.6%. However, testing was not available to all respondents with complaints during this initial period. Over half of the respondents estimated that even with additional measures there is an increased risk of infection to oral healthcare providers during their work. The efficacy of the various additional measures in oral healthcare practices related to COVID-19 is still unknown.

Candida albicans alters the bacterial microbiome of early in vitro oral biofilms.

The yeast Candida albicans is an oral commensal microorganism, occurring in the oral cavity of 50-70% of healthy individuals. Its effect on oral ecology has mostly been studied using dual-species models, which disregards the complex nature of oral biofilms. The aim of this study was to culture C. albicans in a complex model to study its effect on oral biofilms. Biofilms, inoculated using pooled stimulated saliva with or without addition of C. albicans, were grown under anaerobic, aerobic, or aerobic +5% CO2 conditions. Red autofluorescence was quantified using a spectrophotometer and visualized in fluorescence photographs. The microbiome of 5 h biofilms was determined using 16S rDNA sequencing. C. albicans was only able to proliferate in biofilms grown under aerobic conditions. After 48 h, C. albicans did not induce differences in total biofilm formation, lactic acid accumulation (cariogenic phenotype) or protease activity (periodontitis phenotype). In vitro, anaerobically grown biofilms developed red autofluorescence, irrespective of inoculum. However, under aerobic conditions, only C. albicans-containing biofilms showed red autofluorescence. Facultative or strict anaerobic Veillonella, Prevotella, Leptotrichia, and Fusobacterium genera were significantly more abundant in biofilms with C. albicans. Biofilms without C. albicans contained more of the aerobic and facultative anaerobic genera Neisseria, Rothia, and Streptococcus. The presence of C. albicans alters the bacterial microbiome in early in vitro oral biofilms, resulting in the presence of strictly anaerobic bacteria under oxygen-rich conditions. This in vitro study illustrates that C. albicans should not be disregarded in healthy oral ecosystems, as it has the potential to influence bacteria significantly.

Detecting Short-Term Changes in the Activity of Caries Lesions with the Aid of New Technologies.

This paper discusses the use of new technologies for the assessment of caries and more in particular changes in caries activity. Over the past decades, we have seen a shift from restorative treatment caries to a prevention-driven approach. Also there is a need for shorter and less expensive caries clinical trials. These demand earlier detection of lesions and the monitoring of lesion changes longitudinally in time, which has led to the development of new technologies to aid clinical visual examination. Also clinical visual inspection indices have been refined to fit this purpose. There is a constant flow of technologies emerging and disappearing. This review discusses the merits of recent developments regarding their respective uses for research purposes in testing new caries prevention strategies as well as in clinical caries management in dental private practice. Which technique to choose highly depends on the needed resolution of information.

Carbon nanotube growth for through silicon via application.

Through silicon via (TSV) technology is key for next generation three-dimensional integrated circuits, and carbon nanotubes (CNT) provide a promising alternative to metal for filling the TSV. Three catalyst preparation methods for achieving CNT growth from the bottom of the TSV are investigated. Compared with sputtering and evaporation, catalyst deposition using dip-coating in a FeCl2 solution is found to be a more efficient method for realizing a bottom-up filling of the TSV (aspect ratio 5 or 10) with CNT. The CNT bundles grown in 5 min exceed the 50 µm length of the TSV and are multi-wall CNT with three to eight walls. The CNT bundles inside the TSV were electrically characterized by creating a direct contact using a four-point nanoprober setup. A low resistance of the CNT bundle of 69.7 Ω (297 Ω) was measured when the CNT bundle was contacted midway along (over the full length of) the 25 µm deep TSV. The electrical characterization in combination with the good filling of the TSV demonstrates the potential use of CNT in fully integrated TSV applications.

Effects of casein phosphopeptide amorphous calcium fluoride phosphate paste on white spot lesions and dental plaque after orthodontic treatment: a 3-month follow-up.

The effects of casein phosphopeptide amorphous calcium fluoride phosphate (CPP-ACFP) paste vs. control paste on the remineralization of white spot caries lesions and on plaque composition were tested in a double-blind prospective randomized clinical trial. Fifty-four orthodontic patients, with multiple white spot lesions observed upon the removal of fixed appliances, were followed up for 3 months. Subjects were included and randomly assigned to either CPP-ACFP paste or control paste, for use supplementary to their normal oral hygiene. Caries regression was assessed on quantitative light-induced fluorescence (QLF) images captured directly after debonding and 6 and 12 wk thereafter. The total counts and proportions of aciduric bacteria, Streptococcus mutans, and Lactobacillus spp. were measured in plaque samples obtained just before debonding, and 6 and 12 wk afterwards. A significant decrease in fluorescence loss was found with respect to baseline for both groups and no difference was found between groups. The size of the lesion area did not change significantly over time or between the groups. The percentages of aciduric bacteria and of S. mutans decreased from 47.4 to 38.1% and from 9.6 to 6.6%, respectively. No differences were found between groups. We observed no clinical advantage for use of the CPP-ACFP paste supplementary to normal oral hygiene over the time span of 12 wk.

Bacterial composition and red fluorescence of plaque in relation to primary and secondary caries next to composite: an in situ study.

BACKGROUND/HYPOTHESIS: Secondary caries has been suggested as the main reason for restoration replacement. We hypothesized that more caries-associated bacteria are found on composite resin restoration material, compared to sound tooth tissue. METHODS: Both restored and unrestored dentin and enamel samples were placed in a full denture of eight subjects for 20 weeks. The microbiological composition of approximal plaque and the association between caries-associated bacteria and red autofluorescence of dental plaque was studied. Every 4 weeks the specimens were microradiographed using transversal wavelength independent microradiography (T-WIM). After 1 and 20 weeks red fluorescence pictures and plaque samples were taken. Samples were cultured for total anaerobic counts, mutans streptococci, lactobacilli, candida and Actinomyces odontolyticus. RESULTS: Lesion depth in the dentin and enamel was positively associated with lactobacilli, and lesion depth in dentin was positively associated with A. odontolyticus, whereas no association was found between mutans streptococci and lesion depth. The red-fluorescent bacteria A. odontolyticus and lactobacilli did not correlate with red-fluorescent plaque, indicating that red fluorescence is probably not caused by a single species of these bacteria. After 20 weeks, a higher proportion of combined mutans streptococci and lactobacilli was found on restored tissue compared to non-restored tissue (P = 0.04). CONCLUSION: The higher proportion of caries-associated bacteria on restored tissue indicates that the ecology on the surface of primary lesions differs from that on lesions next to composite, and that secondary caries next to composite may differ from the primary caries process.

Caries lesions after orthodontic treatment followed by quantitative light-induced fluorescence: a 2-year follow-up.

The aim of this study was to monitor, by means of quantitative light-induced fluorescence (QLF), the natural behaviour of white spot lesions detected immediately after orthodontic treatment and 2 years post-treatment. The buccal tooth surfaces of 51 subjects (>or=12 years), 24 males and 27 females, were examined with QLF for the presence of caries immediately after debonding (T0), and 6 weeks (T1), 6 months (T2), and 2 years (T3) thereafter. The fluorescence loss [Delta F (per cent)] and area [A (mm(2))] of any lesions were determined using dedicated software. The lesion development and influence of gender were determined by a general linear model (Friedman repeated-measures analysis and two-way repeated-measures analysis of variance). Using QLF, 370 carious surfaces were recorded at T0. During the study, 19 lesions were lost from QLF analysis of which 16 lesions (Delta F(0)=7.6-39.2 per cent) in two subjects were restored and three teeth with lesions were extracted or crowned. This resulted in 351 lesions that were included in this study with a median Delta F at T0 of 8.5 per cent (quartiles 6.6 per cent; 11.9 per cent). The lesions varied from incipient (Delta F<10 per cent, n=227) to advanced (Delta F>25 per cent, n=6). Overall, the lesions showed improvement between T0 and T2 (P<0.01) but no further significant improvement at T3. Thirty-five lesions became significantly worse after 2 years. The majority of lesions (n=171) were considered to be stable, and 145 lesions improved significantly of which only 10 lesions improved to such an extent that they disappeared. White spot lesions developed during orthodontic treatment have very limited ability to improve after appliance removal. Further research to investigate the potential of preventive measures to enhance lesion improvement is necessary.

Red autofluorescence of dental plaque bacteria.

Red autofluorescence of plaque and its relation to fluorescence of a single species in the biofilm was studied. Fluorescence images of non-disclosed and disclosed plaque of 28 first-year students were captured. The plaque samples were assessed by culture methods and studied for red autofluorescence. Species capable of producing red autofluorescence were cultivated from subjects with and without red plaque autofluorescence. Red autofluorescence was observed from Actinomyces odontolyticus, Prevotella intermedia and from Porphyromonas gingivalis and Peptostreptococcus micros grown together. The microbial findings indicated that the intrinsic characteristics of the mature biofilm itself are more responsible for the red autofluorescence than the characteristics of the single species.

Caries prevalence measured with QLF after treatment with fixed orthodontic appliances: influencing factors.

Caries prevalence on the buccal surfaces of teeth in orthodontic patients was determined with QLF and visual examination immediately after removal of fixed appliances. The number of lesions found by QLF far outnumbered that found by visual examination, but the distribution pattern was similar. 97% of all subjects and on average 30% of the buccal surfaces in a person were affected. On average, in males 40% of surfaces and in females 22% showed white spots (p < 0.01). Caries prevalence was lower (p < 0.01) in incisors and cuspids than in molars and premolars. A positive correlation with caries prevalence was found for the bleeding scores 6 weeks after debonding and lactobacillus counts before debonding. Mutans streptococci counts, age, treatment duration, socioeconomic status and dietary habits showed no correlation with caries prevalence.

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 approximately = 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 (approximately 0.1 vol% microm(-1)).

Optimal camera and illumination angulations for detection of interproximal caries using quantitative light-induced fluorescence.

The aim of the study was to find the optimal illumination and camera angulations for interproximal use of quantitative light-induced fluorescence (QLF). A multiaxis optical bench was developed and interproximal tooth assemblies were investigated using a modified version of QLF. Extracted human premolars without caries (n = 8) and with interproximal D1, D2 and D3 caries (n = 20) were selected. Tooth-pair models without caries and with interproximal caries of matching size, location, and shape were imaged with varying camera and illumination directions from buccal (0 degrees) to occlusal (90 degrees) to lingual (180 degrees) in steps of 30 degrees using a PC and framegrabber and examined for observed presence. Interproximal lesions could be detected in all teeth, but observed presence was dependent on camera angulation (p < 0.05), rather than on illumination angulation (p = 0.32). No caries could be detected with the camera in the 90 degree position.

[Lasers in dentistry 2. Diagnosis of dental caries with lasers]. / Lasers in de tandheelkunde. 2. Cariësdiagnostiek met lasers.

When enamel, dentine and substances in caries lesions are exposed to (laser) light of a specific colour, fluorescence may be induced. This principle is at the basis of two caries diagnostic methods, DIAGNOdent and Quantitative Laser (Light-induced) Fluorescence (QLF). Only the DIAGNOdent is commercially available. Bacterial porphyrins evoke fluorescence when illuminated with red light and the intensity of the emitted light is related to the size of the caries lesion. Published research indicates that the DIAGNOdent is particularly suitable for detecting small bacteria containing caries lesions, and to monitor such lesions. QLF is based on the fluorescence decrease in demineralised enamel upon exposure to blue-violet (laser) light. The intensity of the emitted light is related to the amount of mineral loss in the caries lesion. Using QLF the mineral loss in caries lesions can be measured quantitatively. Like the DIAGNOdent, QLF is particularly suitable to monitor caries lesions.

Comparative study to quantify demineralized enamel in deciduous and permanent teeth using laser- and light-induced fluorescence techniques.

Caries is a disease that affects both deciduous and permanent dentitions. Caries progresses more rapidly in deciduous enamel than in permanent enamel. Therefore, new caries diagnostic methods need to be tested on the deciduous teeth as well. Quantitative laser-induced fluorescence (QLF I) as well as the quantitative light-induced fluorescence (QLF II) seem promising for the quantification of mineral loss from dental caries but have only been tested on the permanent dentition. The objective of this study was to determine and compare the ability of QLF I and QLF II to quantify mineral loss from carious lesions in both deciduous and permanent teeth. Thirty sound deciduous and 30 sound permanent teeth were cleaned and divided into three groups each containing 10 deciduous and 10 permanent teeth. Windows on the buccal or labial enamel surfaces were demineralized for 48, 72, or 96 h. Images of demineralized enamel were captured using QLF I and QLF II. The images were analyzed to determine the mean change in fluorescence radiance (Delta F, %). The teeth were then sectioned for assessment of lesion depth (microm) and integrated mineral loss (IML, vol% x microm) using transverse microradiography (TMR), as the 'gold standard' for lesion analysis. The results indicated a good correlation for Delta F between QLF I and QLF II in both deciduous (r = 0.96) and permanent teeth (r = 0.98). There was a good correlation between Delta F and TMR (lesion depth and IML) in deciduous teeth (r = 0.76 and 0.84 with QLF I, r = 0.81 and 0.88 with QLF II). In permanent teeth, the correlation between Delta F and TMR (lesion depth and IML) was lower than in deciduous teeth (r = 0.07 and 0.53 with QLF I, r = 0.15 and 0.62 with QLF II). From these results it can be concluded that either QLF method is capable of quantifying mineral loss in early carious lesions in deciduous teeth. Moreover, under the conditions of this study, the use of either QLF method to quantify mineral loss in early carious lesions in deciduous teeth is slightly more accurate than in permanent teeth.

Application of quantitative light-induced fluorescence for assessing early caries lesions.

Quantitative light induced fluorescence (QLF) is a nondestructive diagnostic method for the longitudinal assessment of early caries lesions in time. When a tooth becomes carious the fluorescence radiance at the location of the caries lesion decreases. The fluorescence image of enamel with incipient lesions can be digitized and then the fluorescence loss in the lesion can be quantified in comparison to the fluorescence radiance level of sound enamel. Changes in fluorescence radiance and lesion area can be followed in time to measure lesion development. The amount of fluorescence radiance loss is related to the mineral loss in the lesion. The technique can be used in vitro, in situ and in vivo to monitor mineral changes in lesions. Applications of QLF are found in the testing of products designed to inhibit demineralization and promote remineralization of caries. The method has been successfully applied to smooth surfaces as well as occlusal surfaces, but application on approximal lesions is not yet possible.

X-ray-induced photoelectron spectroscopy of dentin as a function of duration of Ar(+)-ion etching.

XPS, or ESCA, measures the atomic concentration in the outermost layers of the sample. The surface is often etched with Ar(+)-ions before any measurement. We investigated the role thereof on XPS measurements of root dentin. Nine slices were cut from premolars. Slices were ground or broken. XPS was measured before etching. Six samples were then subjected to Ar(+)-ion etching (10 kV ions, 0.25 microA/mm2). A gold sample was also included. Relative concentrations of N and C decreased with etching time, while O, P, and Ca increased. N and C curves were analyzed assuming a sum of two exponential decays and a final level. On average, tau 1 = 20 sec for C and 17 sec for N. On average, tau 2 = 278 sec for C and 350 sec for N. No differences between differently prepared samples were apparent. The gold sample showed a single decay to noise for C and N, with tau 1 = 8 and 7 sec, respectively. We conclude that two decay processes are present, due to gas removal and to the removal of organic material from the dentin matrix, respectively. Thus, true values can be obtained by extrapolation to t = 0 of only the data obtained by summing the slow decay and the final level.

A fiber-optic setup for quantification of root surface demineralization.

A fiber-optic fluorescence observation (FOFO) technique has been developed for the quantification of demineralized root dentin. The method was tested on 40 specimens of in vitro demineralized parts of human root dentin. Fluorescein sodium salt was used as a penetrating dye. The fluorescein sodium salt was excited using light around 465 nm. The fluorescence signal around 527 nm measured for demineralized dentin was corrected for lamp output and then divided by the corrected fluorescence signal for the sound control dentin on the same root, resulting in a FOFO-value. FOFO-values correlate linearly (r = 0.91) with mineral loss measured by transverse microradiography. Therefore, it was concluded that the FOFO-technique provides a good, non-destructive measure of the severeness of in vitro demineralized human root dentin, and is applicable on bulk dentin. Future work on natural lesions in vivo will be needed to investigate the applicability of the technique in a clinical situation.

The influence of mineral loss on the auto-fluorescent behaviour of in vitro demineralised dentine.

The aim of this study is to investigate the influence of demineralisation on the fluorescent properties of dentine. The fluorescence emission at 529 nm due to 515 nm excitation of in vitro demineralised lesions was determined with a micro-Raman spectroscope as a function of location. Results were compared with the mineral loss profiles of the same lesions measured by microradiography. The root surfaces of 6 in vitro demineralised human third molars (lactic acid CMC gel, pH 5; six groups: 0, 4, 7, 14, 18 and 21 days) were used in the experiment. Thin slices of +/- 130 microns were cut perpendicular to the tooth axis. The fluorescence scans corresponded to mineral loss profiles. Confocal microscope images showed increasing fluorescence with increasing mineral loss. From these results it is concluded that this mineral loss causes an increase in auto-fluorescence by a factor of at least 10, therefore the chromophore causing this green fluorescence must be organic in nature. De-quenching or modification of this fluorophore due to the demineralisation process is probably the cause for the increase of the green fluorescence.

Evaluation of sodium fluorescein for quantitative diagnosis of root caries.

The diagnosis of root caries, in particular the judgment of the activity of a visually observed lesion, is difficult. Quantitative determination of lesion severity would allow the lesion to be monitored with time, so that an indication of lesion activity could be obtained. This paper describes a step in the development of a method that provides such a quantitative determination. Specifically, fluorescein sodium salt is used as a penetrating dye, the subject of study being the relationship between dye concentration and porosity in demineralized root dentin. Fourteen human third molars were demineralized in vitro (lactic acid CMC-gel, pH 5; in each of 6 groups for 4, 7, 11, 14, 18, and 21 days). Fluorescein sodium salt (0.2 g/L) was applied for 2 min. Thin slices (+/- 130 microns) were cut from the root surfaces without water cooling. The dye fluorescence radiance in the demineralized dentin was determined by means of a micro-Raman spectroscope and compared with the mineral loss profiles measured with transverse microradiography (TMR). The TMR data were corrected for the difference in measurement area between the two measurement systems. Corrected TMR profiles were compared with the corresponding fluorescence scans, showing linear correspondence. The correlation coefficient was r = 0.96. We conclude that, after uptake of fluorescein sodium salt for 2 min, the dye concentration in an artificially produced root-surface caries lesion is proportional to the amount of mineral lost from that lesion.

Autofluorescence of bulk sound and in vitro demineralized human root dentin.

The aim of this paper is to report on the demineralization-induced changes in dentin autofluorescence. Confocal laser scanning microscopy (CLSM) images and fluorescence excitation and emission spectra in vitro demineralized root surfaces and sound controls on the same tooth roots were compared. When observed in CLSM images, demineralized dentin, excited at 488 nm, gave an increased emission at 529 nm compared to sound dentin. The difference in fluorescence decreased deeper into the root, as the sound dentin underneath the lesion was reached. In contrast, when using fluorescence spectrophotometry, excitation around 460 and 488 nm yielded a lower emission around 520 nm for demineralized dentin than for sound dentin, but in a more pronounced peak. From excitation spectra for emission around 520 nm, it could be seen that in demineralized dentin the contribution of excitation between 480 and 520 nm was more important than in sound dentin. The recorded fluorescence in CLSM images was not affected by demineralization-caused changes in scattering and absorption properties, due to the small measurement volume. Thus, the increased fluorescence for demineralized dentin implies an increased quantum yield. In fluorescence spectrophotometry, where the measurement volume is large, changes in scattering and absorption do have an influence on the fluorescence signal. Then, increased absorption by non-fluorescing chromophores and increased re-absorption around the emission wavelength may compensate for the increase in quantum yield and absorption around the excitation wavelength by fluorophores.