Improve Endodontic Outcomes With Laser Irradiation

Who wouldn't like to improve their endodontic outcomes? More than 15 percent of root canals (RCT) end up needing re-treatment, and of those, approximately 65 percent were found to have failed due to poor quality obturation, particularly on the challenging apical third of the canal(s).

In addition to difficulty accessing the canal and completely removing infected tissue (while avoiding a separated file), getting the disinfectant to penetrate into the dentinal tubules is challenging. On occasion, complete disinfection is not always achieved, and when combined with microgaps in the gutta-percha, can lead to reinfection.

The true problem here lies with the anatomy of the dentin; microorganisms can penetrate as far as 1mm into the dentinal tubules, while the antiseptic rinse can only penetrate 100μm. Thus, if the canal is not properly sealed with gutta-percha penetrating somewhat into the tubules, the bacteria may emerge and cause relapse of symptoms.

Semiconductor lasers are emerging as an adjunctive step in the root canal process. Their light spectrum easily penetrates the dentinal tubules to kill bacteria, and slightly melts the outer dentin to seal the dentinal tubules. The enamel is not affected by this treatment.

The Experiment:
Researchers from the Ohio State University College of Dentistry partnered with Quingdao University in China to investigate how laser therapy might improve the prevention of microleakage through sealing the dentinal tubules, compared to conventional therapy. In their experiment, 60 single-rooted human teeth that had been recently extracted were divided into six groups. The first two groups (A, B) received the laser treatment at 1W for 20 seconds and were then obturated with gutta-percha using standard RCT technique. The second two groups (C, D) were ultrasonically rinsed for 60 seconds prior to RCT. The last two groups (E, F) received no special canal treatment prior to RCT.

Results:
Groups A, C and E were put through a dye test that indicates apical microleakage, while groups B, D, and F were sectioned and imaged with scanning electron microscopy. The apical sealing of the laser irradiated group was significantly better than that of the control group E, and not significantly different from the ultrasonic group C.

Scanning electron microscopy of the laser group B revealed complete sealing of the dentinal tubules via a thin layer of melted dentin. The ultrasonic group D was found to have reasonable gutta-percha penetration of the dentinal tubules, but this quality declined proceeding towards the apex. The control group F experienced incomplete gutta-percha sealing of the tubules throughout.

From these results, the authors concluded that laser irradiation was an effective method to achieve more complete sealing of the apices of endodontically treated teeth, but also acknowledged a few drawbacks. Chief among them was heat, which in excess can damage the periodontal ligament and increase the likelihood that the tooth will fall out. This can be mitigated using a pulsed output from the laser, and frequent cooling with irrigation fluid to only heat the innermost layer of dentin to melting temperature.

Sources:
Tabassum, S., and Khan, F. R. (2016). Failure of endodontic treatment: The usual suspects. European Journal of Dentistry, 10(1), 144–147. http://doi.org/10.4103/1305-7456.175682

Su, D., Hu, X., Wang, D., Cui, T., Yao, R., and Sun, H. (2017). Semiconductor laser irradiation improves root canal sealing during routine root canal therapy. PLoS One. Retrieved 28 November 2017, from https://doi.org/10.1371/journal.pone.0185512

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