A new shading concept based on natural tooth color applied to direct composite restorations.

OBJECTIVE: Patient demands have prompted manufacturers to improve intrinsic optical properties of resin composites and clinicians to refine application procedures. The aim of this study is to present a shading concept based on colorimetric L*a*b* and contrast ratio data of human dentin and enamel. METHOD AND MATERIALS: Extracted teeth of the A and B Vita shade groups (n = 8 per group) were sectioned according to 2 different planes to measure specific color (using the CIE L*a*b* system) and opacity (contrast ratio). Standardized samples of enamel and dentin shades of a new composite system (Miris, Coltène Whaledent) were submitted to the same colorimetric evaluation for comparison with natural tissues. RESULTS: Comparison of teeth from the Vita groups A and B having the same chroma showed limited variations regarding a* (green to red) and b* (blue to yellow) values; the only significant variation was the increasing b* values (yellow) with increasing chroma (A1 to A4 and B1 to B3). As for dentin contrast ratio, limited differences were reported, while enamel proved to increase in translucency with age (reduced contrast ratio). CONCLUSION: These data served as the foundation of the so-called natural layering concept, which makes use of 2 basic composite masses (dentin and enamel) that optically mimic natural tissues. This concept allows for simplified clinical application and layering of composite, as it uses only 1 universal dentin hue with several chroma levels and 3 enamel types for young, adult, and old patients, each exhibiting specific tints and translucency levels.     

Direct visualization of aorto-coronary bypass grafts by two-dimensional echocardiography: A new clinical application

An attempt was made to assess noninvasively the patency of aorto-coronary bypass grafts by two-dimensional echocardiography (2-D echo) in 21 patients who underwent myocardial revascularization. Fifteen patients had one graft while the other six had two grafts. All 21 patients underwent angiography 6–18 months after operation. A day before angiography a 2-D echo was performed with the aim of visualizing the bypass grafts. In 18 patients with 23 grafts (13 with 1 graft and 5 with 2 grafts) it was possible to visualize the tract of the graft, by 2-D echo; 16 were judged patent on 2-D echo and confirmed by selective angiography, while 5 grafts were considered occluded both on 2-D echo and angiography. The other 2 grafts were considered to be occluded on 2-D echo but angiographic control displayed their patency. In 3 patients 2-D echo failed to visualize grafts that were patent angiographically. These data must be considered preliminary and need validation in a larger number of patients. However it is reasonable to conclude that 2-D echo has a reliable capacity to predict graft patency. Such an application may be of value in sequential control of patients with aorto-coronary bypass surgery, especially when combined with other clinical and/or technical data.     

Prolonged apnea and oxyhemoglobin desaturation in asymptomatic premature infants.

Seventy-eight longitudinal four-channel recordings of heart rate, thoracic impedance, nasal thermistry, and pulse oximetry were performed on 26 asymptomatic premature infants (gestational age, 29.9 +/- 1.58 weeks; birth weight, 1,753 +/- 226 grams; postconceptional age, 34.3 +/- 2.0 weeks; postnatal age, 4.41 +/- 2.40 weeks; all values mean +/- SD). Tracings were scored for central and obstructive apnea, bradycardia, periodic breathing, apnea density, and prolonged apnea. The studies demonstrated 585 episodes (7.41/recording) of oxyhemoglobin desaturation with less than 90%. Recordings had a mean of 16.1 episodes of central apnea, 3.04 episodes of obstructive apnea, and 2.34 episodes of bradycardia. Periodic breathing and short obstructive apneas correlated significantly with the total number of oxyhemoglobin desaturations of less than 80% and 90%. Episodes of prolonged apnea were seen in 20 of 78 recordings. In the latter a significantly higher number of total desaturations (less than 90%), desaturations less than 80% and 90% in association with apnea and with bradycardia, longer desaturations, desaturations during sleep, and isolated bradycardia were observed. Variations in heart rate, thoracic impedance, nasal air flow, and pulse oximetry are associated with episodes of oxyhemoglobin desaturation in asymptomatic premature infants. These infants, although asymptomatic, may be at risk for impaired tissue oxygenation.     

Early-onset ataxia with cardiomyopathy and retained tendon reflexes maps to the friedreich's ataxia locus on chromosome 9q

Absence of lower limb tendon reflexes has been considered an essential diagnostic criterion for Friedreich's ataxia (FA). However, preservation of knee and ankle jerks has been reported in a few patients. Linkage analysis to FA locus (FRDA) on chromosome 9q13-21.1 was performed in 11 patients from 6 families with FA phenotype, including cardiomyopathy, but retained reflexes (FARR). A maximal lod score of 3.38 at recombination fraction theta equal to 0.00 was obtained demonstrating that FARR maps to the FRDA locus. These results suggest that FARR is a variant phenotype of FA.     

Ethanol administration in vivo alters calcium ions control in rat striatum

The present paper investigates the effect of chronic ethanol treatment administered through drinking water on [3H]nitrendipine binding and 45Ca uptake in rat striatum. The calcium-independent [3H]nitrendipine binding was slightly increased in treated rats, while the calcium stimulation of the binding was reduced to one fifth of the controls. In striatal slices prepared from a similar group of ethanol-treated rats the K+-stimulated 45Ca uptake was greatly reduced. These results are the first evidence of calcium-antagonist binding-site 'plasticity' following an in vivo pharmacological manipulation correlated with a change in calcium ion transport. In addition, the effect of ethanol on calcium-entry regulation may be a mechanism important for the understanding of its neurotoxic action.     

The contribution of the corpus callosum to receptive fields in the lateral suprasylvian visual areas of the cat

In both ordinary cats and ‘Boston’ Siamese cats the visual areas in the lateral parts of the middle and posterior suprasylvian gyri (LSA) contain an extensive representation of the ipsilateral half of the visual field. In addition, in both groups of cats the overwhelming majority of neurons in LSA can be driven from both eyes. In Siamese cats this binocular interaction is in marked contrast with what is found in area 17 where neurons are almost exclusively activated through the contralateral eye. Transection of the posterior $\text{1}\text{3}$ to $\text{1}\text{2}$ of the corpus callosum had a different effect on the physiological organization of LSA in the two types of cats. In ordinary cats it caused the loss of the ipsilateral hemifield representation in the eye ipsilateral to the side of recording and reduced this representation in the other eye. However, after the section of the corpus callosum LSA neurons remained binocular. In Siamese cats the callosal transection left the representation of the ipsilateral hemifield in LSA unaffected, but totally abolished the input from the ipsilateral eye. These findings suggest that the visual callosal input to LSA has a different functional significance in ordinary and Siamese cats. In the former cats it may be related to perceptual equivalence across the vertical meridian of the visual field, whereas in the latter cats it may subserve interocular equivalence.