Forums › Diode Lasers › General Diode Forum › Continuous vs. pulsed ?????
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dkimmelSpectatorRon was asking me about setting on a case I had posted. Since then I have been thinking about the differences between Continuous and pulsed.
Anyone have a easy explanation about what the effect is on soft tissue using each of these different setting?
The next question deals with just Repeat pulse. In this mode you can change the pulse duration and the interval. Again what changes do we see by increasing or decreasing these values ? Do they need to be the same setting or kept within a range of each other?Thanks
David
Robert Gregg DDSSpectatorHi David,
Generally speaking, the idea with pulsing is to allow for some thermal “relaxation” of the tissues before the next pulse hits the tissue.
Varing the pulse duration will vary the amount of time the laser is “on” in each pulse delivered, and the pulse interval will vary the rate that pulse duration repeats itself in the “pulse train”, which is what I think of when i hear reference to “Repeat pulse mode” versus continuous wave.
What diode device do you have and what parameters do you have to select from?
Bob
dkimmelSpectatorBob, Thanks. I have the Lasersmile. Usually in the Pulsed mode with 20 sec duration and 20 sec interval at 1.5W. I have been trying to go into a periodontal pocket and remove granulation tissue , like in curretage. So far I might as well be pissing into the wind. It would be nice to degranulate a pocket prior to the use of a perioscope. It would make visiblity much easier.
David
Robert Gregg DDSSpectatorHi David,
Do you mean 0.20 seconds?
Anyway, try continuous wave instead of pulsed with your diode, and “activate” your tip against a tongue blade or something. See if that dries up your pocket.
Bob
dkimmelSpectatorYou are right .20 sec. I do activate the tip at these settings. I have tried doing this with continuous using an activated tip. It appears to be too hot.
Daivd
Robert Gregg DDSSpectatorDavid,
That is the challenge with CW diodes–finding the happy medium between too hot and no good clinical effect.
Bob
AnonymousGuestDavid,
Try 1.0CW and if the tissue is fibrous bump it up to 1.1 or 1.2 with an activated tip.
Did you notice how many responses you got to the ‘pulse’ question. I knew they’d come just that fast and furious with how many people understand pulse duration, duty cycle, etc 😉
Using the Periolase MVP 7 I’m starting to get a little understanding of the pulse thing (thanks Bob&Del) but it sure can get complicated when you start adding in focused vs defocused, intervals, peak and average powers.
Robert Gregg DDSSpectatorRon,
Complicated? Sure……but do you like the control over tissue, and the results?
Bob
AnonymousGuestThis afternoon I seated the first crown that I used the FR nd:YAG for troughing. Margin was exactly where I had it to begin with and the tissue was very healthy.
So yes I like the tissue control and results.
dkimmelSpectatorRon, When I first posted the question I thought that maybe it was one of those obvious things that I just didn’t get! Like when my wife asks me if I want to help her out in the yard and I say NO! Then later very much regret saying NO !
I think I understand that with pulse duration, the longer this is the greater the thermal necrosis/coagualtion. The longer the period between the pulses (interval) the more relaxation of the tissue.
How important is this relaxation.?The more you have the less damaging affects. Does it affect pentration? What occurs with a rapid cycle of relaxation? Does this cause futher changes to the tissue? Does the relaxation/stimualtion have anything to do with Biostimulation?
I could see inceasing the pulse duration until you see the desired results. What of the interval. What will you see by incerasing/decreasing this?
What is the difference in tissue reaction to an activated tip vs an inactivated? Is it just that the tip gets hotter?Better yet, here I am trying to remove granulation tissue in an active periodontal pocket and is this entirely a good idea? The presence of granulation tissue is involved in the healing process. Does removing all the granulation tissue slow the healing process?
How selective is the use of the laser in this process of removing the granulation tissue? Am I able to just remove this tissue or is there profound deeper tissue consequnces?
It sounds that you are finding Periolase MVP 7 less more useful then the Lasersmile?
DAvid
AnonymousGuestQuote: from dkimmel on 10:54 pm on July 3, 2003
How important is this relaxation.?The more you have the less damaging affects. Does it affect pentration? What occurs with a rapid cycle of relaxation? Does this cause futher changes to the tissue? Does the relaxation/stimualtion have anything to do with Biostimulation?Wow!
David, couldn’t you have started this post and directed it at Bob or Del , instead of Ron? 😉
I hope one of the experts will help me out here and do some correction where needed, but I’ll give it a try.With less relaxation time I think you will have more of a thermal effect to a greater depth.
As far as biostim, with CW there is generally 1 maxima where you get the desired effect and then when going past that you can get inhibition. Pulsed has several maxima. Most of what I have read seems to indicate dose is more important than pulsed vs CW in biostim. Not sure what you mean by rapid cycle of relaxation.Quote: from dkimmel on 10:54 pm on July 3, 2003
I could see inceasing the pulse duration until you see the desired results. What of the interval. What will you see by incerasing/decreasing this?
What is the difference in tissue reaction to an activated tip vs an inactivated? Is it just that the tip gets hotter?If you decrease the time between pulses (in a set time frame) then you will be delivering more eneregy (dose) in that given time frame.
If you increase the pulse duration, you also will deliver more energy in a given time frame.As far as hot or activated tip goes- I understand activation to be a process whereby you are trying to keep the energy localized at the tip to use as ‘hot glass’
Quote: from dkimmel on 10:54 pm on July 3, 2003 Better yet, here I am trying to remove granulation tissue in an active periodontal pocket and is this entirely a good idea? The presence of granulation tissue is involved in the healing process. Does removing all the granulation tissue slow the healing process?
How selective is the use of the laser in this process of removing the granulation tissue? Am I able to just remove this tissue or is there profound deeper tissue consequnces?
I think the answers here depend on how you’re going about removing the granulation tissue (hot glass diode vs. FR nd:YAG). Even with the perioscope, can you be sure you removed all the granulation tissue anyway?
Using an activated tip, if you stay too long in one place there can be profound deeper tissue consequences (I guess the same is true for unactivated, but I think the zones of abalation, necrosis, hemostatsis and hyperemia would be different ) .
I think the selectivity is greater when you have the ability to vary the pulse duration, allow use of the proper amount of energy to accomplish the effect while still allowing for relaxation.Quote: from dkimmel on 10:54 pm on July 3, 2003
It sounds that you are finding Periolase MVP 7 less more useful then the Lasersmile?
DAvid
I originally bought the lasersmile with the idea of doing perio. I didn’t buy it for whitening. I got pretty good results in that we consistantly got 5-7 mm pockets down to 3’s or less. The amount of chair time in Tx was a big pain. Number of visits was calculated by taking pocket depth and subtracting three. 7 mm pockets would be treated 4 times (each visit 1mm shorter). Scheduling all these appts 1 week apart and getting patients to be consistent was difficult.
I am very happy with the Periolase MVP7 in the short time I’ve had it. The perio patients I’ve treated have been very happy. I did one last week with generalized 6-8mm pockets and where # 4 was vertically compressible w/11mm still tested vital. Did Bob and Del’s protocol and splinted #4 as well. Patient took 2 motrin the next day. Pt had to miss one week followup, because of family emergency out of state, but called to say that side of her mouth hadn’t felt that good in years. On another patient last week did extractions 22-27 (27 surgical root tip ) on a patient taking Plavix. Pt’s physician saw no reason to take off Plavix (PDR says 7 days- I’ll withhold my comment on the physician). Did extractions and used the laser to ‘clot’. No bleeding problem afterward at all. I know I haven’t even scratched the surface in what you can do with this FR nd:YAG. The laser is well thought out- meter for testing output (which I also use to check my Waterlase tips now), you can record and print out on paper the energies you used along with the patient name and procedure -talk about making chart entry easier. Finally, as you can probably tell from Bob and Del’s posts-they know what they are doing and the training you get from them is awesome.
Robert Gregg DDSSpectatorHi David,
For what it’s worth, I’m very impressed with your desire to understand laser tissue interactions to the depth you have clearly thought it through to make the most sense of it all. Your thoughtfulness, quality of questions, and desire to know the actual physics involved and consequent tissue interactions remind me of the same sort of questions that our host Ron asked early in his quest for understanding.
And Ron, I think your answers and explanations were excellent.
David’s questions are many and detailed, and go to the very heart of the clinical goal to optimize beneficial laser tissue interactions, while minimizing detrimental side effects.
Maybe some historical perspective and details Del and I learned along our discovery process when researching the effects of varying pulse duration in “free-running” pulsed lasers versus CW/gated lasers (e.g.diodes) would be helpful.
Basically our investigations showed that free-running pulsed near-infrared lasers maximized desirable clinical outcomes, gave the widest safety margin, and minimized undesirable thermal side effects.
Why?
Well, because of the way the devices output their energy.
Free-running (10-6 seconds) pulsed Nd:YAG laser—are truly pulsed lasers that have an “on” time of, for example, 150 microsecond pulse duration (with peak powers of 1500 watts per pulse) and “off” times (pulse interval) of 49,850 microseconds (at 20 Hz)—nearly 500 times the thermal tissue relaxation time than a diode. That laser capability means a whole lot more and different work is possible with less thermal risk to surrounding tissues, than CW lasers.
So pulsed lasers are have more efficiency and are more forgiving to the surrounding tissues.
Our investigations confirmed what the dermatology literature was saying at the time (1996), that the thermal relaxation threshold for tissue was around 700 microseconds. Once our pulsed lasers exceeded 700 usec pulse duration, we started losing that control and forgiveness we had at shorter pulse durations. A diode at the shortest pulse duration attainable with today’s devices is .001 second 1 millisecond = 1000 microseconds. And the pulse interval might be 2 to 10 times (versus 500 times) with a CW laser, and without the energy density (intensity of 1500 watts/pulse) sufficient to do the work desired.
So, when you simplify what’s actually going on with the way in which different lasers output their energy, and the way in which tissues respond to the energy delivery–it’s a lot easier to understand.
Hope that helps a little.
Happy 4th!
Bob
(Edited by Robert Gregg DDS at 5:34 pm on July 4, 2003)
dkimmelSpectatorRon,Bob
You have given me more to think about and soon to follow more questions.
For now they will have to wait. If my wife catches me on logged on today— I am dead. I’ve got to get back to the relatives!
One qick question – Any perticular literature sorces that deal with this?
I hear foot steps!!!!!!
DAvid
Kenneth LukSpectatorDavid,
I’m almost banned from logging on!
I’ pretty good at hearing the faintest advancing movement to my direction! Good Luck!Ron,
you must be able to type with lightening speed OR your wife is very much occupied. Very detailed answers!Ken
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