Imaging carious dental tissues with multiphoton fluorescence lifetime imaging microscopy

In this study, multiphoton excitation was utilized to image normal and carious dental tissues noninvasively. Unique structures in dental tissues were identified using the available multimodality (second harmonic, autofluorescence, and fluorescence lifetime analysis) without labeling. The collagen in dentin exhibits a strong second harmonic response. Both dentin and enamel emit strong autofluorescence that reveals in detail morphological features (such as dentinal tubules and enamel rods) and, despite their very similar spectral profiles, can be differentiated by lifetime analysis. Specifically, the carious dental tissue exhibits a greatly reduced autofluorescence lifetime, which result is consistent with the degree of demineralization, determined by micro-computed tomography. Our findings suggest that two-photon excited fluorescence lifetime imaging may be a promising tool for diagnosing and monitoring dental caries

Laser-induced breakdown spectroscopy: a tool for real-time, in vitro and in vivo identification of carious teeth

BACKGROUND: Laser Induced Breakdown Spectroscopy (LIBS) can be used to measure trace element concentrations in solids, liquids and gases, with spatial resolution and absolute quantifaction being feasible, down to parts-per-million concentration levels. Some applications of LIBS do not necessarily require exact, quantitative measurements. These include applications in dentistry, which are of a more "identify-and-sort" nature – e.g. identification of teeth affected by caries. METHODS: A one-fibre light delivery / collection assembly for LIBS analysis was used, which in principle lends itself for routine in vitro / in vivo applications in a dental practice. A number of evaluation algorithms for LIBS data can be used to assess the similarity of a spectrum, measured at specific sample locations, with a training set of reference spectra. Here, the description has been restricted to one pattern recognition algorithm, namely the so-called Mahalanobis Distance method. RESULTS: The plasma created when the laser pulse ablates the sample (in vitro / in vivo), was spectrally analysed. We demonstrated that, using the Mahalanobis Distance pattern recognition algorithm, we could unambiguously determine the identity of an "unknown" tooth sample in real time. Based on single spectra obtained from the sample, the transition from caries-affected to healthy tooth material could be distinguished, with high spatial resolution. CONCLUSIONS: The combination of LIBS and pattern recognition algorithms provides a potentially useful tool for dentists for fast material identification problems, such as for example the precise control of the laser drilling / cleaning process

W-Nb-O oxides with tunable acid properties as efficient catalysts for the transformation of biomass-derived oxygenates in aqueous systems

[EN] W-Nb-O oxide bronzes, prepared hydrothermally, have been characterized and studied as catalysts for both the gas-phase dehydration of glycerol and the liquid-phase selective condensation of light oxygenates derived from primary treatments of biomass (a mixture containing acetic acid, ethanol, propanal, hydroxyacetone and water). By controlling the nominal composition of the catalysts, it is possible to tune their textural and acid properties (concentration and nature of acid sites) to selectively produce acrolein from glycerol or C-5-C-10 hydrocarbons (with low O contents and with high yields) from light oxygenates. Interestingly, these catalysts are stable when working in gas phase reactions and they are re-usable, with high resistance to leaching, when working in aqueous media.Financial support by the Spanish Government (CTQ-2015-68951-C3-1, CTQ-2015-67592, MAT2016-78362-C4-4-R and SEV-2016-0683) and Generalitat Valenciana (GVA, PROMETEO/2018/006) is gratefully acknowledged. A. F.-A. and D. D. thank the "La Caixa-Severo Ochoa" Foundation and Severo Ochoa Excellence Program (SVP-2016-0683), respectively, for their fellowships. The authors thank the ICTS Centro Nacional de Microscopia Electronica (UCM) for instrumental facilities.Delgado-Muñoz, D.; Fernández-Arroyo, A.; Domine, ME.; García-González, E.; López Nieto, JM. (2019). W-Nb-O oxides with tunable acid properties as efficient catalysts for the transformation of biomass-derived oxygenates in aqueous systems. Catalysis Science & Technology. 9(12):3126-3136. https://doi.org/10.1039/c9cy00367cS31263136912Huber, G. W., Iborra, S., & Corma, A. (2006). Synthesis of Transportation Fuels from Biomass:  Chemistry, Catalysts, and Engineering. Chemical Reviews, 106(9), 4044-4098. doi:10.1021/cr068360dCorma, A., Iborra, S., & Velty, A. (2007). Chemical Routes for the Transformation of Biomass into Chemicals. Chemical Reviews, 107(6), 2411-2502. doi:10.1021/cr050989dTuck, C. O., Perez, E., Horvath, I. T., Sheldon, R. A., & Poliakoff, M. (2012). Valorization of Biomass: Deriving More Value from Waste. Science, 337(6095), 695-699. doi:10.1126/science.1218930Alonso, D. M., Bond, J. Q., & Dumesic, J. A. (2010). Catalytic conversion of biomass to biofuels. Green Chemistry, 12(9), 1493. doi:10.1039/c004654jHuber, G. W., & Corma, A. (2007). Synergies between Bio- and Oil Refineries for the Production of Fuels from Biomass. Angewandte Chemie International Edition, 46(38), 7184-7201. doi:10.1002/anie.200604504Lari, G. M., Pastore, G., Haus, M., Ding, Y., Papadokonstantakis, S., Mondelli, C., & Pérez-Ramírez, J. (2018). Environmental and economical perspectives of a glycerol biorefinery. Energy & Environmental Science, 11(5), 1012-1029. doi:10.1039/c7ee03116eSun, D., Yamada, Y., Sato, S., & Ueda, W. (2017). Glycerol as a potential renewable raw material for acrylic acid production. Green Chemistry, 19(14), 3186-3213. doi:10.1039/c7gc00358gCespi, D., Passarini, F., Mastragostino, G., Vassura, I., Larocca, S., Iaconi, A., … Cavani, F. (2015). Glycerol as feedstock in the synthesis of chemicals: a life cycle analysis for acrolein production. Green Chemistry, 17(1), 343-355. doi:10.1039/c4gc01497aKatryniok, B., Paul, S., Bellière-Baca, V., Rey, P., & Dumeignil, F. (2010). Glycerol dehydration to acrolein in the context of new uses of glycerol. Green Chemistry, 12(12), 2079. doi:10.1039/c0gc00307gVenderbosch, R., & Prins, W. (2010). Fast pyrolysis technology development. Biofuels, Bioproducts and Biorefining, 4(2), 178-208. doi:10.1002/bbb.205Graça, I., Lopes, J. M., Cerqueira, H. S., & Ribeiro, M. F. (2013). Bio-oils Upgrading for Second Generation Biofuels. Industrial & Engineering Chemistry Research, 52(1), 275-287. doi:10.1021/ie301714xAsadieraghi, M., Wan Daud, W. M. A., & Abbas, H. F. (2014). Model compound approach to design process and select catalysts for in-situ bio-oil upgrading. Renewable and Sustainable Energy Reviews, 36, 286-303. doi:10.1016/j.rser.2014.04.050Pinheiro, A., Hudebine, D., Dupassieux, N., & Geantet, C. (2009). Impact of Oxygenated Compounds from Lignocellulosic Biomass Pyrolysis Oils on Gas Oil Hydrotreatment. Energy & Fuels, 23(2), 1007-1014. doi:10.1021/ef800507zBui, V. N., Toussaint, G., Laurenti, D., Mirodatos, C., & Geantet, C. (2009). Co-processing of pyrolisis bio oils and gas oil for new generation of bio-fuels: Hydrodeoxygenation of guaïacol and SRGO mixed feed. Catalysis Today, 143(1-2), 172-178. doi:10.1016/j.cattod.2008.11.024Wang, F., Dubois, J.-L., & Ueda, W. (2010). Catalytic performance of vanadium pyrophosphate oxides (VPO) in the oxidative dehydration of glycerol. Applied Catalysis A: General, 376(1-2), 25-32. doi:10.1016/j.apcata.2009.11.031Foo, G. S., Wei, D., Sholl, D. S., & Sievers, C. (2014). Role of Lewis and Brønsted Acid Sites in the Dehydration of Glycerol over Niobia. ACS Catalysis, 4(9), 3180-3192. doi:10.1021/cs5006376Nogueira, F. G. E., Asencios, Y. J. O., Rodella, C. B., Porto, A. L. M., & Assaf, E. M. (2016). Alternative route for the synthesis of high surface-area η-Al2O3/Nb2O5 catalyst from aluminum waste. Materials Chemistry and Physics, 184, 23-30. doi:10.1016/j.matchemphys.2016.08.032Massa, M., Andersson, A., Finocchio, E., & Busca, G. (2013). Gas-phase dehydration of glycerol to acrolein over Al2O3-, SiO2-, and TiO2-supported Nb- and W-oxide catalysts. Journal of Catalysis, 307, 170-184. doi:10.1016/j.jcat.2013.07.022Massa, M., Andersson, A., Finocchio, E., Busca, G., Lenrick, F., & Wallenberg, L. R. (2013). Performance of ZrO 2 -supported Nb- and W-oxide in the gas-phase dehydration of glycerol to acrolein. Journal of Catalysis, 297, 93-109. doi:10.1016/j.jcat.2012.09.021Dalil, M., Carnevali, D., Dubois, J.-L., & Patience, G. S. (2015). Transient acrolein selectivity and carbon deposition study of glycerol dehydration over WO3/TiO2 catalyst. Chemical Engineering Journal, 270, 557-563. doi:10.1016/j.cej.2015.02.058Dalil, M., Carnevali, D., Edake, M., Auroux, A., Dubois, J.-L., & Patience, G. S. (2016). Gas phase dehydration of glycerol to acrolein: Coke on WO3/TiO2 reduces by-products. Journal of Molecular Catalysis A: Chemical, 421, 146-155. doi:10.1016/j.molcata.2016.05.022Soriano, M. D., Concepción, P., Nieto, J. M. L., Cavani, F., Guidetti, S., & Trevisanut, C. (2011). Tungsten-Vanadium mixed oxides for the oxidehydration of glycerol into acrylic acid. Green Chemistry, 13(10), 2954. doi:10.1039/c1gc15622eMurayama, T., Nakajima, K., Hirata, J., Omata, K., Hensen, E. J. M., & Ueda, W. (2017). Hydrothermal synthesis of a layered-type W–Ti–O mixed metal oxide and its solid acid activity. Catalysis Science & Technology, 7(1), 243-250. doi:10.1039/c6cy02198kLa Salvia, N., Delgado, D., Ruiz-Rodríguez, L., Nadji, L., Massó, A., & Nieto, J. M. L. (2017). V- and Nb-containing tungsten bronzes catalysts for the aerobic transformation of ethanol and glycerol. Bulk and supported materials. Catalysis Today, 296, 2-9. doi:10.1016/j.cattod.2017.04.009Chieregato, A., Basile, F., Concepción, P., Guidetti, S., Liosi, G., Soriano, M. D., … Nieto, J. M. L. (2012). Glycerol oxidehydration into acrolein and acrylic acid over W–V–Nb–O bronzes with hexagonal structure. Catalysis Today, 197(1), 58-65. doi:10.1016/j.cattod.2012.06.024Chieregato, A., Soriano, M. D., García-González, E., Puglia, G., Basile, F., Concepción, P., … Cavani, F. (2014). Multielement Crystalline and Pseudocrystalline Oxides as Efficient Catalysts for the Direct Transformation of Glycerol into Acrylic Acid. ChemSusChem, 8(2), 398-406. doi:10.1002/cssc.201402721Chieregato, A., Bandinelli, C., Concepción, P., Soriano, M. D., Puzzo, F., Basile, F., … Nieto, J. M. L. (2016). Structure-Reactivity Correlations in Vanadium-Containing Catalysts for One-Pot Glycerol Oxidehydration to Acrylic Acid. ChemSusChem, 10(1), 234-244. doi:10.1002/cssc.201600954Deleplanque, J., Dubois, J.-L., Devaux, J.-F., & Ueda, W. (2010). Production of acrolein and acrylic acid through dehydration and oxydehydration of glycerol with mixed oxide catalysts. Catalysis Today, 157(1-4), 351-358. doi:10.1016/j.cattod.2010.04.012Delgado, D., Chieregato, A., Soriano, M. D., Rodríguez-Aguado, E., Ruiz-Rodríguez, L., Rodríguez-Castellón, E., & López Nieto, J. M. (2018). Influence of Phase Composition of Bulk Tungsten Vanadium Oxides on the Aerobic Transformation of Methanol and Glycerol. European Journal of Inorganic Chemistry, 2018(10), 1204-1211. doi:10.1002/ejic.201800059Pham, T. N., Sooknoi, T., Crossley, S. P., & Resasco, D. E. (2013). Ketonization of Carboxylic Acids: Mechanisms, Catalysts, and Implications for Biomass Conversion. ACS Catalysis, 3(11), 2456-2473. doi:10.1021/cs400501hFaba, L., Díaz, E., & Ordóñez, S. (2014). One-pot Aldol Condensation and Hydrodeoxygenation of Biomass-derived Carbonyl Compounds for Biodiesel Synthesis. ChemSusChem, 7(10), 2816-2820. doi:10.1002/cssc.201402236Gaertner, C. A., Serrano-Ruiz, J. C., Braden, D. J., & Dumesic, J. A. (2009). Catalytic coupling of carboxylic acids by ketonization as a processing step in biomass conversion. Journal of Catalysis, 266(1), 71-78. doi:10.1016/j.jcat.2009.05.015Gangadharan, A., Shen, M., Sooknoi, T., Resasco, D. E., & Mallinson, R. G. (2010). Condensation reactions of propanal over CexZr1−xO2 mixed oxide catalysts. Applied Catalysis A: General, 385(1-2), 80-91. doi:10.1016/j.apcata.2010.06.048Wang, S., & Iglesia, E. (2017). Experimental and theoretical assessment of the mechanism and site requirements for ketonization of carboxylic acids on oxides. Journal of Catalysis, 345, 183-206. doi:10.1016/j.jcat.2016.11.006Wang, S., Goulas, K., & Iglesia, E. (2016). Condensation and esterification reactions of alkanals, alkanones, and alkanols on TiO2: Elementary steps, site requirements, and synergistic effects of bifunctional strategies. Journal of Catalysis, 340, 302-320. doi:10.1016/j.jcat.2016.05.026Fernández-Arroyo, A., Delgado, D., Domine, M. E., & López-Nieto, J. M. (2017). Upgrading of oxygenated compounds present in aqueous biomass-derived feedstocks over NbOx-based catalysts. Catalysis Science & Technology, 7(23), 5495-5499. doi:10.1039/c7cy00916jNakajima, K., Hirata, J., Kim, M., Gupta, N. K., Murayama, T., Yoshida, A., … Ueda, W. (2017). Facile Formation of Lactic Acid from a Triose Sugar in Water over Niobium Oxide with a Deformed Orthorhombic Phase. ACS Catalysis, 8(1), 283-290. doi:10.1021/acscatal.7b03003Goto, Y., Shimizu, K., Kon, K., Toyao, T., Murayama, T., & Ueda, W. (2016). NH3-efficient ammoxidation of toluene by hydrothermally synthesized layered tungsten-vanadium complex metal oxides. Journal of Catalysis, 344, 346-353. doi:10.1016/j.jcat.2016.10.013Omata, K., Matsumoto, K., Murayama, T., & Ueda, W. (2016). Direct oxidative transformation of glycerol to acrylic acid over Nb-based complex metal oxide catalysts. Catalysis Today, 259, 205-212. doi:10.1016/j.cattod.2015.07.016Blanch-Raga, N., Soriano, M. D., Palomares, A. E., Concepción, P., Martínez-Triguero, J., & Nieto, J. M. L. (2013). Catalytic abatement of trichloroethylene over Mo and/or W-based bronzes. Applied Catalysis B: Environmental, 130-131, 36-43. doi:10.1016/j.apcatb.2012.10.016BOTELLA, P. (2004). Selective oxidative dehydrogenation of ethane on MoVTeNbO mixed metal oxide catalysts. Journal of Catalysis, 225(2), 428-438. doi:10.1016/j.jcat.2004.04.024Yun, Y., Araujo, J. R., Melaet, G., Baek, J., Archanjo, B. S., Oh, M., … Somorjai, G. A. (2017). Activation of Tungsten Oxide for Propane Dehydrogenation and Its High Catalytic Activity and Selectivity. Catalysis Letters, 147(3), 622-632. doi:10.1007/s10562-016-1915-2Yun, Y. S., Lee, K. R., Park, H., Kim, T. Y., Yun, D., Han, J. W., & Yi, J. (2014). Rational Design of a Bifunctional Catalyst for the Oxydehydration of Glycerol: A Combined Theoretical and Experimental Study. ACS Catalysis, 5(1), 82-94. doi:10.1021/cs501307vSoriano, M. D., Chieregato, A., Zamora, S., Basile, F., Cavani, F., & López Nieto, J. M. (2015). Promoted Hexagonal Tungsten Bronzes as Selective Catalysts in the Aerobic Transformation of Alcohols: Glycerol and Methanol. Topics in Catalysis, 59(2-4), 178-185. doi:10.1007/s11244-015-0440-7Nadji, L., Massó, A., Delgado, D., Issaadi, R., Rodriguez-Aguado, E., Rodriguez-Castellón, E., & Nieto, J. M. L. (2018). Gas phase dehydration of glycerol to acrolein over WO3-based catalysts prepared by non-hydrolytic sol–gel synthesis. RSC Advances, 8(24), 13344-13352. doi:10.1039/c8ra01575aEmeis, C. A. (1993). Determination of Integrated Molar Extinction Coefficients for Infrared Absorption Bands of Pyridine Adsorbed on Solid Acid Catalysts. Journal of Catalysis, 141(2), 347-354. doi:10.1006/jcat.1993.1145Murayama, T., Kuramata, N., Takatama, S., Nakatani, K., Izumi, S., Yi, X., & Ueda, W. (2012). Synthesis of porous and acidic complex metal oxide catalyst based on group 5 and 6 elements. Catalysis Today, 185(1), 224-229. doi:10.1016/j.cattod.2011.10.029HIBST, H., ROSOWSKI, F., & COX, G. (2006). New Cs-containing Mo–V4+ based oxides with the structure of the M1 phase—Base for new catalysts for the direct alkane activation. Catalysis Today, 117(1-3), 234-241. doi:10.1016/j.cattod.2006.05.045Shannon, R. D. (1976). Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides. Acta Crystallographica Section A, 32(5), 751-767. doi:10.1107/s0567739476001551Szilágyi, I. M., Madarász, J., Pokol, G., Király, P., Tárkányi, G., Saukko, S., … Varga-Josepovits, K. (2008). Stability and Controlled Composition of Hexagonal WO3. Chemistry of Materials, 20(12), 4116-4125. doi:10.1021/cm800668xMaczka, M., Hanuza, J., Kojima, S., Majchrowski, A., & van der Maas, J. H. (2001). Vibrational spectra of KNbW2O9 hexagonal tungsten bronze. Journal of Raman Spectroscopy, 32(4), 287-291. doi:10.1002/jrs.697McConnell, A. A., Aderson, J. S., & Rao, C. N. R. (1976). Raman spectra of niobium oxides. Spectrochimica Acta Part A: Molecular Spectroscopy, 32(5), 1067-1076. doi:10.1016/0584-8539(76)80291-7Jehng, J. M., & Wachs, I. E. (1991). Structural chemistry and Raman spectra of niobium oxides. Chemistry of Materials, 3(1), 100-107. doi:10.1021/cm00013a025Jehng, J.-M., & Wachs, I. E. (1990). Niobium Oxalate. ACS Symposium Series, 232-242. doi:10.1021/bk-1990-0437.ch021Soriano, M. D., García-González, E., Concepción, P., Rodella, C. B., & López Nieto, J. M. (2017). Self-Organized Transformation from Hexagonal to Orthorhombic Bronze of Cs–Nb–W–O Mixed Oxides Prepared Hydrothermally. Crystal Growth & Design, 17(12), 6320-6331. doi:10.1021/acs.cgd.7b00999Oshihara, K., Hisano, T., & Ueda, W. (2001). Topics in Catalysis, 15(2/4), 153-160. doi:10.1023/a:1016630307377Suwannakarn, K., Lotero, E., & Goodwin, J. G. (2007). Solid Brønsted Acid Catalysis in the Gas-Phase Esterification of Acetic Acid. Industrial & Engineering Chemistry Research, 46(22), 7050-7056. doi:10.1021/ie070536

Preparation, characterization and catalytic behavior for propanepartial oxidation of Ga-promoted MoVTeO catalysts

[EN] Two sets of Ga-promoted MoVTeO catalysts were synthesized hydrothermally and heat-treated at 600 degrees C in N-2: (i) materials prepared from gels with Mo/V/Te/Ga atomic ratios of 1/0.60/0.17/x (x=0-0.12) (A-series) and (ii) materials prepared from gels with Mo/V/Te/Ga atomic ratios of 1/0.60-x/0.17/x (x=0.15 or 0.25) (B-series). In addition, a Ga-containing MoVTeO catalyst was also prepared from M1-containing MoVTeO material by impregnation with aqueous solution of gallium and heat-treated at 450 degrees C in N-2. Catalysts were characterized by means of powder XRD, TEM, Raman spectroscopy, NH3-TPD and XPS and tested in the partial oxidation of propane. The results showed that the addition of small amount of gallium significantly increase the selectivity to acrylic acid (AA) at low propane conversion. However, at high propane conversion, the selectivity to AA strongly depends on both the catalyst composition and the gallium incorporation method. The higher selectivity to acrylic acid over Ga-containing MoVTeO catalysts has been related to: (i) structural changes in the M1 phase by the incorporation of Ga3+ into the octahedral structural framework and/or (ii) incorporation of Ga3+ species on the catalyst surface thus modifying catalysts acid properties. (C) 2014 Elsevier B.V. All rights reserved.Financial support from DGICYT in Spain (Project CTQ2012-37925-C03-1 and Program Severo Ochoa SEV-2012-0267) is gratefully acknowledged. EGG acknowledges finantial support through spanish project MAT2010-19837-C06-05 and the ICTS-Microscopia Electronica in Madrid for facilities.Hernández Morejudo, S.; Massó Ramírez, A.; García-González, E.; Concepción Heydorn, P.; López Nieto, JM. (2015). Preparation, characterization and catalytic behavior for propanepartial oxidation of Ga-promoted MoVTeO catalysts. Applied Catalysis A: General. 504:51-61. https://doi.org/10.1016/j.apcata.2014.12.039S516150

Fluorescence-Based Methods for Detecting Caries Lesions: Systematic Review, Meta-Analysis and Sources of Heterogeneity

Background Fluorescence-based methods have been proposed to aid caries lesion detection. Summarizing and analysing findings of studies about fluorescence-based methods could clarify their real benefits. Objective We aimed to perform a comprehensive systematic review and meta-analysis to evaluate the accuracy of fluorescence-based methods in detecting caries lesions. Data Source Two independent reviewers searched PubMed, Embase and Scopus through June 2012 to identify papers/articles published. Other sources were checked to identify non-published literature. Study Eligibility Criteria, Participants and Diagnostic Methods The eligibility criteria were studies that: (1) have assessed the accuracy of fluorescence-based methods of detecting caries lesions on occlusal, approximal or smooth surfaces, in both primary or permanent human teeth, in the laboratory or clinical setting; (2) have used a reference standard; and (3) have reported sufficient data relating to the sample size and the accuracy of methods. Study Appraisal and Synthesis Methods A diagnostic 2×2 table was extracted from included studies to calculate the pooled sensitivity, specificity and overall accuracy parameters (Diagnostic Odds Ratio and Summary Receiver-Operating curve). The analyses were performed separately for each method and different characteristics of the studies. The quality of the studies and heterogeneity were also evaluated. Results Seventy five studies met the inclusion criteria from the 434 articles initially identified. The search of the grey or non-published literature did not identify any further studies. In general, the analysis demonstrated that the fluorescence-based method tend to have similar accuracy for all types of teeth, dental surfaces or settings. There was a trend of better performance of fluorescence methods in detecting more advanced caries lesions. We also observed moderate to high heterogeneity and evidenced publication bias. Conclusions Fluorescence-based devices have similar overall performance; however, better accuracy in detecting more advanced caries lesions has been observed

Mid-Infrared Laser Ablation of Stratum Corneum Enhances In Vitro Percutaneous Transport of Drugs

The precise removal of stratum corneum from cadaveric swine skin by a mid-infrared erbium: yttrium scandium gallium garnet laser (λ = 2.79 μm; 250 μsec pulse width) was assessed by electrical resistance measurements and documented by histology. The effects of stratum corneum removal by laser ablation and by adhesive tape-stripping on the in vitro penetration of 3H-hydrocortisone and 125I-γ-interferon were determined. Excised swine skin was irradiated with laser (1 J/cm2 31 mJ/pulse; 1 Hz; 2mm spot diameter). For skin penetration studies, laser pulses were delivered to discrete 2-mm areas to ablate up to 12.6% of the total 3-cm2 stratum corneum diffusional area. Franz in vitro skin penetration chambers were used to measure the cumulative 48-h penetration of 3H-hydrocortisone and 125I-γ-interferon in laser-treated and tape-stripped skin. Electrical resistance measurements and histologic studies demonstrated that 10-14 laser pulses at the above energy density were required to abolish skin resistance and selectively ablate stratum corneum without damage to adjacent dermal structures. Laser ablation of 12.6% of the surface area of stratum corneum produced a 2.8 and 2.1-times increase in permeability constant (kp) for 3H-hydrocortisone and 125I-λ-interferon, respectively. These studies demonstrate that a pulsed mid-infrared laser can reliably and precisely remove the stratum corneum, facilitating penetration of large molecules such as 125I-λ-interferon that cannot penetrate intact skin. This new technique may be useful for basic and clinical investigation of skin barrier properties

Fluorescence devices for the detection of dental caries

BACKGROUND: Caries is one of the most prevalent and preventable conditions worldwide. If identified early enough then non‐invasive techniques can be applied, and therefore this review focusses on early caries involving the enamel surface of the tooth. The cornerstone of caries detection is a visual and tactile dental examination, however alternative methods of detection are available, and these include fluorescence‐based devices. There are three categories of fluorescence‐based device each primarily defined by the different wavelengths they exploit; we have labelled these groups as red, blue, and green fluorescence. These devices could support the visual examination for the detection and diagnosis of caries at an early stage of decay. OBJECTIVES: Our primary objectives were to estimate the diagnostic test accuracy of fluorescence‐based devices for the detection and diagnosis of enamel caries in children or adults. We planned to investigate the following potential sources of heterogeneity: tooth surface (occlusal, proximal, smooth surface or adjacent to a restoration); single point measurement devices versus imaging or surface assessment devices; and the prevalence of more severe disease in each study sample, at the level of caries into dentine. SEARCH METHODS: Cochrane Oral Health's Information Specialist undertook a search of the following databases: MEDLINE Ovid (1946 to 30 May 2019); Embase Ovid (1980 to 30 May 2019); US National Institutes of Health Ongoing Trials Register (ClinicalTrials.gov, to 30 May 2019); and the World Health Organization International Clinical Trials Registry Platform (to 30 May 2019). We studied reference lists as well as published systematic review articles. SELECTION CRITERIA: We included diagnostic accuracy study designs that compared a fluorescence‐based device with a reference standard. This included prospective studies that evaluated the diagnostic accuracy of single index tests and studies that directly compared two or more index tests. Studies that explicitly recruited participants with caries into dentine or frank cavitation were excluded. DATA COLLECTION AND ANALYSIS: Two review authors extracted data independently using a piloted study data extraction form based on the Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS‐2). Sensitivity and specificity with 95% confidence intervals (CIs) were reported for each study. This information has been displayed as coupled forest plots and summary receiver operating characteristic (SROC) plots, displaying the sensitivity‐specificity points for each study. We estimated diagnostic accuracy using hierarchical summary receiver operating characteristic (HSROC) methods. We reported sensitivities at fixed values of specificity (median 0.78, upper quartile 0.90). MAIN RESULTS: We included a total of 133 studies, 55 did not report data in the 2 x 2 format and could not be included in the meta‐analysis. 79 studies which provided 114 datasets and evaluated 21,283 tooth surfaces were included in the meta‐analysis. There was a high risk of bias for the participant selection domain. The index test, reference standard, and flow and timing domains all showed a high proportion of studies to be at low risk of bias. Concerns regarding the applicability of the evidence were high or unclear for all domains, the highest proportion being seen in participant selection. Selective participant recruitment, poorly defined diagnostic thresholds, and in vitro studies being non‐generalisable to the clinical scenario of a routine dental examination were the main reasons for these findings. The dominance of in vitro studies also means that the information on how the results of these devices are used to support diagnosis, as opposed to pure detection, was extremely limited. There was substantial variability in the results which could not be explained by the different devices or dentition or other sources of heterogeneity that we investigated. The diagnostic odds ratio (DOR) was 14.12 (95% CI 11.17 to 17.84). The estimated sensitivity, at a fixed median specificity of 0.78, was 0.70 (95% CI 0.64 to 0.75). In a hypothetical cohort of 1000 tooth sites or surfaces, with a prevalence of enamel caries of 57%, obtained from the included studies, the estimated sensitivity of 0.70 and specificity of 0.78 would result in 171 missed tooth sites or surfaces with enamel caries (false negatives) and 95 incorrectly classed as having early caries (false positives). We used meta‐regression to compare the accuracy of the different devices for red fluorescence (84 datasets, 14,514 tooth sites), blue fluorescence (21 datasets, 3429 tooth sites), and green fluorescence (9 datasets, 3340 tooth sites) devices. Initially, we allowed threshold, shape, and accuracy to vary according to device type by including covariates in the model. Allowing consistency of shape, removal of the covariates for accuracy had only a negligible effect (Chi(2) = 3.91, degrees of freedom (df) = 2, P = 0.14). Despite the relatively large volume of evidence we rated the certainty of the evidence as low, downgraded two levels in total, for risk of bias due to limitations in the design and conduct of the included studies, indirectness arising from the high number of in vitro studies, and inconsistency due to the substantial variability of results. AUTHORS' CONCLUSIONS: There is considerable variation in the performance of these fluorescence‐based devices that could not be explained by the different wavelengths of the devices assessed, participant, or study characteristics. Blue and green fluorescence‐based devices appeared to outperform red fluorescence‐based devices but this difference was not supported by the results of a formal statistical comparison. The evidence base was considerable, but we were only able to include 79 studies out of 133 in the meta‐analysis as estimates of sensitivity or specificity values or both could not be extracted or derived. In terms of applicability, any future studies should be carried out in a clinical setting, where difficulties of caries assessment within the oral cavity include plaque, staining, and restorations. Other considerations include the potential of fluorescence devices to be used in combination with other technologies and comparative diagnostic accuracy studies

Surfing the spectrum - what is on the horizon?

Diagnostic imaging techniques have evolved with technological advancements - but how far? The objective of this article was to explore the electromagnetic spectrum to find imaging techniques which may deliver diagnostic information of equal, or improved, standing to conventional radiographs and to explore any developments within radiography which may yield improved diagnostic data. A comprehensive literature search was performed using Medline, Web of Knowledge, Science Direct and PubMed Databases. Boolean Operators were used and key-terms included (not exclusively): terahertz, X-ray, ultraviolet, visible, infra-red, magnetic resonance, dental, diagnostic, caries and periodontal. Radiographic techniques are primarily used for diagnostic imaging in dentistry, and continued developments in X-ray imaging include: phase contrast, darkfield and spectral imaging. Other modalities have potential application, for example, terahertz, laser doppler and optical techniques, but require further development. In particular, infra-red imaging has regenerated interest with caries detection in vitro, due to improved quality and accessibility of cameras. Non-ionising imaging techniques, for example, infra-red, are becoming more commensurate with traditional radiographic techniques for caries detection. Nevertheless, X-rays continue to be the leading diagnostic image for dentists, with improved diagnostic potential for lower radiation dose becoming a reality