Effect of Solea Laser Treatment on Bacteria Viability

Objectives: The recent introduction of Solea 9.3μm CO₂ laser systems (Convergent Dental Natick, MA) into the marketplace has afforded controlled ablation of hard and soft tissues using the same laser system. There has been great speculation as to whether the controlled ablation of carious tissues results in high enough temperature within the lased tooth material and the plume itself to render disruption of bacterial integrity and subsequent death of the bacteria.
In this project we examined the viability of streptococcus mutans contained in the plume from a 5 second laser treatment of a carious lesion.

Methods: Extracted human teeth (N=5) with large carious lesions were selected. They were subsequently immersed in BHI broth (supplemented with 3% sucrose), inoculated with s. mutans and allowed to grow in a shaking incubator overnight at 37°. Teeth were rinsed in running water and blotted dry. The carious region of the teeth were subjected to laser irradiation treatment (with a water mist) with a fluence of approximately 50 J/cm2 , using a 0.5 mm spot size for a total time of 30 seconds. During the laser use, a sterile high speed dental evacuation tube, fitted with a sterile gauze filter, was used to collect the ejecta along with the plume vapor around the treatment region. Each of the gauze filters was transferred to a sterile tube of BHI broth, allowed to grow overnight, serially diluted to 10^-6 and plated for counting. A non-carious tooth, cleaned with a cavitron and stored in chloramine-t was also lased and had its gauze filter identically handled as a control.

Results: All plates from carious teeth showed greater than 50 CFU. The control samples had no visible bacterial growth.
Conclusions: The CO₂ laser systems did not provide sterilization of a prepared carious lesion and left a large number of viable bacteria.