Mechanisms underpinning community stability along a latitudinal gradient: Insights from a niche-based approach.

At large scales, the mechanisms underpinning stability in natural communities may vary in importance due to changes in species composition, mean abundance, and species richness. Here we link species characteristics (niche positions) and community characteristics (richness and abundance) to evaluate the importance of stability mechanisms in 156 butterfly communities monitored across three European countries and spanning five bioclimatic regions. We construct niche-based hierarchical structural Bayesian models to explain first differences in abundance, population stability, and species richness between the countries, and then explore how these factors impact community stability both directly and indirectly (via synchrony and population stability). Species richness was partially explained by the position of a site relative to the niches of the species pool, and species near the centre of their niche had higher average population stability. The differences in mean abundance, population stability, and species richness then influenced how much variation in community stability they explained across the countries. We found, using variance partitioning, that community stability in Finnish communities was most influenced by community abundance, whereas this aspect was unimportant in Spain with species synchrony explaining most variation; the UK was somewhat intermediate with both factors explaining variation. Across all countries, the diversity-stability relationship was indirect with species richness reducing synchrony which increased community stability, with no direct effects of species richness. Our results suggest that in natural communities, biogeographical variation observed in key drivers of stability, such as population abundance and species richness, leads to community stability being limited by different factors and that this can partially be explained due to the niche characteristics of the European butterfly assemblage.

Near-IR transillumination and reflectance imaging at 1,300 nm and 1,500-1,700 nm for in vivo caries detection.

INTRODUCTION: Several studies suggest that near-IR imaging methods at wavelengths longer than 1,300 nm have great potential for caries detection. In this study, the diagnostic performance of both near-IR transillumination and near-IR reflectance was assessed on teeth scheduled for extraction due to orthodontic treatment (n = 109 teeth on 40 test subjects). METHODS: Three intra-oral near-IR imaging probes were fabricated for the acquisition of in vivo images using a high definition InGaAs camera and near-IR broadband light sources. Two transillumination probes provided occlusal and approximal images using 1,300 nm light which manifests the highest transparency in enamel. A third reflectance probe utilized cross-polarization and operated at wavelengths greater than 1,500 nm where water absorption is higher which reduces the reflectivity of sound tissues, significantly increasing lesion contrast. Teeth were collected after extraction and sectioned and examined with polarized light microscopy and microradiography which served as the gold standard. In addition, radiographs were taken of the teeth and the diagnostic performance of near-IR imaging was compared with radiography. RESULTS: Near-IR imaging was significantly more sensitive (P < 0.05) than radiography for the detection of lesions on both occlusal and proximal surfaces. CONCLUSION: Near-IR imaging methods are ideally suited for screening all tooth surfaces for carious lesions. Lasers Surg. Med. 48:828-836, 2016. © 2016 Wiley Periodicals, Inc.

Clinical monitoring of smooth surface enamel lesions using CP-OCT during nonsurgical intervention.

INTRODUCTION: Studies have shown that cross-polarization optical coherence tomography (CP-OCT) can be used to image the internal structure of carious lesions in vivo. The objective of this study was to show that CP-OCT can be used to monitor changes in the internal structure of early active carious lesions on smooth surfaces during non-surgical intervention with fluoride. METHODS: Lesions on the smooth surfaces of teeth were imaged using CP-OCT on 17 test subjects. Lesion structural changes were monitored during fluoride varnish application at 6-week intervals for 30 weeks. The lesion depth (Ld ), integrated reflectivity (ΔR), and surface zone thickness (Sz ) were monitored. RESULTS: A distinct transparent surface zone that may be indicative of lesion arrestment was visible in CP-OCT images on 62/63 lesions before application of fluoride varnish. The lesion depth and internal structure were resolved for all the lesions. The overall change in the mean values for Ld , ΔR, and Sz for all the lesions was minimal and was not significant during the study (P > 0.05). Only 5/63 lesions manifested a significant increase in Sz during intervention. CONCLUSION: Even though it appears that most of the lesions manifested little change with fluoride varnish application in the 30 weeks of the study, CP-OCT was able to measure the depth and internal structure of all the lesions including the thickness of the important transparent surface zone located at the surface of the lesions, indicating that CP-OCT is ideally suited for monitoring lesion severity in vivo. Lasers Surg. Med. 48:915-923, 2016. © 2016 Wiley Periodicals, Inc.

Near-IR image-guided laser ablation of demineralization on tooth occlusal surfaces.

INTRODUCTION: Studies have shown that reflectance images at near-IR wavelengths coincident with higher water absorption are well-suited for image-guided laser ablation of carious lesions since the contrast between sound and demineralized enamel is extremely high and interference from stains is minimized. The objective of this study was to demonstrate that near-IR reflectance images taken at a wavelength range of 1,500-1,700 nm can be used to guide a 9.3 µm CO(2) laser for the selective ablation of early demineralization on tooth occlusal surfaces. METHODS: The occlusal surfaces of ten sound human molars were used in this in vitro study. Shallow simulated caries lesions with random patterns and varying depth and position were produced on tooth occlusal surfaces. Sequential near-IR reflectance images at 1,500-1,700 nm were used to guide the laser for the selective removal of the demineralized enamel. Digital microscopy and polarization sensitive optical coherence tomography (PS-OCT) were used to assess selectivity. RESULTS: Images taken before and after lesion removal suggest that the demineralized areas were removed with high selectivity. Although the estimated volume of tissue ablated was typically higher than the initial lesion volume measured with PS-OCT, the volume of enamel removed by the laser correlated well with the initial lesion volume. CONCLUSION: Sequential near-IR reflectance images at 1,500-1,700 nm can be used to guide a 9.3 µm CO(2) laser for the selective ablation of early demineralization on tooth occlusal surfaces.

Enhanced detection of dentinal lesions in OCT images using the RKT transformation.

Several studies have shown that optical coherence tomography (OCT) can be used to measure the remaining enamel thickness and detect the location of subsurface lesions hidden under the sound enamel. The purpose of this study was to develop algorithms to enhance the visibility of subsurface structures such as hidden occlusal lesions and the dentinal-enamel junction. Extracted teeth with natural occlusal lesions were imaged with OCT with and without added high index fluids. A Rotating Kernel Transformation (RKT) nonlinear image processing filter was applied to PS-OCT images to enhance the visibility of the subsurface lesions under the sound enamel. The filter significantly increased (P<0.05) the visibility of the subsurface lesions.

Selective removal of dental caries with a diode-pumped Er:YAG laser.

Selective removal of caries lesions with high precision is best accomplished using lasers operating at high pulse repetition rates utilizing small spot sizes. Conventional flash-lamp pumped Er:YAG lasers are poorly suited for this purpose, but new diode-pumped Er:YAG lasers have become available operating at high pulse repetition rates. The purpose of this study was to measure the ablation rate and selectivity of sound and demineralized enamel and dentin for a 30 W diode-pumped Er:YAG laser operating with a pulse duration of 20-30-µs and evaluate it's potential for the selective removal of natural occlusal lesions on extracted teeth. Microradiography was used to determine the mineral content of the demineralized enamel and dentin of 300-µm thick sections with natural caries lesions prior to laser ablation. The ablation rate was calculated for varying mineral content. In addition, near-IR reflectance measurements at 1500-1700-nm were used to guide the laser for the selective ablation of natural occlusal caries lesions on extracted teeth.

Selective removal of demineralized enamel using a CO2 laser coupled with near-IR reflectance imaging.

Detection and diagnosis of early dental caries lesions can be difficult due to variable tooth coloration, staining of the teeth and poor contrast between sound and demineralized enamel. These problems can be overcome by using near-infrared (NIR) imaging. Previous studies have demonstrated that lasers can be integrated with NIR imaging devices, allowing image-guided ablation. The aim of this study was to demonstrate that NIR light at 1500 - 1700 nm can be used to guide a 9.3-µm CO2 laser for the selective ablation of early demineralization on tooth occlusal surfaces. The occlusal surfaces of ten sound human molars were used in this in-vitro study. Shallow simulated caries lesions of varying depth and position were produced on tooth occlusal surfaces using a demineralization solution. Sequential NIR reflectance images at 1500 - 1700 nm were used to guide the laser for selective ablation of the lesion areas. Digital microscopy and polarization sensitive optical coherence tomography (PS-OCT) were used to assess the selectivity of removal. This study demonstrates that high contrast NIR reflectance images can be used for the image-guided laser ablation of early demineralization from tooth occlusal surfaces.

Serial removal of caries lesions from tooth occlusal surfaces using near-IR image-guided IR laser ablation.

Previous studies have established that caries lesions can be imaged with high contrast without the interference of stains at near-IR wavelengths greater than 1300-nm. It has been demonstrated that computer controlled laser scanning systems utilizing IR lasers operating at high pulse repetition rates can be used for serial imaging and selective removal of caries lesions. In this study, we report our progress towards the development of algorithms for generating rasterized ablation maps from near-IR reflectance images for the removal of natural lesions from tooth occlusal surfaces. An InGaAs camera and a filtered tungsten-halogen lamp producing near-IR light in the range of 1500-1700-nm were used to collect crosspolarization reflectance images of tooth occlusal surfaces. A CO2 laser operating at a wavelength of 9.3- µm with a pulse duration of 10-15-µs was used for image-guided ablation.

Image-guided removal of occlusal caries lesions with a λ= 9.3-µm CO2 laser using near-IR transillumination.

Previous studies have shown that near-IR transillumination is well suited for imaging deep occlusal lesions. The purpose of this study was to determine if near-IR images can be used to guide a CO2 laser for the selective removal of natural occlusal lesions on extracted teeth. Near-IR occlusal transillumination images of extracted human teeth with natural occlusal caries lesions were acquired using an InGaAs camera and near-IR light at wavelengths from 1290 to 1470-nm from a filtered tungsten halogen source. A CO2 laser operating at 9.3-µm with a pulse duration of 10-15-µs and a pulse repetition rate of 100-300-Hz was used for caries removal. Optical Coherence tomography was used to confirm lesion presence and serial scans were used to assess selective removal. Teeth were also sectioned for histological examination using polarized light microscopy. This study suggests that near-infrared transillumination is a promising method for the image guided laser ablation of occlusal caries lesions but the use of serial near-IR transillumination imaging for monitoring lesion removal was limited.

A method for monitoring enamel erosion using laser irradiated surfaces and optical coherence tomography.

INTRODUCTION: Since optical coherence tomography (OCT) is well suited for measuring small dimensional changes on tooth surfaces, OCT has great potential for monitoring tooth erosion. Previous studies have shown that enamel areas ablated by a carbon dioxide laser manifested lower rates of erosion compared to the non-ablated areas. The purpose of this study was to develop a model to monitor erosion in vitro that could potentially be used in vivo. METHODS: Thirteen bovine enamel blocks were used in this in vitro study. Each 10 mm × 2 mm block was partitioned into five regions, the central region was unprotected, the adjacent windows were irradiated by a CO2 laser operating at 9.3 µm with a fluence of 2.4 J/cm(2) , and the outermost windows were coated with acid resistant varnish. The samples were exposed to a pH cycling regimen that caused both erosion and subsurface demineralization for 2, 4 and 6 days. The surfaces were scanned using a time-domain polarization sensitive optical coherence tomography (PS-OCT) system and the degree of surface loss (erosion) and the integrated reflectivity with lesion depth was calculated for each window. RESULTS: There was a large and significant reduction in the depth of surface loss (erosion) and the severity of demineralization in the areas irradiated by the laser. CONCLUSION: Irradiation of the enamel surface with a pulsed carbon dioxide laser at sub-ablative intensities results in significant inhibition of erosion and demineralization under the acid challenge employed in this study. In addition, these results suggest that it may be feasible to modify regions of the enamel surface using the laser to serve as reference marks to monitor the rate of erosion in vivo.

Near-infrared imaging of demineralization under sealants.

Previous studies have shown that near-infrared (NIR) reflectance and transillumination imaging can be used to acquire high contrast images of early caries lesions and composite restorative materials. The aim of the study was to determine the optimum NIR wavelengths for imaging demineralized areas under dental sealants. Fifteen natural human premolars and molars with occlusal lesions were used in this in vitro study. Images before and after application of sealants were acquired using NIR reflectance and NIR transillumination at wavelengths of 1300, 1460, and 1500 to 1700 nm. Images were also acquired using polarization sensitive optical coherence tomography (OCT) for comparison. The highest contrast for NIR reflectance was at 1460 nm and 1500 to 1700 nm. These NIR wavelengths are coincident with higher water absorption. The clear Delton sealant investigated was not visible in either copolarization or cross-polarization OCT images. The wavelength region between 1500 and 1700 nm yielded the highest contrast of lesions under sealants for NIR reflectance measurements.

Transillumination and reflectance probes for in vivo near-IR imaging of dental caries.

Previous studies have demonstrated the utility of near infrared (NIR) imaging for caries detection employing transillumination and reflectance imaging geometries. Three intra-oral NIR imaging probes were fabricated for the acquisition of in vivo, real time videos using a high definition InGaAs SWIR camera and near-IR broadband light sources. Two transillumination probes provide occlusal and interproximal images using 1300-nm light where water absorption is low and enamel manifests the highest transparency. A third reflectance probe utilizes cross polarization and operates at >1500-nm, where water absorption is higher which reduces the reflectivity of sound tissues, significantly increasing lesion contrast. These probes are being used in an ongoing clinical study to assess the diagnostic performance of NIR imaging for the detection of caries lesions in teeth scheduled for extraction for orthodontic reasons.

Monitoring the inhibition of erosion by a CO2 laser with OCT.

Since optical coherence tomography (OCT) is well suited for measuring small dimensional changes on tooth surfaces, OCT has great potential for monitoring tooth erosion. Previous studies have shown that enamel areas ablated by a carbon dioxide laser manifested lower rates of erosion compared to the non-ablated areas. The purpose of this study was to develop a model to monitor erosion in vitro that could potentially be used in vivo. Teeth surfaces were irradiated with a carbon dioxide laser at low sub-ablative fluence to create an acid-resistant reference layer without damaging the enamel. The laser treated areas were compared with the unprotected areas using OCT during exposure to a pH cycling model for up to 6 days. The laser treated areas markedly reduced the rate of erosion.

Near-IR imaging of demineralization under sealants.

Previous studies have shown that near-IR reflectance and transillumination imaging can be used to acquire high contrast images of early caries lesions and composite restorative materials. The aim of the study was to determine the optimum near-IR wavelengths for imaging demineralized areas under dental sealants. Fifteen natural human premolars and molars with occlusal lesions were used in this in vitro study. Images before and after application of sealants were acquired using near-IR reflectance and near-IR transillumination at wavelengths of 1300 nm, 1460 nm, and 1500 - 1700 nm. Images were also acquired using polarization sensitive optical coherence tomography for comparison. The highest contrast for near-IR reflectance was at 1460 nm and 1500 - 1700 nm. These near-IR wavelengths are coincident with higher water absorption. The clear Delton sealant investigated was not visible in either co-polarization or cross-polarization OCT images. The wavelength region between 1500-1700-nm yielded the highest contrast of lesions under sealants for near-IR reflectance measurements.

High contrast optical imaging methods for image guided laser ablation of dental caries lesions.

Laser based methods are well suited for automation and can be used to selectively remove dental caries to minimize the loss of healthy tissues and render the underlying enamel more resistant to acid dissolution. The purpose of this study was to determine which imaging methods are best suited for image-guided ablation of natural non-cavitated carious lesions on occlusal surfaces. Multiple caries imaging methods were compared including near-IR and visible reflectance and quantitative light fluorescence (QLF). In order for image-guided laser ablation to be feasible, chemical and physical modification of tooth surfaces due to laser irradiation cannot greatly reduce the contrast between sound and demineralized dental hard tissues. Sound and demineralized surfaces of 48 extracted human molar teeth with non-cavitated lesions were examined. Images were acquired before and after laser irradiation using visible and near-IR reflectance and QLF at several wavelengths. Polarization sensitive-optical coherence tomography was used to confirm that lesions were present. The highest contrast was attained at 1460-nm and 1500-1700-nm, wavelengths coincident with higher water absorption. The reflectance did not decrease significantly after laser irradiation for those wavelengths.