Effect of disinfectant solutions on gutta-percha and resilon cones

The aim of this study was to evaluate the effects of the 5.25% sodium hypochlorite (NaOCl), 2% chlorhexidine (CHX), and MTAD solutions on the surface of gutta‐percha and Resilon cones by using atomic force microscopy (AFM). Accessory cones were washed and dried. The cones were randomly divided into six groups: gutta‐percha immersed in NaOCl, CHX, and MTAD, and Resilon immersed in NaOCl, CHX, and MTAD. AFM images of the same area were made in different periods of time. JPK? Image Processing Software was used to evaluate the images. The parameters used to evaluate the changes were RMS and line profiles. No statistically significant change was observed in the RMS values. The line profiles detected changes only for gutta‐percha surfaces after immersion in NaOCl and MTAD solutions. In conclusion, 5.25% NaOCl and MTAD are associated with local changes in surface roughness of gutta‐percha cones. No change was observed when 2% CHX was used. The use of all tested solutions did not produce any changes on Resilon surface. Microsc. Res. Tech. 75:791–795, 2012. © 2012 Wiley Periodicals, Inc.     

Evaluation of surface alterations in different retreatment nickel‐titanium files: AFM and SEM study

The aim of this study was to evaluate the surface changes of nickel titanium (Ni‐Ti) rotary retreatment files after three and five uses. Furthermore, the effects of 2% sodium hypochlorite and chloroform solutions and sterilization procedures on the NiTi rotary retreatment surfaces were investigated. ProTaper Retreatment files, R‐endo files, and Mtwo retreatment files were used for this study. The palatinal roots of maxillary molar teeth were obturated with gutta percha and Ah26. Retreatment procedures were performed with these retreatment file systems. The surface changes of untreated NiTi rotary files that were used three and five times, immersed in NaOCl and chloroform and subjected to sterilization procedures were investigated with atomic force microscopy (AFM) and scanning electron microscopy (SEM). The RMS values, three dimensional images and SEM images at various magnifications were obtained. RMS values showed that all three NiTi rotary retreatment file systems showed significant deteriorations after three and five uses. Cracks, damages and spiral construction deteriorations were detected in the SEM images after three and five uses. Furthermore, the Mtwo 15 file was broken off after five uses. AFM data indicated that 2% NaOCl caused significant surface deteriorations on NiTi rotary files and both AFM and SEM evaluation showed that chloroform solution and sterilization procedures did not cause significant surface deteriorations. In conclusion, ProTaper retreatment, R‐endo, and Mtwo retreatment files showed surface damages depending on retreatment procedures. Clinicians have to consider that retreatment files always have a tendency to break off after the third time they have been used. Microsc. Res. Tech. 78:356–362, 2015. © 2015 Wiley Periodicals, Inc.     

Effect of different irrigation protocols on the radicular dentin interface and bond strength with a metacrylate‐based endodontic sealer

This study assessed the influence of different endodontic chemical substances on the adhesion of the Epiphany SE/Resilon system (with and without resinous solvent) to radicular dentin walls, using the push‐out test and scanning electron microscopy (SEM). Forty‐eight root canals of human canines were prepared biomechanically with ProTaper rotary files (crown‐down technique) and the radicular dentin was treated with either 17% EDTA, 2% chlorhexidine gel (CHX) or 2.5% NaOCl (control). The root canals were filled with Resilon cones and Epiphany SE sealer with and without resinous solvent. Six groups of eight canals each had their roots sectioned transversally to obtain 1‐mm thick slices. Data were subjected to statistical analysis by ANOVA and Tukey's tests. The specimens treated with 17% EDTA (1.59 ± 0.91) presented higher bond strength (P < 0.05) than those treated with 2.5% NaOCl (0.93 ± 0.27) and 2% CHX (0.92 ± 0.22). Significantly higher bond strength (P < 0.05) was observed when the Epiphany SE was prepared with (1.37 ± 0.78) than without (0.92 ± 0.33) solvent. Adhesive failures were predominant in all groups. SEM analysis showed greater homogeneity of the filling mass when the solvent was added to the sealer. Treatment of root canal walls with 17% EDTA, and addition of a resinous solvent to Epiphany SE produced the highest adhesion to radicular dentin. Microsc. Res. Tech. 77:446–452, 2014. © 2014 Wiley Periodicals, Inc.     

Comparison of influence of different manufacturing methods on the cleaning efficiency of rotary nickel–titanium files

The purpose of this study was to evaluate and compare cleaning effectiveness of TwistedFile, GT series X, Revo‐S, RaCe, Mtwo, and ProTaper Universal rotary files in curved canals. Seventy mesiobuccal canals of extracted human first maxillary molars were divided into seven groups of 10 samples each. Canals were prepared with six nickel–titanium (NiTi) rotary systems and manual K‐Flexofile. Irrigation was performed with 2 mL 2.5% NaOCl solution after each file, and 5 mL 2.5% NaOCl was used for the final flush. After the roots were split longitudinally, the presence of debris and smear layer was visualized using scanning electron microscopic photomicrographs taken at coronal, middle, and apical third. Mean scores for debris and the smear layer were calculated and statistically analyzed for significance between groups using the Kruskal–Wallis nonparametric analysis of variance (P < 0.05) and Mann–Whitney U test (P < 0.001). There was no significant difference among the groups in terms of debris and smear layer scores (P > 0.05). Without considering the preparation method used, while no statistically significant difference was found between the coronal third and the middle third (P > 0.05), higher amount of debris and smear layer were found in apical third (P = 0.001). The new generation of NiTi rotary files including the Twisted File and GT Series X presented similar cleaning effectiveness compared with traditionally ground NiTi rotary files. Microsc. Res. Tech. 76:231–236, 2013. © 2012 Wiley Periodicals, Inc.     

The effect of final irrigation with MTAD,QMix, and EDTA on smear layer removal and mineral content of root canal dentin

To compare the smear layer removal ability and mineral content of root canal dentine after initial irrigation with NaOCl and final irrigation with MTAD, QMix, and 17% EDTA. Forty extracted human maxillary incisors before root canal preparation and irrigation with NaOCl were randomly divided into four groups (n = 10) according to the type of final irrigants used: MTAD, QMix, 17% EDTA, and control (sterile distilled water). Scanning electron microscopy (SEM) was used to assess the presence of smear layer. SEM energy‐dispersive X‐ray spectroscopy was used to quantify dentin mineral composition in MTAD, QMix, 17% EDTA group, and in no‐treatment samples (no‐treatment group; n = 10). Among the various chelating agents, there were no significant differences in the smear layer removal in the middle and coronal thirds (p > .05). In the apical third, QMix removed significantly more smear layer than 17% EDTA (p < .05), but similarly to MTAD (p > .05). Final irrigation with MTAD resulted in a significant increase in the carbon (C) value compared to EDTA (p < .001). There was no significant difference in the mineral composition between the MTAD and the QMix group, although the values of the mineral elements were significantly altered in the MTAD group. QMix had smear layer removal capability similar to MTAD but better than EDTA in the apical third. MTAD yielded the most pronounced effect on mineral component of root dentin; however, differences were significant only for C level compared to 17% EDTA.     

Evaluation of surface topography changes in three NiTi file systems using rotary and reciprocal motion: An atomic force microscopy study

Aim: To evaluate the surface topography changes in three nickel‐titanium (NiTi) file systems using either rotary or reciprocal motion using atomic force microscopy (AFM), and to determine the effect of scanning area on the AFM results in this study. Methodology: Five points on a F2 Protaper file, R25 Reciproc file, and a Primary file from WaveOne systems were scanned preoperatively in 1 × 1 and 5 × 5 µm² with an AFM device that can scan an intact (not sectioned) file. One standardized resin block was used for each instrument, according to the manufacturer's recommendations. Points were re‐scanned postoperatively using the same AFM and settings. Root‐mean‐square (RMS) and roughness average (Ra) values were obtained. The preoperative and postoperative surface topographies were compared separately in terms of RMS and Ra values. The surface topography change scores were analyzed using Kruskal–Wallis and Mann–Whitney U tests using a 0.10 significance level. Results: There were no significant differences preoperatively among the NiTi file systems in 1 × 1 or 5 × 5 µm² areas. Postoperatively, the WaveOne Primary had more surface irregularities (significant for 5 × 5 µm² scan in Ra evaluation). Conclusions: Three‐dimensional AFM images of instrument surfaces showed topographic irregularities preoperatively and postoperatively. AFM results differ depending on the scanning area and file used. Microsc. Res. Tech. 77:177–182, 2014. © 2013 Wiley Periodicals, Inc.     

Cleaning capacity of octenidine as root canal irrigant: A scanning electron microscopy study

The aim of this study was to assess the cleaning capacity of the octenidine hydrochloride (OCT) used as root canal irrigant by scanning electron microscopy (SEM) analysis. Sixty human unirradicular extracted teeth were randomly distributed in 6 groups (n = 10) according to irrigant solutions which were used during root canal preparation: G1, 0.1% OCT; G2, 2% chlorhexidine (CHX); G3, 2.5% sodium hypochlorite (NaOCl); G4, OCT + 17% ethylenediaminetetraacetic acid (EDTA); G5, 2.5% NaOCl + 17% EDTA and G6, distilled water. All specimens were instrumented with ProTaper system up to F4. Teeth were sectioned and prepared for SEM. The smear layer was evaluated using a 5‐score system and the data were analyzed by Kruskal–Wallis and Dunn (α = 0.05). In all root canal thirds there was no significant difference between OCT, CHX, NaOCl, and water groups (p > .05), and these groups showed higher smear layer values than NaOCl + EDTA and OCT + EDTA groups (p < .05). There was no significant difference between NaOCl + EDTA and OCT + EDTA groups (p > .05). It was concluded that OCT used as a single root canal irrigant presented poor cleaning capacity and could be used in association with a final irrigation with EDTA to obtain smear layer removal.     

Topography of four different endodontic rotary systems, before and after being used for the 12th time

Root canal preparation may damage NiTi instruments resulting in wear and deformation. The aim of this study was to make a comparative evaluation of the surface topography of the cervical third of four different rotary systems, before and after being used twelve times, in 1.440 resin blocks with simulated root canals with standardized 45° curvatures, and analyzed by atomic force microscopy &#150; AFM. The blocks were divided into four groups and prepared according to the manufacturers recommendations: Group 1 ‐ K3®; Group 2 ‐ Protaper Universal®; Group 3 ‐ Twisted Files® and Group 4 ‐ Biorace®. After each preparation, the instruments were washed and autoclaved. A total of 240 instruments were selected, being 30 new instruments and 30 after having been used for the 12th time, from each group. These instruments were analyzed by AFM and for quantitative evaluation, the mean RMS (Root mean square) values of the cervical third of the specimens from the four groups were used. The result showed that all the rotary files used for the 12th time suffered wear with change in the topography of the cervical region of the active portion of the file (ANOVA p < 0.01). Classifying the specimens in increasing order, from the least to the greatest wear suffered, Group 3 (2.8993 nm) presented the least wear, followed by Group 4 (12.2520 nm), Group 1 (36.0043 nm) and lastly, Group 2 (59.8750 nm) with the largest amount of cervical surface wear. Microsc. Res. Tech., 2012. © 2011 Wiley Periodicals, Inc.     

Ultrastructural analysis of the root canal walls after simultaneous irrigation of different sodium hypochlorite concentration and 0.2% chlorhexidine gluconate

To determine whether sodium hypochlorite (NaOCl) with 0.2% chlorhexidine gluconate (CHX) leads to colour change and precipitate formation, and to ultrastructurally analyse the dentine surface after simultaneous irrigation with 0.5% NaOCl and 0.2% CHX. Four tubes in which 5ml of different NaOCl concentrations and 5ml 0,2% CHX were placed, were observed every 15 minutes in the first two hours and after 7 days. Mixture solutions were centrifuged at 800 rpm/4 min. A precipitate is observed under light-microscopy. Thirty-five single-rooted teeth were instrumented using crown-down technique with irrigation: Positive control: distilled water, Negative control: 0,5% NaOCl+15% EDTA, Experimental group: identical to the negative control, then canals were treated with 0.5% NaOCl+0.2% CHX. The longitudinal root sections were observed under scanning-electron-microscopy. The amount of debris was assessed with 5/score-system, and the results were analysed using the Mann-Whitney U test (p < 0.001). Change in colour was noticed immediately after the merger and it did not change with time. Mixture solutions showed considerable turbidity, but precipitate was observed only after centrifugation. Statistical analysis showed a significant difference in the dentinal wall purity when comparing the cervical and middle root canal thirds between the experimental and negative control group. The difference was also observed between the cervical and middle thirds compared to the apical third of the root canal within these groups. Interaction between NaOCl and CHX, as well as the creation of precipitates, depends not only on the concentration of NaOCl, but also on the concentration of CHX.     

Evaluation of different irrigation protocols concerning the formation of chemical smear layer

The aim of this work was to evaluate, by means of scanning electron microscopy (SEM) and electron dispersive spectroscopy (EDS), the different irrigation protocols concerning the formation of chemical smear layer (CSL). Fifty‐five teeth were instrumented by using distilled water (DW) as irrigant. Next, the teeth were submitted to a protocol for removal of the mechanical smear layer produced. The teeth were divided into 11 groups, according to irrigation regimen. Then, the teeth were prepared and analyzed with SEM and EDS. Only in Group 1 [1 mL sodium hypochlorite (NaOCl) + 10 mL DW + 1 mL chlorhexidine (CHX) solution], Group 2 [1 mL NaOCl + 10 mL DW + 1 mL ethylenediaminetetraacetic acid (EDTA) + 10 mL DW + 1 mL CHX solution], and Group 3 [1 mL NaOCl + 10 mL DW + 1 mL citric acid (CA) + 10 mL DW + 1 mL CHX solution], the formation of CSL was observed. In the groups where CHX gel was used alone or in association with EDTA, CA, phosphoric acid (PA), and CHX solution, no formation of CSL was observed. According to the results found in the cases in which one wants to associate NaOCl with CHX, the protocol using PA (1 mL NaOCl + 10 mL DW + 1 mL PA + 10 mL DW + 1 mL CHX solution) did not induce formation of CSL. Microsc. Res. Tech., 2013. © 2012 Wiley Periodicals, Inc.     

Atomic force microscopy and energy dispersive X‐ray spectrophotometry analysis of reciprocating and continuous rotary nickel‐titanium instruments following root canal retreatment

The aim was to examine the effect of retreatment process on the surface roughness and nickel titanium (NiTi) composition of ProTaper Universal Retreatment (PTUR; consists of 3 files; D1, D2, D3) and WaveOne Gold (WOG) (primary) instruments. Twenty extracted mandibular molar teeth with severe curved (30–40°) mesial roots were selected and divided into two groups (n = 10) based on the instrument used for the removal of the root canal filling. Before and after using the instruments in two canals, they were subjected to atomic force microscopy (AFM) and energy dispersive X‐ray spectrophotometry (EDX) analysis. The EDX analysis data and roughness average (Ra) and root mean square (RMS) values were analyzed statistically using a one‐way analysis of variance and post hoc Tukey's test at the 5% significant level. There was no significant difference between the new and used D1 and D2 PTUR and WOG instruments in terms of the Ni composition (p > .05). The Ti contents of the used D2 and D3 PTUR instruments were lower those of the new instruments (p < .05). In both new and used instruments, PTUR and WOG have no difference in terms of Ra and RMS values. (p > .05). The Ra and RMS values of the PTUR and WOG systems significantly increased after removal of the root canal filling (p < .05). The use of PTUR and WOG instruments for removal of root canal filling in severely curved root canals affected the surface topography of the files. The NiTi composition of the WOG instruments was unaffected by the retreatment process.     

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.     

The effect of a root‐dentin pretreatment technique combining PIPS with MTAD aiming to improve the bond strength of glass fiber post

The aim of this study was to evaluate the combined effect of MTAD and photon‐induced photoacoustic streaming (PIPS) technique on the smear layer removal and the bond strength of glass fiber post. Fifty‐five human mandibular premolars were chosen. After root canal therapy and post space preparation, the teeth were equally divided to five groups according to the methods of root‐dentin pretreatment: G1: distilled water (control); G2: 2.5% NaOCl+17% EDTA; G3: MTAD; G4: PIPS; G5: MTAD+PIPS. One sample was randomly selected from each group, and scanning electron microscope (SEM) was used to observe the microscopic morphology of the coronal, middle and apical level of the root‐dentin. The remaining ten samples from each group were glued to glass fiber posts, and the bond strength was assessed by push‐out test. SEM evaluation showed that the most complete smear layer removal was found in MTAD + PIPS group, especially in coronal third. Push‐out test results exhibited that there was a statistically significant interaction between the experimental groups and root canal third (p < .0005). Significant differences could be found among five groups (p < .05): G5 > G4 > G3 > G2 > G1. G5 had the highest bond strength. In conclusion, post space pretreatments with MTAD or PIPS technique can significantly remove smear layer and improve the bond strength of glass fiber post, and combination of them works best.     

Efficacy of the photon‐initiated photoacoustic streaming combined with different solutions on Enterococcus faecalis in the root canals

This study aimed to evaluate the efficacy of different irrigation solutions used in photon‐initiated photoacoustic streaming (PIPS) or conventional needle irrigation (CNI) for eradication of Enterococcus faecalis from artificial root canals. Altogether, 240 artificial root canal samples were included. The models were split and incubated for 2 days to allow formation of E. faecalis biofilm. The models were randomly divided into two groups (n = 120): CNI and laser‐activated irrigation (LAI). Each group was divided into six subgroups according to different irrigation solutions: distilled water, 1% sodium hypochlorite (NaOCl), 2% NaOCl, 5.25% NaOCl, MTAD, and chlorhexidine, respectively. After irrigation, half of the samples (n = 10) were assessed immediately, and the other half of the samples (n = 10) were incubated for 6 hr. Bacterial suspensions were obtained from all samples before and after irrigation, and after incubation, and were quantified adenosine 5′‐triphosphate (ATP) assay kit. The biofilms were examined using fluorescent microscopy and analyzed by Image Pro Plus software. Significant reduction of ATP, average fluorescence density after irrigation, and growth after incubation was obtained in LAI group than in CNI group (p < .05). LAI can improve bacteriostasis effect of 2% NaOCl (p < .05). PIPS improved the antibacterial effect of the 2% NaOCl used in root canal therapy.     

Effect of sodium hypochlorite on the cyclic fatigue resistance: A scanning electron microscopy evaluation

The main purpose of this study was to compare the cyclic fatigue resistances of the three different nickel–titanium files in 2.5% sodium hypochlorite solution and distilled water at physiologic intracanal temperature (35°C). Three NiTi files such as One Curve (OC) (Micro‐Mega, Besancon, France), OneShape (OS) (Micro‐Mega), and Protaper Next (PTN) X2 (Dentsply Sirona, Ballaigues, Switzerland) were tested for cyclic fatigue resistance inside artificial stainless steel canal block with curvature 60° and 5 mm radius. The block was fixed inside a hot water bath of distilled water or 2.5% sodium hypochlorite and the temperature was set at 35 ± 1°C. The number of cycles to fracture data were recorded and all the fracture surfaces of files were evaluated by using scanning electron microscopy. The number of cyclic to fracture data were analyzed statistically via Kruskal–Wallis and Mann–Whitney U tests. OC showed the highest cyclic fatigue resistance at distilled water while PTN X2 showed the lowest cyclic fatigue resistance at 2.5% sodium hypochlorite. When cycling fatigue test medium were changed from distilled water to sodium hypochlorite solution, the resistance of the files to cyclic fatigue were decreased. SEM analysis confirmed that all scanned samples were fractured due to cyclic fatigue. The OC rotary instruments have more cyclic resistance than OS and PTN X2. The sodium hypochlorite solution reduces the resistance of the rotary instruments.     

Response of E. faecalis biofilms to different associations of auxiliary substances during root canal preparation: A confocal laser microscopy analysis

Objective: This in vitro study evaluated the effect of different endodontic auxiliary chemical substances over Enterococcus faecalis (Ef) biofilm through confocal laser scanning microscopy (CLSM). Methods: Forty‐five bovine incisors were infected with Ef for 21 days. Teeth were divided into five groups: group 1: 2.5% NaOCl + EDTA, group 2: 2% CHX gel + EDTA, group 3: 2% CHX liquid + EDTA, group 4: 2.5% NaOCl + 2% CHX gel + EDTA, group 5: 2.5% NaOCl + 2% CHX liquid + EDTA and a negative and a positive control group (NCG; PCG). The samples were stained with SYTO9 and propidium iodide and analyzed by CLSM. Bacterial viability was quantitatively analyzed by the proportions of dead and live bacteria in the biofilm remnants. Scores were standardized according to the total bacterial load (TBL)—1: ≤25%, 2: >25 ≤50%, 3: >50 ≤75%, 4: >75% and debris—1: absence of debris; 2: presence of debris. Statistical analysis was carried out through the Kruskal–Wallis and the Fischer exact tests (P = 0.05). Results: No statistical differences were observed to CFU, debris and bacterial viability. Conclusion: None of the tested substances could completely eliminate Ef from the root canal space. Microsc. Res. Tech. 76:658–662, 2013. © 2013 Wiley Periodicals, Inc.     

Morphological alterations of radicular dentine pretreated with different irrigating solutions and irradiated with 980-nm diode laser

Background: The topographical features of intraradicular dentine pretreated with sodium hypochlorite (NaOCl) or ethylenediamine tetraacetic acid (EDTA) followed by diode laser irradiation have not yet been determined. Purpose: To evaluate the alterations of dentine irradiated with 980‐nm diode laser at different parameters after the surface treatment with NaOCl and EDTA. Study design: Roots of 60 canines were biomechanically prepared and irrigated with NaOCl or EDTA. Groups were divided according to the laser parameters: 1.5 W/CW; 1.5 W/100 Hz; 3.0 W/CW; 3.0 W/100 Hz and no irradiation (control). The roots were splited longitudinally and analyzed by scanning electron microscopy (SEM) in a quali‐quatitative way. The scores were submitted to two‐way Kruskal–Wallis and Dunn's tests. Results: The statistical analysis demonstrated that the specimens treated only with NaOCl or EDTA (control groups) were statistically different (P < 0.05) from the laser‐irradiated specimens, regardless of the parameter setting. The specimens treated with NaOCl showed a laser‐modified surface with smear layer, fissures, and no visible tubules. Those treated with EDTA and irradiated by laser presented absence of smear layer, tubules partially exposed and melting areas. Conclusions: The tested parameters of 980‐nm diode laser promoted similar alterations on dentine morphology, dependent to the type of surface pretreatment. Microsc. Res. Tech., 2009. © 2008 Wiley‐Liss, Inc.     

Comparative atomic force and scanning electron microscopy: an investigation on fenestrated endothelial cells in vitro

Rat liver sinusoidal endothelial cells (LEC) contain fenestrae, which are clustered in sieve plates. Fenestrae control the exchange of fluids, solutes and particles between the sinusoidal blood and the space of Disse, which at its back side is flanked by the microvillous surface of the parenchymal cells. The surface of LEC can optimally be imaged by scanning electron microscopy (SEM), and SEM images can be used to study dynamic changes in fenestrae by comparing fixed specimens subjected to different experimental conditions. Unfortunately, the SEM allows only investigation of fixed, dried and coated specimens. Recently, the use of atomic force microscopy (AFM) was introduced for analysing the cell surface, independent of complicated preparation techniques. We used the AFM for the investigation of cultured LEC surfaces and the study of morphological changes of fenestrae. SEM served as a conventional reference.
AFM images of LEC show structures that correlate well with SEM images. Dried-coated, dried-uncoated and wet-fixed LEC show a central bulging nucleus and flat fenestrated cellular processes. It was also possible to obtain height information which is not available in SEM. After treatment with ethanol or serotonin the diameters of fenestrae increased (+6%) and decreased (−15%), respectively. The same alterations of fenestrae could be distinguished by measuring AFM images of dried-coated, dried-uncoated and wet-fixed LEC. Comparison of dried-coated (SEM) and wet-fixed (AFM) fenestrae indicated a mean shrinkage of 20% in SEM preparations. In conclusion, high-resolution imaging with AFM of the cell surface of cultured LEC can be performed on dried-coated, dried-uncoated and wet-fixed LEC, which was hitherto only possible with fixed, dried and coated preparations in SEM and transmission electron microscopy (TEM).     

Influence of passive ultrasonic irrigation on the efficiency of various irrigation solutions in removing smear layer: a scanning electron microscope study

To evaluate the influence of passive ultrasonic irrigation (PUI) to remove the smear layer with different irrigation solutions. Seventy‐eight single rooted mandibular premolars were used. The working lengths were measured and the root canals were prepared by using nickel titanium rotary files. The specimens were subjected to six different irrigation regimens: sodium hypochloride (NaOCl) with classic irrigation (CI); NaOCl with PUI; EDTA with CI; EDTA with PUI; QMix with CI; and QMix with PUI. The specimens were split longitudinally. Scanning electron microscopy images were taken to evaluate the amount of residual smear layer and scored. Statistical analysis was performed with the Kruskal–Wallis test. The Dunn's test was used for post hoc testing after the Kruskal–Wallis test. The smear layer scores of apical thirds were significantly higher than coronal and middle thirds except for NaOCl + CI group (p < 0.001). The irrigation with PUI improved the efficacy of all irrigation solutions on removal of smear layer in both coronal and middle thirds (p < 0.001). The PUI activation increased the activity of NaOCl, EDTA, and QMix, respectively without any significance. All irrigation regimens were significantly more effective in coronal and middle thirds compared to apical third. PUI significantly increased the efficacy of smear layer removal regardless of irrigation solution.