Oral Health Group

ABSTRACT: Evolution of Bacterial Suckback in Three Dental Handpieces

June 1, 2001
by J.I. Nicholls Ph.D, Professor, Restorative Denistry, University


Sterilization of air turbine handpieces is standard protocol in dental practice. This study shows that some sterilized handpieces can exhaust contaminated air into the tray table or inside the dental unit, thus creating an unhealthy work environment for dentists, dental assistants and hygienists.

The study was conducted in two series. The first study was planned to show the bacterial contamination of three air turbine handpieces when they were run in a bacterial solution similar to mouth conditions. A turbine type handpiece, under positive pressure, prevents the entrance of external debris but when the air supply is terminated the coasting turbine sends air back into the handpiece and the exhaust line. Air pressure supply to all handpieces was 34 psi.


Specific steps were taken to ensure the proper environment and technique for the tests. This included many steps, some of which were;

Sterilization of all handpieces tested with the turbine in place;

Sterilization of all instruments used to contact turbines etc.;

Uniform running times and procedures.

Control studies were required to verify the final results and proved the following:

No vital bacteria remained after the initial pretest sterilization;

No bacteria were found in the air supply;

Some bacteria would be present if they were sucked into the handpiece.

The bacteria could not be eliminated from the blades by centrifugal force. The whirling action of the air and the speed of the turbine were not enough to eliminate bacteria from the inner walls.OH

Robert Clappison, DDS, FRCD(C), FACD


TestBacteria #HandpieceTurbinePresent
1NSK – NewNSK – NewNo*
2NSK – OldNSK – OldNo*
3NSK – OldNSK – NewNo*

*Results were consistent for all trials.

The second series was to evaluate the presence (or absence) of a bacteria at the distal end of the handpiece. The protocol was mainly similar to those in the first series.

TestBacteria #HandpieceTurbinePresent
6NSK – NewNewNo*
7Kavo – NewNewYes*

* Results were consistent for all 3 trials run on each handpiece brand.

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