Effect of 3D printed teeth and virtual simulation system on the pre-clinical access cavity preparation training of senior dental undergraduates.

BACKGROUND: The objective of the present study was to evaluate the effect of 3D printed teeth and virtual simulation system on the pre-clinical access cavity preparation training of senior dental undergraduates. METHODS: The 3D printed teeth were manufactured based on the micro-CT data of an extracted lower first molar. Ninety-eight senior dental undergraduate students were required to finish the access cavity preparation of lower first molar within 20 min on plastic and 3D printed teeth on the manikin system as well as on a virtual simulation machine respectively with randomly selected sequences. Expert dentists scored the operated teeth. The scores from the virtual simulation system were also recorded. All the scores were analyzed and compared. Following the procedure, two questionnaires were sent to students to further evaluate the feelings and optimal training sequence. RESULTS: No significant differences were found between plastic and 3D printed teeth scores, while virtual simulation achieved a valid/invalid area removal ratio of 96.86% ± 5.08% and 3.97% ± 1.85%, respectively. Most students found plastic teeth training the easiest and favored the three-training combination (36.36%). 71.42% of the students thought the virtual simulation training should be put at the first place of the three trainings. Over 80% of students agreed with incorporating 3D printed teeth and virtual simulation into their routine training courses. In addition, the general advantages and disadvantages of the virtual simulation system and 3D printed teeth training received almost equal recognition by students. CONCLUSIONS: Virtual simulation system training + plastic teeth training + 3D printed teeth training might be the optimal training sequence. Virtual simulation system training could not completely replace the traditional training methods on the manikin system at the moment. With further modifications, 3D printed teeth could be expected to replace the plastic teeth for the pre-clinical access cavity preparation training.

Mechanisms of Triton X-100 reducing the Ag+-resistance of Enterococcus faecalis.

To investigate the mechanism of Triton X-100 (TX-100) reducing the Ag+-resistance of Enterococcus faecalis (E. faecalis), and evaluate the antibacterial effect of TX-100 + Ag+ against the induced Ag+-resistant E. faecalis (AREf). The minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of AgNO3 against E. faecalis with/without TX-100 were determined to verify the enhanced antibacterial activity. Transmission electron microscopy (TEM) was used to observe the morphological changes of E. faecalis after treatment. The intra- and extracellular concentration of Ag+ in treated E. faecalis was evaluated using inductively coupled plasma mass spectrometer (ICP-MS). The changes in cell membrane potential and integrity of treated E. faecalis were also observed using the flow cytometer. Moreover, AREf was induced through continuous exposure to sub-MIC of Ag+ and the antibacterial effect of TX-100 + Ag+ on AREf was further evaluated. The addition of 0.04% TX-100 showed maximal enhanced antibacterial effect of Ag+ against E. faecalis. The TEM and ICP-MS results demonstrated that TX-100 could facilitate Ag+ to enter E. faecalis through changing the membrane structure and integrity. Flow cytometry further showed the effect of TX-100 on membrane potential and permeability of E. faecalis. In addition, the enhanced antibacterial effect of TX-100 + Ag+ was also confirmed on induced AREf. TX-100 can facilitate Ag+ to enter E. faecalis through disrupting the membrane structure and changing the membrane potential and permeability, thus reducing the Ag+-resistance of E. faecalis and enhancing the antibacterial effect against either normal E. faecalis or induced AREf.

Enhanced in vitro antibacterial effect against Enterococcus faecalis by using both low-dose cetylpyridinium chloride and silver ions.

BACKGROUND: Enterococcus faecalis (E. faecalis) is frequently isolated from root canals with failed root canal treatments. Due to the strong ability of E. faecalis to resist many often-used antimicrobials, coping with E. faecalis infections remains a challenge. The aim of this study was to investigate the synergistic antibacterial effect of low-dose cetylpyridinium chloride (CPC) and silver ions (Ag+) against E. faecalis in vitro. METHODS: The minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and the fractional inhibitory concentration index (FICI) were used to confirm the existence of the synergic antibacterial activity between low-dose CPC and Ag+. Colony-forming unit (CFU) counting, time-killing curve and dynamic growth curve were used to evaluate the antimicrobial effects of CPC and Ag+ combinations against planktonic E. faecalis. Four weeks biofilms were treated with drug-contained gels to determine the antimicrobial effect on biofilm-resident E.faecalis, and the integrity of E.faecalis and its biofilms were observed by FE-SEM. CCK-8 assays was used to test the cytotoxicity of CPC and Ag+ combinations on MC3T3-E1 cells. RESULTS: The results confirmed the synergistic antibacterial effect of low-dose CPC and Ag+ against both planktonic and 4-week biofilm E. faecalis. After the addition of CPC, the sensitivity of both planktonic and biofilm-resident E. faecalis to Ag+ improved, and the combination showed good biocompatibility on MC3T3-E1 cells. CONCLUSIONS: Low-dose CPC enhanced the antibacterial ability of Ag+ against both planktonic and biofilm E.faecalis with good biocompatibility. It may be developed into a novel and potent antibacterial agent against E.faecalis, with low toxicity for root canal disinfection or other related medical applications.

Influences of thioalcohols on the release of aromas in sesame-flavor baijiu.

This study investigated the interactions between 2-furylmethanethiol, benzenemethanethiol, and 18 skeletal aroma-active compounds as well as four aroma notes in sesame-flavor baijiu based on the Feller Additive Model, the Odor Activity Value (OAV) Approach, and the Sigma-Tau (σ-τ) plots. In addition, a predictive model for the interactions between 2-furylmethanethiol and esters was developed, and the determinants of the interaction results in complex systems were explored. The results reveal that both thioalcohols interacted with the skeletal aroma-active compounds in a similar trend, where 2-furylmethanethiol tends to enhance the release of fruit and acid aroma. Moreover, the intensity of the thiols and their intensity ratio to the notes were the determinants of the interaction results in the multivariate blended system, with the lower the concentration of the thiols, the closer the ratio was to 1, and the more likely that additive interactions would take place. Predictive modeling showed that 2-furylmethanethiols were more likely to have additive or synergistic effects with esters when the olfactory thresholds of the esters were between 75.86 and 199.53 µg/L. Conversely, masking effects were more likely.

Optimisation and characterisation of KOH-activated carbon obtained from Baijiu spent grains for the mitigation of risk factors in alcoholic beverages.

This study aims to repurpose waste grain from the Baijiu brewing process into activated carbon for mitigating risk factors in alcoholic beverages, enhancing quality and ensuring safety. For attaining the most effective activated carbon, tailored carbon synthesis conditions were identified for diverse alcoholic beverages, optimising strategies. For beverages with low flavour compound content, optimal conditions include 900 °C calcination, 16-hour activation and a 1:2 activation ratio. In contrast, for those with abundant flavour compounds, 800 °C calcination, 16-hour activation and a 1:1 activation ratio are recommended. Post-synthesis analyses, employing nitrogen physisorption-desorption isotherms, FT-IR and SEM, validated a significant BET surface area of 244.871 m2/g for the KOH-activated carbon. Critical to adsorption efficiency, calcination temperature showcased noteworthy micro-porosity (0.8-1 nm), selectively adsorbing higher alcohols (C3-C6) and acetaldehyde while minimising acid and ester adsorption. Sensory evaluations refined optimal parameters, ensuring efficient spent grain management and heightened beverage safety without compromising aroma.

Comprehensive analysis of risk factors (methanol, acetaldehyde and higher alcohols) in alcoholic beverages and their reduction strategies: GC-MS analysis and modified activated carbon adsorption and characterization.

This study endeavors to examine the levels of risk factors in alcoholic beverages and propose mitigation strategies. GC-MS analysis was utilized to assess risk factors in various distilled-spirits. The content of such risk factors in spirits ranked as follows: vodka ≈ gin < baijiu < whiskey < brandy, and all were adhering to the Chinese national standard. Additionally, a method was refined to alleviate these risks, employing various reagents for activated carbon modification and evaluating their adsorption efficiency for risk factors reduction. Oxalic acid-modified activated carbon exhibited promising adsorption rates for risk factors with acceptable flavor compounds loss, rendering it a prospective solution for health hazard reduction. Characterization via SEM and nitrogen-adsorption-desorption was conducted on the optimal material, complemented by sensory experiments to optimize its application. This study offers valuable insights into the content of risk factors in alcoholic beverages, aiding in improving quality and safety of alcoholic beverages.

Characterization of key aroma compounds in soy sauce flavor baijiu by molecular sensory science combined with aroma active compounds reverse verification method.

The distinctive flavor profile of soy sauce flavor baijiu (SAB) is shaped by its unique aroma compounds. The characteristic aroma compounds in Langjiu soy sauce flavor baijiu (LSAB) were explored based on molecular sensory science. A total of 66 aroma active compounds were identified by gas chromatography-olfactometry (GC-O) combined with aroma extract dilution analysis (AEDA), and 6 important unknown sulfur compounds were identified using the aroma active compounds reverse verification method (ACRVW). A total of 39 key aroma compounds were determined to have odor activity values (OAVs) ≥ 1. The aroma contribution of aroma components was verified by aroma recombination and aroma omission experiments. 15 characteristic aroma compounds were identified in LSAB. Meanwhile, a simple and easy-to-understand sensory expression language was described to fully understand the style characteristics of LSAB. Overall, the present paper offers insights into research uncovering the key "sauce flavor" of soy sauce flavor baijiu.