Evaluation of antifungal efficacy of erbium, chromium: yttrium-scandium-gallium-garnet laser against Candida albicans

Caspofungin at Sub-inhibitory Concentration Promotes the Formation of Candida Albicans Persister Cells

AIMS

Low caspofungin exposure is frequently encountered in patients with invasive candidiasis caused by Candida albicans (C. albicans). This study aimed to investigate the effects of caspofungin on C. albicans at sub-inhibitory concentrations.

METHODS AND RESULTS

First, a comparative transcriptomics analysis was performed on C. albicans receiving caspofungin at sub-minimum inhibitory concentrations (sub-MIC). The results showed that caspofungin significantly changed the mRNA expression profile in DAY185, with DE-mRNAs enriched in the functions of cell wall biosynthesis, metabolism, etc. Subsequently, cellular fitness, cell aggregation, energy metabolism activity, and the proportion of persister cells of C. albicans were quantitatively and/or qualitatively assessed after sub-MIC caspofungin exposure. No significant changes in cell fitness and aggregation formation were observed during treatment of C. albicans with sub-MIC caspofungin. In C. albicans aggregation treated with sub-MIC caspofungin, we observed a decrease in respiratory metabolism and an increase in persister cells; this effect was more pronounced in als1ΔΔ than in DAY185.

CONCLUSIONS

Pre-exposure to sub-MIC caspofungin suppresses C. albicans respiratory metabolism and promotes persister cell development.

SIGNIFICANCE AND IMPACT OF STUDY

Caspofungin should be used with caution in patients with C. albicans infections, as anti-infection therapy may fail due to persister cells.

The effect of low level laser on number of Candida albicans colonies in-vitro: a new finding

Background

Candida albicans is a commensal organism that causes a wide variety of diseases in humans. One of these diseases is oral candidiasis, which occurs at a high recurrence rate in spite of available treatments. The purpose of this study was to compare the effect of low-level laser therapy (LLLT) with the use of nystatin on in-vitro growth of Candida albicans.

Method

We prepared two samples of Candida albicans at different concentrations: 10⁴ viable cells/ml and 10⁶ viable cells/ml. Specimens from each sample were divided into a control group, a nystatin-treated group, and a group treated with LLLT. The control group was cultured without any intervention. The second group was treated with nystatin and the solution was vibrated for 30 s or 60 s. The third group was irradiated with a gallium-aluminum-argon (Ga-Al-Ar) diode laser (Epic 10; Biolase Inc.)in continuous mode using a wavelength of 940 nm and a power of 1 W for 30 s or 60 s (38 J/cm² and 76 J/cm²). The specimens from the nystatin group and the LLLT group were cultured and the number of colony-forming units (CFU/ml) for each group was counted and compared.

Results

Nystatin completely eliminated the colonies (0 colonies) in all specimens. There was an increase in the number of colonies in the LLLT group for both cell concentrations at 30 s and at 60 s. However, this increase was statistically significant only for a concentration of 10⁴ viable cells/ml at an exposure time of 30s. The increase in the concentration of 10⁶ viable cells/ml at both 30 s and 60 s was statistically significant compared with the control group, although the highest number of colonies remained after an exposure time of 60s.

Conclusion

LLLT led to an increase in the growth of Candida colonies. However, there was no significant difference related to the exposure time between the different cell concentrations.

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.

The Bactericidal Effect of 2780 and 940 nm Laser Irradiation on Enterococcus faecalis in Bovine Root Dentin Slices of Different Thicknesses

OBJECTIVE

The aim of this in vitro study was to investigate the antibacterial effect of the dual wavelength (2780 nm Er,Cr:YSGG and 940 nm diode) laser in elimination of Enterococcus faecalis in comparison with a 2780 nm Er,Cr:YSGG laser alone.

BACKGROUND DATA

Various laser wavelengths have been introduced as an adjunct in root canal treatment because of laser's bactericidal effect.

MATERIALS AND METHODS

Seventy- five slices of dentin with thicknesses of 300, 500, and 1000 μm (n = 25 each) obtained from caries-free bovine teeth were inoculated with 1 μL of E. faecalis suspension [1.67 × 10(7) colony-forming units (CFU)] and divided randomly into three groups: (A) samples indirectly irradiated with power settings of 1.06 W, 50 Hz, and 50 μs for Er,Cr:YSGG laser; (B) samples indirectly irradiated with Er,Cr:YSGG laser with the same power settings as group A and simultaneously with a 940 nm diode laser of 0.51 W in pulsed mode; and five samples from each thickness that were chosen as an unirradiated control group (Co). After irradiation, the CFU of E. faecalis were counted and the bacterial reduction was analyzed using Kruskal-Wallis nonparametric and post-hoc Dunnett tests.

RESULTS

There were statistical differences between groups A and B compared with the control group over all the three dentin slice thicknesses (p < 0.001). However, there was no statistical difference between groups A and B in killing of E. faecalis on 500 μm dentin slices. There were significantly more viable bacteria in group A than in group B in 300 and 1000 μm dentin slices (p < 0.01).

CONCLUSIONS

The results of this in vitro study showed that the dual wavelength laser system obtained a significantly higher bactericidal effect on E. faecalis than Er,Cr:YSGG laser, reaching a depth of 1000 μm of dentin.

Effect of Er,Cr:YSGG laser irradiation with radial firing tips on Candida albicans in experimentally infected root canals

Aim. To compare the disinfection effect of Er,Cr:YSGG laser using radial firing tips with NaOCI in root canals infected with C. albicans and to evaluate the irradiation effect on the dentinal surfaces. Material and Methods. In total seventy-six mandibular premolar teeth were used. In order to standardize the incubation and sterilization procedure, eight teeth were used. Sixty-eight of the root canals were incubated with C. albicans suspension for 72 hours. The specimens were divided into 5 experimental groups. Two groups were constituted as Group 1 was irradiated with 1.5 W laser (n = 8) and group 2, which was irradiated with 2 W laser (n = 8). Two more groups were formed as Group 3 (2 W laser (n = 25) and Group 4 NaOCI (5%) (n = 25). Group 5 (n = 2) did not receive any treatment. Mann-Whitney U and Kruskal-Wallis H tests were used to compare the different laser output powers. Wilcoxon Signed Ranks Test was used in order to compare the Candida cfu/ml levels according to treatment protocols (P < 0.05). Results. Both 1.5 W and 2 W laser resulted in a major reduction of C. albicans without a significant difference. The comparison of the dentin surfaces irradiated with Er,Cr:YSGG laser at two power settings resulted in similar morphological changes. However, NaOCI was found to be more effective in reduction of C. albicans than 2 W laser application. Conclusion. According to the results of the present study, the Er,Cr:YSGG laser with radial firing tips presented less antifungal effects on C. albicans in root canals of infected teeth than NaOCl solution.

Can the Cure Time of Endodontic Sealers Affect Bond Strength to Root Dentin?

The cure time of endodontic sealers may influence the bond strength of fiber posts to root dentin. Forty teeth were selected and endodontically filled using calcium hydroxide cement and then divided into 2 groups according to the time elapsed between endodontic filling and post luting (n = 20): Immediately - glass fiber post luting immediately after endodontic filling; and Delayed - post luting performed 7 days after endodontic filling. The roots were also subdivided according to resin cement used for post luting (RelyX ARC and RelyX Unicem). The specimens were stored at 37°C for 24 h and sectioned in six 1-mm-thick slices from cervical, middle and apical thirds. The slice specimens were submitted to a push-out test at a crosshead speed of 0.5 mm/min, and the bond strength values obtained (MPa) were submitted to two-way ANOVA in a split-plot arrangement and Tukey's test (α=0.05). For both RelyX ARC and Unicem, the bond strength was significantly higher when the posts were cemented 7 days after the endodontic treatment. RelyX Unicem showed significantly higher bond strength values than RelyX ARC for both cementation periods. It was concluded that post luting should be made after the complete setting of the root canal sealer. Self-adhesive resin cement should be preferred for fiber post luting.

Effect of Er:YAG laser-activated irrigation solution on Enterococcus Faecalis biofilm in an ex-vivo root canal model

Abstract Objective: The purpose of this study was to evaluate mineral content and surface morphology of root canals coated with Enterococcus faecalis biofilm after treatment with several endodontic irrigation solutions, with and without Er:YAG laser-activated irrigation (LAI).

BACKGROUND DATA

LAI has been introduced as a powerful method for root canal irrigation resulting in smear-layer removal from the root canal wall.

METHODS

Distal and palatal roots from 60 freshly extracted human molars were used in this study. The coronal of each tooth was removed. Roots were split longitudinally and placed in an ultrasonic bath to remove the smear layer, creating conditions for the formation of E. faecalis biofilm. After incubation, the two halves were reassembled in impression material to simulate clinical conditions. Specimens were divided into two main groups: roots rinsed with irrigation solutions and roots subjected to laser irradiation combined with irrigation solutions. Solutions tested were 2% chlorhexidine and 17% ethylenediaminetetraacetic acid (EDTA) and saline.

RESULTS

Surface morphology: 17% EDTA irrigant solution combined with Er:YAG laser showed the best results for removing bacteria from the root canal walls. Chemical analysis: all samples treated with combined laser irradiation and irrigation solution had low surface levels of Ca compared with samples treated with irrigation alone. The Ca/P ratio was highest in the laser-EDTA group. Overall, mineral changes caused by laser with irrigation solutions were minimal, and statistically nonsignificant.

CONCLUSIONS

In vitro irrigation solutions, combined with Er:YAG laser irradiation, were effective in removing E. faecalis biofilm from root canal walls. Irrigation solutions without laser irradiation were less effective, leaving a layer of biofilm on the dentin surface.