Hydrokinetics Article

[Anonymous]

Hi all,

It was recently suggested that a category for literature and websources would be a good addition to the site. So they have been added. If you come across literature or websites in old posts or have others you think are valuable , please copy and post them in the appropriate category. This should keep things a little handier for quick reference(great idea D.K.!). I also think that if you have comments regarding an article it would be better to copy it and post it in one of the regular forums. This will keep people from having to read a bunch of comments while searching articles.

Lasers in Surgery and Medicine
Volume 31, Issue 3, 2002. Pages: 186-193

Published Online: 10 Sep 2002

Copyright © 2002 Wiley-Liss, Inc.

Article
Mechanism of water augmentation during IR laser ablation of dental enamel
Daniel Fried, PhD 1 *, Nahal Ashouri, DDS 2, Thomas Breunig, PhD 1, Ramesh Shori, PhD 3
1Department of Preventive and Restorative Dental Sciences, University of California, San Francisco, San Francisco, California 94143
2Department of Growth and Development, University of California, San Francisco, San Francisco, California 94143
3Department of Electrical Engineering, University of California, Los Angeles, Los Angeles, California 90095

email: Daniel Fried (dfried@itsa.ucsf.edu)

*Correspondence to Daniel Fried, Department of Preventive and Restorative Dental Sciences, University of California, San Francisco, 707 Parnassus Ave., San Francisco, CA 94143.

Funded by:
NIH/NIDCR; Grant Number: ROI-DE14554, R29-DE12091, T35-DE07103
DOE; Grant Number: DE-AC03-76SF00098

Keywords
erbium laser • CO2 laser • dental enamel • laser ablation • infrared spectromicroscopy

Abstract

Background and Objectives
The mechanism of water augmentation during IR laser ablation of dental hard tissues is controversial and poorly understood. The influence of an optically thick applied water layer on the laser ablation of enamel was investigated at wavelengths in which water is a primary absorber and the magnitude of absorption varies markedly.

Study Design/Materials and Methods
Q-switched and free running Er: YSGG (2.79 m) and Er:YAG (2.94 m), free running Ho:YAG and 9.6 m TEA CO2 laser systems were used to produce linear incisions in dental enamel with and without water. Synchrotron-radiation IR spectromicroscopy with the Advanced Light Source at Lawrence Berkeley National Laboratory was used to determine the chemical changes across the laser ablation profiles with a spatial resolution of 10-m.

Results
The addition of water increased the rate of ablation and produced a more desirable surface morphology during enamel ablation with all the erbium systems. Moreover, ablation was markedly more efficient for Q-switched (0.15 microsecond) versus free-running (150 microsecond) erbium laser pulses with the added water layer. Although the addition of a thick water layer reduced the rate of ablation during CO2 laser ablation, the addition of the water removed undesirable deposits of non-apatite mineral phases from the crater surface. IR spectromicroscopy indicates that the chemical composition of the crater walls deviates markedly from that of hydroxyapatite after Er:YAG and CO2 laser irradiation without added water. New mineral phases were resolved that have not been previously observed using conventional IR spectroscopy. There was extensive peripheral damage after irradiation with the Ho:YAG laser with and without added water without effective ablation of enamel.

Conclusions
We postulate that condensed mineral phases from the plume are deposited along the crater walls after repetitive laser pulses and such non-apatitic phases interfere with subsequent laser pulses during IR laser irradiation reducing the rate and efficiency of ablation. The ablative recoil associated with the displacement and vaporization of the applied water layer removes such loosely adherent phases maintaining efficient ablation during multiple pulse irradiation. Lasers Surg. Med. 31:186-193, 2002. © 2002 Wiley-Liss, Inc.

[Anonymous]

Of course I couldn’t forget Glenn’s favorite 😉

Pulsed erbium laser ablation of hard dental tissue: the effects of atomized water spray versus water surface film
Freiberg, Robert J., IMC Associates; Cozean, Colette D., ENO Vision, LLC
Publication: Proc. SPIE Vol. 4610, p. 74-84, Lasers in Dentistry VIII, Peter Rechmann; Daniel Fried; Thomas Hennig; Eds.
Publication Date: 6/2002

---

Abstract:
It has been established that the ability of erbium lasers to ablate hard dental tissue is due primarily to the laser- initiated subsurface expansion of the interstitial water trapped within the enamel and that by maintaining a thin film of water on the surface of the tooth, the efficiency of the laser ablation is enhanced. It has recently been suggested that a more aggressive ablative mechanism, designated as a hydrokinetic effect, occurs when atomized water droplets, introduced between the erbium laser and the surface of the tooth, are accelerated in the laser’s field and impact the tooth’s surface. It is the objective of this study to determine if the proposed hydrokinetic effect exists and to establish its contribution to the dental hard tissue ablation process. Two commercially available dental laser systems were employed in the hard tissue ablation studies. One system employed a water irrigation system in which the water was applied directly to the tooth, forming a thin film of water on the tooth’s surface. The other system employed pressurized air and water to create an atomized mist of water droplets between the laser hand piece and the tooth. The ablative properties of the two lasers were studied upon hard inorganic materials, which were void of any water content, as well as dental enamel, which contained interstitial water within its crystalline structure. In each case the erbium laser beam was moved across the surface of the target material at a constant velocity. When exposing material void of any water content, no ablation of the surfaces was observed with either laser system. In contrast, when the irrigated dental enamel was exposed to the laser radiation, a linear groove was formed in the enamel surface. The volume of ablated dental tissue associated with each irrigation method was measured and plotted as a function of the energy within the laser pulse. Both dental laser systems exhibited similar enamel ablation rates and comparable ablated surface characteristics. The results of the study suggest that, although the manner in which the water irrigation was introduced differed, the mechanism by which the enamel was removed appeared basically the same for both dental laser systems, namely rapid subsurface expansion of the interstitially trapped water. It is the conclusion of this study that if the proposed hydrokinetic effect exists, it is not effective on hard materials, which are void of water, and it does not contribute in any significant degree in the ablation of dental enamel.

[Robert Gregg]

Very nice resource section. Thanks Ron. Nice job as always.

Bob

[lagunabb]

You guys still bumping chests over this? Here is one just to stir the pot more for fun.

A more confined approached to energized water ablation induced by laser. Research conducted at:

<a href="http://ceres.ifs.tohoku.ac.jp/~swrc/

Application” target=”_blank”>http://ceres.ifs.tohoku.ac.jp/~swrc/

Application of laser-induced liquid jet and shock waves to medicine
Makoto Komatsu
Water vapor bubble is produced by energy absorption of water. And large energy supply for a extraordinary short time brings about formation of underwater shock waves. Energy source for these phenomena is laser emission, electric discharge, explosive and so on.
In SWRC, production of bubble and shock waves in water with laser irradiation has been studied. Laser which has wavelength close to light absorption spectrum of water have to be employed as effective energy source. Holmium YAG (Ho:YAG) laser beam has 2.1 ƒÝm wavelength, which is close to 1.9 ƒÝm of a light absorption spectrum of water. Therefore, Ho:YAG laser is suitable to generate bubbles and shock waves in materials including a large amount of water.
Living body has large including ration of water. Hence, behavior of bubbles and shock waves in living body is similar to that in water. Based on these backgrounds, development of medical technique with laser-induced liquid jet and shock waves has been conducted for application of this novel to medicine.
Laser-induced jet is produced by laser emission in narrow capillary tube. Fig. 1 explains the process of laser-induced liquid jet production. Optical fiber is inserted into a capillary tube filled with water. Laser beam transmitted via the fiber produces water vapor bubble growing toward the capillary exit, and then water is expelled from the exit by expanding bubble. Water flow generated by the emanation of water produces liquid jet finally. Development of fibrinolytic treatment for cerebral arteries and surgical knives with the laser-induced liquid jet has been performed with Department of Neurosurgery, Tohoku University Graduate School of Medicine.

[Robert Gregg DDS]

Hey Ray,

Good to see you. Nice reference material as always.

Is that article suggesting I can create HK with my free-running Holium YAG?

Bob

[lagunabb]

Bob, the Kodak patent does not specify the phenomena as being unique to any wavelength in particular although they did refer specifically to Biolase’s patent and Er,Cr:YSSG for its high water absorbance and used it in their experiments. If your question is about the Japanese work, I am not sure why the SWRC folks chose Ho:YAG for their experimental setup. Could be finances – you know how research gets funded in grad schools. I am surprised that their apparatus worked as well as it did using a lousy wavelength. Makes me wonder what the apparatus could have done with an Er source.

[lagunabb]

Does anyone here have a PDF file for Fried et al’s “Mechanisms of Water Augmentation During IR Laser Ablation of Dental Enamel” Lasers is Surgery and Medicine 31:186-193 (2002) paper? I have the paper copy and it doesn’t scan well for discussion purposes. I would greatly appreciate a copy if you have it. Thanks.

[Robert Gregg DDS]

Hi Ray,

We have an awesome scanner. What’s it worth to ya?

Give me another chance too, to show you photoacoustics with FR Nd:YAG……..;)

Bob

[2thlaser]

You guys crack me up! Bob, good to see some of your other posts with photos. I really can’t wait when i can get into a P-7 someday. Won’t be too long!
Mark

[lagunabb]

Hey Bob,

But my scanner has got HK and it still doesn’t do the figures well enough.

HK = hong kong

[Swpmn]

Ray:

Sent you the requested .pdf file as well as the SEM’s you were requesting on Dental Town.

Al

[lagunabb]

Al: Thanks. Does Dr Fried et al monitor the discussions. If so, I would surely like to ask him some specific questions about his paper(s).

[lagunabb]

If anyone has SEMs of entire ablation craters from either the DElight or Waterlase. I would greatly appreciate copies. I have close up SEMs showing surface morphology. Thanks.

[ericbornstein]

This is from the Biolase web site.

What are benefits of the Waterlase™ ?

•Waterlase™ uses a cool-water spray to cut teeth without generating heat. Conventional drills and lasers can overheat teeth during procedures, inducing discomfort and irreversibly damaging the soft tissue or pulp underneath.

How does Waterlase™ work?

•The Waterlase™ system uses laser-energized water to cut teeth.

•The Waterlase™ emits a laser beam that energizes a highly precise spray of air and water.

Water droplets absorb the laser energy and become laser-energized water particles that, when directed at the tooth, rapidly remove enamel, dentin and decay/caries.

Now, before one deals with the question of hydrokinetics, one must first deal with two laws of physics that at this point in our history should be irrefutable.

1) Newton’s third law of Motion:

Newton states that whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first. In other words, to every action there is always opposed an equal reaction. Neither force exists without the other, and forces come in pairs. The action and reaction pair of forces makes up one interaction between two things.

Now, lets extend the ideas in Newton’s third law to propulsion. Because in effect, hydrokinetics theorizes that water particles are propelled toward the tooth with enough force to exert ablation. For a rocket to be propelled into the sky, it has nothing to do with the impact of the exhaust against the atmosphere. That is a very common misconception. What propels a rocket, is the recoil force of the exhaust molecules (system #1) pushing against the rocket itself (system #2). A pair of forces, opposing each other, with system #1 overcoming system #2 and the rocket moving up through the atmosphere.

You always need two systems. Here is another maybe easier example.

If your car runs out of gas, and you get out of the car and behind the bumper and push, as long as your force overcomes the force of the car and the friction of the pavement and surrounding air, the car will move forward. However, if it is raining outside, and you say “Hey , I do not want to get wet”, and push the car with the same force on the dashboard in the front seat (as you previously did out of the car and on the bumper), the car will not move at all.

Why?

Because you and the car (with you still in the front seat) are now the same system. For Newton’s third law to apply, there must be two separate systems (ie. You pushing behind the bumper or the exhaust molecules pushing against the rocket).

With the hydrokinetic theory as presented (in my understanding) we are only dealing with one system. There is nothing to push against. The theory as presented, has erbium incident energy vaporizing part of a water molecule and propelling the rest of the water molecule towards the tooth, with enough direct vector momentum to cause ablation of enamel. My main problem with this is Newton’s third law. Where is the equal and opposite force, to such an extent, to cause up to 16,000+ psi of pressure on the remaining water “particles” to propel them forward. To me it is all the same system, (one original water droplet) just like sitting in the front seat of your car, trying to move the car by pushing on the dashboard. This is my problem with it from Newton’s perspective.

2) Einstein’s Relativity

The second postulate of special relativity states that the speed of light in free space has the same measured value for all observers, regardless of the motion of the source or the motion of the observer: that is, the speed of light is a constant at 300,000 kilometers/sec.

If incident erbium energy (infrared light) strikes a water droplet in front of the beam, and the reaction (vaporization, hydokinetics, whatever) begins; long before even 1% of the reaction causing the hydrokinetics takes place, the rest of the erbium photons that did not interact with the water must have already hit the tooth and begun the thermal-mechanical ablative reaction that we all know. To state any different logic than this (because remember light travels at 300,000 kilometers/sec) is to say that the hydrokinetics is faster than the speed of light. Einstein says that is impossible. This is my problem with it from Einstein’s perspective.

Eric Bornstein DMD

[Swpmn]

QUOTE

If anyone has SEMs of entire ablation craters from either the DElight or Waterlase.  I would greatly appreciate copies.  I have close up SEMs showing  surface morphology.  Thanks.

Let me see what I can find, will probably be able to help you with the DELight.

Al

[Author]

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