Pulpal reaction to polycarboxylate and zinc phosphate cements used with inlays in deep cavity preparations

The purpose of the present investigation was to compare histologically pulpal reactions beneath inlays cemented with either a zinc phosphate or a polycarboxylate cement. No inflammatory reaction was seen beneath any of the 39 deep cavity preparations in teeth without pulpal lesions and with an inlay cemented with polycarboxylate cement. In the contralateral teeth, under 39 inlays cemented with zinc phosphate cement, an inflammatory reaction was seen beneath two cavity preparations. In one, bacteria were found on the floor of the preparation. On the basis of this result and the findings of our earlier investigations, it may be warranted to conclude that neither the polycarboxylate cement nor the zinc phosphate cement has any notable irritating effect on the pulp. If the irritation occurs after cementation of the restoration, it may be caused by debris containing bacteria and left behind on the prepared surfaces by bacterial growth from the surface of the tooth. The findings underline the importance of removing grinding debris and bacteria before cementation of the restoration.

Reactions of human platelets with microspheres of poly(hydroxymethyl methacrylate) and polyacrylamide

We have studied the contact interaction of platelets with hydrogels. In the form of microspheres, 0.6-1.0 mu, poly(glycol methacrylate) (polyHEMA) and poly(methyl methacrylate) beads cause platelets to aggregate at concentrations of about 10(8) beads/ml. Polyacrylamide and (20/80) poly(acrylamide-HEMA) copolymer were ineffective in aggregating platelets. The admixture of 20% methacrylate to polyHEMA rendered the beads inactive. Blood plasma components other than fibrinogen were found essential to the interaction of the beads with platelets. Near-infrared spectra of the hydrogels polyacrylamide and polyHEMA showed the water hydrogen bonds to be the same for both and different from those in pure water. The monomer HEMA is an inhibitor of platelet aggregation and the release reaction at levels of 0.1%. It is concluded that the two hydrogels have different blood compatibilities, which depend more on the network structures than the water structures in the respective gels.

[Mechanisms of action of synthetic polyelectrolytes and polyampholytes on the immune response]

We investigated the effect of polyacrilic acid (PAA) on the immune response in mice of various strains on sheep red blood cells and also the influence of poly-2-methyl-5-vinyl-pyridine (PMVY), PAA and their statistical copolymers on antibody-forming cells (AFC) production in cultures of T- and B-lymphocytes in vivo. PAA was seen to increase accumulation of AFC in the spleen of mice depending on their genotypes. PMVP and PAA were found to intensify the cooperating interaction of T- and B-lymphocytes, whereas their copolymers exert quite an opposite effect. The injection of copolymers to the recipients of cooperating T- and B-lymphocytes practically results in the complete elimination of the cooperation effect between T- and B-lymphocytes in the immune response to sheep erythrocytes without cytostatic action of cell proliferation.

Stabilization of a psychrotrophic Pseudomonas protease by calcium against thermal inactivation in milk at ultrahigh temperature

The heat-stable extracellular protease of Pseudomonas sp. (isolate MC60) was investigated. Heat resistance of the enzyme in milk at sterilization temperature was dependent on the presence of Ca2+. The half-life of the enzyme at ultrahigh temperature (149 C) in skim milk or milk-salts buffer with Ca2+ was approximately 7.0 s. Treatment of milk with chelators completely removed the heatstabilizing effect of milk. The enzyme was partially purified by ammonium sulfate precipitation and column chromatography on Sephadex G-100. At 21 C the enzyme retained greater than 85% activity after exposure to pH values between 5 and 10. Enzyme activity was reduced by metal chelating agents. Both Ca2+ and Zn2+ were required for optimal enzyme activity. Molecular weight was estimated at 48,000 by gel filtration.

Polymethacrylic acid: induction of lymphocytosis and tissue distribution

Polmethacrylic acid (PMAA) induces up to a three-fold increase in the lymphocyte population of peripheral blood in rats, goats and calves after intravenous administration. Other routes of administration are less effective. A maximum lymphocytosis is achieved after 3 hr with all doses in excess of 30 mg PMAA/kg body weight; over the next few hours the lymphocyte level declines to normal. Granulocytes increase steadily for the first 7 hr before declining. Multiple doses of PMAA 2 hr apart failed to maintain or significantly alter the lymphocytosis. PMAA was labelled with 125I and 14C, and was traced to various sites in the rat. The greatest accumulation of radioactivity was in the spleen, lungs, liver, kidney, adrenals and mesenteric lymph nodes (with 14C-PMAA). The accumulation appeared more specific for spleen and lymph nodes since there was only a small loss of activity following removal of blood by whole body perfusion. This supports previous findings indicating that these two tissues play a major role in the development of lymphocytosis. Accumulation in the bone marrow may be indicative of stem cell mobilization. The results are discussed in terms of the lymphocytosis-inducing mechanism and the site of action of PMAA and the possible clinical application to ECIB therapy is considered.

Cardiovascular effects of acrylic bone cement in rabbits and cats

The cardiovascular responses to forcing acrylic bone cement, Plasticine, or soft paraffin wax into the medullary cavity of the femur have been studied in rabbits and cats. An acute fall in blood pressure, occurring within a few seconds of insertion, was demonstrated with each substance. In a few of the animals the blood pressure response had a second more protracted component and it is suggested that more than one mechanism is involved. The cardiovascular effects that have been observed in man when acrylic cement is used in prosthetic hip surgery also may be due to more than one mechanism.

Effects of acrylic restorations on the periodontium of monkeys

Replanted teeth that had an acrylic restoration in the middle third of their roots were studied from three days to six months after grafting. The study revealed that the acrylic obturator elicited epithelial proliferation, fibrous encapsulation, moderate chronic inflammation, and adjacent alveolar bone loss.

Pulpal response of monkeys to modifications of a bisphenol A composite resin and cement

This investigation demonstrated the minimal pulpal response of the teeth of monkeys to bisphenol A restorative materials in the form of a cement and as a composite resin. Each material was thinned with a monomer of methyl methacrylate or of dimethacrylate.