Lars-Erik Moberg

Metal release from plates used in jaw fracture treatment. A pilot study

This study investigated the occurrence of corrosion associated with the use of metallic implants to stabilize jaw fractures. Three different types of plates, Co-Cr and Ni-Cr alloys and Titanium, were connected in vivo to the mandibular bone surface of monkeys (Cercopithecus aethiops). The animals were killed after 3 and 6 months. The mucous membrane and bone tissue were analysed for concentrations of Co, Cr, Ni, Mo, Al, and Ti by atomic absorption spectrophometry and a radiochemical neutron activation technique. With the exception of Ti, higher concentrations of all the above elements were found in the tissue near the implants when compared with contralateral controls. However, no signs of corrosion, macroscopic or microscopic, were observed on the surface of the implants.

Dental implant installation without antibiotic prophylaxis

The objective of this study was to retrospectively compare the outcomes of dental implant treatment with and without antibiotic prophylaxis. Two groups of patients with edentulous or partially edentulous maxillas or mandibles (or both) were treated with dental implants. One group, consisting of 147 patients (790 implants), was given prophylaxis with oral phenoxymethylpenicillin; 1 g of antibiotic was administered 1 hour preoperatively, and 1 g was administered every 8 hours for 10 days postoperatively. The other group, consisting of 132 patients (664 implants) was not given any antibiotics preoperatively or postoperatively. There were no significant differences with respect to early and late postoperative infections or with respect to implant survival between the two groups. It appears that antibiotic prophylaxis for routine dental implant surgery offers no advantage for the patient.

The microstructure of corroded amalgams

One conventional amalgam and two amalgams with a high copper content were stored in 0.9% NaCl solution buffered with phosphate to pH 6. In one experimental series the amalgams were placed in contact with a gold alloy. Every 7 weeks the solutions were changed and analyzed with regard to elements released from the amalgams. The microstructure of the specimens was studied in a scanning electron microscope before immersion and after 7 and 35 weeks in the solution. All the amalgams corroded along the grain boundaries in the gamma 1 phase. Corrosion was greatest in the gamma 2 phase of ANA 68, in the eta phase of ANA 2000 and in the reaction zone (eta + gamma 1) surrounding the Ag-Cu-eutectic particles of Dispersalloy. The microstructure of the corroded amalgams showed similarities to amalgams corroded in vivo. The change in microstructure observed in cross-sections of the corroded specimens was related to the amounts of corrosion products released into the saline solution.

Long-term corrosion studies in vitro of amalgams and casting alloys in contact

One conventional amalgam and two amalgams with higher copper content were stored in contact with various dental casting alloys in phosphate-buffered 0.9% NaCl solution, pH 6, at 37 degrees C during 35 weeks. Every 7 weeks the solutions were changed, and the corrosion was measured by analyzing the solutions for the amount of Cu, Zn, Sn, Hg, Ag, Co, Cr, and Ni. In the first 7 weeks the amalgams immersed in contact with acrylic or Co-Cr alloys released small amounts of elements, whereas the release was larger when the amalgams were in contact with the gold alloys. During the rest of the experiment the release of elements tended towards the same level, independent of the casting alloy in contact. In general, the high copper amalgams released more corrosion products into the solutions than the conventional one. The release of corrosion products was strongly pH-dependent. Changing the solutions more often and saturating the solutions with oxygen decreased the amounts of Hg and Ag released.

Long-term corrosion studies in vitro of gold, cobalt-chromium, and nickel-chromium alloys in contact

Specimens of various types of dental casting alloys were stored in phosphate-buffered 0.9% NaCl solution for 35 weeks. Every 7 weeks the solutions were changed and analyzed with regard to elements released from the alloys. The release of Cu from type III gold alloy increased in contact with gold alloys for metallo-ceramic use in a 1:2 area relation. However, when the area relation was reversed, no difference in the amounts of elements released was observed. Crevice corrosion was initiated with one of the Co-Cr alloys in contact with type III gold alloy. The crevice corrosion increased the amounts of Co and Cr released into the solutions. The release of Ni and Cr from the Ni-Cr alloys was prominent. These alloys were very susceptible to crevice corrosion. With one of the Ni-Cr alloys the release of elements increased in contact with type III gold alloy.

Effects of mercuric ions on isolated guinea-pig ileum

The possible physiological significance of low concentrations of Hg2+ in the guinea-pig ileum has been investigated. Responses to nerve stimulation by single electrical shocks, acetylcholine (ACh), and histamine (Hi) and the response to ACh of a depolarized preparation were examined. A stimulant effect of Hg2+, in the concentration range of 10 nM-1 microM, dominated in intestine accommodated in biological saline solution. This excitatory effect was probably mainly due to stimulation of a depolarization-coupled initiation of the contraction. The inhibitory effect of Hg2+, 10 nM-1 microM, observed in depolarized muscle was presumably due to a decreased Ca2+ availability for the contractile process. In the higher concentration range, 1-100 microM, a probably direct action on the contractile elements causing irreversible deterioration of the preparation seems to be present.

Uranium content in porcelain denture teeth and in porcelain powders for ceramic crowns

Some porcelain denture teeth and porcelain powders marketed in Sweden haven been analyzed for the content of uranium. The fission track method and the delayed neutron technique were the methods used. Compared to results published previously the content of uranium was generally found to be lower in the brands analyzed. The denture teeth contained 23-186 ppm for Anatoform, 35-137 ppm for Myerson, 15-45 ppm for Candulor G and 20-53 ppm for Vivopearl. The baked and fired porcelain powders showed values of about 2.8 ppm at most, those in the form of powder about 25 ppm at most. The radiation dose to the mucosa of the upper lip was calculated and is discussed.

Low concentrations of inorganic mercury inhibit in vitro autonomic transmission in the presence of albumin

The influence of albumin, 4.5 and 45 g/l, on the effects of Hg2+, 10(-9)-10(-3) M, on the neuromuscular transmission of the isolated guinea-pig ileum and vas deferens was investigated. Hg2+, 10(-9)-10(-6) M, transiently increased the basal tone of the ileum in Tyrode solution without albumin. Albumin, 4.5 g/l, reversed this stimulant effect but enhanced the contractile response to direct muscle stimulation. This contractile response also increased in the vas deferens. Albumin, 45 g/l, obliterated the stimulant effects of Hg2+ on the smooth muscle of the ileum but not of the vas deferens. The effects caused by higher concentrations of Hg2+, 10(-5)-10(-4) M, were only partly inhibited when albumin was present. When neurogenic contractions were elicited in the presence of albumin (45 g/l), Hg2+, 10(-9)-10(-4) M, reduced the contractions in both organs. Consequently, Hg2+ in concentrations presently considered acceptable in blood plasma (10(-9)-10(-8) M) suppressed both cholinergic and adrenergic neuromuscular transmission even in the presence of albumin.

Albumin inhibits effects of Cu2+ on autonomic postganglionic transmission of guinea-pig ileum and vas deferens

The influence of albumin, 4.5 and 45 g/l, on the effects of Cu2+, 10(-9)-10(-3) M, on the neuromuscular transmission of the isolated guinea-pig ileum and vas deferens was investigated. Low concentrations of Cu2+, 10(-9)-10(-6) M, caused a slight and transient increase of the contractile response to direct muscle stimulation of the vas deferens. Albumin at 4.5 g/l inhibited this effect. The basal tone of the ileum increased transiently when Cu2+ was added in the presence of albumin, 4.5 g/l. A stimulant action of Cu2+, 10(-9)-10(-6) M, was seen on both organs, when contractions were induced by nerve stimulation. All these effects were inhibited by albumin, 45 g/l. Higher concentrations of Cu2+, 10(-5)-10(-4) M, increased the basal tone of the ileum and the vas deferens. In the presence of albumin, 45 g/l, this stimulating effect of Cu2+ appeared in higher concentrations. The results suggest that Cu2+ is more likely to influence the function of neuronal tissues when the concentration of protein is low.

Long-term corrosion studies in vitro of amalgams in contact.

Three types of amalgams, one conventional and two with a high copper content, were stored in phosphate-buffered 0.9% NaCl solution, at pH 6, for 35 weeks. Every 7 weeks the solutions were changed and analyzed with regard to Cu, Zn, Sn, Hg, and Ag. In one of the amalgam combinations, the conventional amalgam and one of the copper-rich amalgams in an area ratio of 2:1, contact between the amalgams clearly increased the amounts of Cu, Hg, and Ag released the first 14 weeks compared with when immersed in separate solutions. With the reversed area relation, Cu, Hg, and Ag decreased when they were in contact. The conventional amalgam in contact with the other copper-rich amalgam, in an area ratio of 2:1, reduced the amount of Cu but increased the Zn released. Polishing initially decreased the amounts of Cu and Zn released compared with the unpolished amalgams.