Forums Other Topics Continuing Education Featherstone & hydroxyapetite

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  • #3034 Reply

    dkimmel
    Spectator

    According to Featherstone-
    As Ron stated

    er:YAG not absorbed in hydroxyapetite
    er,cr:YSGG absorbed in hydroxyapetite

    According 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???

    #8262 Reply

    Robert Gregg DDS
    Spectator

    Yeah,

    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

    #8260 Reply

    lagunabb
    Spectator

    “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.

    #8259 Reply

    dkimmel
    Spectator

    I 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

    #8261 Reply

    lagunabb
    Spectator

    That’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, 1993

    and 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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