Forums › Other Topics › Continuing Education › Featherstone & hydroxyapetite
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dkimmelSpectatorAccording to Featherstone-
As Ron stateder:YAG not absorbed in hydroxyapetite
er,cr:YSGG absorbed in hydroxyapetiteAccording to Featherstone the info in Dental Applications of Advanced Lasers ™ – 2003 by Manni is incorrect.
I really am not sure I understand it and I was standing next to Ron when he asked Dr Featherstone.
Thoughts???
Robert Gregg DDSSpectatorYeah,
Hydroxtapatite has a Hydroxyl (OH)2 group.
Featherstone may be talking about OH absorption in water being more dominant than HA alone.
I think his statement needs to be supported with data.
It was not appropriate to make that statement w/o data to support.
Bob
lagunabbSpectator“er:YAG not absorbed in hydroxyapetite
er,cr:YSGG absorbed in hydroxyapetite”Featherstone was the co-author on 2 experimental papers that measured absorbance at 2.94 and 2.79 um. He probably didn’t mean to give an impression that there is zero absorbance at the 2.94 um wavelength. There is a big difference in absorbance in HA between the 2.79 and 2.94 um wavelengths.
dkimmelSpectatorI was hoping to get John to join us and explain. Here was his response :
I will reply to this on the forum in a week or so when I am back from the IADR meeting. Simply thiugh, the Er:YAG is absorbed by dental enamel and dentin because of the water in the tissue. There is no hydroxyapatite absorption at the wavelength of the Er:YAG. The Er:YSGG is at a lower wavelength and is also mostly absorbed by the water. However in that case it also overlaps with the very sharp absorption band of the OH- group in the apatite. This is too far away from the Er:YAG, and hence the Er:YAG does not get absorbed by any component of hydroxyapatite. Both lasers work because of their absorption in water, NOT because of absorption in hydroxyapatite, which is mostly by the phosphate groups at wavelengths between 9.2-10.6 microns, namely the CO2 laser.DAvid
lagunabbSpectatorThat’s interesting. In Hibst and Stock’s paper, they reference data from the following paper:
A. V. Belikov, A.V. Erofeev, V. V: Shumilin, and A. M. Tkachuk, “Comparative study of the 3 µm laseraction
on different hard tissue samples using free running pulsed Er-doped YAG, YSGG, YAP, and YLF lasers“, SPIE Proc.
of dental applications of lasers, Vol. 2080, pp. 60-67, 1993and the absorption numbers they gave in Table 1 does show a higher absorbance for 2790 nm compared with 2940 nm. However, it was 30% difference. Could a 10 nm shift to 2780 nm result in a such an increase in HA absorbance? I suppose it is possible but I would love to review the data.
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