Electric Handpiece Repairs and Maintenance
By: Mike McQueen
On:
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Electric handpieces offer never-ending torque yet require a high initial and continued maintenance cost.
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Manufacturers replace all internal drive parts regardless the problem, causing excessive repair costs, even if only one bearing or water line seal is bad.
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Independent repair centers can do a minor rebuild that involves replacing just the bearings and water line seals for a much lower cost extending the time before a major rebuild is required.
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Costly Gear Repairs, occur when a handpiece is used after the bearings start to breakdown, therefore the shaft no longer rotates on its correct axis putting gears in a bind and causing rapid wear resulting in handpiece failure and high repair costs.
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Coarse burs also cause damage to gears with excessive vibration which is not a problem in air driven highspeed handpieces because of feathering. But in the electric highspeed the added torque available allows the user to keep the bur in constant contact with the tooth surface. The vibration caused by the coarse bur is transmitted directly back to the bearings causing rapid bearing failure. Therefore eventual gear damage.
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To extend the life of electric handpieces, make sure you have enough drive air pressure used to cool the motor and the attachment. Consult the manufacturer's recommendation for proper PSI settings. We recommend having at least 65 PSI at the dental unit.
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In addition, be sure to use as much Chip Air and Water while the handpiece is in use to cool the bearings within the head prolonging the bearings life span.
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STOP using your electric handpiece as soon as you feel an unusual vibration or unusual noise begin. This could save you hundreds of dollars in repairs.
Minimize your Electric Handpiece Repair Costs by:
- Using fine to medium burs
- Running the manufacturers PSI air settings
- Using as much Chip Air and Water as possible
- Seeking a minor rebuild as soon as there is any problem
Mike McQueen - Dentool in Colorado Springs
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Glossary of Dental Handpiece Terms
By: Steve Aucremann
On:
Air Motor – A slow speed handpiece without internal reduction gears or attachments, usually rotating at speeds near 20,000 rpm.
Attachment – a nose cone or angle that quick disconnects on and off the front of a low speed motor to provide various bur holding options.
Auto Chuck – A mechanism enabling the operator to change a bur without the use of a wrench, by pressing a button or raising a lever.
Autoclave – A steam sterilizer which destroys all living organisms through the medium of heat and pressure. Temperatures are raised to 270-275°F while the pressure is raised to 30 psi.
Bur – A rotary dental instrument, which when placed in a handpiece is used to cut or carve tooth structure. Burs come in a variety of shapes and sizes and can be made of high speed steel, carbide, or diamond coated material.
Canister Turbine – A closed cylinder which houses a rotating turbine assembly inside the head of the handpiece. Designed for easy replacement.
Chemiclave – A sterilizer which uses a chemical to generate chamber pressure instead of steam. The absence of water in the process reduces rust and oxidation of instruments.
Chip Air – Air supplied through the handpiece from the dental unit tubing to the cutting surface to cool the tooth or disperse the water spray, while flushing away residual material resulting from the removal of tooth structure. In a High Speed electric attachment the chip air is also an important source of cooling for the head of the attachment.
Chuck – The part in the handpiece turbine used to hold the bur.
Collet – Another word for the chuck, generally refers to part of the chuck that actually grips the bur.
Connector – Attaches the handpiece to the dental delivery unit that supplies air and water to the handpiece. There are four types of standard U.S. connectors. They include the 2, or 3-Line (also called a Borden) and 4-Line. The 4-Line (also known as a Midwest) is the most popular connector. In a 4-Line connector, the holes are (1) drive air, (2) chip air, (3) water, and (4) exhaust. Sometimes a fifth line or hole is added for a fiber optic bundle. A newer type of connector, 6 Pin, is now available which provides
an electrical connection for a fiber optic light bulb. Hole size and location are indicated by a standardized ISO specification.
Contra Angle – The front section of a handpiece which changes the desired angle to provide better bur access and visibility to the operator during use.
Coolant – Refers to the water and air spray directed at the bur to cool the tooth when cutting. Doriot handpiece - Often used to refer to the handpiece for a belt drive but it actually refers to any handpiece motor that accepts a standard 3/32 bur shank or an angle or attachment which slides on to the nosecone and has the 3/32 shaft that fits into the chuck.
Doriot or Universal Angle –Any angle that operates on the front of a nose cone that has a protruding shaft designed to fit into the nose cone chuck.
Drive Air – The compressed air used to rotate the turbine or vain motor in a dental handpiece. In the Electric operatory motor the drive air pressure controls the RPM of the motor and provides cooling to the motor.
Electric lab Handpiece – Hand held electric motor that takes 3/32 shank burs used in a lab for trimming and grinding. They operate at maximum speeds from 25k to 50k RPM and are either a brush motor that runs off DC current or a brushless motor which runs off a 3 phase signal.
Electric operatory motor – These electric powered motors are normally attached to the dental unit in the place of a Highspeed handpiece and can drive a variety of attachments that that achieve different speeds at the bur by a system of gears to step up or step down the speed of the motor. “E” Type Motor – A motor with a standardized male connection (ISO standard) that accepts attachments with the matching female connection.
End Cap – The cap or cover which is removed to install the turbine may also contain the button or lever to actuate the chuck.
Exhaust – The air discharged from a dental handpiece after spinning the turbine. Fiber Optic Handpiece – A handpiece through which a transparent fiber or glass rod optic bundle transmits light to illuminate the area around the bur.
Friction Grip Chuck – A chuck which holds the bur strictly by friction generated from an internal spring assembly. The bur is simply pushed in and out of the chuck with a special tool using force to overcome friction.
Handpiece – A handheld device which engages rotary instruments for cutting, cleaning or polishing the teeth. A handpiece can be belt-driven, pneumatic (air or gas driven) or electric.
High Speed Handpiece – A handpiece which operates at a speed greater than 50,000 RPM.
Jacobs Chuck – A mechanism which utilizes a wrench to tighten the chuck. This design incorporates slots which create jaws that are compressed onto the bur shank when tightened with the corresponding wrench.
Latch Angle – An attachment that holds a specialized bur which is mechanically retained by the use of a swinging hook that engages a recess in the bur shank.
Low Speed Handpiece (or Slow Speed) – A handpiece which operates at speeds ranging from 5,000 to 40,000 rpm.
Lubricant or Oil – A liquid applied to moving parts of a handpiece or attachment in order to reduce friction, heat, or wear, or applied to surfaces in close contact to prevent them adhering to one another. May also include a solvent for cleaning.
Nosecone – A straight attachment used with a slow speed motor which holds a lab type bur (3/32” shank) or any standard doriot attachment.
Prophy Angle – An angle that holds a brush or cup containing prophy paste used by a hygienist for cleaning teeth.
Quick-Disconnect – A handpiece attachment or fitting designed to allow easy separation of the handpiece from the supply tubing.
Replacement Cartridge – Another name for a high speed turbine, usually self-contained to allow easy replacement.
Rotary Vane Motor – A type of low speed motor utilizing small vanes instead of a turbine to trap drive air in a rotor assembly to generate rotation.
R.P.M. – Revolutions Per Minute. A unit of measurement indicating speed.
Straight Handpiece – Same as a low or slow speed handpiece. Often refers to a handpiece with a nosecone permanently “fixed” to the motor.
Swivel – Instead of threads at the rear of a handpiece, the swivel is usually a separate part that threads into the supply tubing and incorporates a quick disconnect. Designed to allow the handpiece to rotate where it attaches to the air supply tubing in order to reduce fatigue on the operators wrist.
Turbine – Located in the head of a high speed handpiece, the turbine holds the bur or cutting instrument while rotating from high pressure compressed air. A turbine consists of five components: spindle; chuck; impeller; bearings; and two “O” rings
Our Thanks Joe Pellegrino of Superior Handpiece Service who created the original list.
http://www.superiorhandpiece.com/terminology.html
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Copeland Air Compressors
By: Steve Aucremann
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Last year we were able to purchase several core compressors which has dramatically increased our production of rebuilt compressors. It has also come to my attention that some of our dealers don't know we do this. So I need to make two important announcements:
We sell rebuilt exchange Copeland 1hp compressor heads!
We buy your old Copeland 1hp heads!
Now that I've got that out of my system let me give you a few tips about dealing with compressors. When a Doctor calls and says "I DON'T HAVE ANY AIR" it’s a bad thing. The air compressor is the heart if the dental office without it, everything stops. The best thing is to be proactive and catch a problem before it becomes a crisis. You should make yourself a check list:
- Check the oil level (if it has oil) it should be at least the middle of the sight glass and not over the top. Sometimes the sight glass is stained so always jiggle or shake the head to see the oil moving before you decide if it is OK or needs more oil. Most manufacturers recommend checking the oil every week I would say never less than every month.
- Listen for knocking noises or leaking sounds, while the compressor is on and the office is working is the best but you may have to do this after hours. You want to pay attention to the run time because you want the compressor to be off longer than it is on while the office is working. If it runs all the time or cycles very quickly check the compressor system and the office for leaks. If a problem seems to exist and it is a twin or triple head run each head separately to see if only one head needs work.
- Drain the tank if it has any water in it you should check the air-drier to make sure it is working properly.
- If you find that a head only hums then clicks off, hum click, hum click, then you should check a few things. First (after making sure the power is off) check the oil again, without oil the crank shaft could have seized. The best way to check this is to drain the oil and see if it has any metal in it, (if it does that is probably ground up piston rod) If you still are not sure then take the rear cover off (that's the big round end with 14 half inch bolts) and see if the rotor turns freely. If all that seems OK then check the resistance of the winding by taking off the top electrical cover and check the resistance between R and S which should be between 5 and 8 ohms. If it is much over or under that the motor might be bad.
- If you determine that a head should be good, then check the components in the start box which should have a potential relay, a start capacitor and a run capacitor the easy way to test these is by replacing them. Often you can find these locally from an appliance or refrigeration supply.
- A few final notes, these things are heavy (85 -100Lb), and they are often dirty and oily, be prepared. If you need to replace one get the voltage from the name plate typically 115, 230, or 208-230 and make sure it is 1Hp.
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Stainless Steel and Microbial Erosion
By: Steve Aucremann
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Sonix 4 Corporation uses stainless steel in manufacturing the industry's leading ultrasonic cleaning systems. As such it is important for our customers to have some level of education in regards to the makeup of stainless steel which will ultimately say something about the integrity of the metal when in the working environment.
Over time some users may have noticed the creation of holes within the stainless steel tank. These holes, or pits, can cause serious problems once moisture is allowed to leak into the electronic components of the ultrasonic unit. Once a pit is created, and the unit is run for any period of time, we can expect the hole to exponentially increase in size. This is due to the powerful cavitations that occur when a Sonix 4 ultrasonic unit is in operation. So the question that becomes important is, "How can I prevent pits from being created in the first place?"
The answer comes from the knowledge of the chemical makeup of stainless steel, and the dangers that the working environment can introduce into the ultrasonic tank. Stainless steel differs from carbon steel in the fact that it contains more Chromium. Carbon steel will corrode when it comes in contact with the air and moisture due to the active film of iron oxide (Fe(OH)3), or rust, on the surface. Stainless steel with Chromium is resistant to, but not free of this reaction. There is an active film of Chromium oxide (Cr(OH)3) on the surface of stainless steel, and this active film causes concern when in the working environment. In the instruction manual that accompanies the Sonix 4 product there is a list of solutions known to be harmful to the stainless steel tank due to their low pH, or acidic content. The easiest way to think about the reaction that happens to the surface of the stainless steel is with the net ionic equation of any acid base H20).óreaction (H+ + OH- From this equation we can see that the addition of any acid onto the basic surface (due to active film of chromium oxide) of stainless steel will indeed react. The product of the reaction can be visually seen over a period of time in the form of holes, or pits, in the tank.
There is yet another way that acid can be introduced into the tank other than direct addition of acidic solution. They way to think about this is cavities in your teeth. We spend lots of money and time cleaning our teeth to keep them free of bacteria because bacteria produce acids which will react with tooth enamel (Ca5(PO4)3(OH)). This is the basis for the Sonix 4 recommendation that regular cleaning maintenance is necessary to prolong the life of the ultrasonic tank. If the unit is used to sterilize, but is not cleaned after use then there are microscopic bacteria hard at work producing acid solution that will react with the stainless steel creating microbial erosion of the tank. Over time this microscopic process becomes more and more visible as the holes get larger. Furthermore, as stated earlier, once the smallest amount of erosion has occurred the ultrasonic cavitations will be cannibalistic in that they will aid in the rapid erosion of the ultrasonic tank.
So, in summary, "How can I prevent pits from being created in my ultrasonic tank?" Prevention primarily comes from the regular cleaning maintenance of the ultrasonic tank after use. The list of solutions not to be used in Sonix 4 ultrasonic units (Instruction Manual) should also be consulted.
Used by permission from Sonix IV
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Setting the Bur
By: Steve Aucremann
On:
Setting the bur is a simple step in installing a high speed bur in a handpiece which causes the chuck to grip the bur more securely. It requires putting slight pressure on the end of the bur after releasing the button on the handpiece. Any friction grip chuck with a button or a lever (does not apply to manual chucks) will benefit from this procedure but Star Dental has put this step in their "Handpiece maintenance PDF" (see the quote below). This will improve the bur retention and increase the life of the chuck by reducing wear.
Proper Bur Placement to prevent bur walkout
- Insert bur into the autochuck until resistance is felt.
- Depress autochuck end cap button and continue to feed-in bur until it clicks and stops.
- Release end cap button.
- Apply light inward force to the dental bur. This will help set the chucking mechanism for initial start up.
- Always tug on the bur after it has been installed to confirm that it is secured.
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Assistina Again
By: Steve Aucremann
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Many of you have commented on the usefulness of the "Assistina how does this thing work" and the "What you should know about highspeed electric handpieces" articles in a past issues. Thanks for the positive feedback. As a result of our conversations, we want to share some new information about both. The issue came up that an office using an Assistina to clean and lube their Kavo 25-LPA was having a high failure rate. As a result, we did some testing and we found, when we put a high speed attachment in the Assistina and ran it for one cycle there was no evidence that the oil had reached the head of the handpiece. It took at least 2 cycles to adequately lubricate and clean the attachment. All of this makes perfect sense when you look at the difference between the air driven high speed and high speed electric attachment (see illustration below).
In the air driven handpiece the air and oil from the Assistina goes directly through the drive air tube to the turbine bearings (of which there are only 2). However in the high speed attachment. The oil and air enter the body of the attachment where it must spread over 6 or more bearings, as well as gears, springs, and drive shafts before it can do its job. The obvious solution is to use multiple cycles to add more lubricant. The Assistina delivers approximately 1cc of oil into the air line when the button is released. If you press and release the button 3 times you have only used 3cc of lubrication which is a small price to pay for a longer lasting attachment. I hope this information will help you and your customers to get a better result from their equipment and your repairs.
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Assistina
By: Steve Aucremann
On:
As you know handpiece lubrication is the key to bearing life and handpiece performance. Many of your customers may use the Assistina and it will help you to know how this unit works. First of all, the cleaner on the right side is primarily alcohol and is used to clean and disinfect the water line in the handpiece - it has no effect on the turbine or bearings. The oil on the left side is injected into the drive air with the exhaust blocked off, so that it is forced through the turbine and the bearings, and out the back cap and around the chuck opening by a blast of air which lasts about 30 seconds. This forces out any debris and leaves a film of oil to lubricate the bearings.
The Assistina operates like this. With a hand piece in the Assistina and the proper fluids in the reservoirs you press the start button holding it down for 2 seconds then release. When you press the button a 2 chambered pump is activated, pushing a small amount of cleaner up to the water line of the handpiece. The air you hear is blowing the cleaner through and out of the handpiece. When you release the button, the second chamber of the pump pushes the oil into the drive air line *(the reason you hold the button for 2 seconds is because the oil is thick and needs time to draw into the pump chamber). Again the air is blowing the oil through the handpiece to force out any debris and leaving behind a film of oil to lubricate it.
The primary problems happen here. When the air is pushing the oil out through the bearings it is also pushing back against the oil in the tube coming from the pump and if there is any leaking along the line it pushes back the oil so the next time there is no oil at the end of the line to lubricate the handpiece. Now the Doctor thinks he has lubricated the handpiece, but he hasn't. Usually this goes on till the Doctor says that the bearings you just put in aren't lasting long enough. I think you should be pro-active, and check the Assistina for proper operation before you repair the handpieces.
Here is the easy way to test the unit. Take off any attachments or adapters so you can see what looks like a standard e-type connector inside the Assistina. First, look to see that it has 2 o-rings in good condition. Shine a flash light on the connector and press the start button. You should see the burst of cleaner spray down from the connector. When you release the button then you should see a mist or fog of oil. if these are not present close the cover and press the button repeatedly until you can see the green indicator balls popping up - the right one when you press and the left one when you release the button. Now repeat the first test, if it still is not pumping properly, it needs repair. If it works then go away for 30 min. then come back and test it again (sometimes it leaks very slowly). If the unit is working properly then you will get the same burst of fluids every time. If the Assistina is not working just send it to us, we can fix it.
* I am told by by technicians in the field that not holding the button for 2 seconds is the leading causes of malfunction.
Here are a few more tips and tricks.
- You really can't over-lubricate so tell the Doctor to push the button 2 or 3 times if he is not sure enough oil is coming out.
- Many times people put the wrong liquids in the unit I have even seen things like bio-cide and film developer in these units which can be very bad. Open the chambers and check the fluids for contamination.
- The Assistina also lubricates e-type attachments and has a turbine and drive-dog to turn the attachment while the oil is being blown through. Pressing the start button multiple times is always a good idea for these.
- W&H makes many different adaptors for different handpieces. Be sure they have all the proper o-rings.
- Always use the proper lubricant in the Assistina. The viscosity of the oil is key to the proper function of the unit.
Assistina is a registered Trademark of A-dec Inc. manufactured by W&H Dentalwerk (Austria) and imported and distributed in the United States by A-dec. These comments are from our own experience and not necessarily the opinion of A-dec or W&H.
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High Speed Electric Handpieces
By: Phil Leinbach, President of Florida Dental Repair
On:
Electric high speed handpieces are a great innovation. Unlike the air driven highspeed, they offer infinite torque over the entire RPM range of the handpiece. This allows the dentist to reduce chair time per patient and make more money.
The downside is the initial and maintenance costs are high. A typical factory rebuild could easily be over $500. Almost all of the parts are proprietary and manufacturers do not openly sell these parts which makes it very expensive for the independent dealers like us to get parts and repair these handpieces. Because of this, it is difficult for Independents to compete with factory repair centers on a major rebuild.
When the manufacturer rebuilds one of these handpieces they unconditionally replace the spindle cartridge and drive shaft assemblies even if only one bearing is bad. We independents can do a minor rebuild that involves replacing just the bearings and water line seals for a much lower cost. This gives the customer a good value by extending the time before a major rebuild is required. In order to do that, we have set guidelines for determining what gears can be reused and which ones must be replaced.
Why do gears go bad? Usually because dentists continue to use there handpieces after the bearings have gone bad and/or they use of burrs that are too course. If the shafts rotate on their correct axis the wear to a gear is minimal since the geometry of that gear is designed for that axis. Under ideal conditions, when the teeth of gears mesh, they push against one another and do not rub. When a bearing wears the shaft no longer rotates on its correct axis which causes gears to rub against each other and hastens their demise. Coarse burrs cause excess vibration which is not a problem in air driven highspeed handpieces because of feathering, but in the electric highspeed the added torque available allows the dentist to keep the burr in constant contact with the tooth surface. The vibration caused by the coarse burr is transmitted directly back to the bearings.
Another way to help your customer extend the life of their electric highspeed is to make sure they have enough drive air pressure. The drive air is not used to drive the handpiece but it is used to cool the motor and the attachment. It is always best to consult the manufacturer's recommendation before setting the drive air pressure. Some manufacturers sell a flow-meter that attaches to the handpiece for setting the drive air pressure. This is the most accurate way to set the pressure because it is air flow that provides the cooling. We recommend having at least 65psi at the dental unit.
The following pictures show the life span of a gear and what is deemed usable and unusable. 
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