Disinfection of Root Canals Using Er:YAG Laser at Different Frequencies

Root Surface Temperature Increases during Root Canal Filling In Vitro with Nd:YAG Laser-Softened Gutta-Percha

The aim of this in vitro study was to measure the temperature increases produced on the mesial and vestibular root surfaces of premolar teeth during a laser-softened gutta-percha obturation technique. We studied 12 extracted human premolar teeth with a single canal. After root canal cleaning and shaping, the teeth were obturated with gutta-percha that had been softened with a neodymium-doped yttrium aluminium garnet (Nd:YAG) laser (CTL 1503) at a wavelength of 1.064 nm. The laser setup parameters included a 30 Hz frequency and a 200 mJ/pulse with optical fiber tips of 0.320 mm diameter. A sectional warm gutta-percha condensation was used. Temperature changes on the whole mesial and vestibular outer surfaces of the roots were measured at approximately 2 s intervals with an infrared thermal imaging camera. A significantly higher increase in temperature was observed for the mesial root surface (7.5°C) compared to the vestibular surface (3.7°C) (p ≈ 0). The findings suggested that root canal filling with Nd:YAG laser-softened gutta-percha in premolar teeth is not likely to damage the surrounding periradicular tissues. To obtain valid temperature results, the measurement should be performed on the surface with the thinnest root wall.

In Vitro Effect of Er:YAG Laser on Different Single and Mixed Microorganisms Being Associated with Endodontic Infections

Objective: The purpose of this in vitro study was to evaluate the antimicrobial effect of activated irrigation with different modes of erbium-doped yttrium aluminum garnet (Er:YAG) laser application on microorganisms related to secondary endodontic infection. Background: Er:YAG laser has been recommended as an adjuvant tool for root canal disinfection during endodontic treatment. Materials and methods: Laser-activated irrigation (LAI) with 300 or 600 μm tips were tested with or without intermittent irrigation with 0.9% sodium chloride (NaCl) solution against different microorganisms (five single strains and dual species (Streptococcus gordonii combined with Actinomyces oris or Fusobacterium nucleatum) in root canals after 3 days of incubation. In a 21-day infection model, LAI was used together with intermittent rinsing with sodium hypochlorite (NaOCl) against the dual-species mixtures; here the incidence of microbial regrowth after up to 7 days was monitored. Results: In the 3-day root infection model, LAI protocols did not show any significant reduction of the microbial load when compared with manual irrigation with saline solution. In the 21-day infection, S. gordonii combined with A. oris were not detectable anymore after applying the LAI protocol with a 600 μm tip (30 mJ/10 pps) up to 7 days after treatment. Conclusions: Application of LAI with a 600 μm tip by using an Er:YAG laser might be advantageous in treatment of endodontic infections.

Temperature variation on the external root surface during intracanal Er:YAG laser irradiation

OBJECTIVE

To evaluate the temperature changes on the root's external surface during Er:YAG laser irradiation with different tips and pulse repetition rates.

BACKGROUND DATA

There have been limited reports that correlate temperature variations with Er:YAG laser irradiation using different tips and pulse repetition rates.

MATERIALS AND METHODS

Sixty roots of central incisors were sectioned 10 mm from the apex, biomechanically prepared, embedded in acrylic resin, and randomly distributed into six groups: the teeth in group I, group II, and group III were irradiated with an Opus 20 laser with a sapphire tip at 8, 10, and 15 Hz, respectively; the teeth in group IV, group V, and group VI were irradiated with the fiberoptic tip of a Kavo Key laser at 6, 10, and 15 Hz, respectively. Laser irradiation was applied for 20 sec to all teeth and temperature changes were recorded with thermocouples in the root surfaces.

RESULTS

There were significant differences (p < 0.05) among pulse repetition rates: 6 and 8 Hz (2.36 degrees +/- 0.91 degrees C), 10 Hz (4.92 degrees +/- 1.60 degrees C), and 15 Hz (8.23 degrees +/- 2.78 degrees C); and radicular thirds: apical (8.33 degrees +/- 2.69 degrees C), middle (4.70 degrees +/- 1.60 degrees C), and cervical (2.48 degrees +/- 0.83 degrees C). No significant differences were seen between the two types of laser tips used (p > 0.05).

CONCLUSION

The temperature changes on root external surfaces remained above the critical threshold (13 degrees C) during Er:YAG laser irradiation, except for irradiation with 15 Hz in the apical third. However, the type of Er:YAG laser tip used (sapphire or fiberoptic) did not affect the temperature variation.