Magnesium in tooth enamel and synthetic apatites

Terpstra, R.A.; Driessens, F. C. M.

doi:10.1007/bf02555203

Cited by 65 publications

(37 citation statements)

References 23 publications

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“…The limited magnesium incorporation into the HA structure is in agreement with the principle that ions significantly larger than Ca 2+ can be substituted, but smaller ions do not tend to substitute extensively for calcium (Lang, 1981). However, theoretical considerations of magnesium incorporation in the apatite lattice suggest that the substitution of Mg for Ca cannot be excluded on the basis of ionic radii, although magnesium represents a borderline case (Terpstra & Driessens, 1986). Magnesium substitution for calcium into the HA structure induces a slight contraction of the unit cell, as expected for a low level of magnesium incorporation.…”

Section: Discussionmentioning

confidence: 99%

Rietveld structure refinements of calcium hydroxylapatite containing magnesium

Bigi¹,

Falini²,

Foresti³

et al. 1996

Acta Crystallogr Sect B

101

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The crystal structures of four hydroxylapatite (HA) samples prepared from solutions in the presence of 10, 15, 25 and 30 Mg-atom-% have been investigated by X-ray powder pattern fitting. The total magnesium content of the solid samples, as determined by chemical analysis, was 4.9, 14.1, 20.4 and 30.6 Mg-atom-%, respectively. Rietveld analysis was performed using the computer program PREFIN implemented with routines which allow the refinements of the average crystallite sizes. Different refinement procedures were carried out in order to evaluate the effect of the amorphous and background profiles on the occupancy factor data. For comparison, magnesium-free hydroxylapatite was refined with the same strategies. The results of the different approaches indicate that the degree of magnesium substitution for calcium in the HA structure can be at most ,-~ 10 atom-%. Magnesium substitutes calcium preferentially at the 6(h) site. The broadening of the diffraction peaks increases on increasing the total magnesium content in the solid phase, which is always significantly higher than the amount incorporated into the HA structure. The excess is probably located in the amorphous phase and/or on the crystallite surface.

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Section: Discussionmentioning

confidence: 99%

Rietveld structure refinements of calcium hydroxylapatite containing magnesium

Bigi¹,

Falini²,

Foresti³

et al. 1996

Acta Crystallogr Sect B

101

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“…Sodium in this way would reflect carbonate concentrations. The suggestion has also been made that the centers of the crystals may be less well-ordered and accommodate carbonate as a result of (or even responsible for) screw dislocations in the direction of the c-axis (Daculsi and Kerebel, 1977;Marshall and Lawless, 1981 (C) MAGNESIUM Calcium can be replaced to some extent by magnesium, although this is thought to be limited, possibly to about 0.33% (Featherstone et al, 1983;Terpstra and Driessens, 1986). Magnesium is thought to be located on crystal surfaces or in separate, more acid-soluble, phases as described below.…”

Section: Incorporation Of Extraneous Ions Into Enamel Apatite (A) Flumentioning

confidence: 99%

The Chemistry of Enamel Caries

Robinson

Shore

Brookes

et al. 2000

Critical Reviews in Oral Biology & Medicine

315

316

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The chemical changes which occur during the process of carious destruction of enamel are complex due to a number of factors. First, substituted hydroxyapatite, the main component of dental enamel, can behave in a very complex manner during dissolution. This is due not only to its ability to accept substituent ions but also to the wide range of calcium phosphate species which can form following dissolution. In addition, the composition, i.e., the extent of substitution, changes throughout enamel in the direction of carious attack, i.e., from surface to interior. Both surface and positively birefringent zones of the lesion clearly illustrate that carious destruction is not simple dissolution. Selective dissolution of soluble minerals occurs, and there is the probability of reprecipitation. The role of fluoride here is crucial in that not only does it protect enamel per se but also its presence in solution means that rather insoluble fluoridated species can form very easily, encouraging redeposition. The role of organic material clearly needs further investigation, but there is the real possibility of both inhibition of repair and facilitation of redeposition. For the future, delivering fluoride deep into the lesion would appear to offer the prospect of improved repair. This would entail a delivery vehicle which solved the problem of fluoride uptake by apatite at the tooth surface. Elucidation of the role of organic material may also reveal putative mechanisms for encouraging repair and/or protecting the enamel mineral.

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“…Skład chemiczny szkliwa zostaje ustalony w trakcie jego rozwoju, jednak dzięki dużej reaktywności chemicznej i zdolności wymiany jonów między kryształami hydroksyapatytu i środowiskiem zewnętrznym zęba, są możliwe zmiany składu mineralnego szkliwa (19,20).…”

Section: Skład Chemiczny Szkliwa: Pierwiastki I Ich Rolaunclassified