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How Many Shields Should There Be On A Dental Bearing?Posted By: Nancy Cogliandro, Marketing Director, PKB (Nancy, pacamor at msn dot com) 07/21/2010
How Many Shields Should There Be On A Dental Bearing? Pacamor Kubar Bearings (PKB) is a ball bearing manufacturer in Troy, NY. We make a wide range of custom bearings. If you want your ball bearing to have 0 or 1 or even 2 shields, we’re happy to make it for you. We have a variety of shield and seal options for many, many unique applications. But, just because we CAN put two shields on a dental bearing, doesn’t necessarily mean that this is the right choice for your dental handpiece. Recently, the PKB team saw an article claiming that 2 shields on a dental handpiece bearing will keep the bearings cleaner than it would be with one shield. This is essentially true on a very basic level. By adding the second shield, contamination should be decreased. But, if you keep things OUT of the bearing by adding a second shield, it stands to reason that you are also keeping things INSIDE the bearing with the same second shield. Things that you might not want to keep in the bearing are WATER and HEAT. HEAT: If a high speed dental bearing with two shields is put in a dental handpiece that was originally designed to have one shield, the shield can rub against mating parts and cause the bearing to overheat. An overheated bearing is likely to result in a melted retainer, burnt grease, and catastrophic failure of the bearing and handpiece. WATER: Proper handpiece maintenance includes sterilization in an autoclave. This is very hot steam that gets into all the parts of the handpiece and sanitizes the dental handpiece between patients. As the handpiece cools, the water condenses. Water droplets form wherever steam was prevented from escaping during the drying process. A bearing with two shields takes much more effort to dry the internal workings than a bearing with one shield. Historically, this is why dental handpiece bearings have just one shield….so the internal parts of the handpiece can dry.
The theory is that a shield is important on the front side to keep debris from getting sucked back into the bearing after high speed operation. But the bearing also needs to be open so that the moisture from autoclave can dry out. Oil and water are a bad mixture inside a ball bearing assembly. A ball bearing that is full of water can have wettability issues (think of driving a car in the pouring rain, tires slip, gain traction, slip again). Bearings can vibrate noisily and no longer run smoothly as the lube gets squeezed out by the water competing for the same small space. After repeated autoclave and poor drying cycles, the bearing can experience premature catastrophic failure. Handpiece manufacturers work closely with ball bearing manufacturers to ensure that we are producing a bearing that will perform optimally in their handpiece. The handpiece manufacturer and the ball bearing manufacturer both have their reputations attached to the quality of the end product.
PKB manufactures a wide range of high speed and slow speed dental handpiece options. Popular ceramic ball upgrades are available for ALL models.
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When a handpiece manufacturer (OEM) wants to discuss alternate shield and seal options for their handpiece design, we are always happy to work with them.