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Improved methods are needed to assess the structure and activity of lesions on root surfaces in order to improve clinical decision making. Conventional visual and tactile methods for assessing lesion activity are not reliable, and the clinician is often unable to evaluate if the lesion is progressing or has remineralized. An important marker of an arrested lesion is a highly mineralized surface zone that forms when mineral is deposited in the outer layer of the lesion. In vitro studies have shown that a mineralized surface zone influences the kinetics of water evaporation and the surface temperature while drying. Temperature changes can be monitored by measuring the thermal emission with thermal imaging. Studies have also shown that the depth and severity of demineralization and the thickness of the highly mineralized transparent surface zone on arrested lesions can be measured nondestructively with optical coherence tomography (OCT). Thermal imaging at 8-µm to 13-µm wavelengths was completed on 30 test subjects with a suspected active root caries lesion by monitoring thermal emission from the tooth surfaces during 30 s of air drying. Lesions were also evaluated using cross-polarization OCT (CP-OCT) during lesion dehydration to identify transparent surface zones indicative of arrested lesions and determine if shrinkage occurred during drying. The overall thermal emission recorded during drying was significantly different (P < 0.001) when comparing sound tooth surfaces, lesion areas identified as arrested, and lesion areas identified as active, demonstrating that thermal imaging is a promising approach for the clinical assessment of lesion activity on root surfaces. Ten of the lesions in this study had distinct areas with transparent surface zones that were visible in CP-OCT images. Shrinkage was detected with CP-OCT during drying for 12 lesions. This study confirms that these novel approaches for assessing lesion activity on root surfaces can be implemented in vivo.

The diagnosis of root caries and root fractures is of increasing importance due to our aging population. The objective of this study is to show that optical clearing agents can be used to increase the visibility of subsurface structures in tooth roots to aid in the diagnosis of root caries depth and extension and to differentiate from subsurface defects. Previous studies have shown that high refractive index fluids can increase the depth penetration of optical coherence tomography (OCT) for imaging caries lesions on tooth enamel. Extracted teeth with suspected root caries were imaged with (OCT) with and without the addition of water (W), glycerol (G), and propylene glycol (PG). The reflectance was monitored in sound and demineralized areas before and after application of W, G, and PG. The visibility of subsurface root canals was also measured before and after application of the respective fluids. In addition, shrinkage in lesion areas was measured after lesion dehydration to aid in the assessment of lesion activity. This study shows that optical clearing agents can be used to increase the performance of OCT for the diagnosis of root caries and other defects on root surfaces.

The terahertz (THz) and sub-THz region of the electromagnetic spectrum bridges the infrared and the microwave. This boundary region is beyond the normal reach of optical and electronic measurement techniques normally associated with these better-known neighbors. Only over the past decade has this THz region become scientifically accessible withbroadband sources of moderate intensity being produced by ultra-fast laser pulses incident on biased semiconductors or non-linear crystals [1,2]. Very recently, a much higher power source of THz radiation was demonstrated: coherent synchrotron radiation (CSR) from short, relativistic electron bunches [3-5]. Coherent synchrotron radiation will open up new territory in the THz frequency range with intensities many orders of magnitude higher than previous sources. The energy range between microwave and the far infrared, 3 33 cm-1 (0.1 1 THz), has proven to be challenging to accesses and is therefore referred to as the THz gap . However, with the new CSR source at BESSY [3,5] we have been able to extend traditional infrared measurements down into this sub-terahertz frequency range. This source is broadband and is made up of longitudinally coherent single-cycle sub-picosecond pulses with a high repetition rate (100 s of MHz). With the combination of high intensity and short pulse duration new opportunities for scientific research and applications are enabled across a diverse array of disciplines from condensed matter physics, to medical, technological, manufacturing, space and defense industries. Imaging, spectroscopy, femtosecond dynamics, and driving novel non-linear processes are all among the potential applications. The high average power of the CSR source allows one to extend experimental conditions to lower frequencies than have been possible with thermal and conventional synchrotron sources (Figure 1). In this paper, we make use of the stable CSR THz source at BESSY for threeinitial scientific demonstration experiments.

Background: While Veterans with 50%+ service connection are entitled to VA disability compensation and prioritised VA care, little is known about disability compensation and medical care expenditures/utilisation among Vietnam Era Veterans with 50%+ service connection Methods: We analysed 836 917 Vietnam Era Veterans with service-connected disabilities in 2013 For males (n=828 861) and females (n=8056), we describe total and per-patient FY2013 VA disability compensation and medical care expenditures/utilisation associated with 50%+ service-connection status (0-40% vs 50%+), and Medicare-eligible age status (age <65 vs age 65+) Results: Overall, those with 50%+ service connection (males = $10 315/28 visits; females = $12 146/36 visits) had higher mean per-patient FY2013 VA medical care expenditures and outpatient utilisation, relative to those rated 0-40% (males = $5520/17 visits; females = $6735/22 visits) By contrast, those who were Medicareeligible age (males = $9779/27 visits; females = $10 575/32 visits) had lower VA mean per-patient FY2013 medical care expenditures and outpatient utilisation, relative to those below Medicare-eligible age (males = $11 377/31 visits; females = $13 290/39 visits) Conclusions: For Vietnam Era Veterans with 50%+ service connection, lower per-patient VA medical care expenditures and outpatient utilisation among those of Medicare-eligible age raises the possibility that medical care substitution effects may occur even among those with cost-free VA care Prospective follow-up studies based on VA/Medicare data are needed to evaluate this possibility. [ABSTRACT FROM AUTHOR]