[Studies of the resistance of phosphate cements, silicate cements and autopolymer preparations to bacteria].
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This study aimed to compare the fluoride release from a fluoride-containing amalgam, a silicate cement and a glass ionomer cement in artificial saliva. After storing specimens in an artificial saliva for 7 weeks, the fluoride content in the solvent was measured by a spectrophotometric method. The fluoride release from silicate cement was about 5 times greater than from glass ionomer cement, which again showed a release 4 times greater than the fluoride-containing amalgam. The fluoride release relative to fluoride content in test specimens was greater from fluoride-containing amalgam and silicate cement than from glass ionomer cement.
Silicate cement was inserted in deep unlined cavities in 70 human teeth; 35 cavities were cleaned with an antibacterial cleanser, and the other 35 cavities in the contralateral teeth were treated with water spray only. In all teeth, invasion of bacteria from the tooth surface was prevented with a surface seal. Histologic examinations after 4 weeks revealed bacterial growth on dentinal walls in 9 of the uncleaned and in 2 cleaned cavities. Only in these 11 teeth was an inflammatory reaction seen in the pulp. Under eight cavities without bacterial growth and with silicate cement placed directly on an exposed pulp, no serious injury and no inflammatory reactions were observed. It was concluded that silicate cement per se does not seriously irritate the pulp. Infection of cavity walls should be avoided, not only by removing grinding debris and antibacterial cleansing, but also by use of a liner to prevent invasion of bacteria from the surface of the tooth.
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Six brands of silicate cements have been characterized by means of optical emission spectrography with respect to the contents of elements in minor or trace quantities in a search for presence of possible toxic elements. Beryllium was observed in two powders at levels of 1.3 and 1.6% Cadmium was found in two powders at levels of 0.02 and 0.03%. Lead was measured in three powders at levels of 0.001-0.003%. Bismuth, boron, copper, gallium, iron, manganese, titanium, tin and zirconium were found in various brands in either powder or liquid at levels of 0.001-0.1%. Upper limits of the amounts of the various elements that might be transferred to the gastrointestinal tract after dissolution of the cement matrix in the oral cavity have been calculated.
Silicate cement specimens have been exposed to infrared radiation for the purpose of improving the erosion resistance. Exposure for periods of 3-10 min, corresponding to a surface temperature of about 60-70 degrees C, resulted in a reduced phosphate release of about 3-5 times that of a non-exposed group. The temperature distributions on the surface, as well as in a position 5 mm beneath the surface, were measured with thermocouples during irradiation. A difference in temperature of about 20 degrees C was registered between the surface and interior positions. The technique may be clinically exploited by exposing the restoration after insertion to a small infrared radiation source, available on the commercial market.
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The literature relating to the dissolution of the silicate cements is reviewed, including the methodology, intrinsic factors relating to composition and method of mixing, curing etc. and extrinsic factors, i.e. the medium, pH, ionic strength etc. to which the sample of cement is exposed. New experimental data is shown relating the dissolution rate to solution composition and ionic strength. It is seen that samples of silicate cement can take up phosphate from solution as well as releasing this species and a dissolution process based on a reversible equilibrium is advanced. Also considered are the effects of sample volume:area ratio and the effect of agitation.
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The biologic compatibility of two composite materials (Cosmic, Epstic) based on Bowen's resin and two silicate cements (Frontasil, Silicap) and theirs components were assessed in cell culture. The compounds eluated from the material specimens under physiological conditions affected monolayer cultures of rat fibroblasts and rat epithelial cells (linr RL-19). Silicate cement eluate brings about death of cells due to high concentration of H-ions. Neutralized eluate of freshly prepared Cosmic, Estic and Frontasil caused the same cell damage which was less pronounced following Silicap eluate. The toxicity was markedly reduced following use of an eluate material which had a setting time of 24 hours. After the 2nd and 3rd elution of same specimen the cytoxicity was noticeably weakened, however, it was still demonstrable. The patterns of injury were different following composite material and silicate cement. All tested components soluted in Eagle medium have an irritating effect on the cultivated cells.
Recently, vital pulp treatment (VPT), including direct pulp capping, which preserves pulp vitality and extends the functional lifespan of teeth, has garnered significant attention. The purpose of this study was to evaluate the performance of calcium silicate cement, the gold standard for VPT, alongside hydraulic calcium silicate cement (Pro-MTA), a material with extensive evidence of effectiveness, Bis-GMA resin-modified calcium silicate cement (TH), and a newly developed material, methacrylate resin-modified calcium silicate cement (RM-MTA), in a model of pulpitis induced by caries progression. Additionally, the calcium ion (Ca2+) release capacity of these materials and their comprehensive effects on pulpal wound healing were assessed using RNA sequencing (RNA-seq). In both sound pulp models and caries-induced pulpitis models, RM-MTA and Pro-MTA exhibited similar performances. Unlike TH, they induced significant tertiary dentin formation within the dental pulp beneath the material, without any residual inflammatory cells. Inflammation was specifically assessed with a focus on M1/M2 macrophages. While the timing of Ca2+ ion release differed among the materials, the total amount released was comparable, although the release of calcium ions (Ca2+) from TH was significantly lower compared to that observed for the above materials. Moreover, comprehensive genetic analysis revealed that the expression of cell proliferation-related genes was selectively reduced in TH, suggesting that differences in resin composition may account for these variations in behavior. These findings suggest that RM-MTA induces tertiary dentin and demonstrates biocompatibility comparable to that of Pro-MTA. This makes it suitable for the treatment of both sound and mildly inflamed pulp tissues. Additionally, its resin properties are expected to enhance both mechanical performance and clinical handling.