Treatment of root canal biofilms of Enterococcus faecalis with ozone gas and passive ultrasound activation.

INTRODUCTION: Biofilms of resistant species such as Enterococcus faecalis pose a major challenge in the treatment of root canals with established periapical disease. This study examined the effects of gaseous ozone delivered into saline on biofilms of E. faecalis in root canals of extracted teeth with and without the use of passive ultrasonic agitation. METHODS: Biofilms of E. faecalis were established over 14 days in 70 single roots that had undergone biomechanical preparation followed by gamma irradiation. The presence and purity of biofilms were confirmed using scanning electron microscopy and culture. Biofilms were treated with saline (negative control), 1% sodium hypochlorite for 120 seconds (positive control), ozone (140 ppm ozone in air at 2 L/min delivered into saline using a cannula for 120 seconds), saline with passive ultrasonic activation (70 kHz and 200 mW/cm(2) applied to an ISO 15 file held passively within the canal, for 120 seconds), and ozone followed immediately by ultrasonic agitation. After treatment, samples were taken from the biofilm and serially diluted for plate counting. RESULTS: Analysis revealed that 1% sodium hypochlorite was the most effective disinfecting agent followed by ozone combined with ultrasonic agitation, ozone alone, and finally ultrasonic alone. CONCLUSIONS: Although none of the treatment regimes were able to reliably render canals sterile under the conditions used, ozone gas delivered into irrigating fluids in the root canal may be useful as an adjunct for endodontic disinfection.

Temperature changes accompanying near infrared diode laser endodontic treatment of wet canals.

INTRODUCTION: Diode laser endodontic treatments such as disinfection or the generation of cavitations should not cause deleterious thermal changes in radicular dentin. METHODS: This study assessed thermal changes in the root canal and on the root surface when using 940 and 980 nm lasers at settings of 4 W/10 Hz and 2.5 W/25 Hz, respectively, delivered into 2000-mum fibers to generate cavitations in water. The root surface temperature in the apical third was recorded, as was the water temperature in coronal, middle, and apical third regions, by using thermocouples placed inside the canal. Lasing was undertaken with either rest periods or rinsing between 5-second laser exposures. RESULTS: Both diode lasers induced only modest temperature changes on the external root surface at the settings used. Even though the temperature of the water within the canal increased during lasing by as much as 30 degrees C, the external root surface temperature increased by only a maximum of 4 degrees C. Irrigation between laser exposures was highly effective in minimizing thermal changes within the root canal and on the root surface. CONCLUSIONS: Diode laser parameters that induce cavitation do not result in adverse thermal changes in radicular dentin.

Cavitational effects in aqueous endodontic irrigants generated by near-infrared lasers.

INTRODUCTION: Laser-generated pressure waves may have application for removing debris and smear layers from root canals. Past work has employed middle infrared erbium lasers. The present study examined whether near infrared 940 and 980 nm diode lasers (Biolase Ezlase and Sirona Sirolaser, respectively) could induce cavitations in aqueous media. METHODS: Laser energy was delivered into a capillary tube using a 200 microm fiber, and the formation of cavitations observed with a microscope. In the first part of the study, a range of laser parameters were trialled to establish conditions which form cavitations within 5 seconds of the commencement of laser irradiation. The second part of the study compared cavitation in distilled water, aerated tap water, degassed distilled water, ozonated water, 3 and 6% hydrogen peroxide using panel setting of 2.5 W/25 Hz for the Sirolaser, and 4 W/10 Hz for the Ezlase. RESULTS: Both diode laser systems could induce cavitation in water-base media by the formation and implosion of water vapour. Laser power played a more important role than pulse frequency or pulse interval. Optimal laser-initiated cavitation occurred when weak (3%) peroxide solutions were used as the target irrigant, rather than water. CONCLUSION: This phenomenon has potential for enhancing debridement in endodontics.

Laser fluorescence assessment of the root canal using plain and conical optical fibers.

INTRODUCTION: Traditional culture-based techniques for assessing infection of the root canal system are difficult to use and prone to error. Real-time assessment of the microbial status of the root canal system using laser fluorescence would help address these limitations. METHODS: This study evaluated the performance of thin optical fibers of different diameters, with either plain or conically modified ends, connected to a KaVo KEY 3 laser with an inbuilt 655-nm laser fluorescence diagnostic system. Penetration was tested on sectioned extracted teeth. Fluorescence recordings were made ex vivo in the canals of extracted teeth with known periapical pathology. Several endodontic medicaments and irrigants were also tested for autofluorescence. RESULTS: The fibers could reach the apical third of the root canal, unless the canals had distal curvatures greater than 15 degrees . Penetration was greater for conical than for plain fibers. Fluorescence readings were significantly higher in infected canals (range, 19-99) than in noninfected canals and sound radicular dentin (range, 2-8). Of the medicaments examined, only tetracycline-based medicaments gave false-positive fluorescence signals. CONCLUSIONS: Fluorescence analysis of root canals with optical fiber probes has the potential for real-time assessment of the microbial status of the root canal system in clinical practice.