An energy conversion relationship predictive of conversion profiles and depth of cure for resin-based composite

Predicting the polymerization throughout resin-based composite (RBC) has been reduced to a set of variables involving irradiance of the light source, exposure duration and RBC transmission properties, together with an energy-conversion relationship (ECR) derived from Fourier Transform Infrared Spectroscopic analysis (FTIR) of a single shade of photo-polymerized RBC. The ECR describes the localized energy density required to achieve a desired conversion independent of shade. Using this ECR, conversion was predicted and experimentally verified throughout different opacities of RBC based on knowledge of their transmission properties and the incident radiant energy density (irradiance times exposure time). Also, using RBC transmission properties, a critical scrape-back energy of approximately 32 mJcm(-2) was determined from cylindrical samples of photo-polymerized RBC in which the poorly polymerized material was removed. This value correlates to approximately 22% conversion. The critical scrape-back energy was then used to predict scrape-back lengths obtained from samples polymerized at various energy densities. These results confirm the logarithmic relationship between depth of cure and energy of exposure and the reciprocal relationship between irradiance and time of exposure.

An event-related optical topography study of cortical activation induced by single-pulse transcranial magnetic stimulation

To visualize cortical activations during transcranial magnetic stimulation (TMS), it is necessary to measure those activations at high spatiotemporal resolution while preventing interference with the magnetic property of a coil. One suitable method that satisfies these demands is optical topography (OT), which has been used in cortical activation studies. In the present study, single-pulse TMS was applied to the left primary motor area, and cortical responses at the stimulation site were measured simultaneously with event-related OT. When TMS was applied at 110% motor threshold (MT), we observed significant oxyhemoglobin increases that were both time-locked and correlated with the hemodynamic basis function. Moreover, when TMS was applied at 90% MT, significant oxyhemoglobin increases were detected even though there were no motor-evoked potentials. These results demonstrate that OT can directly measure cortical responses to subthreshold single-pulse TMS, independent of the afferent feedback from the peripheral neuromuscular activity.

Optical recordings of membrane potential using genetically targeted voltage-sensitive fluorescent proteins

Optical imaging of electrical activity using voltage-sensitive dyes has been envisaged for many years as a powerful method to investigate multineuronal representation of information processing in brain tissue. This article describes the advent of novel genetically targeted voltage-sensitive fluorescent proteins. This new class of membrane voltage sensors overcomes previous limitations related to the nonselective staining of membranes associated with conventional voltage-sensitive dyes. Here, we discuss the methodology, applications, and potential advantages of this novel technique.

Probing neural circuits in the zebrafish: a suite of optical techniques

The ability to image neural activity in populations of neurons inside an intact animal, while obtaining single-cell or subcellular spatial resolution, has led to several advances in our understanding of vertebrate locomotor control. This result, first reported in a 1995 study of motoneurons in larval zebrafish, was the beginning of a series of technical developments that exploited the transparency and simplicity of the larval CNS. Presented here, in chronological fashion, is a suite of imaging techniques that have extended the ability to probe and optically dissect neural control systems. Included are methodological details pertaining to: (1). the in vivo optical recording of neural activity, (2). the optical dissection of complex neural architectures, and (3). additional fluorescence imaging-based techniques for the anatomical and physiological characterization of these systems. These approaches have provided insights into the descending neural control of escape and other locomotive behaviors, such as swimming and prey capture. The methods employed are discussed in relation to complementary and alternative imaging techniques, including, for example, the Nipkow disk confocal. While these methodologies focus on descending motor control in the larval zebrafish, the extension of such approaches to other neural systems is viewed as a promising and necessary step if neurobiologists are to bridge the gap between synaptic and brain region levels of analysis. The efficiency of optical techniques for surveying the cellular elements of intricate neural systems is of particular relevance because a comprehensive description of such elements is deemed necessary for a precise understanding of vertebrate neural architectures.

Optical dating of dune sand from Blombos Cave, South Africa: II--single grain data

A sequence of optically stimulated luminescence measurements was made on each of 8,961 grains from three sand samples from Blombos on the southern Cape coast. One sand unit overlay Middle Stone Age deposits in Blombos Cave. The measurement sequence, the single aliquot regenerative dose protocol, was used to obtain values for the total effective radiation dose to which each grain had been exposed since burial. A series of checks was carried out on each grain to ensure that the luminescence signals were reproducible, and that they were derived from quartz. This led to acceptance of less than 5% of the grains. An estimate of the radiation dose for the sand unit was obtained by combining the values using the central age model. In order to use a larger number of grains that might be representative of the sand unit, the radiation dose was also estimated by using the signal from the above grains, combined with the signals from those grains that had lower signals, but nonetheless contributed to the total light sum; this utilised between 9 and 18% of the grains. This enables us to obtain estimates of the ages as 67.3+/-3.8 ka, 65.6+/-2.8 ka and 68.8+/-3.0 ka for the three samples. These values agree with ages obtained using the single aliquot regenerative dose protocol for aliquots composed of several hundred grains.

Albumin-based drug delivery as novel therapeutic approach for rheumatoid arthritis

We reported recently that albumin is a suitable drug carrier for targeted delivery of methotrexate (MTX) to tumors. Due to pathophysiological conditions in neoplastic tissue, high amounts of albumin accumulate in tumors and are metabolized by malignant cells. MTX, covalently coupled to human serum albumin (MTX-HSA) for cancer treatment, is currently being evaluated in phase II clinical trials. Because synovium of patients with rheumatoid arthritis (RA) shares various features observed also in tumors, albumin-based drug targeting of inflamed joints might be an attractive therapeutic approach. Therefore, the pharmacokinetics of albumin and MTX in a mouse model of arthritis was examined. Additionally, uptake of albumin by synovial fibroblasts of RA patients and the efficacy of MTX and MTX-HSA in arthritic mice were studied. The results show that when compared with MTX, significantly higher amounts of albumin accumulate in inflamed paws, and significantly lower amounts of albumin are found in the liver and the kidneys. The protein is metabolized by human synovial fibroblasts in vitro and in vivo. MTX-HSA was significantly more effective in suppression of the onset of arthritis in mice than was MTX. In conclusion, albumin appears to be a suitable drug carrier in RA, most likely due to effects on synovial fibroblasts, which might increase therapeutic efficacy and reduce side effects of MTX.

Re-evaluation of differential phase contrast (DPC) in a scanning laser microscope using a split detector as an alternative to differential interference contrast (DIC) optics

In this paper, differential phase imaging (DPC) with transmitted light is implemented by adding a suitable detection system to a standard commercially available scanning confocal microscope. DPC, a long-established method in scanning optical microscopy, depends on detecting the intensity difference between opposite halves or quadrants of a split photodiode detector placed in an aperture plane. Here, DPC is compared with scanned differential interference contrast (DIC) using a variety of biological specimens and objective lenses of high numerical aperture. While DPC and DIC images are generally similar, DPC seems to have a greater depth of field. DPC has several advantages over DIC. These include low cost (no polarizing or strain-free optics are required), absence of a double scanning spot, electronically variable direction of shading and the ability to image specimens in plastic dishes where birefringence prevents the use of DIC. DPC is also here found to need 20 times less laser power at the specimen than DIC.

Inverse problem in optical diffusion tomography. III. Inversion formulas and singular-value decomposition

We continue our study of the inverse scattering problem for diffuse light. In particular, we derive inversion formulas for this problem that are based on the functional singular-value decomposition of the linearized forward-scattering operator in the slab, cylindrical, and spherical geometries. Computer simulations are used to illustrate our results in model systems.

Imaging spatio-temporal patterns of long-term potentiation in mouse hippocampus

Spatio-temporal patterns of neuronal activity before and after the induction of long-term potentiation in mouse hippocampal slices were studied using a real-time high-resolution optical recording system. After staining the slices with voltage-sensitive dye, transmitted light images and extracellular field potentials were recorded in response to stimuli applied to CA1 stratum radiatum. Optical and electrical signals in response to single test pulses were enhanced for at least 30 minutes after brief high-frequency stimulation at the same site. In two-pathway experiments, potentiation was restricted to the tetanized pathway. The optical signals demonstrated that both the amplitude and area of the synaptic response were increased, in patterns not predictable from the initial, pretetanus, pattern of activation. Optical signals will be useful for investigating spatio-temporal patterns of synaptic enhancement underlying information storage in the brain.

Depolarization waves in the embryonic CNS triggered by multiple sensory inputs and spontaneous activity: optical imaging with a voltage-sensitive dye

Previously, we discovered a novel type of depolarization wave in the embryonic chick brain by using a multiple-site optical recording technique with a fast voltage-sensitive dye. This depolarization wave traveled widely over almost all the region of the CNS. This profile has raised the possibility that the depolarization wave plays some global roles in development of the CNS, rather than contributing to a specific neuronal circuit formation. To obtain more information concerning this issue, in the present study, we examined whether the depolarization wave was triggered by various types of peripheral nerve inputs. Stimulation applied to the vagus, glossopharyngeal, cochlear and trigeminal nerves evoked widely spreading depolarization waves with similar spatiotemporal distribution patterns. The developmental sequence of wave expression was parallel to the development of the excitatory postsynaptic potentials in each sensory nucleus. The depolarization wave was accompanied by a Ca(2+)-wave, suggesting that not only electrical synchrony, but also large-scale Ca(2+)-transients may affect developmental processes in the embryonic brain. Furthermore, we found that the depolarization wave also occurred spontaneously. The waveform and distribution patterns of the spontaneous optical signals were similar to those of the cranial nerve-evoked depolarization wave. These results demonstrated that the depolarization wave in the embryonic chick brain is triggered by multiple sources of external and endogenous activity. This profile supports the idea that this depolarization wave may not serve as a simple regulator of specific neuronal circuit formation, but might play more global roles in CNS development.

NAD(P)H fluorescence imaging of postsynaptic neuronal activation in murine hippocampal slices

We examined mechanisms contributing to stimulus-evoked changes in NAD(P)H fluorescence as a marker of neuronal activation in area CA1 of murine hippocampal slices. Three types of stimuli (electrical, glutamate iontophoresis, bath-applied kainate) produced biphasic fluorescence changes composed of an initial transient decrease ("initial component," 1-3%), followed by a longer-lasting transient increase ("overshoot," 3-8%). These responses were matched by inverted biphasic flavin adenine dinucleotide (FAD) fluorescence transients, suggesting that these transients reflect mitochondrial function rather than optical artifacts. Both components of NAD(P)H transients were abolished by ionotropic glutamate receptor block, implicating postsynaptic neuronal activation as the primary event involved in generating the signals, and not presynaptic activity or reuptake of synaptically released glutamate. Spatial analysis of the evoked signals indicated that the peak of each component could arise in different locations in the slice, suggesting that there is not always obligatory coupling between the two components. The initial NAD(P)H response showed a strong temporal correspondence to intracellular Ca+ increases and mitochondrial depolarization. However, despite the fact that removal of extracellular Ca2+ abolished neuronal cytosolic Ca2+ transients to exogenous glutamate or kainate, this procedure did not reduce slice NAD(P)H responses evoked by either of these agonists, implying that mechanisms other than neuronal mitochondrial Ca2+ loading underlie slice NAD(P)H transients. These data show that, in contrast to previous proposals, slice NAD(P)H transients in mature slices do not reflect neuronal Ca2+ dynamics and demonstrate that these signals are sensitive indicators of both the spatial and temporal characteristics of postsynaptic neuronal activation in these preparations.

Electro-optic response of second-harmonic generation membrane potential sensors

We quantify and ascertain the nature of the second-harmonic generation (SHG) response of amphiphilic push-pull chromophores to a transmembrane electric field. Our technique is based on the application of an alternating field across labeled giant unilamelar vesicles. For chromophore responses that are purely electro-optic, our technique provides an estimate of photoinduced charge shifts based on the observed dispersion of the field response, in accord with a two-level perturbation theory. These results are applicable to the optimization of membrane potential sensors for SHG microscopy.

Arrhythmogenic substrate of the pulmonary veins assessed by high-resolution optical mapping

BACKGROUND

It has recently been recognized that atrial fibrillation can originate from focal sources in the pulmonary veins (PVs). However, the mechanisms of focal atrial fibrillation have not been well characterized. We assessed the electrophysiological characteristics of the PVs using high-resolution optical mapping.

METHODS AND RESULTS

Coronary-perfused, isolated whole-atrial preparations from 33 normal dogs were studied. Programmed electrical stimulation was performed, and a 4-cm2 area of the PV underwent optical mapping of transmembrane voltage to obtain 256 simultaneous action potentials. Marked conduction slowing was seen at the proximal PV, compared with the rest of the vein, on both the epicardial (31.3+/-4.47 versus 90.2+/-20.7 cm/s, P=0.001) and endocardial (45.8+/-6.90 versus 67.6+/-10.4 cm/s, P=0.012) aspects. Pronounced repolarization heterogeneity was also noted, with action potential duration at 80% repolarization being longest at the PV endocardium. Nonsustained reentrant beats were induced with single extrastimuli, and the complete reentrant loop was visualized (cycle length, 155+/-30.3 ms); reentrant activity could be sustained with isoproterenol. Sustained focal discharge (cycle length, 330 to 1100 ms) was seen from the endocardial surface in the presence of isoproterenol; each focus was localized near the venous ostium.

CONCLUSIONS

The normal PV seems to have the necessary substrate to support reentry as well as focal activity. Although reentry occurred more distally in the vein, focal activity seemed to occur more proximally.

Light microscopy techniques for live cell imaging

Since the earliest examination of cellular structures, biologists have been fascinated by observing cells using light microscopy. The advent of fluorescent labeling technologies plus the plethora of sophisticated light microscope techniques now available make studying dynamic processes in living cells almost commonplace. For anyone new to this area, however, it can be daunting to decide which techniques or equipment to try. Here, we aim to give a brief overview of the main approaches to live cell imaging, with some mention of their pros and cons.

Enhancing vapor sensor discrimination by mimicking a canine nasal cavity flow environment

This paper discusses the use of flow dynamics in a model nasal cavity as a novel way to expand the information available from a fiber optic vapor sensor. Nasal cavities are known to play an important role in vertebrate olfaction; however, they have not previously been incorporated into gas-phase sensor technology. By exposing identical sensors to different flow environments, we found that measurements of the combined sensor responses provided increased discrimination of a series of alcohols as compared to measurements obtained from a single sensor at the anterior of the cavity. This methodology is potentially useful for improving the discriminatory power of sensors employed in "artificial noses" and could be used to model the effects of flow dynamics in vertebrate olfaction.

Quantifying enamel demineralization from teeth with orthodontic brackets--a comparison of two methods. Part 2: validity

This is Part 2 of an in vitro study investigating two techniques for recording and quantifying demineralization surrounding orthodontic brackets. In Part 1 the repeatability of computerized image analysis from digitally converted photographic slides and quantitative light-induced fluorescence (QLF) was explored. In Part 2 of the investigation the validity of each technique was examined. Thirty halved human molars, shaped to look like incisors and with an orthodontic bracket bonded to the buccal surface were used. A small area of each of the four edges of the bracket was variously exposed to a demineralizing gel for 0, 3, 7, or 14 days. Images of the teeth were taken and analysed using the two techniques. Repeat images and analysis were carried out blind. The sensitivity, specificity, positive, and negative predictive values were calculated. A negative result confirmed that there was no demineralization present in the majority of cases. A positive result was less reliable particularly for the occlusal and gingival regions. The 7- and 14-day demineralization patterns were detected every time using the photographic technique. The discrimination of the 0- and 3-day patterns was less reliable. The results of this study were extrapolated to allow for the prevalence of the condition following orthodontic treatment, and the implications of this for a putative clinical trial are discussed, together with the advantages and disadvantages of each method. Either technique would be applicable to use in a clinical trial.

Immediate indocyanine green angiography and optical coherence tomography evaluation after photodynamic therapy for subfoveal choroidal neovascularization

PURPOSE

To better understand the mechanisms of action of photodynamic therapy (PDT) with verteporfin for subfoveal choroidal neovascularization (CNV), the authors evaluated the retinal and choroidal response immediately after treatment with serial optical coherence tomography (OCT) and indocyanine green angiography (ICGA).

METHODS

This study was a prospective, noncomparative case series. PDT was performed on nine eyes of nine consecutive patients who presented with subfoveal CNV due to age-related macular degeneration, and serial evaluation with OCT as well as ICGA was performed at 20-minute intervals for the first 2 hours and then at 1 week, 1 month, and 3 months.

RESULTS

In the first 2 hours after PDT, OCT showed an increase in the thickness of the retina in the treatment area due to fluid leakage from the neovascular complex as confirmed by ICGA. At 1 week, marked reduction of intraretinal/subretinal fluid was observed in all patients. Neovascular complex nonperfusion by ICGA was associated with some degree of choroidal hypoperfusion in the treatment area. Return of the foveal contour by OCT was optimal after 1 month of treatment. At 3 months, choroidal reperfusion by ICGA and recurrent intraretinal/subretinal fluid by OCT were observed.

CONCLUSIONS

Serial OCT and ICGA evaluation after PDT suggests that the initial successful CNV nonperfusion as shown by fluorescein angiography at 1 week occurs by means of selective PDT damage to the lesion and/or reduced choroidal blood flow in the treatment area, thereby decreasing intraretinal/subretinal fluid and facilitating restoration of the retinal architecture.

Numerical evaluation of Hankel transforms for oscillating functions

Six methods for the numerical calculation of zero-order Hankel transforms of oscillating functions were evaluated. One method based on Filon quadrature philosophy, two published projection-slice methods, and a third projection-slice method based on a new approach to computation of the Abel transform were implemented; alternative versions of two of the projection-slice methods were derived for more accurate approximations in the projection step. These six algorithms were tested with an oscillating sweep signal and with the calculation of a three-dimensional diffraction-limited point-spread function of a fluorescence microscope. We found that the Filon quadrature method is highly accurate but also computationally demanding. The projection-slice methods, in particular the new one that we derived, offer an excellent compromise between accuracy and computational efficiency.

Quantifying enamel demineralization from teeth with orthodontic brackets--a comparison of two methods. Part 1: repeatability and agreement

The aim of this investigation was to compare the repeatability of measuring enamel demineralization surrounding an orthodontic bracket using two techniques: computerized image analysis from digitally converted photographic slides and quantitative light-induced fluorescence (QLF). Fifteen human molars were halved and shaped to look like incisors. The teeth were individually numbered and orthodontic brackets bonded to the buccal surface. The crowns were covered with acid resistant varnish, except for windows approximately 1.5 x 3 mm adjacent to the gingival, occlusal, mesial, and distal edges of the bracket. The windows were variously exposed to a demineralizing gel for 0, 3, 7, or 14 days, and the acid resistant varnish was removed. Standardized photographic slides and QLF images of the teeth were taken. These were repeated after 1 week. The slides were converted to grey scale digital format and analysed using Image-Pro Plus 3.0. The QLF images were stored, processed, and analysed using customized software. All images were recoded for blind analysis. The four surfaces of the bracket were inspected and only areas of suspected demineralization were analysed. This was repeated after 1 week. The limits of agreement and mean difference between repeat readings of the area of demineralization were similar for both techniques (-0.04 +/- 0.43 for photographs and -0.10 +/- 0.63 for QLF). Mean grey level (photographs) and mean loss of fluorescence from that area (deltaF) (QLF) showed acceptable limits of agreement. The Intra Class Correlation (ICC) was below 0.81 for the measurement of area from QLF, suggesting that random error needs to be reduced. There was evidence of systematic bias for the repeat readings of the grey levels from the photographs (P < 0.001). Enamel demineralization surrounding an orthodontic bracket can be measured reproducibly using these two techniques.

[Assessment of the optical image quality of the eye using raytracing technique of corneal topography data]

BACKGROUND

Optical aberrations in the optical system may downgrade image quality and cannot be fully compensated by spherocylindrical glasses. The subjectively evaluated visual acuity may be significantly reduced. The purpose of this study was to calculate the image forming properties of the eye using a spotlight source or alternatively extended objects.

METHODS

A convex and first derivative continuous (C1) surface from the rough height data of the anterior corneal surface (TMS-1, Tomey, Erlangen) or the anterior and posterior corneal surface (Orbscan, Orbtec, USA) was calculated by means of an interpolating subdivision scheme (modified Butterfly algorithm). The characteristics of the residual refractive surfaces were used according to Navarro's eye model. The focal distance was calculated from the exact raytracing calculation (Snellius' law) of the point-spread function by minimising the variance of the point-spread function. The diffraction property of the aperture stop was implemented with a transmission characteristic according to a radially symmetrical Bessel function within the entrance pupil. The algorithm was realised with a C code on the LINUX platform and applied to a normal eye (example 1, TMS-1), an eye with severe keratoconus (example 2, TMS-1) and an eye with corneal scars (example 3, Orbscan).

RESULTS

The focal distance in example 1 (22.5 mm, 22.6 mm, and 22.8 mm) increased with the pupil diameter (2 mm, 3 mm, and 5 mm). The variance of the approximately radially symmetrical point-spread function in the focal plane attained a minimum value with a pupil size of 3 mm (0.164, 0.104, and 0.230). In example 2, the focal distance changed inconclusively (21.1 mm, 21.0 mm, and 21.3 mm) with the pupil size (2 mm, 3 mm, and 5 mm). The variance of the markedly asymmetrical point-spread function in the focal plane was systematically higher compared to the values of example 1 and reached a minimum value with a pupil size of 3 mm (0.255, 0.224, and 0.371). The imaging of the sinus-modulated pattern is anisotropic due to the asymmetry of the point-spread function. In example 3, the focal distance (22.3 mm, 22.3 mm, and 22.5 mm) did not change systematically with the pupil size (2 mm, 3 mm, and 5 mm). The variance of the nearly radially symmetrical point-spread function changed only marginally between pupil sizes of 2 mm and 3 mm (0.231, 0.239, and 0.338).

CONCLUSIONS

Raytracing of corneal topography height data based on refined eye models with the option of auto-focussing has the potential to trace the optical resolution of the eye for arbitrary objects. Further studies on contrast sensitivity and the conversion of the real image to a perceived image by the retina and brain are required for complete modeling of subjective visual acuity.

Guidance of aortic ablation using optical coherence tomography

PURPOSE

There is a significant need for an imaging modality that is capable of providing guidance for intravascular procedures, as current technologies suffer from significant limitations. In particular, laser ablation of in-stent restenosis, revascularization of chronic total occlusions, and pulmonary vein ablation could benefit from guidance. Optical coherence tomography (OCT), a recently introduced technology, is similar to ultrasound except that it measures the back-reflection of infrared light instead of sound. This study examines the ability of OCT to guide vascular laser ablation.

METHODS

Aorta samples underwent laser ablation using an argon laser at varying power outputs and were monitored with OCT collecting images at 4 frames. Samples were compared to the corresponding histopathology.

RESULTS

Arterial layers could be differentiated in the images sequences. This allowed correlation of changes in the OCT image with power and duration in addition to histopathology.

CONCLUSIONS

OCT provides real-time guidance of arterial ablation. At 4 frames, OCT was successfully able to show the microstructural changes in the vessel wall during laser ablation. Since current ablation procedures often injure surrounding tissue, the ability to minimize collateral damage to the adjoining tissue represents a useful advantage of this system. This study suggests a possible role for OCT in the guidance of intravascular procedures.

Corneal power determination after previous corneal refractive surgery for intraocular lens calculation

PURPOSE

To assess the accuracy of different corneal power determination methods in patients who had undergone myopic laser in situ keratomileusis (LASIK), photorefractive keratectomy (PRK), and radial keratotomy (RK).

METHODS

The results for 208 eyes of 116 patients who had had corneal refractive surgery (LASIK, PRK, RK) for myopia were analyzed retrospectively. Keratometry measurements, i.e., autokeratometry readings (K(meas)), simulated keratotopography readings (Sim-K), and topographically measured average central corneal power in a 3-mm zone (ACP) were compared with calculated refraction-derived keratometric value. Correction factors based on the difference between measured and calculated keratometric powers were rated.

RESULTS

Direct power measurements with standard keratometers and planokeratotopography systems overestimate corneal power after myopic PRK and LASIK. The average K(meas) and K(topo) were significantly greater than the average calculated refraction-derived keratometric values. Corneal power overestimation correlated significantly with the spherical equivalent change after refractive surgery (p < 0.001). After RK, there is no significant correlation of the difference between all measured K values and refraction-derived power with the spherical equivalent change. In these cases, the Sim-K value seems the most accurate among measured keratometric powers. The precision of measurement significantly depends on the parameters of the autokeratometer (i.e., measurement place, number of measurement points, keratometric index of refraction).

CONCLUSIONS

To avoid underestimation of intraocular lens power after cataract surgery in the eyes that had previously undergone myopic corneal refractive surgery, the measured corneal power must be corrected. Although correction factors may be calculated for cases after PRK and LASIK, there are no universal and absolutely reliable methods to determine corneal power in these cases. More than one accessible method should be used, and the lowest, most reliable data should be used.

Rehabilitation of endodontically treated teeth using the radiopaque fiber post

Metallic posts fall short of satisfying contemporary guidelines for ideal post/core rehabilitation. Along with technological improvements in adhesive resins, cements, and composite restoratives, the evolution of fiber-reinforced posts allows the rehabilitation of endodontically treated teeth with greater esthetics and virtually no predisposition to root fracture. At least one fiber post system now complies with all of the ideal post characteristics described in the endodontic text. This article describes the potential for displacement of metal posts by low-modulus fiber posts, the differences between them, and the development and placement of a radiopaque, translucent, double-tapered fiber post.