I read your article about the new electric dental drill (DN 01.08.02). While the new dental electric handpieces have high torque, they actually run considerably slower than their air-driven cousins. Say 160,000 RPM vs. 350-400,000 RPM. That means more perceptible vibration to the patient. This comes as feeling and noise. Noise almost as aggravating as the old air turbines. Plus vibration.
The electrics are pretty horrendous on maintenance. And, without warning, they can heat up big time. They can get almost red hot in literally seconds, leading to some rather nasty lip and palate burns.
And, contrary to your suggestions, they are far from "painless." Injections for treatment are definitely called for when using either type of handpiece.
Best regards
William C. Domb, DMD, Upland CA
Editor's note: William Domb, DMD is a general dentist from Upland, using electric handpieces for the last two years and says he cannot remember a single day when they have not had one sort of problem or another. We appreciate his input.
Regarding your recent editorial on stout pouring technology (DN Editorial 04.08.02), I recently opened a bottle of English beer. I think it was Guinness and there was a plastic thing inside resembling a rocket. If they wanted me to stop buying English beer (as I have), all they had to do was send me an e-mail. It would have been more environmentally safe. The only thing I want in my beer is bubbles.
The nerve of them to mess with Guinness! I also wasn't aware that they were owned by the British, that sounds like a possible conflict of interest.
It was a very interesting and enjoyable editorial, even if I wasn't a big fan of Guinness Stout, and I look forward to your follow-up. It's articles like these that make Design News the most interesting magazine in the engineering field.
By the way, in my younger days I had a Jaguar, and enjoyed working on it all week so that I could drive it on Sunday.
I did not see the movie "A Beautiful Mind" and I didn't know it was based on a true story (DN Editorial 03.25.02). You've sparked my interest to read about John Nash. I've been in manufacturing for almost 12 years. For 9 of those years I've been in maintenance, in some form or another. I'm currently going to college for an electrical/electronics degree. I wish I'd done this years ago.
I just thought I'd drop a couple of lines to let you know that I enjoy your editorials and your clothes are cool, too. The camo dress was my favorite.
The excellent article about lights ("Car headlights get on the level" DN 03.11.02) did not mention another reason for being blinded by lights of oncoming cars and by cars following you (their lights being reflected in the rear-view mirror): the height of headlights above the road. Back in the good old days, all cars were about the same size, thus headlights were BELOW the driver's eye level. Highway dividers were built to match the headlight height, blocking the glare of the oncoming cars.
Now, in the age of SUVs, large vans, etc., things are getting out of hand; unless you are driving one of those, you are guaranteed to be blinded by lights of the oncoming cars and by lights of cars behind you, reflected in the rear-view and side-view mirrors.
This situation cannot be corrected, unless ALL NEW CARS are built with headlights on the same height above the ground. But what about the OLD CARS already on the road?
Editor's note: A reader questioned the following statement in the 03.25.02 Z Files column: "If a car is struck from the rear, unconstrained occupants would be accelerated toward the rear of the car until impacting car structures accelerated them forward." Zirkle clarifies the statement: Although the statement is counter-intuitive, it is correct. What may be confusing to you is the concept of relative motion. The passengers are in fact accelerated backward "with respect to the car" until something restrains their motion. Think about standing on a hay wagon. If someone gave it a pull forward or a push from the rear, which way do you fall? Not off the front. You fall off the back. The reason is Newton's law (paraphrased), "a body at rest tends to stay at rest until acted upon by an unbalanced force". You tend to stay where you are as the trailer moves off, so you fall off the back as the trailer moves forward. Because of the friction on your feet, you would move forward slightly with respect to the ground, but you move backwards with respect to the trailer. It works the same in a car except you are in a "box." Of course, the secondary reaction is forward after you bounce off the seatback toward the front.
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