Moving bacteria around

Sept. 1, 2004
Have you ever wondered during probing if the bacteria from a deep pocket stick to the probe and move to the next healthy site you probe?

by Trisha E. O'Hehir

Have you ever wondered during probing if the bacteria from a deep pocket stick to the probe and move to the next healthy site you probe? That maybe your good intentions of full-mouth probing are actually contributing to the infection of new sites? Some have even suggested — in jest, I hope — that you have a probe on your tray for each probing site. Depending on the patient, that could be a whopping 192 probes! Maybe you should just dip the probe in chlorhexidine between measurements. I don't even want to think how much time that would add to probing.

When wondering about the potential for bacteria to adhere to probe tips, dental hygiene researchers at the University of Missouri-Kansas City designed and carried out a research study to answer the question. Their results were published in the March 2004 issue of the Journal of Periodontology.

They measured bacterial adherence to four different probe designs. One was a plastic ball tip probe with two identical halves molded together, leaving a seam with flashing around the outside of the ball tip. Another was the University of North Carolina probe, with indentations for every millimeter up to 12. The third probe had indentations at 3, 6, 9, and 12 mm. The fourth probe was a metal ball tip design with indentations at 3.5 mm and 5.5 mm.

Two of each probe design was used to measure a deep pocket and a shallow pocket. The probes were inserted subgingivally, held there for two seconds, removed directly to a vial of transport medium and sealed with wax. Each probe was then processed for evaluation under a scanning electron microscope. This gave the researcher a highly magnified visual image of the probe and the microbes that remained attached to it after just two seconds.

The researchers were surprised to see just how rough the probe surfaces in general were. Striations around the metal probes indicated use of a lathe in the manufacturing process. Roughness and barbed edges were typical of the cuts for millimeter markings. It was in these cuts and rough areas that bacteria and epithelial cells were observed, as well as on the probe tip. The sharp edges probably scraped the tissue as the probe was inserted and again as it was removed, bringing out both bacteria and epithelial cells.

No differences were observed between the four probe types for retention of bacteria on the probes. The number of bacteria and the number of epithelial cells was similar for all probes in both deep and shallow pockets.

This answers the question about whether or not bacteria adhere to the probe when we take it out of the pocket. Now we need to know what happens when we insert that probe into a healthy site. Do we inoculate that site and trigger an infection? Are we moving bacteria from infected sites to non-infected sites and spreading disease? Bacterial transmission is successful only if the bacteria are able to colonize in the healthy sulcus.

In 1985 researchers reported the translocation of Actinobacillus actinomycetemcomitans (Aa) from infected sites to healthy sites. Although the bacteria were moved, they were unable to survive the ecology of the healthy sulcular environment. These researchers showed that while inoculation is possible with Aa, suitable growth conditions are required for successful colonization. The bacteria are going to compete for essential nutrients and must live in an environment different from the one they just left. It didn't work for the Aa bacteria, but we don't know about the other periodontal pathogens. More research is needed in this area.

Bacterial translocation between healthy and diseased sites leads to the topic of bacterial transmission between spouses. Research has established that another periodontal pathogen, Porphyromonas gingivalis (Pg), is found not only in periodontal pockets, but also in the saliva and on the mucous membranes of infected individuals. This makes transmission a possibility between those who kiss. When bacteria were analyzed between spouses, identical enzyme patterns were found, which confirms bacterial transmission between spouses.

Contrary to the evidence that bacteria can be transmitted between spouses, you probably have couples in your practice with different levels of disease — one healthy, the other a periodontal disaster. How can that be?

Two steps are needed for transmission of bacteria between spouses to result in periodontal disease. Just as in the translocation of bacteria from healthy to diseased sites, the bacteria must be able to colonize a healthy sulcus. Secondly, the host must be susceptible. If the receiving spouse is at risk for periodontal disease and the bacteria successfully colonize, there is potential for destruction. If the receiving spouse does not possess the risk factors and is resistant, disease will not occur.

You can move bacteria between diseased and healthy sites and spouses can share bacteria, but this doesn't automatically lead to disease. Successful colonization and the individual's immune response are essential factors.

Trisha E. O'Hehir, RDH, BS, is a senior consulting editor of RDH. She is also an international speaker, author, instrument designer, inventor, and oral health detective. Her Web sites are and She can be reached at (800) 374-4290 or at [email protected].