1. What are the design differences between radial and angular

contact ball bearings?

The main difference between radial ball bearings (fig. 1) and angular

contact ball bearings (fig. 2) is the retainer type: radial bearings include

a crown retainer (fig. 1) whereas angular contact bearings include a full

retainer (fig. 2).

2. What are the benefits of radial and angular contact ball bearings?

Which design offers better performance and longer life?

Radial ball bearings (fig. 1) are more convenient to use because they

may be installed and axially loaded from either side.

Angular contact ball bearings (fig. 2) perform better at higher speeds

and operate longer, on average, than radial bearings. Angular contact

bearings can only be axially loaded from one side.

Keep in mind that bearing life can be significantly impacted by other

factors, like whether or not your customers follow appropriate maintenance

protocols, use a quality cleaner/lubricant, or avoid immersing

their handpieces in aggressive or corrosive cleaning chemicals.

3. What is the difference between a ball bearing manufactured with

a phenolic retainer and one manufactured with a Torlon® retainer?

Phenolic (fig. 1) is a porous material that may be impregnated with oil

at the factory. During operation, a phenolic retainer provides continuous

bearing lubrication by releasing micro-droplets of oil contained within

its body.

Torlon® (fig. 2) is not porous and cannot be impregnated with oil.

However, it contains solid lubricating additives, like graphite and

Teflon®, which help to lubricate a dental bearing during conditions of

conventional-lube starvation. Torlon® handles autoclave sterilization

much better than phenolic, which has a tendency to develop micro-cracks

during repeated sterilization.

4. What is the advantage of using a hybrid ceramic ball bearing

(fig. 3), which includes hardened steel rings and silicon nitride

(ceramic) balls, instead of a typical bearing with steel rings and

steel balls?

Ultimately, a hybrid ceramic ball bearing runs cooler and extends

bearing life.

A ceramic ball is approximately 60% lighter than the same size steel

ball. As a result, the lighter ceramic ball-set generates less centrifugal

force when operating at super-high speeds, which minimizes wear on

the raceway of the outer ring.

Surface wear is further reduced because ceramic and steel are such

different materials. Ceramic balls are harder than heat-treated steel

balls, so it’s less likely that external contaminants or bearing wear debris

will damage them and cause the bearing to fail. Also, a hybrid ceramic

bearing operates better than an all-steel ball bearing in low-lubrication

conditions.

5. How does sterilization affect open (unshielded) and

shielded ball bearings?

In open bearings the lubricant tends to migrate out of the bearing

during the autoclave cycle (sterilization process). Single-shielded,

double-shielded, and integral-shielded bearings (fig. 4) are better

equipped to protect against external contamination, lubricant

migration, and autoclave steam.

6. What does NHBB/myonic suggest for maintaining a

handpiece after sterilization?

NHBB and myonic suggest that your customers follow the

manufacturer’s recommendations for cleaning and lubricating

their dental handpieces after each patient-use and sterilization

procedure (autoclaving).

7. If I receive a grease-packed vs. oiled ball bearing from the

manufacturer, do I need to perform any other lube operation

before using the bearing in a handpiece repair?

In terms of lubrication, NHBB and myonic supply two kinds of

dental bearings: an oiled bearing, which requires intermittent

oil lubrication in the field, and a maintenance-free (grease-packed)

bearing, which is pre-lubricated at the factory with a specified

amount of special grease.

Spraying a maintenance-free bearing with oil will likely flush the

grease from the bearing. Therefore, if oil is used, the bearing

should no longer be treated as maintenance-free; it should be

treated as an oiled bearing that requires intermittent oil lubrication.

Please note that steel and hybrid ceramic bearings that are

lubricated with oil or a small amount of grease for run-in purposes

are ready for turbine installation and initial handpiece operation.

Even still, it’s always a good idea to remind your customers

about the necessity of intermittently lubricating high-speed

bearings according to the recommended handpiece maintenance

procedure.

8. What is a “lube-free” bearing?

A “lube-free” bearing — or what NHBB and myonic refer to

as a “maintenance-free” bearing — is a bearing that has been

pre-lubricated at the factory with a specified amount of special

grease; it does not require intermittent lubrication with oil.

When working with a maintenance-free bearing, your customers

should keep in mind that most grease lubricants tend to migrate

out of the bearing when an external oil lubricant is used. Once

oil is used to lubricate a maintenance-free bearing, that bearing

must from then on be lubricated with oil.

9. What does NHBB/myonic recommend if a handpiece has

been returned due to bad bearing performance?

If a handpiece has been returned due to bad bearing performance,

it’s best simply to replace the bearings.

Frequently asked questions

about Dental BEARIN GS

nhbb.com

fig. 2

Angular Contact

Full Retainer (Torlon®)

Unshielded

fig. 3

Radial Hybrid Ceramic

Crown Retainer (Phenolic)

Single Shield

fig. 4

Angular Contact

Full Retainer (Torlon®)

Integral Shield

          Major Causes of Handpiece Failure

Dental handpieces have many reasons for failure but most common that we see as a repair facility can be prevented if proper care and understanding of the instrument is used.

These are:

1. Sterilization

2. Lack of lubrication or proper lubrication

3. Being dropped

4. Ran with a bent bur or no bur at all

5. Using the wrong handpiece for the job

Handpieces must be purged of any debris prior to sterilization. The debris may become hard or gummy after the sterilization process. This will dramatically affect the bearings performance and consequently the handpiece life.

Bearings are made of an inner race, outer race, retainer cage and 7 to 8 solid ball bearings. Each ball is about the size of a pen tip. The bearing balls ride on a grooved surface between the inner and outer raceways. The retainer keeps the balls equally spaced as they rotate around the inner race.

    Outer Ring            Cage                   Ball Bearings         Inner Ring        Complete Bearing                                                         

The ball bearings spin between 350,000-400,000 rpm which is needed for the handpiece to function properly. It is easy to see that any small amount of foreign substance inside the bearing will dramatically affect its ability to perform.

• When air pressure exceeds the recommended settings of 32-35psi, the bearing will turn greater than 350,000-420,000 rpms that they are rated for. When this happens ball bearings that are held equally spaced by the retainer will start to oval the retainer holes. Eventually one hole will meet the next hole and so on until the retainer will break in half for a complete bearing failure.

                                                              Black Retainer Ring

• If heavy side pressure on the handpiece is used it will cause the bearing balls to roll vertically in the retainer. The holes will enlarge causing increased radial play of the bur.

• When handpieces are repeatedly over sterilized and or sterilizer is not temperature calibrated correctly the excessive heat will cause the retainers to creak on top part of the ball hole at the weakest point this will also cause the bearing to fail.

• If a bur is bent and is used it will cause the bearings to run out of concentricity. It is similar to a tire being out of balance. This will also cause the bearing balls to roll vertically leading to failure. Running without a bur may cause the chuck to back out into the cap.

• If a handpiece is dropped, the head may become dented. The dent will put pressure on the o-rings and bearings. If the dent is severe enough the bearings may become squeezed and also lead to premature failure.

• Handpieces must always have a backend gasket and swivel styles must have good pliable O-rings. If a good seal is not made, either air or water will find the path of least resistance and flow where it is not supposed to causing poor performance.

Using the correct handpiece for the job at hand is important. The use of torque style (Large head) handpieces should be used for heavy cutting when needed. Small heads should be used for lighter applications.

It’s not recommended to extend the bur due the chance it may walk out of the handpiece.

How To Properly Lubricate You Handpieces

Motors & Highspeed        Prophy Angle              Sheath

Lubricate second largest hole         Lubricate top middle and bottom     Lubricate both ends of Sheath

Heads & Prophy Angles

Take them apart and lube the top, middle and bottom. Re-install. We recommend adding lubricate 2-3 times per week based on use.

Sheath & Contra Angles

Lubricate the top and bottom with 1-2 drops of oil. Sheaths do not have to be oiled every day. We recommend adding oil 2-3 times per week based on use.

Low Speed Lubrication

Lubricate air intake with 2-3 drops of oil after each use. Never autoclave a detachable motor.

Highspeed Lubrication

Lubricate air intake with 2-3 drops of oil. Add one drop into the chuck also. Highspeeds should be lubricated every time before use. Be sure to expel excess lubricant before you put them into the autoclave.

Always clean the surface with alcohol (Do not use harsh cleaners, or ultrasonic cleaner)

     Common Handpiece Maintenance Mistakes

1. Using a chemical wipe –down on handpieces before sterilizing: This may cause harmful reactions when the handpiece is subject to heat.

2. Using an ultrasonic cleaner: Handpieces should never be immersed in any fluids.

3. Lubricating in the wrong hole. The drive airline leads directly to the turbine.

4. Not applying enough lubricant- It is important to ensure oil is getting to the bearings, by seeing oil leave the handpiece.

5. Not running the handpiece prior to autoclaving-failure to operate the handpiece following lubrication will gum up the turbine and excess oil gets baked into the bearings.

6. Leaving the bur in the chuck during autoclaving-This shorten the life of the auto chuck and will lead to build up of debris in the chuck.

7. Failing to maintain autoclaves-If the autoclave is not properly cleaned, buildup can occur that contaminates the entire system, including the handpiece.

Handpieces are precision instruments but will not last forever. They will wear out over time. If proper care and regular maintenance are preformed they should provide several years of excellent service.