Microstructure of SiO2−Al2O3−CaO−P2O5−K2O−F- Glass Ceramics. 2. Time Dependence of Apatite Crystal Growth

Höche, Thomas; Moisescu, C.; Avramov, I.; Rüssel, Christian; Heerdegen, W.; Jäger, Christian

doi:10.1021/cm001204h

Cited by 25 publications

(23 citation statements)

References 8 publications

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“…The phosphate concentration of the supernatant showed less variations, but an overall trend of decreasing with time was frequently observed, although some samples displayed an opposite trend of increased phosphate content later in the process. This effect is attributed to the dissolution of the glass matrix of the glass-ceramic composite comprising the substrates18.…”

Section: Resultsmentioning

confidence: 99%

Enzymatic processing of amelogenin during continuous crystallization of apatite

Uskoković

Kim

et al. 2008

J. Mater. Res.

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Dental enamel forms through a protein-controlled mineralization and enzymatic degradation with a nanoscale precision that new engineering technologies may be able to mimic. Recombinant fulllength human amelogenin (rH174) and a matrix-metalloprotease (MMP-20) were employed in a pHstat titration system that enabled a continuous supply of calcium and phosphate ions over several days, mimicking the initial stages of matrix processing and crystallization in enamel in-vitro. Effects on the self-assembly and crystal growth from a saturated aqueous solution containing 0.4 mg/ml rH174 and MMP-20 with the weight ratio of 1:1000 with respect to rH174 were investigated. A transition from nanospheres to fibrous amelogenin assemblies was facilitated under conditions that involved an interaction between rH174 and the proteolytic cleavage products. Despite continuous titration, the levels of calcium exhibited a consistent trend of decreasing, thereby indicating its possible role in the protein self-assembly. This study suggests that mimicking enamel formation invitro requires the synergy between the aspects of matrix self-assembly, proteolysis and crystallization.

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Section: Resultsmentioning

confidence: 99%

Enzymatic processing of amelogenin during continuous crystallization of apatite

Uskoković

Kim

et al. 2008

J. Mater. Res.

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“…This is consistent with previous studies on fluorapatite glass-ceramics, showing the formation of primary Ca-P rich PSDs and secondary Al-P rich PSDs in the parent glass. 3, 17, 23 The primary PSDs later crystallize into fluorapatite during further heat treatment, while the secondary PSDs remain amorphous. It was shown that the size of the fluorapatite crystals is limited by the size of the PSDs and an isometric shape is retained at lower temperatures and for slow heating rates because diffusion rates are low.…”

Section: Discussionmentioning

confidence: 99%

Effect of crystallization heat treatment on the microstructure of niobium‐doped fluorapatite glass‐ceramics

2012

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Our goal was to study the effect of heat treatment temperature and heating rate on the microstructure and crystalline phases and assess the domain of existence of sub-micrometer fluorapatite crystals in niobium-doped fluorapatite glass-ceramics for biomedical applications. Glass-ceramic specimens were prepared by casting and heat treatment between 700 and 1200°C using a fast or a slow heating rate. The microstructure was characterized by atomic force microscopy and scanning electron microscopy. Crystalline phases were analyzed by x-ray diffraction. AFM of the as-cast glass revealed that amorphous phase separation occurred in this system. XRD confirmed the presence of fluorapatite in all specimens, together with forsterite and enstatite at higher temperatures. Both heating rate and heat treatment temperature strongly influenced microstructure and crystallinity. A dual microstructure with sub-micrometer fluorapatite crystals and polygonal forsterite crystals was obtained when slow heating rates and crystallization temperatures between 950 and 1100°C were used. Needle-shaped fluorapatite crystals appeared after heat treatment above 1100°C. Fast heating rates led to an increase in crystal size. Heat treatment temperatures should remain below 1100°C, together with slow heating rates, to prevent crystal dissolution, and preserve a dual microstructure of finely dispersed sub-micrometer crystals without growth of needle-shaped crystals.

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“…In phosphosilicate glass melts, both P 5+ and Si 4+ have high ionic field strength (43.2 and 23.8, respectively) [23], and have strong attraction to oxygen ions in the glass network. When P 2 O 5 concentration is high enough, the competition in attracting oxygen ions between two network-former ions causes amorphous phase separation (APS), i.e., phosphate-and silicate-rich phases [24,25], and hence induces the subsequent crystallization during cooling; this is reflected by the XRD results. As demonstrated by Ryerson and Mysen [26,27], the structural role of P 2 O 5 can change in metal silicate melts, and it depends on the degree of polymerization.…”

Section: Discussionmentioning

confidence: 99%

Transparent phosphosilicate glasses containing crystals formed during cooling of melts

Liu¹,

Zhang²,

He³

et al. 2011

Journal of Non-Crystalline Solids

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Effect of P 2 O 5 -SiO 2 substitution on spontaneous crystallization of SiO 2 -Al 2 O 3 -P 2 O 5 -Na 2 O-MgO melts during cooling was studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and rotation viscometry. Results show that addition of P 2 O 5 leads to amorphous phase separation (APS), i.e., phosphate-and silicate-rich phases. It is due to the tendency of Mg 2+ to form [MgO 4 ] linking with [SiO 4 ]. Molar substitution of P 2 O 5 for SiO 2 enhances the network polymerization of silicate-rich phase in the melts, and thereby the spontaneous crystallization of cubic Na 2 MgSiO 4 is also enhanced during cooling of the melts. In addition, the sizes of the local crystalline and separated glassy domains are smaller than the wavelength of the visible light, and this leads to the transparency of the obtained glasses containing crystals.

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Microstructure of SiO₂−Al₂O₃−CaO−P₂O₅−K₂O−F^- Glass Ceramics. 2. Time Dependence of Apatite Crystal Growth

Cited by 25 publications

References 8 publications

Enzymatic processing of amelogenin during continuous crystallization of apatite

Enzymatic processing of amelogenin during continuous crystallization of apatite

Effect of crystallization heat treatment on the microstructure of niobium‐doped fluorapatite glass‐ceramics

Transparent phosphosilicate glasses containing crystals formed during cooling of melts

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