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dkimmelSpectatorOne of the potential interactions of laser systems and tissue targets is photodisruption. One of these physical effects of photodisruption is jet formation. This is if the breakdown occurs in tissue or fluids. It seems that when a cavitation bubble collapses in the vicinity of a solid boundary, a high speed liquid jet directed toward the wall is produced. If the bubble is in direct contact with the solid boundary during collapse, the jet can cause high-impact pressure against the wall. An example is a 4mJ pulse canreach a diameters of up to 2-3.5 mm if a gas bubble is attached to the corneal tissue. The appears to be dependent on the repeatition rate of the laser. P.147
Anyone read anything about this? Any idea how it might relate to what we do in dentistry?
David
lagunabbSpectatorIf you go to the HK physics literature thread you will find a link to the Japanese research program that studies the jet phenomenae that Neimz describes. I use the word “shockwave” interchangably with jet, cavitation, recoil, bubble collapse etc because these are all inherent characteristics of shocks observed (when hitting a target) in the Japanese work.
I don’t have Neimz book, is it worth it? Any used copies for sale out there?
(Edited by lagunabb at 8:36 am on Sep. 26, 2003)
ericbornsteinSpectatorRay:
Spend a dime with all of your Biolase winnings in the market and buy the book. You will learn from a real pro why most of your arguements do not hold water with the biological systems we dentists are dealing with.
Or on the other hand, don’t buy the book and keep posting just the way you are.
Taking two days off for the holiday. Happy New Year to all that celebrate.
Eric Bornstein DMD
dkimmelSpectatorRay thanks. The book is worth the read. You might check the ADA library to give it a test run.
Eric may the New Year give you the insight to be more constructive.
DAvid
lagunabbSpectatorDr Bornstein:
Happy Rosh Hashanah to you.
I would be interested in your constructive comments on the Fried et al experimental results in their Water Augmentation paper. Particularly the results related to Figures 2-4. I think the results are germane to the understanding on ablation mechanism and I would be interested in your explanation of what happened based on conventional wisdom of “thermal-mechanical” only mechanism.
I have a pretty clean copy of the paper here:
http://etechadvisors.com/PDF/Fried_water_augmentation..pdf
userid = dentaltown
pw = member
ericbornsteinSpectatorRay:
I cannot pull up the paper from your link.
Please e-mail it to me at drericdmd@mindspring.com
and I would be happy to comment.
Eric Bornstein DMD
ericbornsteinSpectatorDavid:
I re-read the Photodisruption chapter in Niemz and specifically the section on Jet Formation as per your question.
Directly after the Jet formation (a real occurrence and concept) section 3.5.4., there is a nice summary for this chapter Sect 3.5.5
Niemz summarizes this and other interactions as:
Main idea for these interactions:
Fragmentation and cutting of tissue by MECHANICAL FORCES. (sort of sounds like “HK”)
Observations for these interactions:
Generation of SHOCK WAVES, Cavitation and JET FORMATION (again sort of sounds like “HK”)
Typical Lasers:
Nd:YAG, NdYLF, Ti:Sapphire
FAR DIFFERENT ENERGIES and WATER ABSORPTION COEFFICIENTS than the Dental Erbium Lasers that we are using today.
Typical Pulse Durations:
100 femtoseconds to 100 nanoseconds
THESE PULSE DURATIONS are ONE and TWO LOGS different than what we are using currently with Dental Erbium Lasers.
Specifically, Jet velocities (in fluids on a surface)of up to 156m/sec were seen by Vogel (1989) and this translated into a hammer pressure of about 2Kbar.
Even with these values, the speed of light is still 300,000 kilometers/sec, (meaning the rest of the incident photons hit the target long before the jet), and 2 kbar approaches 30,000psi transiently (with the jet pushing on the target ie. two Newtonian systems) possibly enough to cut enamel.
BUT, we are talking apples vs golf shoes as far as the similarities of technology with todays Dental Erbium Lasers.
I do not see a connection.
Other Opinions Please.
Eric Bornstein DMD
dkimmelSpectatorEric,
I am enjoying the Niemz book. I found the jet formation of interest as it is not a concept that a newbie like myself was aware of. The more I learn about the laser tissue interaction the more cautious I become and the more I seek to learn.
I did realize he was discussing a different laser then what we are using in dentistry.
As far as HK.
What I believe is if HK was for real ,then someone would be spending a ton of $ to prove it.
I also believe that the whole discussion of HK is unproductive. It puts everyone into camps,increases the emotional level and the exchange of ideals stops. The key to the advancement of lasers is this exchange of knowedge that occurs on forms like this and when groups of us get together.
David -
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