Candida albicans adhesion on 3D-printed and thermopolymerizable polymethyl methacrylate for removable prostheses.

PURPOSE: To compare Candida albicans adhesion and quantify the biofilm formed on thermopolymerizable (T.PMMA) and 3D printing (3D.PMMA) polymethyl methacrylate through quantitative and qualitative analyses. METHODS: The specimens were made (n= 39/material) by conventional polymerization (T.PMMA) and designed in Autodesk Meshmixer software, followed by 3D printing (3D.PMMA) - CAD-CAM method. After the roughness standardization, the monospecies biofilm of C. albicans (ATCC 10231) was submitted to adhesion analysis, verifying the quantification and microbial load, in triplicate, by the methods of counting colony forming units (CFU/mL) and staining with crystal violet, followed by optical density reading, respectively. Qualitative analyses were performed by scanning electron microscopy to analyze the surface characteristics of the specimens and biofilm formed. The Mann-Whitney U test was used for comparisons between resins regarding the count of CFU/mL (log¹°+ 1) and optical density values (P≤ 0.05). RESULTS: T.PMMA (5.78 ± 0.43) had a CFU/mL count (P< 0.001) higher than 3D.PMMA (4.84 ± 0.39). There was a difference between C. albicans biofilm accumulation (P< 0.001), in which on T.PMMA (1.59 ± 0.31) was higher than 3D.PMMA (1.10 ± 0.14). The qualitative analyses corresponded to the quantitative ones and allowed the visualization of more porosities in T.PMMA. CLINICAL SIGNIFICANCE: The adhesion (microbial load and biofilm accumulation) of C. albicans was lower in the 3D printed polymethyl methacrylate when compared to the thermopolymerizable model.

Disinfection and surface changes of gutta-percha cones after immersion in sodium hypochlorite solution containing surfactant.

In this study, we evaluated the effectiveness of 1 and 5.25% NaOCl solutions, with or without surfactant, in disinfecting gutta-percha cones. Surface changes of the gutta-percha cones after disinfection were also assessed under scanning electron microscopy (SEM). One-hundred and eight gutta-percha cones previously contaminated with Enterococcus faecalis were left in contact for 30 s or 1 min with the following solutions (n = 12): 1% NaOCl; 1% NaOCl + 2% cetrimide; 5.25% NaOCl; 5.25% NaOCl + 2% cetrimide. Positive control group was composed by the remaining contaminated cones (n = 12), and the negative control group by noncontaminated cones (n = 12). The cones were kept in Eppendorf tubes containing Trypticase Soy Broth at 37°C for 24 hr, and then, the presence of turbidity was analyzed. Ten additional cones (n = 2) were observed under SEM to evaluate surface changes after 1 min of disinfection. The data analysis (Kruskal-Wallis test, α = 5%) demonstrated that regardless the presence of surfactant, the NaOCl solutions used were effective in the disinfection when cones were immersed for 1 min. However, at the 30-s period, only the 5.25% NaOCl solution was effective. SEM analysis demonstrated that NaOCl solutions promoted the formation of sodium chloride crystals on cones surface, less visible when the 1% NaOCl associated to surfactant was used. The addition of surfactant did not affect the disinfection capacity of NaOCl solutions. However, the surfactant has apparently inhibited the sodium chloride crystals deposition on the cones surface when associated to 1% NaOCl solution.

Effect of Ultrasonic Activation of Irrigants on Smear Layer Removal.

INTRODUCTION: The objective of this study was to evaluate the efficacy of passive ultrasonic irrigation (PUI) with 17% EDTA and 1% NaOCl solutions on smear layer removal. METHODS: Root canal preparations of 32 human teeth were performed with the ProTaper system. Next, they were longitudinally fractured to permit quantitation of smear layer creation from the cervical, middle, and apical thirds of the roots by using scanning electron microscopy. After reassembling the fractured tooth halves, they were divided into 4 groups according to different final irrigation protocols: group1, EDTA + NaOCl; group 2, EDTA with PUI + NaOCl; group 3, EDTA + NaOCl with PUI; and group 4, EDTA + NaOCl, both with PUI. After irrigation, the tooth halves were separated to permit imaging the same areas by scanning electron microscopy, and a percentage of opened dentinal tubules in irrigated areas as a percent of the total area was obtained. The results were submitted to Kruskal-Wallis, analysis of variance, and Bonferroni tests (α = 0.05). RESULTS: The cervical third of the samples from all groups showed higher percentage of smear layer removal and open dentinal tubule areas, followed by the middle and apical thirds. Among the irrigation groups, there were statistically significant differences in cervical third between group 2 and group 4 samples, with the highest and lowest percentage of smear layer removal, respectively. CONCLUSIONS: PUI by using 1% NaOCl and ultrasonic tip placed within 1 mm of the apical foramen did not show higher efficacy in smear layer removal compared with conventional irrigation.