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PurposeThe primary cause of pulp and periapical diseases is the invasion of bacteria into the root canal, which results from the continuous destruction of dental hard tissues. Effective management of infections during root canal therapy necessitates effectively irrigation. This study aims to investigate the effects of two antimicrobial peptides (AMPs), buCaTHL4B and Im-4, on root canal biofilms in vitro.MethodsTwo-species biofilms (Enterococcus faecalis and Fusobacterium nucleatum) were selected and anaerobically cultivated. The following treatments were applied: 10 μg/mL buCaTHL4B, 10 μg/mL Im-4, 5 μg/mL buCaTHL4B, 5 μg/mL Im-4, 1 μg/mL buCaTHL4B, 1 μg/mL Im-4, 1% NaOCl, and sterile water. Each group was treated for 3 min. Subsequently, the two strains were co-cultured with 10 μg/mL buCaTHL4B, 10 μg/mL Im-4, 1% NaOCl, and sterile water for 24, 48, and 72 h. The biofilms were examined using confocal laser scanning microscopy (CLSM) with fluorescent staining, and the percentages of dead bacteria were calculated. Quantitative real-time PCR (qRT-PCR) was employed to assess the variations in bacterial proportions during biofilm formation.ResultsCompared to 1% NaOCl, 10 μg/mL buCaTHL4B or Im-4 exhibited significantly greater bactericidal effects on the two-species biofilms (p < 0.05), leading to their selection for subsequent experiments. Over a 48-hour period, 10 μg/mL Im-4 demonstrated a stronger antibiofilm effect than buCaTHL4B (p < 0.05). Following a 24-hour biofilm formation period, the proportion of F. nucleatum decreased while the proportion of E. faecalis increased in the sterile water group. In the buCaTHL4B and 1% NaOCl groups, the proportion of F. nucleatum was lower than that of E. faecalis (p < 0.05), whereas in the Im-4 group, the proportion of F. nucleatum was higher than that of E. faecalis (p < 0.05). The proportions of bacteria in the two AMPs groups gradually stabilized after 24 h of treatment.ConclusionbuCaTHL4B and Im-4 exhibited remarkable antibacterial and anti-biofilm capabilities against pathogenic root canal biofilms in vitro, indicating their potential as promising additives to optimize the effectiveness of root canal treatment as alternative irrigants.

This study was aimed at experimentally evaluating the freeze–thaw (F–T) performance of a one-part geopolymer (OPG) paste. A binary precursor (ground granulated blast furnace slag plus fly ash) activated by sodium hydroxide (NaOH (NH)) or sodium metasilicate (Na2SiO3 (NS)) was used to prepare the OPG pastes. To simulate the freezing temperatures in various frozen regions of the world (such as Canada, China, Greenland, Norway, Russia, and the United States), four temperature values were selected: − 5, − 10, − 20, and − 40 °C. The F–T durability of the OPG paste was studied based on the visual appearance, mass loss, pH variation, and compressive strength deterioration under the action of F–T cycles (up to 50 cycles). The experimental results revealed that because of the formation of a dense structure, the NS-activated OPG paste had better F–T resistance than the NH-activated OPG paste. The increase in the number of F–T cycles or decrease in freezing temperature led to an increase in the porosity of the OPG paste, thereby causing mass loss and compressive strength reduction. The increase in porosity was due to the volumetric expansion of ice crystals, and the failure stress was caused by the difference in temperature. These two factors were found to cause the deterioration of the mechanical properties of the OPG paste. Accordingly, a deterioration model of the OPG paste under F–T cycles was proposed based on the experimental observations. The results of this study are expected to provide guidance regarding the use of the novel OPG paste to improve frozen soil layers or build frost-resistant geotechnical structures.

In this paper, the one-part alkali-activated geopolymer was adopted as the soil binder to stabilize the soft clay under the one-dimensional compressive loading. Factors influencing the stiffness and strength of the one-part geopolymer stabilized soil such as the proportion of silicon-aluminum raw materials, the mass ratio of solid NaOH (NH) to raw materials and the water-binder ratio were taken into account. The stiffness development of the one-part geopolymer stabilized soft clay under one-dimensional compressive loading was investigated by an improved transducer system equipped with a pair of bender extender elements and the tactile pressure sensor, from which the time history of earth pressure coefficient (i.e., K0) and elastic wave velocity (i.e., the compression wave velocity VP and the shear wave velocity VS) of the stabilized soil sample could be measured, respectively. Furthermore, the unconfined compressive strength (UCS) of the stabilized soil sample cured under varied one-dimensional compressive loadings was tested to reveal the strength development of the geopolymer stabilized soil sample. Among different mixing proportions, the alkali-activated binary precursor [90% ground granulated blast furnace slag (GGBFS) and 10% fly ash (FA)] exhibits the highest performance in terms of the VS, VP and UCS of the geopolymer stabilized soil sample when the activator/precursor and water/solid ratio are 0.15 and 0.7 (i.e., the 4.67 mol/L of NH solution), respectively. The prediction of UCS for the one-part geopolymer stabilized soft clay was proposed and established based on the elastic wave velocity (i.e., VS and VP). The outcome of the current study sheds light on the practical use of the one-part alkali-activated geopolymer as a soil binder in ground improvement.