Richard S. Callan

Subcutaneously Implanted Alginate as a Continuous-release Source of Fluoride

The fluoride concentrations of seven brands of alginate ranged from 8600 to 30,500 ppm. In acute and chronic in vivo studies, fluoride was continuously released from subcutaneously implanted alginate cylinders for up to three weeks. This technique is a simple and economical method for elevating soft and hard tissue fluoride levels.

Radiofluoride Distribution in Rat Lung, Colon, and Heart

Much information on the tissue distribution of fluoride has been derived from studies using radiofluoride (18F). For example, bone, teeth, and loci of ectopic calcification tend to accumulate fluoride. In most soft tissues, fluoride enters intracellular spaces as judged by tissue water-toplasma (T/P) fluoride concentration ratios which generally fall between 0.4 and 1.0. Certain features of the distribution of fluoride, however, remain unclear. Carlson et al. (PSEBM 103:418, 1960) studied 18F distribution in several soft tissues of the rat and found no evidence of binding (T/P < 1.0), nor did we in a more extensive study (Am £ Physiol 236:F141, 1979). In contrast, several reports have suggested that lung and/or colon accumulate fluoride to levels in excess of the simultaneous plasma concentrations (WallaceDurbin, J Dent Res 33:789, 1954; Bell et al., J Nutr 73:379, 1961; Knaus et al., Tox Appl Pharmacol 38:335, 1976). These results could have been due to including major bronchi or trachea with the lung samples and feces with the colon samples, because these contain high calcium levels and would be expected to bind 18F. The current work was done to evaluate these possibilities. Eight female Wistar rats (265 g) were anesthetized with ether, and high specific activity 18F, 9.1 gCi/rat, was injected i.v. Four of the rats were decapitated at 30 min and the remainder at 60 min. Blood was collected from the neck wound, and the heart, colon, and lungs with trachea were removed. The colon was opened and the fecal pellets were removed. The outer portions of the lobes of the lung were dissected free and the remainder of the lung, including the major bronchi, and then the trachea were collected separately. The samples were weighed, counted for 18F in a well-type scintillation counter, and then dried to determine the water content. All counts were corrected to a common point in time. The data are shown in the figure. The T/P ratios for heart agreed with all published reports. However, there was no evidence of 18F binding by colon or its contents, nor by peripheral lung (T/P < 1.0). The T]P ratios for lung with major bronchi did indicate 1aF binding (T/P > 1.0), and this was especially marked for trachea. We conclude that colon does not bind 18F, and that earlier reports indicating 18F binding by lung were probably based on samples containing major bronchi and perhaps trachea.

Effect of Short‐Duration, Localized Carbamide Peroxide Application to Remove Enamel Staining on Bond Strength of Resin Cement to Enamel

UNLABELLED Objective Peripheral enamel staining is often noticed after removal of long-term veneer or crown provisional restorations. Application of carbamide peroxide (CP) easily removes the stain, but the potential for immediate bonding with a resin-based cement is questionable. This project tested the short-term, shear bond strength of a commercial, photo-curable, resin cement to bovine enamel after application of a 10% concentration of CP placed for different exposure times. MATERIALS AND METHODS Bovine enamel was flattened and polished. Surfaces had either no CP application (control), or 10% CP applied for 10, 20, or 30 seconds. Teeth were acid-etched, rinsed, dried, and controlled sized stubs of a commercial resin cement were photocured onto the treated surfaces. The shear bond strength of each specimen was determined using a universal testing machine, and results were compared using an analysis of variance at a preset alpha of 0.5 (n = 10/group). RESULTS No significant differences (p = 0.819) in shear bond strength were found among any CP cleaning treatments or the experimental (nontreated) control. CONCLUSIONS Short-term application of 10% carbamide peroxide prior to acid etching, to remove enamel stains in teeth prepared to receive ceramic veneers or crowns, does not reduce immediate shear bond strength of resin-based cement to enamel. CLINICAL SIGNIFICANCE Clinicians can confidently apply 10% CP for short-term, localized stain removal on enamel and not be concerned about affecting subsequent bond strength of a resin-based cement to enamel. (J Esthet Restor Dent, 2016).

Fluoride absorption from subcutaneous sites: influence of volume and concentration.

A recent report described the time courses of blood radiofluoride (18F) concentrations and urinary 18F excretions in rats following parenteral administration (WHITFORD ET AL, J Dent Res 56:858-861, 1977). Variations in either the injected volume or fluoride (F) concentration could influence the absorption rate by altering the local microcirculation and, therefore, the time courses of blood concentrations and urinary excretion. This study was done to determine the influence of these two variables after subcutaneous injection. Eighteen, 213 -+3 gm, female Wistar rats were anesthetized with pentobarbital sodium (35 mg/kg, ip). Urine samples were collected via bladder catheters and blood samples were collected from carotid artery cannulae at timed intervals. Injections were given beneath the skin overlying the abdomen lateral to the midline. In the F concentration study, each rat received 0.20 ml. The F concentrations (as NaF) of the injectates for groups Cl, C2, and C3 were 10.4, 51.1, and 772 mM respectively. Thus, these groups received 0.19, 0.91, and 13.74 mg F/kg. The injectates for groups Cl and C2 were made isotonic with NaCl. The injectate for C3 was already hypertonic and was included because this dose is appropriate to acute F toxicity studies. In the volume study, each rat received 0.87 mg F/kg. The animals in groups Vl, V2, and V3 received 0.10, 0.20, and 0.50 ml, respectively. All injectates contained Evans blue dye