Bo Sunzel

Antibacterial Effect of Zinc Oxide in Vitro

Antibacterial activity, zinc concentrations and pH were measured in Müller-Hinton broth containing different amounts of zinc oxide and inoculated with Staphylococcus aureus (10(6) colony forming units/ml). The minimum inhibitory concentrations (MIC) of zinc oxide to different clinical isolates were determined using the Müller-Hinton agar dilution tests. Gram-positive bacteria were most susceptible. Gram-negative aerobic bacteria and streptococci were usually not inhibited even at the highest concentrations used (1024 micrograms/ml), but staphylococci--particularly some isolates of Staphylococcus epidermidis--were sensitive enough to allow determination of their MIC.

Planning and control of vertical dimension in Le Fort I osteotomies

Depending on the different anatomy of the soft and hard tissues, concavity or convexity of the face, measurements of inferior or superior repositioning of the maxilla may be less predictable when using only the osteotomy site for this calculation. A more reliable method would be to measure the distance from a bone mark in the forehead to the incisor edges. This method has been practiced by our clinic during the past five years. The method is thought to offer a more accurate estimation of the position of the upper anterior teeth in relation to the lip, although one must anticipate a certain degree of postoperative relapse especially concerning inferior repositioning. In order to evaluate the accuracy of our method, a comparison has been made of the calculated vertical repositioning and the surgical results in two groups. In group I (12 individuals) conventional estimation of maxillary repositioning in the osteotomy line was made; in group II (12 individuals) measurements were made from a bone mark on the forehead to the incisor edges. A satisfying correlation was found between calculated and achieved results in both groups. In comparison between calculated and immediate postoperative measurements the results showed no statistically significant difference between the two methods.

The protective effect of zinc on rosin and resin acid toxicity in human polymorphonuclear leukocytes and human gingival fibroblasts in vitro.

Combinations of rosin and zinc are used in dentistry as components of periodontal dressings and cements and as root canal sealers. The composition and properties of rosins differ largely depending on source and refinement processes. Rosin (colophony) is composed of approximately 70% resin acids. In order to study the toxic effects of different natural rosins and purified resin acids and the detoxifying effects of zinc, these compounds were analyzed and tested on human polymorphonuclear leukocytes (PMN cells) and human gingival fibroblasts using the radiochromium release method. The rosins and the pure resin acids showed a strong dose-related cytotoxicity, which was inhibited by increased zinc concentrations. The purified resin acids (isopimaric, levopimaric, and neoabietic acid) were more toxic than the natural rosins. The contents of these resin acids might explain the difference in toxicity of the rosins tested. It is concluded that rosin and zinc are not to be considered inert compounds and that the cytoprotective effects of zinc and its role in dentistry products merit further investigations.

Neutralizing effect of zinc oxide on dehydroabietic acid-induced toxicity on human polymorphonuclear leukocytes

The cytotoxic effect of dehydroabietic acid (DHAA), a resin acid found in rosin, was studied on human polymorphonuclear leukocytes using leakage of51Cr from prelabeled cells, supravital staining, and transmission electron microscopy. DHAA caused a strong dose-related release of51Cr, a high uptake of trypan blue, and total cell necrosis, as seen in transmission electron microscopy. Albumin slightly reduced the toxic effects, whereas the addition of zinc in various forms strongly inhibited these toxic effects of DHAA in the concentration range of 10–500 μg/mL. In the presence of albumin, zinc oxide as a suspension inhibited the damage of the cell membranes more than a filtrate of zinc oxide, indicating a subsequent slow release of zinc from the zinc oxide.

The effect of zinc on bacterial phagocytosis, killing and cytoprotection in human polymorphonuclear leucocytes.

An in vitro study examining the effects of zinc treatment on human PMN cell phagocytosis and killing of Staphylococcus aureus and Staphylococcus epidermidis and the cytoprotection of zinc against staphylococcal toxins. Phagocytosis was studied by transmission electron microscopy using different microbiological techniques, one of which was designed to follow the kinetics of bacterial killing. No effect was found on phagocytosis and bacterial killing. The cytotoxic effects of a crude toxin and an α‐toxin extracted from Staphylococcus aureus preparations were studied on human PMN cells using the standard 51Cr release assay. Both toxins induced a dose‐dependent leakage of 51Cr, indicating cell membrane damage. These results were confirmed by electron microscopy during the phagocytosis of S. aureus, where severe PMN cellular degeneration was observed. The addition of zinc to PMN cells strongly inhibited the release of 51Cr. In conclusion, our results show that zinc in higher than physiological concentrations does not inhibit PMN cell functions such as phagocytosis and intracellular killing of S. aureus and S. epidermidis. The addition of zinc may be beneficial in certain clinical situations, such as wound healing, zinc deficiency and infections involving toxin‐producing bacteria, e.g. S. aureus.

The Effect of Zinc Oxide on Staphylococcus Aureus and Polymorphonuclear Cells in a Tissue Cage Model

The effect of zinc oxide on S. aureus (209 P) was studied in steel net tissue cages implanted subcutaneously in guinea pigs and rabbits. Zinc oxide installed in the tissue cages created high, sustained concentrations of zinc in the cage fluid throughout the study. In a concentration of 22 mmol/l zinc oxide reduced viable counts in tissue cage fluid inoculated with S. aureus. No deleterious effect was observed on polymorphonuclear cell function.

The extent of coprophagy in rats with differing iron status and its effect on iron absorption.

The purpose of this study was to determine the prevalence of coprophagy in rats with differing iron status and its effect on the measurement of iron absorption from test meals with and without bran. Two experiments were performed using radioisotope-labelled microspheres added as a non-digestible marker for the ingested faeces and the diet and 59Fe added as a marker for the non-haem iron in the test meal. In this study, coprophagy occurred at group mean rates of between 5 and 22% and was independent of the iron status of the rats or the presence or absence of bran in the diet. The relative absorption of iron, measured as the retention of 59Fe from a single meal, was affected to the same extent in groups with the same iron status, if it was affected at all. Thus comparisons of iron absorption from diets with and without bran should not be affected by coprophagy.

The availability of iron, zinc and cadmium to rats from composite diets with different cereal grains

Abstract Many investigations have been reported in which the effects of varying the concentration of a single factor in grain diets on the availabilities of minerals for absorption have been studied. The purpose of this study in rats was to determine the effects on iron, zinc and cadmium availability of substituting whole grain wheat, oats, barley or rye for iron-supplemented endosperm wheat in a composite diet with one part grain flour and one part non-fat, dried milk with maize oil and vitamins. Iron concentrations varied by a factor of 3 among these diets, zinc by 1.5, cadmium by 5, and both fiber and phytate by a factor of 3.5. The absorption of 59 Fe and 65 Zn from test meals of the diets and the concentrations of iron, zinc and cadmium in selected tissues and body fluids after five weeks on the grain diets were used as independent measures of the mineral availabilities from these diets. Absorption of iron from endosperm wheat and, to a lesser extent, zinc from oats and rye appears to have been overestimated, most likely due to incomplete exchange of the radioisotopes with the supplemented or endogenous minerals in the grains. The variations in the concentrations of iron and cadmium among the diets were by far the most important factors determining the availabilities of these minerals to the rats. The fractional availabilities of iron and zinc were negatively related to the diet phytate concentration and the fractional availability of cadmium was negatively related to the iron status of the rats. The results indicate that substitution of whole grain wheat for endosperm wheat in the diet will increase cadmium accumulation considerably while substitution of oats, barley or rye should result in nearly the same or lower cadmium accumulation. Due to the low availability of iron in barley and rye, substitution of either grain for iron-supplemented endosperm wheat may compromise iron status. As the diets in this study are similar to baby formulas and breakfast cereals, porridge or a sandwich with milk, the probability that these results in rats are applicable to humans strongly suggests that studies similar to this be carried out in humans.

The Availability of Zinc, Cadmium and Iron from Different Grains Measured as Isotope Absorption and Mineral Accumulation in Rats

The purpose of this study in rats was to determine if the absorption and accumulation of zinc, cadmium and iron differ amoung diets based on different grains and, if so, what differences among the grains might account for the differences in mineral absorption.