Dentaltown February 2018 - 43

a broken lower incisor after I finished working on #18. Please provide us with an X-ray. Sorry
about your bad luck! It could have been worse. What if it had injured the eye? ■
11/18/2017

First and foremost. You are doing the right thing for your patient. Bravo.
Back in the day, high speed was friction grip, low speed was latch style. Times have changed,
burs and diamonds have changed with them.
The diameter of the bur or diamond is really important when we spin it at really high rpm.
Do not use large diameter burs and diamonds at high rpm. I promise it will bite your backside
sooner, not later. I will bet a dollar for a doughnut that there is an rpm limit for that big barrel
shaped diamond. That limit is not 200,000rpm. Probably 40,000rpm or 50,000rpm. I have not
taken the time to look it up, I can tell by the pic it is too damn big for high rpm.
Electric handpieces are great. It's also great that with the right electric motor you can go all
friction grip for all your burs and diamonds. Makes inventory simpler, latch burs will someday
be an anachronism. Way back when we needed that D-shaped shaft to keep the chuck from
slipping under high load. That is no longer the case.
Technology and metallurgy have made it possible for a friction grip chuck to "do it all" with
regard to high load.
You the clinician have to be aware of the rpm limits for the instruments employed. The
control for your electric will allow you to set a maximum rpm. You must use the control for the
electric motor to set an rpm limit for the bur or diamond in use.
Do not count on your foot on the rheostat to limit the rpm. It takes a blink of an eye to
cause the bur or diamond to fly apart. And yes, that sucker is hauling ass when it breaks off the
shaft. Be glad it hit a tooth, far preferable to a hole in the patient's cheek. After all it did fracture
a tooth. ■

ricklin
Member Since: 08/19/04
Post: 42 of 127

11/18/2017

Others are saying, "Happens every week" and "I have had hundreds of burs break."
I have had three surgical burs break on me in 25 years and they were all in 1994-1995
when I bought some cheap ones. I might have had another 10 operative burs break and all when
cutting off a crown or sectioning a bridge.
I can't wrap my mind around these other posts about burs breaking all the time
Some of you who have burs breaking all the time, can you enlighten me on how? What are
you doing that causes them to break all the time? ■

drtommymurph
Member Since: 04/05/02
Post: 53 of 127

11/19/2017

F=MA. Wonder if the core is aluminum or steel (which is denser). We could figure the
velocity (and there fore, the force) if we know the weight of the fragment as well as the angular
velocity (simple physics). Finally, a real-world use for physics mechanics. An Excel spread sheet
would be kind of fun.
But a bur head that size compared to a 557 fragment? I bet the force varies exponentially. ■

alanrw
Member Since: 05/16/11
Post: 55 of 127

11/19/2017

It's pretty easy for a diamond to be slightly out of balance, it's the way they are made. The
large diameter instruments must be used at limited rpm.
It's not a manufacturer issue per se, it's those pesky physics. Even the highest quality burs
or diamonds will do the same thing if used above their rpm limits. The cheapo imports will be
more likely to fail. Anything that goes in the mouth should not come from offshore suppliers. In

ricklin
Member Since: 08/19/04
Posts: 56 and 60 of 127

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