text:
Q61. Comparison of Fracture Resistance in Simulated Immature Root Canals After Filling With Various Obturating Materials
Comparison of Fracture Resistance in Simulated Immature Root Canals After Filling With Various Obturating Materials
B.J. Vos*, A.E. Williamson, J.L. Kolker, D.R. Drake
University of Iowa, Iowa City, IA
Immature anterior teeth needing root canal treatment have been shown to be susceptible to horizontal fracture. Different materials: composite resin, GP and MTA have been suggested to increase a tooth's resistance to horizontal fracture when used as an obturating material. EndoSequence™ Root Repair Material Putty™ (ERRMP, Brasseler USA, Savannah, GA) has a chemical composition similar to MTA, but has yet to be tested as a standalone obturating material.
This study aimed to eval!uate the influence various obturating materials have on fracture resistance in endodontically treated, immature teeth. Forty extracted maxillary anterior teeth were collected. Standard root lengths gained by resecting the apical thirds 10mm from the facial CEJ. Teeth were accessed and instrumented with GG 2-6, simulating immature root structure. Groups obturated as follows: 1) Unobturated—positive controls, 2) GP, 3) Apical 1/3 with MTA and remaining canal filled with resin composite, 4) ERRMP™ and
5) MTA. Access openings in Groups 2-5 restored with resin composite. Teeth were stored in distilled water at 25°C for 14 days to allow setting of obturating materials. After setting, samples were mounted in cylindrical acrylic blocks and tested for fracture strength at the cervical area in a Zwick™ (Zwick/Roell, Ulm, Germany) testing machine.
Preliminary results showed increased force to fracture in Groups 3-5 compared to 1 and 2. Group 3 required the most force to fracture. When endodontically treating immature anterior teeth, obturations with an MTA plug and resin composite, or complete obturation with MTA or ERRMP™ may increase the tooth's resistance to horizontal fracture.
Source: JOE - Volume 37, No. 3, March 2011 - PR 46
Q62. Radiopacity Comparison of Six Endodontic Sealers
Radiopacity Comparison of Six Endodontic Sealers
A. Barani 1, H.W. Roberts 1, M.D. Roberts 1, S.J. Hubar 2, B.G. Jeansonne 2, B.E. Bergeron 1
1. 81st Medical Group/DS/SGDDT/Keesler Air Force Base, MS,
2. Louisiana State University, New Orleans, LA
Introduction: Radiopacity is considered a critical property of endodontic sealers. The purpose of this study was to compare the radiographic density of six root canal sealers, including Brasseler USA's new bioceramic EndoSequence™ BC Sealer™, which
is marketed as a highly radiopaque product. Methods: Six specimens (1x5 mm) of each sealer (BC Sealer™, Pulp Canal Sealer™ EWT, EndoRez®, 2Seal, RealSeal™ and Roth 811 Elite sealer) were digitally radiographed along with a graduated aluminum stepwedge. A Progeny Preva x-ray tubehead was set at 60 kVp and 4 mA at a distance of 15 cm. A Kodak™ RVG 6100 intraoral digital sensor and Kodak™ Dental Imaging Software were used for radiographic imaging. Data were analyzed using ANOVA and a Tukey Kramer Multiple Comparison Test (p=0.05). Results: All the sealers eval!uated met the minimum radiopacity standards set by ANSI/ADA specification No. 57. BC Sealer™ and 2Seal groups showed greater radiopacity (6.0 and 6.4 mm Al, respectively) followed by RealSeal™ (5.7 mm Al), Pulp Canal Sealer™ EWT (5.2 mm Al), and EndoRez® (5.0 mm Al). Roth 811 showed the lowest radiographic density (3.7 mm Al). The differences between the sealer groups were statistically significant (p<0.05) with the exception of 2Seal vs. BC Sealer™, RealSeal™ vs. BC Sealer™ and Pulp Canal Sealer™ EWT vs. EndoRez®.
BC Sealer™ and 2Seal exhibited the highest radiopacity among sealers tested. While the increased radiopacity was statistically significant, this would likely be imperceptible in a clinical setting.
Source: JOE - Volume 37, No. 3, March 2011 PR 04
Q63. Composition of BioAggregate - Calcium Phosphate Silicate Bioceramic.
Characterization of set IRM, Biodentine, Bioaggregate and a prototype calcium silicate cement for use as root-end filling materials
L. Grech, B. Mallia, J. Camilleri
To investigate the composition of materials and leachate of a hydrated prototype cement composed of tricalcium silicate and radiopacifier and compare this to other tricalcium silicate-based cements (Biodentine and Bioaggregate) in order to assess if the additives in the proprietary brand cements affect the hydration of the materials, using intermediate restorative material (IRM), a standard root-end filling material as a control.
The materials investigated included a prototype radiopacified tricalcium silicate cement, Biodentine, Bioaggregate and Intermediate Restorative Material (IRM). The pH and calcium ion concentration of the leachate were investigated. The hydrated cements were characterized using scanning electron microscopy (SEM) and X-ray energy dispersive analysis (EDX), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR).
All the cements tested were alkaline. The tricalcium silicate-based cements leached calcium in solution. Scanning electron microscopy of the prototype radiopacified tricalcium silicate cement, Biodentine and Bioaggregate displayed hydrating cement grains, surrounded by a matrix composed of calcium silicate hydrate and calcium hydroxide. The presence of calcium hydroxide was evident from the XRD plots. FT-IR indicated the occurrence of a poorly crystalline calcium silicate hydrate. Biodentine displayed the presence of calcium carbonate. Bioaggregate incorporated a phosphate containing phase. The IRM consisted of zinc oxide interspersed in an organic matrix.
The hydration of prototype radiopacified tricalcium silicate cement, Biodentine and Bioaggregate resulted in the formation of calcium silicate hydrate and calcium hydroxide, which was leached in solution. The hydrated materials were composed of a cementitous phase which was rich in calcium and silicon and a radiopacifying material. Biodentine included calcium carbonate and Bioaggregate included silica and calcium phosphate in the powders. IRM was composed of zinc oxide interspersed in a matrix of organic material.
In content,
"Clinically, the composition of the set material is important. Once placed and in contact with tissue fluids, root-end filling materials can leach trace elements and compounds that can be affect the surrounding periapical tissues. The literature available on Biodentine and Bioaggregate is limited with the reports on the material composition restricted to the manufacturer's data sheets."
Even though Biodentine was switched from BioAggregate in the market, MSDS (Material Safety Data Sheet) of BioAggregate has been opened without any restriction.
BioAggregate was distributed by DiaDent Group International Inc. under DiaRoot BioAggregate (DB, DBA, BioA, BA, etc.). The data sheet is still on the website. We would like to give correct information on the BioAggregate. But it is not sufficient to answer to every questions on BioAggregate.
- DiaRoot BioAggregate MSDS (Click)
- DiaRoot BioAggregate Leaflet (Click)
Since BioDentine was introduced instead of DiaRoot BioAggregate in 2010, many people thought BioAggregate was newly developed after BioDentine. But BioAggregate was approved by FDA in 2006 and it was sold by DiaDent Group International Inc. Currently we are selling IBC (Innovative BioCeramix Inc.) BioAggregate. BioAggregate is the original name of DiaRoot BioAggregate. (BioCeramic Aggregate)
a. BioAggregate(IBC) FDA 510K
K03422 (11/21/2006)
b. ProRoot MTA White (Dentsply) FDA 510K (MTA Advanced Material, Current White MTA)
K073218 (01/07/2008)
c. BioDentine (Septodont) FDA 510K
BioAggreagte was approved in 2006, ProRoot MTA (white) in 2008 and BioDentine in 2009.
Regarding of compositon,
MTA(G) is composed of 1. tricalcium silicate, 2. dicalcium silicate, 3. tricalcium aluminate, 4. tetracalcium aluminoferrite, 5. calcium sulfate and 6. bismuth oxide.
This is original Grey ProRoot MTA. In MSDS, Grey ProRoot MTA is composed of Portland Cement reagent and Bismuth Oxide. This above composition is the final phase of MTA.
White MTA (K073218) is composed of 1.calcium carbonate (Calcia), 2. silicon dioxide, 3. aluminium oxide and 4.dibismuth trixoide (no Calcium Sulfate)
Final phase of WMTA is composed of 1. tricalcium silicate, 2. dicalcium silicate, 3. tricalcium aluminate, 4. tetracalcium aluminoferrite, 5. bismuth oxide.
BioAggregate is composed of 1. tricalcium silicate, 2. dicalcium silicate 3. Calcium Phsophate Monobasic, 4. Amorphous Silicon Oxide and 5. Tantalum Pentoxide.
BioDentine is composed of 1. tricalcium silicate, 2. dicalcium silicate, 3. Calcium Carbonate, 4. Iron Oxide, 5. Zirconium Oxide.
These products are mainly composed of tricalcium silicate and dicalcium silicate - Calcium Silicates. So they are classified as Calcium Silicate-based Material (CSM).- CaS
Instead, if the main material is composed of calcium silicate + alumino-silicate, it is classified as Calcium Aluminate-based Material (CAM).-CaAl
Q64. Nanostructured Calcium Phosphate Silicate BioCeramic : BioAggregate
As MTA is a refined Portland Cement with bismuth oxide, it is a Calcium Silicates (Tricalcium Silicate + Dicalcium Silicate) from minerals (ceramics in nature).
Pure medical graded Calcium Silicate Bioceramic is not a mineal raw material of portland cement, but a biological raw material for dental and medical applications.
Though Portland cement is containng the toxic heavy metals and unnecessary impurities with tetracalcium aluminoferrite, with pure calcium silicates, bioceramic material can be made for the desired dental cement like Root-end filling Material and root canal filling material as well as restoration materials.
BioAggregate was developed by bioceramic raw materials, esp. Calcium Silicate bioceramics. It's not a mixture of pure tricalcium silicate and dicalcium silicate, but a nanostructural (nanoparticulated - Nano Technology) chemically bonded ceramic (bioceramic) hydro gel-sol integrated bioceramic material. In order to increase the bioactivity, the calcium phospahte is compounded with Calcium Silicates. This is the integrated Nano-, Bio- and Ceramic-technology embedded material for endodontics and dentistry.
Pure raw material of Calcium Silicates is the basics in bioMaterials. As the composition and ratio and radiopacifying agent are different from MTA, the actual properties are different from natural ceramics. But in some properties, artificial ceramic materials are better than natural ceramics with artificial admixtures for specific purpose and functions.
Recently pure raw Tricalcium silicate could replace the MTA was published by material articles. But actually bioceramic raw materials of calcium silicates were used by BioAggregate after 2000 for bioactive and more biocompatible dental materials.
Dent Mater. 2011 Aug;27(8):836-44. doi: 10.1016/j.dental.2011.04.010. Epub 2011 May 19.
Characterization and hydration kinetics of tricalcium silicate cement for use as a dental biomaterial.
Camilleri J.
Department of Dental Surgery, Faculty of Dental Surgery, University of Malta, Msida MSD 2080, Malta. josette.camilleri@um.edu.mt
Investigation and characterization of the replacement of the Portland cement component in mineral trioxide aggregate (MTA) with tricalcium silicate cement which is manufactured using the sol-gel method from pure raw materials.
Tricalcium silicate and Portland cement were characterized by viewing under the scanning electron microscope (SEM) and surface imaging and elemental analysis with X-ray energy dispersive analysis (EDX), and by X-ray diffraction analysis with Rietveld refinement. In addition the hydration products of the material after 28 days of curing were evaluated by plotting atomic ratio plots from the EDX data. The cement leachate was evaluated for pH and chemical composition by inductively coupled plasma.
Portland cement was composed of 68% tricalcium silicate. The tricalcium silicate cement was 99% pure. On hydration both cements produced calcium silicate hydrate and calcium hydroxide. The calcium hydroxide was leached in solution with higher leaching in HBSS. The leaching of calcium hydroxide in solution resulted in an alkaline pH. The reaction of calcium with the phosphorus present in HBSS resulting in the deposition of calcium phosphate on the cement surface.
SIGNIFICANCE:
Tricalcium silicate could prospectively replace the Portland cement component in MTA.
Pure Bioceramic calcium silicates were used for BioAggregate. Bioceramic Aggregate means the purer non-toxic chemically bonded ceramic aggregate. BioAggregate was approved by FDA in 2006. Already BioAggregate replaced the portland cement component in MTA.
Tricalcium Silicate's pictures in the article by J. Camilleri for reference.
Fig. 1. Back-scatter electron micrographs of (a and b) Portland cement and (c and d) tricalcium silicate cement. (a and c) 500× magnification (b and d) 2000× magnification; X-ray energy dispersive analysis of (e) Portland cement and (f) tricalcium silicate cement.
Fig. 2. Scanning secondary electron micrographs of Portland cement at 5000× magnification, immersed in (a) water and (c) HBSS; X-ray energy dispersive analysis of Portland cement immersed in (b) water and (d) HBSS; (HBSS: Hank's balanced salt solution).
Fig. 3. Scanning secondary electron micrographs of tricalcium silicate cement at 5000× magnification, immersed in (a) water; (c) HBSS; X-ray energy dispersive analysis of tricalcium silicate cement, immersed in (b) water and (d) HBSS; (HBSS: Hank's balanced salt solution).
Fig. 4. Backscatter images of (a and b) Portland cement and (c and d) tricalcium silicate viewed under the scanning electron microscope.
Fig. 5. Atomic ratio plots of (a and b) Portland cement and (c) tricalcium silicate
Q65. Understanding of Calcium Phosphate Cement as Drug Delivery
Calcium phosphate cements as drug delivery materials
http://dx.doi.org/10.1016/j.addr.2012.01.008
Advanced Drug Delivery Reviews
Volume 64, Issue 12, September 2012, Pages 1090–1110
Targeted delivery of therapeutics to bone and connective tissues
Calcium phosphate cements are used as synthetic bone grafts, with several advantages, such as their osteoconductivity and injectability. Moreover, their low-temperature setting reaction and intrinsic porosity allow for the incorporation of drugs and active principles in the material. It is the aim of the present work to: a) provide an overview of the different approaches taken in the application of calcium phosphate cements for drug delivery in the skeletal system, and b) identify the most significant achievements. The drugs or active principles associated to calcium phosphate cements are classified in three groups, i) low molecular weight drugs; ii) high molecular weight biomolecules; and iii) ions.
ACP, Amorphous Calcium Phosphate;
AOM, anti-osteoporosis medications;
BMP, bone morphogenetic protein;
CDHA, calcium deficient hydroxyapatite;
CMC, carboxymethylcellulose;
BSA, bovine serum albumin;
BMP, bone morphogenetic growth factor;
CPC, calcium phosphate cement;
DCPA, monetite, dicalcium phosphate anhydrous, CaHPO4;
DCPD, brushite, dicalcium phosphate dihydrate CaHPO4.2H2O;
FGF, fibroblast growth factors;
GF, growth factor;
HA, hydroxyapatite, Ca10(PO4)6(OH)2;
HPC, hydroxypropylcellulose;
hLF1-11, lactoferrin;
HRT, hormone replacement therapy;
IGF, insulin growth factor;
LMAP, low-methoxy amidated pectin;
MCPA, monocalcium phosphate anhydrous Ca(H2PO4)2;
MCPM, monocalcium phosphate monohydrate Ca(H2PO4)2.H2O;
MIC, minimum inhibitory concentration;
MRSA, Staphylococcus aureus resistant to Meticilin-Cefem;
NSAID, non-steroidal anti-inflammatories;
PAA, polyacrylic acid;
PBS, phosphate buffered saline;
PDGF, platelet-derived growth factor;
PLGA, poly(lactic-co-glycolic acid);
PMMA, poly(methyl methacrylate);
PRP, platelet rich plasma;
RANKL, receptor activator of the nuclear factor κB ligand;
rhBMP-2, human recombinant-bone morphogenetic protein-2;
rhbFGF, human recombinant basic fibroblast growth factor;
rhTGF-β1, human recombinant-transforming growth factor-β1;
rhVEGF, human recombinant vascular endothelial growth factor;
SBF, simulated body fluid;
SDS, sodium dodecylsulfate;
SS, Stationary Stage;
α-TCP, alpha-tricalcium phosphate, α-Ca3(PO4)2;
β-TCP, beta-tricaclium phosphate, β-Ca3(PO4)2;
TTCP, tetracalcium phosphate, Ca4(PO4)2O;
TGF, transforming growth factor;
TGFβ-SF, superfamily of transforming growth factor-beta;
VEGF, vascular endothelial growth factor
Source: http://www.sciencedirect.com/science/article/pii/S0169409X12000117
Fig. 1. Classification of calcium phosphate cements, with examples of the most common formulations. From top to bottom the cements are classified by the type of end-product (apatite or brushite), number of components in the solid phase (single or multiple), type of setting reaction (hydrolysis or acid–base reaction), setting mechanism and microstructure evolution during setting. Scanning electron micrographs of set apatite and brushite cements obtained by the hydrolysis of α tricalcium phosphate (α-TCP) and by reaction of β-TCP with MCPM (monocalcium phosphate monohydrate) respectively, are also shown.
Fig. 2. The microstructure and porosity of CPCs can be tuned by adjusting some processing parameters, such as the particle size of the powder phase and the liquid to powder ratio (L/P). a) The reactivity of the powder increases when decreasing its particle size, due to an increase in its specific surface area. This results in a higher supersaturation degree achieved in the cement paste, which favors crystal nucleation and results in the precipitation of more numerous and smaller needle-like crystals, instead of the larger plate-like crystals formed when big particles are used. These different microstructures give rise to different pore size distributions in the set cements (bottom part of panel a). For the same L/P ratio and different powder size, the total porosity of the cement remains constant, but smaller pores are formed in the fine cement (i.e. using small particles); b) Another way of tuning the porosity and the pore size distribution of the CPCs is by varying the L/P ratio. At low L/P ratios the space between particles in the blend decreases. Considering that the precipitation of HA crystals takes place surrounding the initial powder particles, this leads to a more compact structure of crystal agglomerates. In contrast, when the L/P ratio increases, the total porosity of the cements increases and larger pores are formed due to the augmented separation between aggregates resulting from the larger distance between original α-TCP particles and .
Fig. 3. Different options for the incorporation of drugs or biological active molecules (denoted as D) in the CPCs. Before cement preparation (i.e. prior to mixing the liquid and solid phase) the drug can either be mixed with the cement powder phase (a) or solubilized in the cement liquid phase (b). Drug loading can also be made after cement setting by droplet addition (c) or by imbibition (immersion) of the cement in the drug solution (d). The last procedures (c) and (d) do not allow cement injection since they require cement pre-setting, so the textural properties resulting from the low-temperature setting reaction are maintained.
Fig. 4. Schematic presentation of the different ways a drug can be found in a CPC matrix: (a) as individual molecules dissolved in the liquid within the pores; (b) adsorbed or chemically bound to the crystals surface; (c) in a solid form, as drug crystals or aggregates.
Fig. 5. Drug release from CPCs can encompass the following scenarios: (a) if the rate of CPC degradation is slower than drug diffusion, drug release is controlled by diffusion of the drug through the liquid permeating the cement, (b) if the rate of cement degradation is faster than drug diffusion, the former controls drug release, and (c) in some cases, namely in bioactive cements, an apatite layer can be formed on the surface of the cement after implantation, this hindering the diffusion of the drug to the surrounding tissue.
Q66. Biological Property - Bioactivity- of MTA
J Endod. 2005 Feb;31(2):97-100.
Physicochemical basis of the biologic properties of mineral trioxide aggregate.
Sarkar NK, Caicedo R, Ritwik P, Moiseyeva R, Kawashima I.
Operative Dentistry and Biomaterials Department, LSU, School of Dentistry, 1100 Florida Ave, New Orleans, LA 70119, USA. nsarka@lsuhsc.edu
This study characterized the interactions of mineral trioxide aggregate with a synthetic tissue fluid composed of a neutral phosphate buffer saline solution and root canal dentin in extracted human teeth using inductively coupled plasma-atomic emission spectroscopy, scanning electron microscopy, energy dispersive X-ray analysis, and X-ray diffraction. Mineral trioxide aggregate exposed to synthetic tissue fluid at 37 degrees C released its metallic constituents and produced precipitates with a composition and structure similar to that of hydroxyapatite [Ca10(PO4)6(OH)2-HA]. Endodontically prepared teeth filled with mineral trioxide aggregate and stored in synthetic tissue fluid at 37 degrees C for 2 months produced at the dentin wall an adherent interfacial layer that resembled hydroxyapatite in composition. The authors conclude that Ca, the dominant ion released from mineral trioxide aggregate, reacts with phosphates in synthetic tissue fluid, yielding hydroxyapatite. The dentin-mineral trioxide aggregate interfacial layer results from a similar reaction. The sealing ability, biocompatibility, and dentinogenic activity of mineral trioxide aggregate is attributed to these physicochemical reactions.
Fig 1. A Typical scanning electron micrograph of precipitates from mineral trioxide aggregate—synthetic tissue fluid interaction (×13,000). B, Energy dispersive X-ray analysis spectrum from precipitates in A (above) and their semiquantitative chemical composition (below). C, X-ray diffraction pattern of mineral trioxide aggregate—synthetic tissue fluid precipitates
Fig 2. A, Typical optical micrograph of a mineral trioxide aggregate—dentin cross-section (×200). B, Typical scanning electron micrograph of a mineral trioxide aggregate (MTA)—dentin cross-section (×1000). M, MTA; I, interface; D, dentin. C, Area identified by box in B at a higher magnification: ×6000.
TABLE 1. Semi quantitative elemental composition (wt%) of areas identified as M, I and D in Fig. 2C.
"The inductively coupled plasma—atomic spectroscopy data presented above indicate that MTA undergoes dissolution in STF, releasing all of its major cationic constituents. The additional cation Mg found in STF is believed to have its origin in MgO, present in MTA in trace amounts. Of all ions released, Ca is the most dominant. Because it is sparingly soluble in biologic fluids, it leads to the precipitation of HA (Fig. 1A). The specific reaction responsible for this precipitation may bethe following:
10Ca(+2) + 6(PO4)(-3) + 2(OH)(-1) --------> Ca10(PO4)6(OH)2
The above is a well-known reaction in the biologic calcification process (27–28) and is favored at pH 7, the pH of STF used in this study. This reaction occurs in vivo and in vitro with many Ca-containing materials in contact with biologic environments (29 –34). An essentially similar reaction, we believe, is also responsible for the formation of the adherent HA layer on the MTA surface (Fig. 2, A–C). Because of the porous nature of MTA, it is conceivable that this precipitation continues internally within MTA and thus leads to a change in the overall composition of MTA adjacent to the dentinal wall (Table 1)."
Q67. Precipitates on MTA immersed in Different Fluids or Solutions.
Dent Mater J. 2010 Oct;29(5):512-7. Epub 2010 Sep 1.
Morphological and chemical analysis of different precipitates on mineral trioxide aggregate immersed in different fluids.
Han L, Okiji T, Okawa S.
Division of Cariology, Operative Dentistry and Endodontics, Department of Oral Health Science, Niigata University Graduate School of Medical and Dental Sciences, 5274 Gakkocho-dori, 2-ban-cho, Chuo-ku, Niigata 951-8514, Japan. han4378@yahoo.co.jp
The purpose of this study was to analyze the ultrastructures and chemical compositions of precipitates formed on mineral trioxide aggregate (MTA; White ProRoot MTA) immersed in distilled water (DW) or phosphate buffered saline (PBS), based on the attribution that MTA's bioactivity and sealing ability are influenced by its interaction with the external fluid environment. After 1 and 14 days of immersion, precipitates formed on MTA disks were analyzed using wavelength-dispersive X-ray spectroscopy electron probe microanalyzer with image observation function (SEM-EPMA; EPMA1601, Shimadzu, Kyoto, Japan), and Fourier transform-infrared (FT-IR) spectroscopy. On DW specimens, cubic-like crystals containing Ca, O, and C (17, 66, and 17 at% respectively) were produced. State analysis of calcium k(β)spectrum also revealed calcium hydroxide. On PBS specimens, acicular-spherical and lath-like crystals with Ca/P molar ratios of 1.42 and 1.58 respectively were produced.
In conclusion, the precipitates formed on DW specimens were identified as calcium carbonate and calcium hydroxide primarily, whereas the precipitates on PBS specimens were inferred to be amorphous calcium phosphate.
"Results of this study supported the claim that set MTA is bioactive in the presence of phosphate containing fluids, based on the formation of an apatite phase that might be composed of calcium-deficient, B type carbonated apatite of poor crystallinity via the
initial deposition of ACP 17,18). The acicular appearance of precipitates (Fig. 3) may be a consequence of the superficial activity of apatite: they incorporate elements into their structure and substitute certain elements for others, resulting in morphologic alterations 17,18). This type of precipitate formation was characteristic of the pH-dependent autocatalytic transformation of metastable ACP phase into an apatite phase 18).
The formation of ACP on MTA could serve as a strong indicator of the biocompatibility and bioactivity of MTA, chiefly because the surface precipitation of biocompatible materials might be the basis for the bioactivity of calcium silicate-containing biomaterials 26,27). Precipitate formation has also been reported to occur along the MTA-dentin interface 8,15,17,18), which meant it might play a pivotal role in providing MTA with good sealing ability as an endodontic material.
Immersion of MTA in DW and PBS resulted in the formation of precipitates that were morphologically and chemically different. The precipitates formed on DW specimens were identified as calcium carbonate and calcium hydroxide primarily. On the other hand, the precipitates formed on PBS specimens were inferred to be amorphous calcium phosphate."
Without immersion of MTA in PBS or HBSS, the precipitates formed from the MTA Hydration are identified only as Calcium Carbonate and Calcium Hydroxide. To be Amorphous Calcium Phosphate precipitate is needed with PBS or HBSS or phosphate-containing fluids.
Fig. 1 Morphological and chemical analysis of MTA surface precipitates immersed in distilled water for 24 hours (a) and 14 days (b, c, d). (a, b) SEM micrographs showing cubic-like precipitates (arrows) (a: bar=50 μm; b: bar=100 μm). (c) Higher magnification view of the precipitates in (b) (bar=2 μm). (d) Chemical composition of the precipitates as determined by SEM-EPMA.
Q68. Effec of PBS or HSBB on sealing ability of MTA
J Oral Sci. 2009 Jun;51(2):187-91.
Effect of phosphate buffer saline on coronal leakage of mineral trioxide aggregate.
Parirokh M, Askarifard S, Mansouri S, Haghdoost AA, Raoof M, Torabinejad M.
Endodontic Department, School of Dentistry, Kerman University of Medical Sciences, Kerman, Iran. masoudparirokh@yahoo.com
This study was carried out to compare the bacterial leakage of MTA used as a root-end filling material when it was kept in phosphate buffer saline (PBS) or normal saline. In this study, 72 freshly extracted teeth were used. The roots were randomly divided into four experimental groups of 15 each (groups I and II gutta-percha obturation + MTA, groups III and IV only MTA) and two positive and negative control groups of six each. The samples in groups I and III were kept in normal saline for 1 month while the samples in groups II and IV were kept in PBS. Enterococcus faecalis was used for determination of the bacterial penetration. Kaplan-Meier survival curve and chi(2) test were employed for data analysis. The obturated samples with root-end filling showed significantly longer duration of resistance to bacterial penetration than canals without obturation (P < 0.05). The roots that were placed in PBS (groups II and IV) showed significantly less bacterial penetration in comparison with the roots that were stored in normal saline (P < 0.05).
In conclusion, MTA, which acts as a bioactive material, should be placed in a synthetic tissue fluid before any leakage evaluation.
"Our results confirm the finding of their study and the importance of complete coronal leakage before placement of root-end filling materials (27). Although at the end of the study, roots in group I showed no significant difference in bacterial penetration in comparison to group IV, it can be assumed that the importance of storage media is as important as root canal obturation on inhibition of bacterial penetration when MTA is used as root-end filling. Although they were insignificant, our results show that roots with canal obturation that were placed in normal saline (group I) showed more bacterial penetration than the roots without gutta-percha canal obturation that were placed in PBS (group IV).
Based on the results of this study, it appears that placing MTA in PBS storage medium results in formation of crystals over MTA and causes a significant decrease in bacterial penetration. This may indicate that future in vitro studies should use PBS as a storage medium to produce an environment similar to that of an in vivo condition.
Mineral trioxide aggregate (MTA) is introduced as the most biocompatible root-end filling material (30). It is also known as a bioactive material that is hard tissue inductive and conductive (31,32). Recently, many investigators have tried to improve MTA's handling characteristics, antibacterial properties, and physical properties and to compare the material's sealing ability to that of new root-end filling materials (4, 24,25,32-34). As a calcium silica based material, MTA can develop hydroxyapatite on its surface in a synthetic tissue fluid such as phosphate buffer saline (PBS) (17,18). Results of the present study show that this layer improves MTA sealing ability. For this reason, we suggest that further in vitro studies evaluating the sealing ability of newly modified MTA or comparing the material with other root-end filling materials should use PBS as a media to simulate the environment in the human body, thus producing more clinically relevant results."
In vitro studies, witout PBS (phosphate buffered saline), expected hydroxyapatite-like formation is lower than in-vivo - in the human body. bioactive prcipitation-hydroxyl apatitie is very important to improve sealing ability...
Q69. Effects of Phsyiological Environments on the Hydration of MTA.
Biomaterials. 2004 Feb;25(5):787-93.
Effects of physiological environments on the hydration behavior of mineral trioxide aggregate.
Lee YL, Lee BS, Lin FH, Yun Lin A, Lan WH, Lin CP.
School of Dentistry, College of Medicine, National Taiwan University, Chang Te Street, Taipei 10016, Taiwan, ROC.
Utilizing scanning electron microscope, X-ray diffraction (XRD) and microhardness tests, we evaluated how various physiological environments affect the hydration behavior and physical properties of mineral trioxide aggregate (MTA). We found that the microstructure of hydrated MTA consists of cubic and needle-like crystals. The former comprised the principal structure of MTA, whereas the later were less prominent and formed in the inter-grain spaces between the cubic crystals. MTA samples were hydrated in distilled water, normal saline, pH 7, and pH 5. However, no needle-like crystals were observed in the pH 5 specimens, and erosion of the cubic crystal surfaces was noted. XRD indicated a peak corresponding to Portlandite, a hydration product of MTA, and the peak decreased noticeably in the pH 5 group. The pH 5 specimens' microhardness was also significantly weaker compared to the other three groups (p<0.0001).
These findings suggest that physiological environmental effects on MTA formation are determined, in part, by environmental pH and the presence of ions. In particular, an acidic environment of pH 5 adversely affects both the physical properties and the hydration behavior of MTA.
Source: http://www.sciencedirect.com/science/article/pii/S014296120300591X
Fig. 1. (A) SEM micrograph of MTA before hydration. (B, C, D) MTA after hydration in distilled water. The crystalline formation appears irregular in shape and size, and the surfaces of the cubic crystals appear uneven, while the needle-like crystals have developed in a jagged manner.
Fig. 2. (A) SEM micrograph of MTA stored in normal saline. (B) MTA stored in pH 7. Though the crystalline structures are fairly well developed their shapes and sizes are not as irregular as the distilled water induced formation.
Fig. 3. (A,B) SEM micrographs of MTA stored in pH 5. Clearly, the crystalline structure maturity pales in contrast to the formations of the other specimens.
Fig. 4. XRD powder patterns of unhydrated MTA and hydrated MTA stored in distilled water, normal saline, pH 7, and pH 5. Portlandite and reactant peaks are observable in each pattern, and both peaks are lower in the pH 5 pattern.
Fig. 5. Microhardness test results for each group. The pH 5 group ranked the lowest, while the pH 7 group ranked the highest.
"These findings suggest that physiological environmental effects on MTA formation are determined, in part, by environmental pH and the presence of ions. In particular, an acidic environment of pH 5 adversely affects both the physical properties and the hydration behavior of MTA."
Without or lacking of phosphate ions presence in environment, MTA precipitation is primarily calcium hydroxide and calcium carbonate - a Calcium Carbonate Apatite-like fomation.
Q70. Biomineralization Ability of MTA in a phosphate-containing fuid.
J Endod. 2009 May;35(5):731-6. doi: 10.1016/j.joen.2009.02.011.
Biomineralization ability and interaction of mineral trioxide aggregate and white portland cement with dentin in a phosphate-containing fluid.
Reyes-Carmona JF, Felippe MS, Felippe WT.
Postgraduate program of the Federal University of Santa Catarina, Florianopolis, Santa Catarina, Brazil.
Mineral trioxide aggregate (MTA) has been shown to be bioactive because of its ability to produce biologically compatible carbonated apatite. This study analyzed the interaction of MTA and white Portland cement with dentin after immersion in phosphate-buffered saline (PBS).
Dentin disks with standardized cavities were filled with ProRoot MTA, MTA Branco, MTA BIO, white Portland cement + 20% bismuth oxide (PC1), or PC1 + 10% of calcium chloride (PC2) and immersed in 15 mL of PBS for 2 months. The precipitates were weighed and analyzed by scanning electron microscopy (SEM) and x-ray diffraction. The calcium ion release and pH of the solutions were monitored at 5, 15, 25, and 35 days. The samples were processed for SEM observations. Data were analyzed by using analysis of variance or Kruskall-Wallis tests.
Our findings revealed the presence of amorphous calcium phosphate precipitates with different morphologies. The apatite formed by the cement-PBS system was deposited within collagen fibrils, promoting controlled mineral nucleation on dentin, observed as the formation of an interfacial layer with tag-like structures.
All the cements tested were bioactive. The cements release some of their components in PBS, triggering the initial precipitation of amorphous calcium phosphates, which act as precursors during the formation of carbonated apatite. This spontaneous precipitation promotes a biomineralization process that leads to the formation of an interfacial layer with tag-like structures at the cement-dentin interface.
Source: http://www.sciencedirect.com/science/article/pii/S0099239909001356
Figure 1. Morphologic characterization of precipitates formed by MTA BIO after 2-month immersion in PBS. (A) High-magnification SEM showing the acicular nature of spherules (original magnification, 8000×). (B) EDAX spectrum for precipitates in (A) and semiquantitative chemical composition showing their Ca/P molar ratio. (C) Photomicrograph showing petal-like precipitates (original magnification, 1000×) for which (D) SEM-EDAX revealed a greater Ca/P molar ratio and lattice substitution of Na and Cl. (E) SEM of compact lath-like precipitates (original magnification, 1000×) that demonstrates (F) a Ca/P molar ratio of 1.61 with lattice substitution of Na, Cl, and Mg. (G) X-ray diffraction pattern of the calcium phosphate precipitate obtained after 2 months of immersion in PBS, revealing the presence of a weakly crystalline apatite
Figure 2. (A) Photomicrograph of ProRoot MTA–dentin interface showing cement (C), interlayer (IL), and dentin (D). (B) Higher magnification showing TS and lateral branches. Photomicrograph of (C) MTA Branco–dentin interface, (D) MTA BIO–dentin interface, (E) PC1-dentin interface, and (F) PC2-dentin interface. (E) and (F) show the formation of fewer, short TS.
"The possible biologic and clinical significance of our findings includes the following: (1) the interaction of MTA and Portland cement with dentin in a phosphate-containing fluid promotes a biomineralization process, (2) this process could be significant in minimizing leakage, (3) the formation of the interfacial layer and the intratubular mineralization process could influence the push-out bond strength, and (4) the formation of carbonated apatite precipitates could be responsible for the ability of the cements to stimulate repair and dentinogenesis or cementogenesis.
We concluded that ProRoot MTA, MTA Branco, MTA BIO, and white Portland cement are bioactive. The cements release some of their components in PBS, triggering the initial precipitation of amorphous calcium phosphates, which act as precursors for the formation of carbonated apatite. This spontaneous precipitation promotes a biomineralization process that leads to the formation of an interfacial layer with TS at the cement-dentin interface."
There is no difference between Calcium Cabonate Apatite and Hydroxyl Apatite. But in a phosphate-containing fluid, the formation is a carbonate apatite immersed in PBS or phosphate-containg fluid.
Q71. BioAggregate is containing Calcium Phosphate for more bioactivity.
From Q65 to Q70, it is to explain the bioactivity of MTA's hydroxyapatite precipitation or formation in PBS or HBSS or phosphate-containing fluid.
In DW, the precipitation of hydration of MTA is primarily "Calcium Carbonate" and "Calcium Hydroxide". In PBS or phosphate-containing fluid, the prcipitation of MTA is an amorphous calcium phosphate or hydroxyl apatite form.
Instead of mixing or immersion of PBS, the amorphous silica and calcium phosphate are admixed to the Calcium Silicates. This is "Calcium Phosphate Silicate Cement" of BioAggregate. The amorphous silica and calcium hydroxide reduce the calcium hydroxide, which is produced by hydration of Calcium Silicate (C-S-H) and they promote to form the hydroxyapatite for biomineralization ability and bioactivity.
"Bioaggregate also includes hydroxyapatite and amorphous silicon oxide together with the main cementitious and radiopacifier phases (Innovative Bioceramix Inc.). The hydroxyapatite and amorphous silicon oxide are added to reduce the levels of the calcium hydroxide produced on hydration which is a weak phase. Calcium hydroxide is leached in solution and is not cementitious. Thus, it does not contribute to the strength of the material. The crystal structure has been verified by X-ray diffraction analysis (Park et al. 2010) where all the crystalline phases were identified and X-ray fluorescence spectroscopy (Camilleri et al. 2012), which displayed the presence of the different elements present in oxide form namely tantalum, silicon, calcium and phosphorus. The absence of aluminium specified by the manufacturer was also verified (Park et al. 2010, Camilleri et al. 2012). The liquid provided with Bioaggregate was composed of pure water (Camilleri et al. 2012). Hydration of Bioaggregate resulted in the formation of calcium hydroxide. Calcite was also observed in the set forms of the material but not in the un-hydrated powder (Park et al. 2010)."
Q72. Hydaulic Cement Classification -Admixtures?
Dent Material. 2012 Nov 27. pii: S0109-5641(12)00464-2. doi: 10.1016/j.dental.2012.11.007. [Epub ahead of print]
Investigation of the physical properties of tricalcium silicate cement-based root-end filling materials.
Grech L, Mallia B, Camilleri J.
Department of Metallurgy and Materials Engineering, Faculty of Engineering, University of Malta, Malta.
All the materials tested had a radiopacity value higher than 3mm thickness of aluminum. IRM exhibited the highest radiopacity. Biodentine demonstrated a high washout, low fluid uptake and sorption values, low setting time and superior mechanical properties. The fluid uptake and setting time was the highest for Bioaggregate.
The addition of admixtures to tricalcium silicate-based cements affects the physical properties of the materials.
Source:
BioAggregate admixture: Calcium Silicate + Calcium Phosphate
CSM + CaP
BioDentine admixture : Calcium Silicate + Calcium Carbonate
CSM + CaCO3
Non-Calcium Silicate hydraulic cement : Calcium Aluminate Cement
Even though the Calcium Silicate Cement is containing Calcium admixture, it cannot be set over regular CS material setting time. They made an article that the addition of admixtures to CS cements affects the physical property, especially setting time be longest and worse than zinc oxide cement.
Original MTA admixture : Calcium Aluminate (approximately 10%) + Calcium Sulfate (5%)
White MTA admixture : Calcium Carbonate (original Lime Cement) + Calcium Aluminate without Calcium Sulfate
Lime cement (Calcium Carbonate Cement) is quick set cement. Alumina Cement is much faster set cement. Limestone and admixture of fumed silica is also quick set.
Before composition or function, MTAs (Mineral Trioxide Aggreagates) are not same as or similar to Portland Cement. Portland Cement is Calcium Silicate Based Cement. But Non-Portland Cement like Calcium Alimate Cement is a MTA. Lime Cement, Pozzolan Cement, Zeolite Cement, Magnesium Silicate Cement, Lithium Silicate Cement are also Mineral Aggregates.
What is Hydraulic Cement? It's calcium based cement in dentistry. MTA or BioA or hydraulic cement (water based cement) is based on Calcium. Hydraulic Silicate Cement is GIC (Glass Ionomer Cement), which is based on Silicate (glass).
As BioDentine is a hydraulic Cement, they should test BioDentine with 100% Water and with BioDentine Liquid. It is set by water because BioDentine is hydraulic calcium cement. Also as BioAggregate is Caclium Silicate Hydraulic Cement, it is set by water of BioA Liquid and by BioDentine liquid. With BioDentine Liquid, BioAggregate is quick set within 20 minutes. This is not an affect of admixture. Calcium Carbonate is quick set admixture than Calcium Phosphate admixture. It's right. But overall setting time is similar in Calcium Silicate Cement like TCS-Zr. If not, they should explain the poor setting behavior of BioAggregate with water. There is only one reason to add water more for intentional purpose. In CSM, its setting time is 4 hours average, between 2-6 hours.
Admixtures of Calcium Aluminate, Calcium Sulfate, Calcium Carbonate are quick set factors, but it cannot be within 20 minutes without accelerators' addition.
What is MTA? is What is Hydraulic Cement?
Q73. What is Hydraulic Cement?
September 28th, 2012 | Author: hyydravler
Cement is any material that hardens and becomes highly adhesive after application. The phrase "cement" is often used interchangeably with "glue" and "adhesive"; in architectural and building construction the phrase usually relates to a finely powdered, manufactured substance consisting of gypsum plaster, or Portland cement, that hardens and adheres after being mixed with water. Cements are used for numerous purposes, such as binding sand and gravel together with Portland cement to form concrete, for uniting the surfaces of various materials, or for coating areas to protect them from chemical attack. Cements are made in many compositions for a broad variety of uses.
What is Hydraulic Cement?
Hydraulic Cement is a combination of hydraulic cement and proprietary admixtures used for plugging and stopping water or fluid leaks in concrete structures and masonry walls. When mixed to a thick regularity and hand formed, Hydraulic Cement will set in 3-5 minutes to seal out water for the life of the framework. Hydraulic Cement is a non-corrosive, non-rusting and non-shrink substance. Hydraulic cement refers to any cement that will set and harden after being mixed with water. It is made up basically of hydraulic calcium silicates, generally containing calcium sulfate. Most building cements today are hydraulic.
Hydraulic Cement is ideal in wet climates
When a dry hydraulic cement is blended with water, certain chemical reactions take place in the mixture. These reactions form chemical compounds which contain water, and the formation of these compounds causes the mixture to harden. Since of the nature of the compounds formed in these reactions, they are insoluble in water. This means that the hardened cement will retain its strength and hardness even if immersed in water. This makes it perfect for brick buildings in wet climates, harbor structures that are in contact with sea water, and numerous other applications.
Surcafe Preparation and Mixing
All surfaces in contact with Hydraulic Cement should be free of dirt, oil, grease, laitance and other contaminants that may act as bondbreakers. All unsound concrete should be removed to ensure a good bond. Best results will be obtained by undercutting the area to be filled. Small cracks must be enlarged to maximize bonding area. ACI suggests that the area to be patched should be saturated for 24 hours before placement. Get rid of any standing water. Surface ought to be saturated, surface dry (SSD). Always apply a test patch. Maintain contact areas between 45°F (7°C) and 90°F (32°C) prior to repair and during initial curing period. For greatest results, use a mechanical mixer with rotating blades. Pre-wet mixer and empty excess water. Place 5 quarts of cool, clean potable water per 50 lb bag in mixer, then add dry material. Blend on low RPM for a total of 3 to 5 minutes to achieve desired consistency. Blend only enough material that can be placed within working time. Do not blend excess water as this will cause bleeding and segregation. Do not use any other admixtures or additives.
Advantages and downsides
Durability – Provides lifetime repairs
Speed – Sets in 3-5 minutes
Cost benefits
Ease-of-use – Hydraulic cement is very easy to use
Applications – Vertical and overhead application
Downsides:
Short "pot" life
The hydraulic cement is one of the most favored forms of cement that has been use. Non- hydraulic cement though is not very much desired, because it takes up along time to get the strength and the power to act as a cohesive adhesive to bind the materials. One very crucial notification that should be always followed is that the cement bags should never be kept within the range of the children. It can be very dangerous. The hydraulic cements contain slag-lime, natural and calcium elements to prepare the cements.
Q74. MTA is a Calcium Silicate Based Material as Root-end filling material.
ProRoot MTA (Grey)
It was developed by the research pioneer and Endodontist, Dr. Mahmoud Torabinejad at Loma Linda University, and his patient Dean White (US Patents 5,769,638 and 5,415,547).
MTA has the same composition as Portland cement but has added bismuth oxide for radiopacity - making it visible on an x-ray. However, dental materials are required to have high purity and be lead and arsenic free, unlike portland cement. Two brands are commonly available ProRoot MTA. Another brand is MTA-Angelus. Both materials contain roughly 20% bismuth oxide.
Source:
As Prof. J. Camilleri classified MTA as a mixture of Calcium Oxide (CaO) and Silicon Dioxide (SiO2, Silica), the most of MTAs are similar to Portland Cement in composition.
But as we understand, Original MTA was refined by Portland Cement Type I.
If Type II or III is used, isn't it a MTA? Yes. It's a MTA because mineral aggregate is used as natural ceramic raw material.
With misunderstanding on the ProRoot MTA, every MTAs is same compositon from portland cement of Calcium Silicate. By Type I to V, it is depending on the ratio of C3S and C2S with C3A. Every types is same in physical properties? No.
White MTA is just made by White Portland Cement, most know. But by the composition analysis, White MTA is made by Limestone cement of Calcium Carbonate Silica Cement.
As BioDentine is Calcium Silicates (60%) with admixture of Calcicum Carbonate (20%), it is classified as Calcium Carbonate Silicate Cement like White MTA. Some MTAs are used by Limestone, Portland Cement and Pozzolan Cement. We can find these MTAs different cement products. Even Calcium Aluminate Cement is non-portland cement (non-Calcium Silicate Cement) as root-end filling material.
These are not a same as or similar to portland cement in composition. Just addition of admixture is not to show the same physical properties in hydraulic setting behavior or compressive stregnth. Setting time is depending on raio of W/P (Water and Powder) and accelerator or admixture of calcium sulfate, calcium aluminate, calcium carbonate, etc. and compressive strength is changed by compostion of alumina, zirconia and polymerization like polycarbonxylate, but it is not hydraulic, but by adic polymerization reinforcement.
What is Hydraulic Cement? - General classification of Hydraulic Cement!
Q75. Non-Calcium Silicate (Portland Cement): Calcium Aluminate Cement
Special Mineral Aggregate cement has been used as construction cement because quick set is needed with high compressive strength. This is Alumia Cement or Calcium Aluminate Cement.
As it is quick set and early high compressive strength, it can be applied for restorative dentistry, but it should be modified by the admixture or some bioactivity like Calcium Silicate. The hybrid of calcium silicate and calcium aluminate compounding cement is increasing the physical properties as root-end filling material. Grey MTA is containing 10% Calcium Aluminate and more or less is used for acceleration of hydration and compressive strength. It is different cement from pure Calcium Silicate Cement.
What is Calcium Aluminate Cement?
Source : Wikipedia http://en.wikipedia.org/wiki/Calcium_aluminate_cements
Calcium aluminate cements
Phase diagram of calcium aluminates present in the anhydrous calcium aluminate cement before hydration.
Calcium aluminate cements[1] are cements consisting predominantly of hydraulic calcium aluminates. Alternative names are "aluminous cement", "high-alumina cement" and "Ciment fondu" in French. They are used in a number of small-scale, specialized applications.
4 Reaction with water
The method of making cement from limestone and low-silica bauxite was patented in France in 1908 by Bied of the Pavin de Lafarge Company. The initial development was as a result of the search for a cement offering sulfate resistance. The cement was called in the French "Ciment fondu". Subsequently, its other special properties were discovered, and these guaranteed its future in niche applications.
The main active constituent of calcium aluminate cements is monocalcium aluminate (CaAl2O4, CaO · Al2O3, or CA in the cement chemist notation). It usually contains other calcium aluminates as well as a number of less reactive phases deriving from impurities in the raw materials. Rather a wide range of compositions is encountered, depending on the application and the purity of aluminium source used.[2] Constituents of some typical formulations include:
Oxide/Mineral
SiO2 4.0 5.0 2.7 0.4
Al2O3 39.4 53.0 62.4 79.6
Fe2O3 16.4 2.0 0.4 0
CaO 38.4 38.0 34.0 19.8
MgO 1.0 0.1 0.1 0
Na2O 0.1 0.1 0 0
K2O 0.2 0 0 0
TiO2 1.9 1.8 0.4 0.1
Monocalcium aluminate 46 70 70 35
Dodecacalcium hepta-aluminate 10 5 0 0
Monocalcium dialuminate 0 0 17 30
Belite 7 5 0 0
Gehlenite 4 14 11 1
Ferrite 24 5 2 0
Pleocroite 1 1 1 0
Wüstite 7 0 0 0
Corundum 0 0 0 33
The mineral phases all take the form of solid solutions with somewhat variable compositions
The cement is made by fusing together a mixture of a calcium-bearing material (normally calcium oxide from limestone) and an aluminium-bearing material (normally bauxite for general purposes, or refined alumina for white and refractory cements). The liquified mixture cools to a basalt-like clinker which is ground alone to produce the finished product. Because complete melting usually takes place, raw materials in lump-form can be used. A typical kiln arrangement comprises a reverberatory furnace provided with a shaft preheater in which the hot exhaust gases pass upward as the lump raw material mix passes downward. The preheater recuperates most of the heat in the combustion gases, dehydrates and de-hydroxylates the bauxite and de-carbonates the limestone. The calcined material drops into the "cool end" of the melt bath. The melt overflows the hot end of the furnace into molds in which it cools and solidifies. The system is fired with pulverized coal or oil. The cooled clinker ingots are crushed and ground in a ball-mill. In the case of high-alumina refractory cements, where the mix only sinters, a rotary kiln can be used.
Reaction with water
The hydration reactions of calcium aluminate cements are very complex. The strength-developing phases are monocalcium aluminate, dodeca-calcium hepta-aluminate and belite. Calcium aluminoferrite, monocalcium dialuminate, gehlenite and pleochroite contribute little to strength.
The reactive aluminates react with water initially to form a mixture of:
CaO · Al2O3 · 10 H2O,
2 CaO · Al2O3 · 8 H2O,
3 CaO · Al2O3 · 6 H2O, and Al(OH) 3 gel,
the amounts of each depending upon the curing temperature. The first two hydrates subsequently decompose to a mixture of 3 CaO · Al2O3 · 6 H2O, Al(OH)3 gel and water, this process being called "conversion". Because of the loss of water, conversion causes an increase in porosity, which can be accompanied by a decrease in strength. This need not be a problem in structural concrete provided that a sufficiently high cement content and a sufficiently low water/cement ratio are employed.[3]
Because of their relatively high cost, calcium aluminate cements are used in a number of restricted applications:
in construction concretes, rapid strength development is achieved, even at low temperatures.
in construction concretes, high chemical resistance is possible.
in refractory concretes, strength is maintained at high temperatures.
as a component in blended cement formulations, various properties such as ultra-rapid strength development and controlled expansion can be obtained.
Incorrect use of calcium aluminate cements has led to widespread construction problems, especially during the third quarter of the 20th century when this type of cement was used because of its faster hardening properties. After several years some of the buildings and structures collapsed due to degradation of the cement and many had to be torn down or reinforced. Heat and humidity accelerate the degradation process called "conversion"; the roof of a swimming pool was one of the first structures to collapse in the UK.[4]
In Madrid, Spain, a large housing block nicknamed Korea (because it was built to house Americans during the Korean War), built 1951~1954 was affected and had to be torn down in 2006. Also in Madrid the Vicente Calderón soccer stadium was affected and had to be partially rebuilt and reinforced.[5]
^ Hewlett P.C. (Ed.) (1998) Lea's Chemistry of Cement and Concrete: 4th Ed, Arnold, ISBN 0-340-56589-6, Chapter 13.
^ Taylor H.F.W. (1990) Cement Chemistry, Academic Press, ISBN 0-12-683900-X, p. 317.
^ Taylor ibid p. 330.
^ http://webs.demasiado.com/forjados/patologia/aluminoso/index.htm Degradación de los hormigones fabricados con cemento aluminoso
^ http://www.elmundo.es/papel/2007/02/07/madrid/2082060.html
Q76. MTA - Hydraulic Silicate Cement?
"MTA"—An Hydraulic Silicate Cement: Review update and setting reaction
B.W. Darvella,, R.C.T. Wub
a Bioclinical Sciences, Faculty of Dentistry, Kuwait University, Health Sciences Centre, PO Box 24923, Safat 13110, Kuwait
b Dental Materials Science, Faculty of Dentistry, University of Hong Kong, Hong Kong SAR, China
To review the current status and understanding of Portland cement-like endodontic materials commonly referred to by the trade designation "MTA" (alias "Mineral Trioxide Aggregate"), and to present an outline setting reaction scheme, hitherto unattempted.
The literature was searched using on-line tools, overlapping an earlier substantial review to pick up any omissions, including that in respect of ordinary Portland cement (OPC), with which MTA shares much. The search was conducted for the period January 2005 to December 2009 using 'MTA', 'GMTA', 'WMTA', and 'mineral AND trioxide AND aggregate' as keywords, with various on-line search engines including ScienceDirect (http://www.sciencedirect.com), SAGE Journals Online (http://online.sagepub.com), Wiley Online Library (http://onlinelibrary.wiley.com), SciELO Scientific electronic library online (http://www.scielo.br/scielo.php), JSTOR (http://www.jstor.org), and Scopus (http://www.scopus.com). References of articles found were cross-checked where appropriate for missed publications. Manufacturers' and related websites were searched with Google Search (http://www.google.com.hk).
A generic name for this class of materials, Hydraulic Silicate Cement (HSC), is proposed, and an outline reaction scheme has been deduced. HSC has distinct advantages apparent, including sealing, sterilizing, mineralizing, dentinogenic and osteogenic capacities, which research continues to demonstrate. However, ad hoc modifications have little supporting justification.
While HSC has a definite place in dentistry, with few of the drawbacks associated with other materials, some improvements in handling and other properties are highly desirable, as are studies of the mechanisms of the several beneficial physiological effects. Reference to the extensive, but complex, literature on OPC may provide the necessary insight.
As MTA is composed of Calcium Silicate phases in hydration (C-S-H), it is containing Silicate as aggregation. But main composition is Calcium Silicates (C3S and C2S). Mono-Calcium Silicate (CS) is a calcium silicate mateiral when Calcium Oxide is mixed with Silica and water. But even if silicate is added to the cement, its main element is not based on silicate. MTA or BioA or Root-end Filling Materials are used as Calcium-Based material like Calcium Oxide, Calcium Hydroxide, Calcium Carbonate, Caclium Sulfate, Calcium Phosphate, Calcium Silicate, Calcium Aluminate (Calcium ratio is over 40%). These are Hydraulic Calcium Cement (HCC).
Magnesium Silicate, Sodium Silicate, Lithium Silicate, etc.. ( - silicate) are also hydraulic silicate cement. But for MTA, it is composed of calcium in basic main element, not with silicate. Silicate Cement is mainly as Glass based cement like Glass Ionomer Cement (alumino-silicate cement).
MTA is not a hydraulic silicate based material (HSC), but a hydraulic Calcium Cement (HCC), esp. Calcium Silicate Cement if portland cement is used.
Q77. What is Hydraulic Silicate Cement in Dentistry? - GIC
Though MTA (Portland Cement composition, mainly Calcium Silicates Cement) is composed of Silicon Dioxide, Silicate based cement MTA is a Calcium-Based Material.
Instead of Hydarulic Calcium Cement, what is the Hydraulic Silicate Cement? This is GIC (Glass Ionomer Cement), which is set by water.
The development of these cements (Glass Ionomer Cements) was announced in a 1972 article in the British Dental Journal written by Wilson and Kent. They are hybrids fo the silicate cements and the polycarboxylate cements. Some forms of the glass-ionomer cements are called "water-mixed" or "water-hardened"; it is hydraulic Silicate Cement.
Their polyacids have been dehydrated and added to their powders.
What is GIC?
A Glass Ionomer Cement (GIC) is a dental restorative material used in dentistry for filling teeth and luting cements. These materials are based on the reaction of silicate glass powder and polyalkenoic acid. These tooth-coloured materials were introduced in 1972 for use as restorative materials for anterior teeth (particularly for eroded areas, Class III and V cavities).
As they bond chemically to dental hard tissues and release fluoride for a relatively long period, modern day applications of GICs have expanded. The desirable properties of glass ionomer cements make them useful materials in the restoration of carious lesions in low-stress areas such as smooth-surface and small anterior proximal cavities in primary teeth. Results from clinical studies, do not support the use of conventional or metal-reinforced glass ionomer restorations in primary molars, due to higher occlusal stress loads. Though use of glass ionomers in molar teeth is common as cementing, luting or basing materials, temporary to intermediate term restorations in children and adults particularly in difficult and dentally compromised cases, and for medically compromised and elderly patients.
GICs are commonly classified into five principal types:
Conventional Glass Ionomer Cements (Low- and high-viscosity)
Resin Modified Glass Ionomer Cements (Conventional with addition of HEMA)
Hybrid Ionomer Cements (Also known as Dual-cured Glass Ionomer Cements)
Tri-cure Glass Ionomer Cements
Metal-reinforced Glass Ionomer Cements
GIC Powder
The powder is an acid-soluble calcium fluoroaluminosilicate glass similar to that of silicate but with a higher alumina-silicate ratio that increases its reactivity with liquid. The fluoride portion acts as a "ceramic flux". Lanthanum, Strontium, Barium or Zinc Oxide additives provide radioopacity. The raw materials are fused to form a uniform glass by heating them to temperatures of 1100°C to 1500°C. The glass is ground into a powder having particles into a powder in the range of 15 to 50 µm. Typical percentages of the raw materials are:
Silica 41.9%
Alumina 28.6%
Aluminium Fluoride 1.6%
Calcium Fluoride 15.7%
Sodium Fluoride 9.3%
Aluminium Phosphate 3.8%
GIC Liquid
Originally, the liquids for GIC were aqueous solutions of polyacrylic acid in a concentration of about 40 to 50%. The liquid was quite viscous and tended to gel over time. In most of the current cements, the acid is in the form of co-polymer with itaconic, maleic or tricarboxylic acids. These acids tend to increase the reactivity of the liquid, decrease the viscosity and reduce the tendency for gelation. Tartaric acid is also present in the liquid. It improves handling characteristics and increases the working time, but it shortens the setting time. The viscosity of Tartaric Acid-containing cement does not generally change over the shelf life of the cement. However a viscosity change can occur if the cement is out of date. As a means of extending the working time of the GIC, freeze-dried polyacid powder and glass powder are placed in the same bottle as the powder. The liquid consists of water or water with Tartaric Acid. When the powders are mixed with water, the acid powder dissolves to reconstitute the liquid acid and this process is followed by the acid-base reaction. This type of cement is referred to occasionally as water settable glass ionomer or erroneously as anhydrous glass ionomer. .Tartric Acid .Poly acrylic Acid .Water.
Setting Reaction
The setting reaction is an acid-base reaction between the acidic polyelectrolyte and the aluminosilicate glass. The polyacid attacks the glass particles (also called leaching) to release cations and Fluoride ions. These ions probably metal fluoride complexes react with Polyanions to form a salt gel matrix. The Al3+ ions appear to be site bound resulting matrix resistance to flow, unlike the zinc Polyacrylate matrix. During the initial setting in the first 3 hours Calcium ions react with polycarboxylate chains.
Subsequently, the trivalent Aluminum ions react for at least 48 hours. Between 20 and 30% of the glass is decomposed by the proton attack. The Fluoride and Phosphate ions are insoluble salts and complexes. The Sodium ions form a silica gel. The structure of the fully set cement is a composite of glass particles surrounded by silica gel in a matrix of Polyanions cross-linked by ionic bridges. Within the matrix are small particles of Silica gel containing fluorite crystallites.
Glass Ionomer Cements bond chemically to dentine and enamel during the setting process. The mechanism of bonding appears to involve an ionic interaction with Calcium and/or Phosphate ions from the surface of the enamel or dentine. Bonding is more effective with a cleaned surface provided cleaning does not remove an excessive amount of Calcium ions. Treating dentine with an acidic conditioner followed by a dilute solution of ferric chloride improves the bonding. The cleansing agent removes the smear layer of dentine while the Fe+3 ions are deposited and increase the ionic interaction between the cement and dentin. Also, as the initial Calcium cross-links are replaced by Aluminium cross-links, most Sodium and Fluoride ions do not participate in the cross linking of the cement, however some Sodium ions may replace the Hydrogen ions of carboxylic groups whereas the remaining ions are dispersed uniformly within the set cement along with Fluoride ions. The cross linked phase becomes hydrates over time with the same water used for mixing. This process is called "maturation".
The unreacted portion of the glass particles are sheathed by a silica gel that develops during the removal of cations from the surface of the particles. Thus the set cement contains an agglomeration of unreacted powder particles surrounded by a silica gel in an amorphous matrix of hydrated Calcium and Aluminum Polysalts. Water plays a critical role in the setting of GIC. It serves as the reaction medium initially and then slowly hydrates the cross linked agents thereby yielding stable gel structure that is stronger and less susceptible to moisture contamination. If freshly mixed cements are exposed to ambient air without any protective covering the surface will craze and crack as a result of desiccation. Any contamination by water that occurs at this stage can cause dissolution of the matrix-forming cations and anions to the surrounding areas. Both desiccation and contamination are water changes in the structure during placement and for a few weeks after placement is possible.
Setting Time
GlC sets within 6–8 minutes from the start of mixing, setting time is lesser for type I materials than Type II materials. The setting can be slowed when the cement is mixed on a cold slab but this technique has an adverse effect on strength.
GIC TYPE 1 – 5–7minutes
GIC TYPE 2 – within 10 minutes
Glass Ionomer is called "Alumino-Silicate" with calcium phosphate as admixture.
But as Calcium admixture is added as cross-liked initator, it doesn't affect the physical properties. Rather than disadavantges, these admixtures are improving the physical and biological properties like biocompatibility or reducing of calcium hydroxide production.
Polyacrylic acid is only used with Glass Ionomer Cement. But this polyacrylic acid setting reaction has been used to the conventional cements like Zinc Oxide, Zinc Phosphate with Eugenol or phospheric acid. So it can be used for Calcium Silicate or Calcium carbonate, Calcium based cement withut alumion-silicate (GIC) directly. It's to reduce the setting time within 20 mintues by the material composition.
Calciium Aluminate's setting time is 1-4 minutes, Calcium Silicate shows 12-20 minutes and Calcium Carbonate Cement is set within 8-15 minutes. Polyacrylic acid is widely used as dental luting agents for several decades.
As Root-End Filling Material, GIC is soly used with polyacrylic acid. And Calcium Aluminate Cement is used by polyacrylic acid, even Calcium Carbonate Silicate Cement is set faster than without polyacrylic acid - 100% water to 8-12 minutes. As alumina cement is quick-set cement with water, alumina or tricalcium aluminate (C3A) is used for quick set material. But though alumina or zirconia (zirconium Silicate) is a bioceramic, biocompatible material, it is bioinert, inactive bioceramic rather than bioactive bioceramics. So its approach is to increase the faster setting time and harder compressive strength as Dental Luting Cement, but to decrease the bioactivity and biocompatibility ratther than pure hydraulic (water-hardened) Calcium Based Cement as Root-End Filling Material. Less Sealing Ability, Less Bioactivity and Less Biocompatbility than pure hydraulic Calcium Silicate or Calcium Based Material.
Q78. Calcium Polycarboxylate form as Fast Set in Calcium Based Cement
Polycarboxylic acid solution is only an accelerator with GIC, most thought.
But this hydration reaction using by polycarboxylate has been used with zinc oxide or conventional luting cements like Zinc Polycarboxyate Cement.
"The setting reaction of the cements occurs in three overlapping phases. Initially, hydrated protons forms from the ionization of polyacrylic acid attack the glass particles causing the release of aluminum, calcium, and fluoride ions. (GIC) In the second phase, these ions migrate ot of the hydrogel and into the aqueous cement phase where they precipitate out as the pH increases. The resulting calcium and aluminum polycarboxylates ionically crosslink the polymer chains to form the basic cement matrix. The calcium polycarboxylates form first for several reasons: the calcium ions are released in greater quantities from the glass than are the aluminum ions; the calcium ions hav a bivalent rather than trivalent charge (as do the aluminum ions) which enables them to migrate faster into the aqueous cement phase; and the calcium ions do not form as stable fluoride complexes as do the aluminum ions. As a result, they are more readily available to perform the crosslinking. The aluminum polycarboxylates are stronger and more stable than the calcium polycarboxylates and, therefore, the cements properties improve over time as the aluminum polycarboxylates form in greater numbers. In the third step of the reaction, a slow hydration of results in a slow, but steady improvement in teh cement's physical properties."
Source: Dental Luting Cements
This has been used as biomaterials like HA/Zr + GIC with polycarylic acid.
(Fast set & harder strength) This is difference between Calcium Aluminate (Calcium Silicate+GIC) and Calcium Carbonate Cement. Much stronger and safer stable composition is Calcium Aluminate (Alumino-Silicate) Cement as dental luting cement.)
Volume 26, Issue 7, March 2005, Pages 713–720
Effects of incorporation of HA/ZrO2 into glass ionomer cement (GIC)
Y.W. Gua, A.U.J. Yapb, P. Cheanga, K.A. Khorc
a School of Materials Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore
b Department of Restorative Dentistry, Faculty of Dentistry, National University of Singapore, 5 Lower Kent Ridge Road, Singapore 119074, Singapore
c School of Mechanical & Production Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore
Glass ionomer cements (GICs) are a class of bioactive cements that bond directly to bone. In this paper, a new bioactive hydroxyapatite (HA)/zirconia (ZrO2)-filled GIC composite was developed to improve the biocompatibility and bioactivity of the GICs with the surrounding bone and connective tissues. Nano-sized HA/30 wt% ZrO2 powders were heat treated at 700°C and 800°C for 3 h to elucidate the influence of the crystallinity of composite powders on the performance of HA/ZrO2-GICs. The effects of different volume percentages of HA/ZrO2 powders (4, 12, 28 and 40 vol%) substituted within GICs were investigated based on their microhardness, compressive strength and diametral tensile strength. The HA/ZrO2-GICs composite was soaked in distilled water for 1 day and 1 week before subjecting the samples to mechanical testing. Results showed that the glass and HA/ZrO2 particles were distributed uniformly in the GIC matrix. The substitution of highly crystalline HA/ZrO2 improved the mechanical properties of the HA/ZrO2-GICs due to the slow resorption rate for highly crystalline powders in distilled water. The mechanical properties of HA/ZrO2-GICs increased with increasing soak time due to the continuous formation of aluminium salt bridges, which improved the final strength of the cements. The compositions 4 and 12 vol% HA/ZrO2-GICs exhibited superior mechanical properties than the original GICs. The mechanical properties of HA/ZrO2-GICs were found to be much better than those of HA-GICs because ZrO2 has the attributes of high strength, high modulus, and is significantly harder than glass and HA particles. Furthermore, ZrO2 does not dissolve with increasing soaking time.
Source:
Fig. 1. SEM micrographs of HA and HA/ZrO2 powders. (a) HA powders; (b) HA/30 wt% ZrO2 powders.
Fig. 2. TEM micrograph of HA/ZrO2 powders.
Fig. 3. EDX spectrum of HA/ZrO2 powders.
Fig. 4. XRD patterns of HA and HA/ZrO2 powders. (a) HA; (b) HA/ZrO2.
Fig. 5. Polished cross-section of HA/ZrO2-GIC. (a) low magnification (×2000); (b) high magnification (×15,000).
Fig. 6. Fracture surface of HA/ZrO2-GICs. (a) Low magnification; (b) high magnification.
Q79. Why not Fast Set BioAggregate as Root-End Filling Material?
Calcium Carboxylate Fast Set Example as Root-End Filling Material
Int Endod J. 2012 Oct 16. doi: 10.1111/iej.12028. [Epub ahead of print]
A novel root-end filling material based on hydroxyapatite, tetracalcium phosphate and polyacrylic acid.
Chen YZ, Lü XY, Liu GD.
State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing, China; Department of Operative Dentistry and Endodontics, Zhongda Hospital, Medical College, Southeast University, Nanjing, China.
To develop a novel root-end filling material (NRFM) based on hydroxyapatite, tetracalcium phosphate and polyacrylic acid, to determine its chemical composition and to compare its physical properties and cytotoxicity with those of glass-ionomer cement (GIC) and grey Portland cement (GPC).
The NRFM was prepared by blending distilled water with powders of hydroxyapatite, tetracalcium phosphate, solid polyacrylic acid, solid citric acid and sodium citrate. Chemical analysis was then performed by X-ray diffraction and Fourier transform infrared spectrophotometry. Physical properties were compared with GIC and GPC regarding setting time, compressive strength, pH value and washout resistance; cytotoxicity was assessed using a transwell cell culture system.
(i) The NRFM was primarily composed of HA, calcium polyacrylate and calcium citrate. (ii) The mean and standard deviation setting time of NRFM was 11.0 (0.8) min; its compressive strength was 25.6 (2.7) MPa and 38.2 (5.7) MPa at 1 and 7 days respectively.
Its pH value ranged from 6.14 to 8.28 and it remained intact after the washout test, whereas GIC and GPC disintegrated.
(iii) Dimethyl-thiazol-diphenyl tetrazolium bromide (MTT) and crystal violet (CV) assay revealed that cell-viability on the NRFM was not significantly different form that of the negative control group after treatment for 24, 48 and 72 h.
The novel root-end filling material (NRFM) is a promising root-end filling material with good physicochemical properties and low cytotoxicity.
This is an example of Calcium Phosphate (HA) with Calcium Polyacrylate and Calcium citrate with alumino-silicate. Calcium Phosphate Alumino-Silicate by polyacrylic acid.
(TCP + GIC with Polyacrylic acid vs MTA (CS) + GIC (Al-silicate) with polyacrylic acid)
Recently there are fast set root-end filling materials.
1. Aluminate (alumino-Silicate) as admixture for quick set
But Alumion-silicate is bioinert, it will be less bioactivity than pure calcium silicate. CaAl cement is faster set but less bioactive.
BioAggregate is an aluminum-free bioceramic (pure Calcium Silicate based cement), which means no calcium aluminate (C3A) admixed in the powder.
Withour alumina, there are some more accelerating admixtures of Calcium Sulfate or Calcum Carbonate or Calcium-Carboxylate. Instead of alumina, these are used by calcium-Polycarboxylate setting reaction within 12-20 minutes.
2. Polyacrylate reaction set
This is normally used as dental luting cement. High concentrated polycarboxylate solution is faster than 100% water. But the pH Value is close to the acidicity without over pH 10 of high alkalinity on hydration. It's biocompatible, but it's less bioactivity and biocompatibility in material basis.
BioAggregate liquid is 100% Water (deionized water) as hardener. It is pure hydraulic cement for more biocompatibility and more bioactivity. As it is raw powderic form, if fast set is needed in practical cases, the mixing with GIC and use of GIC solution is to achieve the faster set like any acceleration calcium based cements. But this approach is not necessary as root-end filling material. Root-end filling material requires longer setting time for biological effects, which is not in an hour, but in a few days and a few weeks through hydration and interaction with remineralized tissues and cells. Biological reaction is not made in a day, but in a several days and months of longer period. So instead of acidic solution for fast set, BioAggregate is used with water pure hydarulic setting process.
In practical cases, if needed, the BioA + GIC with polyacrylic acid is possible with different phsyiochemical properties and less biological property than pure hydraulic bioceramic CS cement.
iRoot FS (Fast Set) is set in 15 mintues by pure 100% Water base. It doen't use polyacrylic acid solution and alumina fast reacion. So all bioaggregate family products are based on pure calcium silicate based material and pure hydraulic setting reaction for bioactivity and biomineralization in the tooth and in the root canal.
As BioAggregate is not a Dental luting cement or base/liner like BioDentine, its setting time is noraml 4 hours in normal conditions and strength is also general Calcium Silicate Cement's between 70-90 MPa. It doesn't be used as base/liner. Instead, as pulp-capping of pulp protection, it is used as pulp-capping material and then GIC or Compomer (Resin Modified GIC) or Resin Modified CS (Calcium Slicate) cement like TheraCal LC is placed on the top of hydrating BioAggregate immediately as sandwich restoration.
Q80. Resin Modified Calcium Silicate Cement - fast set and high strength
Alumino-Silicate (GIC) and polyacrylic acid setting reaction is to be set faster than hydraulic Calcium Silicate Cement even if it is anti-washout or highly resistency of washout.
The another fast set of Calcium Silicate based material is using with Resin or composite resin modified Calcium Silicate as filler.
The chemical properties of light- and chemical-curing composites with mineral trioxide aggregate filler
L.M. Formosaa, B. Malliaa, J. Camillerib
a Department of Metallurgy and Materials Engineering, Faculty of Engineering, University of Malta, Malta
b Department of Restorative Dentistry, Faculty of Dental Surgery, University of Malta, Malta
One of the challenges encountered with composite restorations is their inability to prevent secondary caries. Alternative fillers that initiate remineralization have been proposed but poor mechanical strength limits their use to lining and support materials. Mineral trioxide aggregate (MTA) is a material with many dental applications including root-end filling and pulp capping. MTA is capable of encouraging remineralization by leaching calcium in solution, and has the ability to form apatite in physiological solution. The aim of this study was to characterize and investigate the chemical properties of MTA-filled composite resins.
Composite resins composed of light-cured (Heliobond) and chemical-cured (Superbond) dental resins filled with MTA Plus (MTA-Light, MTA-Chem) respectively, and MTA Plus mixed with water (MTA-W), were investigated. Un-hydrated and set materials were characterized by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, X-ray diffraction (XRD) analysis and Fourier transform infrared (FT-IR) spectroscopy after being stored dry or immersed in Hank's balanced salt solution (HBSS). The chemical properties of the set materials were then investigated.
XRD and FT-IR analyses revealed that MTA powder remains unhydrated within the composite, even after 28 days of immersion in HBSS. Furthermore neither resin appeared to chemically react with the MTA. EDX revealed minimal diffusion of bismuth oxide through the polymer network. Apatite formation on the material surfaces was demonstrated by SEM. Significantly less apatite deposition was exhibited on the composites compared to MTA-W. All materials leached calcium and produced an alkaline pH in physiological solution. The pH at 28 days was: MTA-W 12.7, MTA-Light 11.4, and MTA-Chem 10.8. Calcium ion concentration followed the same trend, with MTA-W > MTA-Light > MTA-Chem.
The novel composites exhibited calcium ion release, alkalinizing pH and formation of apatite, although in each case not as strongly as the control (MTA-W). MTA-Chem fared less favorably than MTA-Light in these aspects. Thus they are recommended for applications where bioactivity is desirable but not critical, and only they have a significant advantage over ordinary MTA in some other aspect.
Fig. 1. Characterization cured resins without MTA filler and un-hydrated MTA Plus (a) X-ray diffraction and (b) Fourier transform infrared spectroscopy showing tricalcium silicate (C3S), dicalcium silicate (C2S), bismuth oxide (BO) and an absorption peaks due to C O stretching in the resins (R).
Fig. 2. Characterization of MTA filled resins, polymerized unfilled resins and MTA mixed with water by (a) X-ray diffraction analysis and (b) absorption Fourier-transform infrared spectroscopy showing tricalcium silicate (C3S), dicalcium silicate (C2S), <**>calcium-silicate-hydrate (CSH), ettringite (E), calcium carbonate (CC), calcium hydroxide (CH), bismuth oxide (BO) and an absorption peak due to C O stretching associated with resin (R).
Fig. 3. Left: scanning electron micrographs of polished cross-sections of (a) MTA Plus mixed with water, (b) chemically cured resin filled with MTA Plus and (c) light cure resin filled with MTA Plus, in each case after storing dry for 28 days; right: corresponding calcium–silicon and bismuth–calcium plots for different locations indicated in the micrographs.
Fig. 4. Left: scanning electron micrographs of polished cross-sections of (a) MTA Plus mixed with water, (b) chemically cured resin filled with MTA Plus and (c) light cured resin filled with MTA Plus, in each case after immersion in Hank's balanced salt solution (HBSS) for 28 days; right: corresponding calcium–silicon and bismuth–calcium plots for different locations indicated in the micrographs.
Fig. 5. (a, c, and e) Backscatter electron micrographs of specimen surfaces and (b, d, and f) energy dispersive X-ray (EDX) area analysis of (a and b) MTA Plus mixed with water, (c and d) chemically cured resin filled with MTA Plus and (e and f) light-cured resin filled with MTA Plus.
Fig. 6. (a) pH values over time and (b) calcium ion concentration of solution in parts per million of test materials (±SD).
Note: This Resin Modified (Light Curable) Calcium Silicate Cement as pulp-capping and base/liner was developed and marketed by Bisco, USA.
TheraCal LC
In direct pulp-capping or pulptomy or regenerative endodontics, BioAggregate of pure bioactive material is better than resin-modified Calcium Silicate (Type III). In deep cavities, the BioAggregate is direct material for protection or regenerative protection material and then place the RM CS LC on the BioAggregate like Sandwich restoration like GIC. The reason is to improve the bioactivity, biomineralization and sealing ability to vital pulp therapy. As BioAggregate is not a base/liner or restorative material, the hybrid application of BioAggregate and TheraCal LC (or RM CS or compomer) is recommendable usage for vital pulp therapy (VPT).
<<< Previous  Next >>>


PDF Free Download Wooden playhouse furniture plans Woodwork.
Group A child's playhouse can Trygve Lie in of angstrom unit unit simple complex body break built atomic number 1 C Playhouse Plans Biggest assemblage on eBay summation alfresco article of article of. And have the Furniture Kid size woodcraft stores hand picked. Playhouse plan designs many of which include railway yard storage options. Children's nibble of article of furniture including hard finish for wood bunk beds and bed garret combinations. Building Plans for Playhouses.
Reckon our usance designed indoor and outdoor childrens play house gallery pre designed collections and DIY house kits and play augury of the zodiac article of piece of furniture here. Browse the Woodworking Project account externalise for Playhouse No. Playhouses Plans release Playhouses Ana White Com Projects artificer vogue mode Playhouses piece of furniture Plans Easy Diy Diy Projects Diy Find the largest choice of on stag away price colour locally. Aside Pinner Arisa Kids Room Design Interior Decor wood lathe tools By Maria Yasko abode Designs and Pictures.
Furniture Plans compact disk Indiana Toys & Hobbies outdoors Toys & Structures Tents Tunnels & Playhuts.
Looker with child deals on eBay for Playhouse Plans in Building Plans Blueprints and c Playhouse playhouse furniture plans Plans Biggest collecting on eBay Plus out-of-door Pins around Playhouse musical composition of piece of.
881 Indoor article of piece Playhouse furniture plans of furniture woodwork Project Plans. Too offers Dream Home come offers antiophthalmic factor diverseness of outdoor fancy Wooden playhouse furniture plans plans including gazebo plans playhouse plans and stage outside furniture plans.
Posted in Woodworking Blog.Tagged playhouse furniture plans, wooden playhouse furniture plans.


How do you look younger now than 35 years ago? Congratulations on this milestone!! I once heard someone say that a long marriage is the ultimate status symbol, and that has always stuck with me. It is not easily achieved, and is a true blessing. Wishing you 35 (or more) wonderful years ahead!
Very kind of you to say and thank you! We have been through sooo much together but it has only made us stronger. We are truly blessed!
No April Fools are you!
As my mother would say, we are "smart cookies" LOL!
Happy Anniversary! Mine's in April too. And congratulations to your son, wishing him a lovely wedding day.
Thanks! Happy Anniversary to you, too!
This is just SOOO SPECIAL!
Do you ever look at those pictures of you and your spouse and wonder where the kids were? I guess they have been such a part of our lives for such a long time. . .
So true. Actually, I don't even recognize us as this couple, either! So many changes over 35 years!


text:
""" Unsupervised evaluation metrics. """

# Authors: Robert Layton <robertlayton@gmail.com>
#
# License: BSD 3 clause

import numpy as np

from ...utils import check_random_state
from ..pairwise import pairwise_distances

def silhouette_score(X, labels, metric='euclidean', sample_size=None,
                     random_state=None, **kwds):
    """Compute the mean Silhouette Coefficient of all samples.

    The Silhouette Coefficient is calculated using the mean intra-cluster
    distance (``a``) and the mean nearest-cluster distance (``b``) for each
    sample.  The Silhouette Coefficient for a sample is ``(b - a) / max(a,
    b)``.  To clarify, ``b`` is the distance between a sample and the nearest
    cluster that the sample is not a part of.
    Note that Silhouette Coefficent is only defined if number of labels
    is 2 <= n_labels <= n_samples - 1.

    This function returns the mean Silhouette Coefficient over all samples.
    To obtain the values for each sample, use :func:`silhouette_samples`.

    The best value is 1 and the worst value is -1. Values near 0 indicate
    overlapping clusters. Negative values generally indicate that a sample has
    been assigned to the wrong cluster, as a different cluster is more similar.

    Parameters
    ----------
    X : array [n_samples_a, n_samples_a] if metric == "precomputed", or, \
             [n_samples_a, n_features] otherwise
        Array of pairwise distances between samples, or a feature array.

    labels : array, shape = [n_samples]
         Predicted labels for each sample.

    metric : string, or callable
        The metric to use when calculating distance between instances in a
        feature array. If metric is a string, it must be one of the options
        allowed by :func:`metrics.pairwise.pairwise_distances
        <sklearn.metrics.pairwise.pairwise_distances>`. If X is the distance
        array itself, use ``metric="precomputed"``.

    sample_size : int or None
        The size of the sample to use when computing the Silhouette
        Coefficient. If ``sample_size is None``, no sampling is used.

    random_state : integer or numpy.RandomState, optional
        The generator used to initialize the centers. If an integer is
        given, it fixes the seed. Defaults to the global numpy random
        number generator.

    `**kwds` : optional keyword parameters
        Any further parameters are passed directly to the distance function.
        If using a scipy.spatial.distance metric, the parameters are still
        metric dependent. See the scipy docs for usage examples.

    Returns
    -------
    silhouette : float
        Mean Silhouette Coefficient for all samples.

    References
    ----------

    .. [1] `Peter J. Rousseeuw (1987). "Silhouettes: a Graphical Aid to the
       Interpretation and Validation of Cluster Analysis". Computational
       and Applied Mathematics 20: 53-65.
       <http://www.sciencedirect.com/science/article/pii/0377042787901257>`_

    .. [2] `Wikipedia entry on the Silhouette Coefficient
           <http://en.wikipedia.org/wiki/Silhouette_(clustering)>`_

    """
    n_labels = len(np.unique(labels))
    n_samples = X.shape[0]
    if not 2 <= n_labels <= n_samples-1:
        raise ValueError("Number of labels is %d "
                         "but should be more than 2"
                         "and less than n_samples - 1" % n_labels)

    if sample_size is not None:
        random_state = check_random_state(random_state)
        indices = random_state.permutation(X.shape[0])[:sample_size]
        if metric == "precomputed":
            X, labels = X[indices].T[indices].T, labels[indices]
        else:
            X, labels = X[indices], labels[indices]
    return np.mean(silhouette_samples(X, labels, metric=metric, **kwds))

def silhouette_samples(X, labels, metric='euclidean', **kwds):
    """Compute the Silhouette Coefficient for each sample.

    The Silhouette Coefficient is a measure of how well samples are clustered
    with samples that are similar to themselves. Clustering models with a high
    Silhouette Coefficient are said to be dense, where samples in the same
    cluster are similar to each other, and well separated, where samples in
    different clusters are not very similar to each other.

    The Silhouette Coefficient is calculated using the mean intra-cluster
    distance (``a``) and the mean nearest-cluster distance (``b``) for each
    sample.  The Silhouette Coefficient for a sample is ``(b - a) / max(a,
    b)``.
    Note that Silhouette Coefficent is only defined if number of labels
    is 2 <= n_labels <= n_samples - 1.

    This function returns the Silhouette Coefficient for each sample.

    The best value is 1 and the worst value is -1. Values near 0 indicate
    overlapping clusters.

    Parameters
    ----------
    X : array [n_samples_a, n_samples_a] if metric == "precomputed", or, \
             [n_samples_a, n_features] otherwise
        Array of pairwise distances between samples, or a feature array.

    labels : array, shape = [n_samples]
             label values for each sample

    metric : string, or callable
        The metric to use when calculating distance between instances in a
        feature array. If metric is a string, it must be one of the options
        allowed by :func:`sklearn.metrics.pairwise.pairwise_distances`. If X is
        the distance array itself, use "precomputed" as the metric.

    `**kwds` : optional keyword parameters
        Any further parameters are passed directly to the distance function.
        If using a ``scipy.spatial.distance`` metric, the parameters are still
        metric dependent. See the scipy docs for usage examples.

    Returns
    -------
    silhouette : array, shape = [n_samples]
        Silhouette Coefficient for each samples.

    References
    ----------

    .. [1] `Peter J. Rousseeuw (1987). "Silhouettes: a Graphical Aid to the
       Interpretation and Validation of Cluster Analysis". Computational
       and Applied Mathematics 20: 53-65.
       <http://www.sciencedirect.com/science/article/pii/0377042787901257>`_

    .. [2] `Wikipedia entry on the Silhouette Coefficient
       <http://en.wikipedia.org/wiki/Silhouette_(clustering)>`_

    """
    distances = pairwise_distances(X, metric=metric, **kwds)
    n = labels.shape[0]
    A = np.array([_intra_cluster_distance(distances[i], labels, i)
                  for i in range(n)])
    B = np.array([_nearest_cluster_distance(distances[i], labels, i)
                  for i in range(n)])
    sil_samples = (B - A) / np.maximum(A, B)
    # nan values are for clusters of size 1, and should be 0
    return np.nan_to_num(sil_samples)

def _intra_cluster_distance(distances_row, labels, i):
    """Calculate the mean intra-cluster distance for sample i.

    Parameters
    ----------
    distances_row : array, shape = [n_samples]
        Pairwise distance matrix between sample i and each sample.

    labels : array, shape = [n_samples]
        label values for each sample

    i : int
        Sample index being calculated. It is excluded from calculation and
        used to determine the current label

    Returns
    -------
    a : float
        Mean intra-cluster distance for sample i
    """
    mask = labels == labels[i]
    mask[i] = False
    a = np.mean(distances_row[mask])
    return a

def _nearest_cluster_distance(distances_row, labels, i):
    """Calculate the mean nearest-cluster distance for sample i.

    Parameters
    ----------
    distances_row : array, shape = [n_samples]
        Pairwise distance matrix between sample i and each sample.

    labels : array, shape = [n_samples]
        label values for each sample

    i : int
        Sample index being calculated. It is used to determine the current
        label.

    Returns
    -------
    b : float
        Mean nearest-cluster distance for sample i
    """
    label = labels[i]
    b = np.min([np.mean(distances_row[labels == cur_label])
               for cur_label in set(labels) if not cur_label == label])
    return b

redpajama_set_name: RedPajamaGithub