Hey Ken

Don’t think our banks aren’t robbing us on a daily basis!
Just a personal observation from looking at the Fontona web site and pictures of their laser. It seems that they are modeling their dental laser after their skin lasers at least in the design of the mirror articulating arm. I don’t think that would be an easy system to use in the oral cavity but as I have never used one I may have something to learn there.

Hi Ken,

Sorry I couldn’t reply in detail earlier.  Lots of catch up work after the AAP meeting and training on the weekend……

Just a few calculations and comments to establish some basic understandings.

According to Fotona and Manni, the Pulse Durations for the Fidelis are 100, 300, 750, 1000.  There is no actual PD of 80 usec.  For the VSP (100 usec is the “nominal” PD +/- 20% = 80 to 120 usec).  

If it is a true Square pulse electronic design, then the pulse duration can be accurately generated to the desired pulse width.  The fact that they are reporting a nominal (average) range is either that they can’t hold the power in “simmer” on the capacitor, or their IGBT switch (for keeping the PD shape “square” ) is not adequate, or they are trying to patronize, market or confuse folks.

I mean, what’s the point of calling it “VSP”, “SP”, “LP”, and “VLP”?  Can’t they just tell us the actual values are and let us learn the parameters?

Their laser can go as low as 80 millijoules per pulse all the way to 1000 mj/p or 10 Watts of average power at 10 Hz.

From your post Ken:

Enamel – Very Short Pulse (100 usec) 400mj and 10hz = 4000 watts of peak power

Dentine – Short Pulse (300 usec) 300mj and 10hz = 1000 watts of peak power

Caries – Short Pulse (300 usec) 120 – 220mj (1.2 – 2.2 Watts) at 10 Hz which = 1.8 – 3.3 watts at 15hz = 400 – 733 watts/pulse @ 10 Hz and at 15 Hz

Bone – Very Short Pulse (100 usec) 200 – 400mj (2 to 4 watts) and 10hz = 2000 to 4000 w/p

Soft Tissue – Long Pulse (750) 100-200mj and 15 – 20hz

Very Short Pulse (80-120 ms/pulse)  It’s really 100 usec “on average”.
Short Pulse (250 ms/pulse)
Long Pulse (750 microseconds)
Very Long Pulse (1000 microseconds)

From their website:

“The removal of the organic debris in the fissure is achieved at lower energies ( 100 mJ) and the retentive surface is obtained. ENERGY: 60 – 160 mJ,  FREQ: 5 – 10 Hz,  PULSEWIDTH: SP”, (300 usec) = 333 watts/pulse.

Let’s look at the Fotona

100 usec Pulse Duration at 10 Hz and 3.0 watts Ave. Power
750 usec Pulse Duration at 10 Hz and 3.0 watts Ave. Power
1000 usec Pulse Duration at 10 Hz and 3.0 watts Ave. Power

Fidelis Pulse Duation = 100 microseconds
Average Power (Consol setting) (3.00 W) divided by
Repitition Rate ( 10 Hz)  divided by
Pulse Duration 100 usec (.000100) {10-6 sec} =
Peak Power/Pulse        (3000 W/pulse)

Fidelis  Pulse Duration = 750 microseconds
Average Power (3.00 W) divided by
Repitition Rate ( 10 Hz)  divided by
Pulse Duration 750 usec (.000750) {10-6 sec} =
Peak Power/Pulse        (400 W/pulse)

Fidelis Pulse Duation = 1000 microseconds
Average Power (Consol setting) (3.00 W) divided by
Repitition Rate ( 10 Hz)  divided by
Pulse Duration 1000 usec (.0010000) {10-6 sec} =
Peak Power/Pulse        (300 W/pulse)

Let’s look at the Fotona at 20 Hz (same settings)

100 usec Pulse Duration at 20 Hz and 3.0 watts Ave. Power
750 usec Pulse Duration at 20 Hz and 3.0 watts Ave. Power
1000 usec Pulse Duration at 20 Hz and 3.0 watts Ave. Power

Fidelis Pulse Duation = 100 microseconds
Average Power (Consol setting) (3.00 W) divided by
Repitition Rate ( 20 Hz)  divided by
Pulse Duration 100 usec (.000100) {10-6 sec} =
Peak Power/Pulse        (1500 W/pulse)

Fidelis  Pulse Duration = 750 microseconds
Average Power (3.00 W) divided by
Repitition Rate ( 20 Hz)  divided by
Pulse Duration 750 usec (.000750) {10-6 sec} =
Peak Power/Pulse        (200 W/pulse)

Fidelis Pulse Duation = 1000 microseconds
Average Power (Consol setting) (3.00 W) divided by
Repitition Rate ( 20 Hz)  divided by
Pulse Duration 1000 usec (.0010000) {10-6 sec} =
Peak Power/Pulse        (150 W/pulse)

So doubling the Hertz at the same setting, reduces Peak Power by 50%.

How about 3.20 Watts, 8 Hz at 1000 usec = 400 Watts/pulse

Or the enamel study comparing 500 mj/p (5 Watts), 10 Hz and 20 Hz.  For the VSP (100 usec “nominal” or average: PD +/- 20% = 80 to 120 usec) the peak power would be 5000 Watts per pulse versus 2000 watts per pulse.  No wonder the “VSP” is more “efficient”!!

So basically, the short pulse durations would be used on enamel, the long pulse durations would be used on soft tissue and for superficial hemostasis and the tissue response for say 1000 usec, 3.00 watts and 20 Hz would be like a CO2 in having better hemostasis than an erbium at 200-400 usec.

Having reviewed all that mathematically, let me say as a clinican, I want choices in my laser parameters!  And for me these days, that means I want user variable/selectable pulse durations, that I can combine with Hertz and millijoules per pulse to control the rate and depth of my free-running pulsed neodymium or erbium photothermalysis.

So I think Fotona is on the right track.  The next generation of erbium lasers will allow user operator parameters to extend the range of tissue interactions.  They will be digitally controlled, smaller, and more efficient.

As far as the waveguide goes, I’ve found that as long as the length is sufficient, these work just fine.  They have different pluses and minuses than a fiber deliver system, but nothing insurmountable.

I’d like to check one out sometime…..

Cheers,

Bob

Thanks Ken,

My point in posting those different calculations is to show that by varying the pulse duration, and alternatively adjusting the Hz, and the mj/p you can vary these parameters and at different settings and get the same Peak Powers.

Then, if one varies the parameters at the extreme settings one gets some intense interactions like at 100 usec, 500 mj/p, 10 Hz = 5,000 watts per pulse.

Now I’m not recommending those parameters for use on teeth, but I like having the range of parameters available for me as the operator to select, not defaults that are factory set.

So, yes, in that sense the Fidelis is very similar to the PerioLase MVP-7, though the MVP-7 has 3 more digital pulse durations even still.

Here’s a graphic comparing Analog and Digital pulse durations, as it might appear on a digital oscilloscope.  Because these are measured in an X/Y axis or relationship, it is often referred to as Pulse “Width” from the perspective of someone reading the scope and measuring the “width” of the display, which in turn is measuring the time on the horizontal axis of the scope.  That’s why there are different terms for the same thing–pulse duration, pulse width, pulse length, pulse time all refer to the time the pulse is on.

The Gausian or Bell shaped Analog pulse “shape” (Green line) that is the dominate form of free-running pulse configurations in the dental market today.  It is also known as a Pulse Forming Network (I don’t remember why).

The Digital or Square shaped Digital pulse (Red line) is new to dentistry, though it has been around in the medical world for many years.  In fact, as far as we can tell, the PerioLase MVP-7 was the first digital (or square pulse) dental laser in the world.  At least as far as Lexis Nexis reports.

The area under the curve representing the pulse duration shows more of the useable energy in the pulse is available in the digital pulse shape.  As measured, the digital pulse is about 20% more efficient per pulse than a similar analog pulse.  10% more efficiency or power is captured on each side of the “curve” where it is cut off and included in the digital pulse.

Does that make a clinical difference?  I don’t know, and I don’t have any research or clinical data to support that.   At first I didn’t think I saw any difference using a digital pulse.  Then I went back to an analog for a case or two and then I wasn’t so sure.  I need to do some comparison tests with the two when I get some time.

I am anxious for the digital technology to be incorporated into erbium based systems as it will reduce size and weight, improve efficiencies, cost less to maintain, be more optically stable, while at the same time increase the number and range of parameters available to the clinician for spectific Tx objectives, not yet possible with single pulse duration devices.

Good questions Ken!

Thanks,

Bob

Hi Ken,

Thanks for the kind words and your support.

Yes, with the freedom to change parameters, training becomes essential.  But with proper training, the extended range give optimal clinical control in the right circumstances.

With the Periolase MVP-7 or the Fidelis, one can vary the parameters and still maintain a long thermal relaxation time in the tissues.

For example:

At 10 Hz, there are 100,000 mirosecond in a second.

Let’s then select a PD of 100 usec.  The pulse is “On” for 100 of the 100,000 microseconds, then the “off” time is 99,900 usec.

Wow, that’s a long time off.  Remaining tissue appreciates that.  But that has to be offset by the power density and Peak powers and adjusted accordingly.

Part of the problem to manage comes from the science that Eric Bornstein has discussed frequently–thermal conseqences of pulse stacking.  That’s where you allow the pulses to hit the tissue in the same place, and allow the effects–vaporization and thermal diffusion (lateral thermal warming) to build up.

If your thermal relaxation interval (aka “pulse interval” ) is too short for the physical properties of the substrate tissues (say 50 Hz versus 20Hz), then damage is easier to occur.  

Continuous Wave lasers and gated pulsed lasers in the millisecond range don’t have much, if any thermal relaxation (pulse interval) time.  They are pretty much always “on” as far as the tissue is concerned.

And you are correct, this pulse durationrep rate variation applies to the free-running nature of erbium lasers in the dental market today, except for lasers fixed at 20 Hz.

When you think about absorption in water, the “very long pulse” of the Fidelis at 1000 usec w/o water should be very much like CO2 in tissue response.

Yes, the Fidelis sounds like it is digital if they are marketing it as a “Square” pulsed laser.  It’s not that hard to do, since the technology to create square pulses has been around in medical for a while.

To make a digital laser one needs to scrap the analog device, and start from scratch using digital components, capacitors and switches.  The parts needed to make a digital laser are about 2/3 less than an analog laser.  So no need to even keep the old “box”.

Bob

(Edited by Robert Gregg DDS at 10:17 pm on Sep. 30, 2003)

Oops!  Typo….

That should have read 99,900 thermal relaxation time NOT 90,900 at 10 Hz and 100 usec.

For 1 Hz at 100 usec = 999,900 usec off.

As far as the fiber question, I’m not sure what you are asking.  Do you mean for erbiums at 100 usec or neodymium.

Hi Ken,

Yes 1 second = 1 million microseconds = 1,000,000 usec

No, the fiber needed to deliver the erbium wavelength that is used in dentistry will not transmitt through the quartz fibers we use in our near IR, even though they can transmitt the 100 usec in the MVP-7

The pulse energies in an erbium fiber (no water or OH) are part of the consideration when designing a system.

That’s probably why Fotona went with a waveguide for those short PD’s, but tha’s just a guess.

Bob

Hi Ken,

Yes.

Bob