An experimental treatment using light to kill bacteria may not improve periodontal disease in residual pockets, a new study shows.
Researchers used photodynamic therapy to blast bacteria in residual periodontal pockets in patients who had already undergone standard therapy. They found no statistical difference in clinical measures between these patients and those who had only undergone standard therapy.
They planned to present their findings at the International Association for Dental Research General Session and Exhibition in Seattle, Washington.
“At the beginning of the last century, researchers found that the photodynamic therapy could inactivate microbes,” Veronica Carvalho, MSc, a researcher at the University of Sao Paulo in Sao Paulo, Brazil, told Medscape Medical News. “We expect that it could add some clinical benefits after non-surgical periodontal treatment, for residual pockets.”
In photodynamic therapy, clinicians first apply a drug such as methylene blue to the treatment area. Bacteria take up the drug. Next clinicians shine a light emitted from a fiberoptic device. The light-sensitive drug absorbs the energy from the light, then releases it to molecules of oxygen in the surrounding air.
The oxygen molecules become singlet oxygen, which oxidizes nearby bacteria.
A photodynamic therapy device (Periowave, Ondine Biomedical) has been approved for dentistry in Canada and some other countries. It is awaiting approval in the United States. The treatment has also been attempted for treating cancer.
For the study, Carvalho and her colleagues recruited 30 patients with a total of 120 residual pockets. After treating all patients with standard therapy, they randomly assigned 4 of these pockets with depths of at least 4 mm, including 1 pocket at least 5 mm deep, to photodynamic therapy or a sham treatment.
They injected 0.01% methylene blue, then shined 90 seconds of laser light with a wavelength of 660 nm in each site.
They provided these interventions at baseline and again after 3 months. They also provided maintenance care every 3 months during the trial.
The following table shows the statistical significance of the differences between the photodynamic therapy group and the sham treatment group. A P value greater than .05 is considered to indicate a statistically insignificant difference.
Variable P Values at 3 Months P Values at 6 Months
Pocket probing depth .78 .52
Clinical attachment level .36 .38
Bleeding on probing .78 .97
Plaque index .82 .80
The patients did improve. Compared with baseline, pocket probing depth, clinical attachment level, and bleeding on probing decreased in both groups. The difference between these measurements at baseline and at 6 months for the 2 groups was statistically significant (P < .001).
Plaque index, however, did not significantly improve in either group (P = .02 in the photodynamic therapy group and .39 in the sham treatment group).
The researchers concluded that the photodynamic therapy added no benefit to scaling and root planing. They plan next to analyze microbiological markers, measuring the quantities of Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola, and Aggregatibacter actinomycetencomitans with real time-polymerase chain reaction.
Asked to comment, Nikos Soukos, DDS, PhD, who was not involved in the study, told that his own review of photodynamic therapy research suggested this type of treatment would not work. “The conclusion here does not surprise me,” said Dr. Soukos, director of the Applied Molecular Photomedicine Laboratory at the Forsyth Institute in Cambridge, Massachusetts. “Photodynamic therapy in this type of application is not very promising.”
It might be more effective if the treatment were repeated more times, he said.
Much remains to be researched about this treatment, he said. “People have vague theories about how much drug to apply and how much light. We don’t have a clear idea of the dosage in photodynamic therapy.”
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