Search PubMed⌕ Search

PubMed · 15851933

MTA solubility: a long term study.

Abstract

The purposes of this long-term study was to assess the amount of soluble material released by Mineral Trioxide Aggregate to a water medium, to determine if the solubility differences between specimens of various water/powder ratio, as demonstrated in a previous study, would be maintained over time, and to measure the pH of the water that was in contact with the specimens. Specimens were processed at 0.28 and 0.33 water/powder ratios, and immersed in water according to the ISO 6876 standard. The specimens were periodically removed to assess salt content release and reimmersed in fresh water. Assay testing was periodically performed over a 78-day period. Results were expressed as Daily Solubility (solubility rate), and Cumulative Solubility. The mathematical projection from Cumulative Solubility to infinite time showed that MTA could solubilize 22.06% at 0.28 water/powder ratio, and 31.095% at 0.33 water/powder ratio of the specimens' mass in regards to their initial dry weight. MTA did maintain a high pH for an extended period of time under these study conditions.

Explore related subjects

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Marcela Fridland, Rafael Rosado. 2005. MTA solubility: a long term study.. https://doi.org/10.1097/01.don.0000140566.97319.3e

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

Dimerisation-dependent GTPase reaction of MnmE: how potassium acts as GTPase-activating element.

MnmE, a Guanine nucleotide-binding protein conserved between bacteria and man, is involved in the modification of tRNAs. Here we provide biochemical and X-ray structural evidence for a new GTP-hydrolysis mechanism, where the G-domains of MnmE dimerise in a potassium-dependent manner and induce GTP hydrolysis. The structure in the presence of GDP-AlFx and potassium shows how juxtaposition of the subunits induces a conformational change around the nucleotide which reorients the catalytic machinery. A critical glutamate is positioned such as to stabilise or activate the attacking water. Potassium provides a positive charge into the catalytic site in a position analogous to the arginine finger in the Ras-RasGAP system. Mutational studies show that potassium-dependent dimerisation and GTP hydrolysis can be uncoupled and that interaction between the G-domains is a prerequisite for subsequent phosphoryl transfer. We propose a model for the juxtaposition of G-domains in the full-length protein and how it induces conformational changes in the putative tRNA-modification centre.

Aluminum Compounds↗

Structure of a GDP:AlF4 complex of the SRP GTPases Ffh and FtsY, and identification of a peripheral nucleotide interaction site.

The signal recognition particle (SRP) GTPases Ffh and FtsY play a central role in co-translational targeting of proteins, assembling in a GTP-dependent manner to generate the SRP targeting complex at the membrane. A suite of residues in FtsY have been identified that are essential for the hydrolysis of GTP that accompanies disengagement. We have argued previously on structural grounds that this region mediates interactions that serve to activate the complex for disengagement and term it the activation region. We report here the structure of a complex of the SRP GTPases formed in the presence of GDP:AlF4. This complex accommodates the putative transition-state analog without undergoing significant change from the structure of the ground-state complex formed in the presence of the GTP analog GMPPCP. However, small shifts that do occur within the shared catalytic chamber may be functionally important. Remarkably, an external nucleotide interaction site was identified at the activation region, revealed by an unexpected contaminating GMP molecule bound adjacent to the catalytic chamber. This site exhibits conserved sequence and structural features that suggest a direct interaction with RNA plays a role in regulating the activity of the SRP targeting complex.

Aluminum Compounds↗