Evaluation of the antibacterial efficacy of different bioactive lining and pulp capping agents

Evaluation of cytotoxicity and antibacterial activity of different pulp capping liners

This study compares the cytotoxicity and antibacterial activity of five pulp capping liners. This in vitro study was conducted on Fuji II LC glass ionomer, Dycal, Calcimol LC, TheraCal LC, and ACTIVA BioACTIVE. For cytotoxicity, the (MTT) methyl thiazolyl tetrazolium assay was performed on 3 samples from each group of human dental pulp cells (HDPSCs) after 24 h of incubation. The direct contact test (DCT) for antibacterial activity, 6 samples (3 for each material, and 3 for negative control), from each liner were made to evaluate Streptococcus mutans (S. mutans), Lactobacillus casei (L. casei), and Lactobacillus acidophilus (L. acidophilus). Data were analyzed by one-way ANOVA and Tukey's post-hoc test (alpha = 0.05). Data analysis showed that the cytotoxicity of the materials was significantly different (p < 0.001). Fuji II LC and ACTIVA BioACTIVE showed strong cytotoxicity, TheraCal LC moderate cytotoxicity, and Dycal and Calcimol LC slight cytotoxicity. The analysis also revealed a significant difference among the materials regarding antibacterial activity (p < 0.001). Tukey's test showed that the mean percentage of reduction in colony count was significant for all liners compared with the positive control (p < 0.001). The mean percentage of reduction in colony count for Dycal was significantly greater than that of Fuji II LC (p = 0.014), Calcimol LC (p = 0.003), and TheraCal LC (p = 0.001). ACTIVA BioACTIVE did not significantly differ from the other materials as regards antibacterial activity. Dycal showed significantly higher antibacterial activity than the other materials.

Mechanical Properties and Antibacterial Effect on Mono-Strain of Streptococcus mutans of Orthodontic Cements Reinforced with Chlorhexidine-Modified Nanotubes

Recently, several studies have introduced nanotechnology into the area of dental materials with the aim of improving their properties. The objective of this study is to determine the antibacterial and mechanical properties of type I glass ionomers reinforced with halloysite nanotubes modified with 2% chlorhexidine at concentrations of 5% and 10% relative to the total weight of the powder used to construct each sample. Regarding antibacterial effect, 200 samples were established and distributed into four experimental groups and six control groups (4 +ve and 2 -ve), with 20 samples each. The mechanical properties were evaluated in 270 samples, assessing microhardness (30 samples), compressive strength (120 samples), and setting time (120 samples). The groups were characterized by scanning electron microscopy and Fourier transform infrared spectroscopy, and the antibacterial activity of the ionomers was evaluated on Streptococcus mutans for 24 h. The control and positive control groups showed no antibacterial effect, while the experimental group with 5% concentration showed a zone of growth inhibition between 11.35 mm and 11.45 mm, and the group with 10% concentration showed a zone of growth inhibition between 12.50 mm and 13.20 mm. Statistical differences were observed between the experimental groups with 5% and 10% nanotubes. Regarding the mechanical properties, microhardness, and setting time, no statistical difference was found when compared with control groups, while compressive strength showed higher significant values, with ionomers modified with 10% concentration of nanotubes resulting in better compressive strength values. The incorporation of nanotubes at concentrations of 5% and 10% effectively inhibited the presence of S. mutans, particularly when the dose-response relationship was taken into account, with the advantage of maintaining and improving their mechanical properties.

In vitro antibacterial activity and durability of a nano-curcumin-containing pulp capping agent combined with antimicrobial photodynamic therapy

BACKGROUND

Considering the antibacterial properties of nano-curcumin (nCur) reinforced with antimicrobial photodynamic therapy (aPDT), this study aimed to assess the antibacterial activity and durability of Activa BioActive Base/Liner (ABBL) containing nCur (nCur-ABBL) as a pulp capping agent against Streptococcus mutans, the most common cause of secondary caries.

MATERIALS AND METHODS

In this in vitro experimental study, ABBL discs containing 0.5 %, 1%, 2%, and 5% (w/w) concentrations of nCur were fabricated. After aPDT using light emitting diode (LED) at 435 ± 20 nm wavelength for 5 min, the discs were undergone aging in artificial saliva for 90 days. The antibacterial activity of the discs against S. mutans was evaluated by the disc agar diffusion test, and the number of bacterial colonies present in the biofilm formed on the disc surfaces was counted after 0, 15, 30, and 60 days of aging.

RESULTS

The maximum growth inhibition zone was noted around the 5% nCur-ABBL discs. Increasing the concentration of nCur from 0.5 % to 5% combined with aPDT significantly decreased the number of S. mutans colonies in the biofilm over time (P < 0.05). nCur-ABBL discs containing 2% and 5% nCur had no difference in antibacterial activity at any time point up to 60 days (P > 0.05).

CONCLUSION

According to our data, 5% nCur-ABBL revealed the largest growth inhibition zone in S. mutans culture. Moreover, 5% nCur can serve as an excellent ABBL additive in aPDT producer against S. mutans biofilms up to 60 days of aging period.

Oroactive dental biomaterials and their use in endodontic therapy

Dental biomaterials have revolutionized modern therapies. Untreated dental caries remains the major etiological factor for endodontic treatment, and together with a decreasing rate of tooth loss escalates the importance of continuously improving the materials used for endodontic therapies. Endodontic biomaterials are used for vital pulp therapies, irrigation, intracanal medicaments, obturation and regenerative procedures. These materials offer several functions including: antimicrobial activity, mechanical reinforcement, aesthetics, and therapeutic effects. Vital pulp therapies have seen an improvement in clinical results with an incremental approach to build on the strengths of past materials such as calcium hydroxide and calcium silicates. While sodium hypochlorite remains the gold standard for canal irrigation, numerous nanoparticle formulations have been developed to promote sustained antimicrobial action. Gutta-percha based bulk fillers remain the most common materials for root filling. However, while multiple studies focus on the development of novel formulations containing drugs, glass derivatives or ionic-, polymeric-, or drug- loaded nanoparticles, a lack of reliable and long-term clinical evidence obligates further study as experienced clinicians prefer to use what has worked for decades. This review delves in to the biochemistry of the materials to scrutinize their shortcomings, and where opportunity lies to further enhance their efficacy in endodontic practice. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 108B:201-212, 2020.

Characterization of Chlorhexidine-Loaded Calcium-Hydroxide Microparticles as a Potential Dental Pulp-Capping Material

This study explores the delivery of novel calcium hydroxide [Ca(OH)₂] microparticles loaded with chlorhexidine (CHX) for potential dental therapeutic and preventive applications. Herein, we introduce a new approach for drug-delivery to deep dentin-surfaces in the form of drug-loaded microparticles. Unloaded Ca(OH)₂ [Ca(OH)₂/Blank] and CHX-loaded/Ca(OH)₂ microparticles were fabricated by aqueous chemical-precipitation technique. The synthesized-microparticles were characterized in vitro for determination of surface-morphology, crystalline-features and thermal-properties examined by energy-dispersive X-ray scanning and transmission electron-microscopy (EDX-SEM/TEM), Fourier-transform infrared-spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and differential scanning-calorimetry (DSC). Time-related pH changes, initial antibacterial/biofilm-abilities and cytotoxicity of CHX-loaded/Ca(OH)₂ microparticles were evaluated. Microparticles were delivered to dentin-surfaces with subsequent SEM examination of treated dentin-substrates. The in vitro and ex vivo CHX-release profiles were characterized. Ca(OH)₂/Blank were hexagonal-shaped with highest z-average diameter whereas CHX-inclusion evidenced micro-metric spheres with distinguishable surface “rounded deposits” and a negative-shift in diameter. CHX:Ca(OH)₂/50 mg exhibited maximum encapsulation-efficiency with good antibacterial and cytocompatible properties. SEM examination revealed an intact layer of microparticles on exposed dentin-surfaces with retention of spherical shape and smooth texture. Microparticles loaded on dentin-surfaces showed prolonged release of CHX indicating substantial retention on dentin-substrates. This study validated the inherent-applicability of this novel drug-delivery approach to dentin-surfaces using micro-metric CHX-loaded/Ca(OH)₂ microparticles.