Evaluation of the Bactericidal Activity of a Hyaluronic Acid-Vehicled Clarithromycin Antibiotic Mixture by Confocal Laser Scanning Microscopy

Abstract

Confocal laser scanning microscopy (CLSM) was used to evaluate the antibacterial effect and depth of action of a novel clarithromycin-containing triple antibiotic mixture, which was proposed for root canal disinfection in dental pulp regeneration. A previous study reported that this mixture had no tooth discoloration effects in vitro. After infection with Enterococcus faecalis for 3 weeks, the dentinal tubules in the cylindrical root specimens were exposed to different antibiotic mixtures: ciprofloxacin, metronidazole and minocycline (3-MIX); ciprofloxacin, metronidazole and clarithromycin (3-MIXC) and ciprofloxacin and metronidazole (2-MIX). Each antibiotic formulation was mixed with macrogol (MG) or hyaluronic acid (HA) vehicles. CLSM and viability staining were used to quantitatively analyze the mean depth of the antibacterial effect and the proportions of dead and live bacteria inside the dentinal tubules. The 3-MIX and 3-MIXC demonstrated a similar depth of action. The mean proportion of dead bacteria was similar in the 3-MIX and 3-MIXC groups, and both were statistically higher than that of 2-MIX (p = 0.014). Each antibiotic mixture showed a higher bactericidal efficacy if conveyed with HA, compared to MG (3-MIX, p = 0.019; 3-MIXC, p = 0.013 and 2-MIX, p = 0.0125). The depth of action and the antibacterial efficacy of 3-MIXC seemed comparable with 3-MIX.

Disinfection and Biocompatibility of Titanium Surfaces Treated with Glycine Powder Airflow and Triple Antibiotic Mixture: An In Vitro Study

“…Imaging was performed using a Leica SP8 confocal system (Leica Microsystems, Wetzlar, Germany) [ 30 ] equipped with an argon ion and a 561 nm DPSS lasers. Specimens were mounted on an inverted microscope illuminated by a krypton/argon laser (488 nm).…”

Confocal Laser Scanner Evaluation of Bactericidal Effect of Chitosan Nanodroplets Loaded with Benzalkonium Chloride

“…The border of the fractured root dentin surface was first localized with the microscope to ensure a reproducible scanning field [ 25 ]. The bacterial presence could not be determined until the images were processed, ensuring a blindfold evaluation [ 25 , 33 ]. Moreover, representative data from all randomly selected areas with an excellent signal-to-noise fluorescence ratio were obtained due to the presence of bacteria in the dentinal tubules [ 25 ].…”

“…However, background fluorescence was occasionally observed within the canal lumen and the root canal samples showed auto-fluorescent materials not to be confused with bacteria [ 23 , 24 , 25 ]. Nevertheless, the background fluorescence intensity was minimal within the tubules and there was no inference with the signal generated from bacteria [ 33 ].…”

“…Confocal-laser scanning microscope visualized the presence of microorganisms in the root canal dentinal tubules due to its ability to penetrate below the surface of the specimen and to include the dentin canals that are not open on the surface [ 2 , 25 , 32 , 33 ].…”

Real-Time Multidepth Multiphoton Microscopy Using Pixel-to-Pixel Focus-Switching

“…In a nonlinear optical process, the emission intensity has a quadratic or high-order dependence on the excitation intensity, which ensures that the signal collected out of the focal volume reaches its minimum. Thus, nonlinear optical microscopy has submicron three-dimensional spatial resolution with higher signal-to-noise ratio and less out-of-focus photobleaching, compared with traditional confocal microscopy [5][6][7][8][9]. In addition, using near infrared (NIR) excitation wavelengths also increases the penetration depth, which is particularly significant for biomedical imaging [10][11][12].…”