Cavity preparation for restorative resins used with dentin adhesives

The marginal adaptation of Silux used with and without previous application of different dentin adhesives was analyzed for correlation between maximum marginal contraction gap (MG) and different combinations of one or more of the following variables: area of cavity walls (A), the total area of cavity bottom and cavity walls (B), cavity depth (h), area of cavity surface (S) and cavity volume (V), The best fit to linear regression was found with MG = a + b V/A with the mean of the correlation coefficients being 0.907. The statistical analysis showed that in order to maintain the V/A ratio at a minimum, root caries lesions should not be prepared after excavation if the retention of the restorative resin can be ensured with an effective dentin adhesive. The greatest influence on the V/A ratio was found to be exerted by the radius of the cavity bottom; variation of the radius of the surface of the cavity also influenced the V/A ratio, but to a minor degree.     

PYCNODYSOSTOSIS: Six Cases with New Symptoms and an Autopsy

Abstract. Lykkegaard Nielsen, E. (Department of Paediatrics, Sundby Hospital, Copenhagen, Denmark.) Pycnodysostosis. Six cases with new symptoms and an autopsy. Acta Paediatr Scand, 63: 437, 1974.–Six patients with pycnodysostosis, all of whom had characteristic case-histories, are presented. Five of the patients had symptoms which have not hitherto been recognized in this condition. They all had varying degrees of respiratory distress, tendency to vomit and long soft palates. One of the patients died at the age of 21 months on account of vomiting and pulmonary aspiration. Autopsy revealed normal conditions in the lungs. The vital prognosis is usually stated to be good in this disease, but this study shows that during the first years of life it is possibly poorer. Occurrence of progressive acmteolysis in pycnodysostosis has been discussed previously. In one of the patients in this material slight increase in the bony substance in the distal phalanges of the fingers was observed on repeated radiografic examination while in another both break-down and new bone formation were observed in the processus unguiculares. In a third patient cyst-like defects in some of the ungual tufts of the fingers were present. These conditions are thus incompletely elucidated at present.     

Plasma noradrenaline correlates to sympathetic muscle nerve activity in normotensive man

Recordings of multiunit sympathetic activity were made in muscle branches of the peroneal nerve in 22 healthy subjects at rest in recumbent position. Nerve activity was quantitated in terms of burst incidence (number of pulse synchronous sympathetic bursts per 100 heart beats or per min). In a separate session, 4–45 months later, blood was drawn from an antecubital vein for noradrenaline analysis. Both sympathetic activity and plasma concentrations of noradrenaline varied widely between subjects and both parameters increased with age. There was a significant positive correlation between a subject's level of sympathetic activity and his plasma concentration of noradrenaline. It is suggested that overflow of transmitter from sympathetic terminals in muscles contributes significantly to plasma levels of noradrenaline at rest.     

Study on the dissolution behaviour of calcium fluoride

Abstract – The dissolution of two analytical calcium fluoride preparations was studied in aqueous solution. Dissolved calcium fluoride was determined from analysis Ca and F in solution. Original samples of the two preparations and the residue after partial dissolution were studied by X-ray diffractometry in comparison with natural fluorite. The dissolution of calcium fluoride was found to be extremely slow. After a period of 1–15 weeks, depending on the experimental conditions, a state was reached where apparently no further dissolution occurred, although the solution was far from saturation. The dissolution rate was obviously closely related to the crystal size. On partial dissolution the mean crystal size increased, probably due to the disappearance of the finest fractions. Placing the salt in a dialysis bag before immersion in the water lowered the dissolution rate and increased the undissolved fraction considerably. The results seem to support the assertion that calcium fluoride accumulated in early carious lesions after topical applications of fluoride may persist for considerable periods of time.     

Modulation of proximal tubular hydraulic conductivity by peritubular capillary oncotic pressure

Fluid absorption from the proximal tubular lumen is probably a multifactorial process. Earlier studies from our laboratory have indicated that a transepithelial hydrostatic and oncotic pressure difference may be the driving force for as much as 30% of the reabsorbed fluid. During saline volume expansion proximal tubular reabsorption declines and the present experiments were undertaken to investigate whether this reduction could be caused by changes in the passively driven flux component. The hydraulic conductivity was therefore determined from the reabsorptive rate in split oil droplets with normal and high hydrostatic pressure gradients across the wall, at the same time as the peritubular capillary net-work was perfused with solutions containing a colloid of high or low concentration. In the reabsorption experiments the split oil droplet radius was measured and in a separate series of experiments the relationship between droplet radius and pressure was determined; this was found to be 7.3 mmHg pressure increase per 1 μm increase in radius. The increase in the rate of reabsorption from the droplets due to increased intraluminal hydrostatic pressure was 1.02±0.13 nl/min/mm tubular length when a solution with a high colloid concentration was perfused through the capillary net-work, compared with 0.41=0.11 nl/min/mm tubular length when a low colloid containing solution was used for perfusion. The hydraulic conductance in the proximal tubular wall at high colloid perfusion was calculated to be 0.54 nl/min mm mmHg while at a low capillary colloid oncotic pressure it was significantly lower 0.025 nl/min mm mmHg. This drop in hydraulic conductance might be one factor responsible for the decline in fluid absorption in animals exposed to saline volume expansion.