The Dissolution Mechanism of Calcium Apatites in Acids - Calcium Orthophosphates: Applications in Nature, Biology and Medicine - page 791

apatite dissolution process at the atomic (ionic) level has been made.
This dissolution mechanism is based on current level of knowledge
and will be updated, corrected, and modified simultaneously with
appearance of new experimental data. Now some missing and
unclear points to be investigated in future can be outlined:

1. Chemical transformations happening with all ions during
diffusion through the Nernst layer;

2. Chemical composition of the apatite surface during

dissolution;
3. Processes of ionic sorption and detachment;
4. Processes of dissolution nuclei formation and growth;
5. Initial stages of etch pits formation at the dislocation outlets;
6. Specific influence of anions to the ionic sorption, surface
diffusion, and detachment.
The above topics should be investigated in order to have better
understanding of all the processes involved. For example, atomic
force microscopy and phase shift interferometry might be useful tools
in investigations on dissolution nuclei and etch pits formation [61,
62]. Micron-sized (better nano-sized) electrodes might be helpful in
studying ionic transformations during diffusion through the Nernst
layer [127]. Modern techniques of the surface state analysis might
be helpful in understanding the surface structure and its chemical
composition.

References and Notes

1. McConnell, D. (1973) Apatite: its crystal chemistry, mineralogy,
utilization, and geologic and biologic occurrences, Applied Mineralogy,

vol. 5 . , Springer-Verlag, New York, p. 111.

2. Aoki, H. (1991) Science and Medical Applications of Hydroxyapatite ,

JAAS, Tokyo, p. 245.

3. Elliott, J. C. (1994) Structure and chemistry of the apatites and other
calcium orthophosphates, Studies in Inorganic Chemistry , vol. 18,

Elsevier, Amsterdam, p. 389.

4. LeGeros, R. Z. (1991) Calcium phosphates in oral biology and medicine,
Monographs in Oral Science , vol. 15, Karger, Basel, p. 201.

5. Dorozhkin, S. V. (2009) Calcium orthophosphate cements and
concretes, Materials , 2 , 221-291.