Ceramic bearing technology enables dental drills to last 2.5 times longer

The Barden Corporation's 25 years (plus) experience of developing high-speed dental turbine handpiece bearings has resulted in the introduction of hybrid ceramic bearings, which operate at speeds up to 500,000rpm. These bearings are revolutionising the performance of dental handpieces in terms of improved life, which has been increased by a factor of 2.5; reduced losses at handpiece build (below 1% with some customers), and reduced returns under warranty.

On a scale of precision bearing applications, high-speed turbine bearings for dental handpieces must be one of the most arduous. In addition to the requirement to operate at speeds up to 500,000 rpm (or 8,333 revs/sec!), repeated sterilisation of the handpiece and the depletion of lubricant can cause the bearing to fail more quickly than expected.

One of the latest initiatives undertaken by Barden to address these adverse operating conditions is the development of miniature bearings employing ceramic (Silicon Nitride) balls. The advantages of using ceramic balls in high-speed precision applications such as machine tool spindles have been known for some time. Barden was keen to prove whether or not these same advantages would apply equally to dental bearings. To achieve this the company undertook a comprehensive testing programme in its dedicated dental test laboratory. The programme was designed to reproduce the tough operating regime of dental bearings in actual use. This was achieved and over time the results proved to be extremely favourable. Armed with this positive test data, Barden took the decision to extend the use of ceramic balls to dental bearings and subsequently manufactured its first production batches.

The advantages resulting from this development are many. Firstly, because ceramic balls are 50% lighter than steel balls the centrifugal forces generated at operating speeds up to 500,000 rpm in a Dental Turbine are significantly reduced, giving lower stress levels and operating temperatures in the ball to race rolling contact zone.

Secondly, the unique properties of silicon nitride ceramic balls drastically reduce the predominant cause of raceway surface wear. In conventional bearings microscopic surface asperities on the balls and races will "cold weld" or stick together even under normal lubrication and load conditions, resulting in wear particles remaining in the bearing rolling contact zone. This results in adhesive wear.

Thirdly, lubricant life is increased using ceramic balls, mainly because less wear particles are produced and held in the rolling contact zone. These particles cause the lubricant to degrade particularly under the marginal lubricant condition that often exists in dental bearings from repeated sterilisation and the build up of debris.

Finally, cage to ball loads are significantly reduced with ceramic balls, under the conditions of outer ring misalignment, that exist, to some degree, in the majority of dental bearings mounted in O rings. As a result, stress on the bearing cage is lower and wear on the ball pocket and cage outside diameter are reduced. These factors are particularly beneficial in prolonging bearing life under repeated Autoclave and Chemclave sterilisation processes, both of which reduce bearing cage strength.

All of the above advantages - first supported by test data in the laboratory, have subsequently been validated with extensive field experience. As a result, Barden is now supplying production quantities of the "hybrid" (i.e. ceramic balled) deep groove and angular contact bearings to major dental bearing customers in both the OEM and repair market sectors.

About The Author:

Mark Harris is a successful author and regular contributor to http://www.bearing-n-bearings.com. Keep things running smoothly with ball bearings, roller bearings, ball thrust bearings and tapered bearings.