L'utilizzo della microscopia elettronica a scansione a pressione variabile nella valutazione delle strutture anatomiche del dente e dei materiali utilizzati in odontoiatria

La microscopia elettronica a scansione (SEM) è una metodica di grande importanza e largamente utilizzata in tutte le comunità scientifiche e tecnologiche. Tuttavia, nel tempo si è resa evidente la necessità di sviluppi e innovazioni concernenti il SEM e il suo utilizzo nell’ambito della ricerca scientifica, specialmente per ciò che riguarda le osservazioni dei campioni biologici. Da qui l'avvento dei SEM che utilizzano gas per la formazione di immagini, fornendo contemporaneamente stabilizzazione della carica elettronica per i campioni non conduttivi. Una delle maggiori difficoltà nel campo della microscopia elettronica a scansione a pressione variabile (VPSEM) è che non ci sono semplici regole che definiscono quali parametri utilizzare. Ogni campione, a seconda delle proprie caratteristiche superficiali e proprietà, avrà dei parametri operativi adottati "su misura" per il campione preso in analisi. Solo tramite l’analisi e la produzione di una corposa letteratura scientifica si potranno ottenere parametri standard e corretti, ovviamente sempre dipendenti dal campione da osservare. Il VPSEM è diventato uno strumento molto importante per l'imaging di campioni idratati e campioni a bassa conduttività. Il vantaggio principale di questo strumento è dato dalla possibilità di osservare campioni senza le varie fasi di preparazione che si attuano prima delle osservazioni tramite SEM convenzionale, le quali possono portare ad artefatti sulla superficie del campione. Pertanto, nella ricerca odontoiatrica, dove la prevalenza delle osservazioni viene effettuata sui denti, e quindi su un tessuto biologico duro ed idratato, il VPSEM può apportare numerosi vantaggi nelle osservazioni, come vedremo più avanti nei vari campi applicativi. Evitando la fase di preparazione del campione, avremo la possibilità di osservare un modello più vicino al reale stato clinico; inoltre, lo stesso campione sarà osservabile più volte, mantenendosi anche idratato, visto che non dovrà subire fasi irreversibili nella preparazione, quali la disidratazione e la metallizzazione. Non ci sono limitazioni per i campi applicativi del VPSEM; infatti è possibile analizzare sia le diverse strutture anatomiche del dente, che i materiali che vengono utilizzati in odontoiatria oppure gli strumenti metallici, come quelli in NiTi utilizzati prevalentemente per i canali radicolari. In particolare, in questo studio sono stati analizzati : 1) Analisi della stabilità nel tempo dell'adattamento marginale di Endosequence Root Repair Material su campioni biologici; 2) Caratterizzazione in vitro della biocompatibilità e delle proprietà antibiotiche dei cementi endodontici a base di calcio e silicati; 3) Studio preliminare di valutazione e misurazione delle fibre di Sharpey su campioni dentali fossili e risalenti ad epoca romana; 4) Ruolo della superficie progettata in piano nel miglioramento della resistenza alla fatica ciclica degli strumenti rotanti endodontici in NiTi; 5) Differenze nella durata di vita a fatica ciclica tra due diversi strumenti rotanti endodontici NiTi trattati termicamente: WaveOne Gold contro EdgeOne Fire. I risultati ottenuti non danno informazioni contrastanti rispetto a quelli finora raggiunti tramite il SEM convenzionale. In conclusione è necessario apprendere al meglio i vantaggi del VPSEM per sfruttare questo tipo di strumento al massimo. Tuttavia, solo la combine dei due strumenti VPSEM e SEM convenzionale potrà fornire risultati certi e precisi, sfruttando le osservazioni senza preparazione del VPSEM e la miglior risoluzione ad alto ingrandimento del SEM convenzionale

Role of the flat-designed surface in improving the cyclic fatigue resistance of endodontic NiTi rotary instruments

The aim of this study was to investigate the role of the flat-designed surface in improving the resistance to cyclic fatigue by comparing heat-treated F-One (Fanta Dental, Shanghai, China) nickel-titanium (NiTi) rotary instruments and similar prototypes, differing only by the absence of the flat side. The null hypothesis was that there were no differences between the two tested instruments in terms of cyclic fatigue lifespan. A total of 40 new NiTi instruments (20 F-One and 20 prototypes) were tested in the present study. The instruments were rotated with the same speed (500 rpm) and torque (2 N) using an endodontic motor (Elements Motor, Kerr, Orange, CA, USA) in the same stainless steel, artificial canal (90° angle of curvature and 5 mm radius). A Wilcoxon-Mann-Whitney test was performed to assess the differences in terms of time to fracture and the length of the fractured segment between the flat- and non-flat-sided instruments. Significance was set at p = 0.05. The differences in terms of time to fracture between non-flat and flat were statistically significant (p < 0.001). In addition, the differences in terms of fractured segment length were statistically significant (p = 0.034). The results of this study highlight the importance of flat-sided design in increasing the cyclic fatigue lifespan of NiTi rotary instruments

Differences in cyclic fatigue lifespan between two different heat treated NiTi endodontic rotary instruments : Waveone gold vs Edgeone fire

Aim of this study is to investigate the cyclic fatigue resistance of the Gold treated WaveOne Gold and the Firewire treated EdgeOne Fire instruments. The null hypotesis was that there were no differences between the lifespan of Gold treated and FireWire treated instruments when subjected to cyclic fatigue tests. 40 new NiTi instruments with a length of 25 mm were tested: 20 Wave One Gold Medium (WOG), tip size 35 and variable taper (Dentsply Maillefer, Ballaigues, Switzerland) and 20 Edge One Fire (EOF) (EdgeEndo, Albuquerque, New Mexico) tip size 35 and the same variable taper. A mobile support for the electric handpiece and a stainless-steel block containing the artificial canals were used. The same artificial root canal with a 90 degrees angle of curvature and 2 mm radius of curvature was used for all the tested instruments and the WOG counter-clock wise reciprocating motion with an engaging angle of 150° and a disengaging angle of 30° at 300 rpm, was selected for the test. All instruments were inserted at the same length (18mm) and then rotated in the same reciprocating motion until fracture occurred: the time was stopped as soon as the fracture was visible and video-recorded with a 1/100 sec chronometer. Differences among groups were statistically evaluated with an analysis of variance test ANOVA (significance level was set at p<0.05). Mean values of time to fracture (TtF) for EOF instruments were 28,00 seconds (SD +/- 2,64) and for WOG instruments were 14,67 seconds (SD +/- 2,41). Statistical analysis found significant differences between the TtF of the two instruments (p<0,05). Firewire instruments resulted to be about two times more resistant to cyclic fatigue when compared with identical instruments made with Gold treatment

The application of a fluoride-and-vitamin D solution to deciduous teeth promotes formation of persistent mineral crystals: a morphological ex-vivo study

Background: The use of effective, low-cost, and easy-to-use products for early caries management will avoid loss of dental vitality and impairment in oral function. The ability of fluoride to re-mineralize dental surfaces has been widely reported as well as vitamin D demonstrated to have significant potential in improving the remineralization of early lesions on enamel surfaces. The aim of the present ex vivo study was to evaluate the effect of a fluoride and vitamin D solution in terms of formation of mineral crystals on the enamel of primary teeth, and their permanence over time on dental surfaces. Methods: Sixteen extracted deciduous teeth were cut to obtain 64 specimens that were divided into two groups. The first consisted of immersion of specimens for 4 days in a fluoride solution (T1); in the second group, the specimens were immersed for 4 days (T1) in fluoride and Vitamin D solution, and for a further 2 (T2) and 4 days (T3) in saline solution. Then, samples were morphologically analyzed by using Variable Pressure Scanning Electron Microscope (VPSEM) and underwent 3D surface reconstruction. Results: After a 4-day immersion in both solutions, octahedral-shaped crystals were formed on the enamel surface of primary teeth, demonstrating any statistically significant differences in terms of number, size, and shape. Moreover, the binding of the same crystals seemed to be strong enough to be maintained until 4 days in saline solution. However, a partial dissolution was observed in a time-dependent manner. Conclusions: A topical application of fluoride and Vitamin D promoted the formation of persistent mineral crystals on enamel surfaces of deciduous teeth and should be further studied to be potentially used as an alternative strategy in preventive dentistry

Mechanical and Metallurgical Evaluation of 3 Different Nickel-Titanium Rotary Instruments: An In Vitro and In Laboratory Study

An in-depth evaluation of the mechanical and metallurgical properties of NiTi instruments is fundamental to assess their performance and to compare recently introduced instrument with widespread ones. According to this, since there are no data on this topic, the aim of the study was to mechanically and metallurgically evaluate an instrument recently introduced into the market (ZenFlex (ZF)), by comparing it with two well-known instruments with similar characteristics: Vortex Blue (VB) and EdgeSequel Sapphire (EES). According to this, 195 instruments were selected: 65 ZF, 65 VB and 65 EES. Each group was divided in subgroups according to the mechanical tests (i.e., cyclic fatigue resistance, torsional resistance and bending ability; (n = 20)) and the metallurgical test (differential scanning calorimetry (n = 5)). A scanning electron microscopy was performed to verify the causes of fracture after mechanical tests (cyclic fatigue and torsional tests). According to results, VB showed the highest flexibility and cyclic fatigue resistance in comparison to the other instruments, with a statistically significant difference (p &lt; 0.05). Regarding torsional resistance, EES showed the lowest value of torque at fracture, with a statistically significant difference, whilst the comparison between ZF and VB showed no statistically significant difference (p &gt; 0.05). DSC analysis pointed out that VB had the highest austenite start and finish temperatures, followed by ESS and then ZF. ESS sample showed the highest martensite start and finish temperatures followed by VB and ZF. Considering the results, it can be concluded that VB showed the best mechanical performance during static tests in comparison to ESS and ZF. This is fundamentally due to the interaction of parameters such as instrument design and heat-treatments that are able to enhance its mechanical performance

Analysis of stability in time of marginal adaptation of endosequence root repair material on biological samples

Introduction: The introduction of mineral trioxide aggregate (MTA) and bioceramic sealers increased the success rate of endodontic surgery and perforation repair. The aim of this study was to evaluate the marginal adaptation at different times of endosequence root repair material (ERMM) in order to evaluate its dimensional stability using variable pressure-scanning electron microscope (VP-SEM). Material and Methods: Fourty-eight teeth were selected shaped up to a master apical size of 25. Then a 3mm cut perpendicular to the long axis and a retrograde cavity preparation were performed. In order to obtain 2mm thick sample a second cut was done and, in this disk, ERMM was inserted. The samples were stored at 37°.The samples were divided into four time-depending groups observed with VP-SE Mat time0 (Group 1) andafter2 (Group2),7(Group 3) and 30 days (Group4) after ERRM setting. Statistical analysis with one way-ANOVA test was performed (95%). Results: None of the four groups analyzed showed a complete marginal adaptation between dentin and ERRM. Instead, in all groups ERRM exhibited a completely preserved marginal adaptation to the dentin wall in all time-dependent groups. The mean (±SD) gap value was fortime0,3.91(±2.55) mmafter2days,4.32(±2.69), after7days4.49(±2.53), and after30days4.81(±2.85) mm. No statistically significant difference was found between the four groups. Conclusions: The results of the present study demonstrate the dimensional stability over time of ERMM

Microscopy methods for biofilm imaging: focus on SEM and VP-SEM pros and cons

Several imaging methodologies have been used in biofilm studies, contributing to deep- ening the knowledge on their structure. This review illustrates the most widely used microscopy techniques in biofilm investigations, focusing on traditional and innovative scanning electron mi- croscopy techniques such as scanning electron microscopy (SEM), variable pressure SEM (VP-SEM), environmental SEM (ESEM), and the more recent ambiental SEM (ASEM), ending with the cutting edge Cryo-SEM and focused ion beam SEM (FIB SEM), highlighting the pros and cons of several methods with particular emphasis on conventional SEM and VP-SEM. As each technique has its own advantages and disadvantages, the choice of the most appropriate method must be done carefully, based on the specific aim of the study. The evaluation of the drug effects on biofilm requires imaging methods that show the most detailed ultrastructural features of the biofilm. In this kind of research, the use of scanning electron microscopy with customized protocols such as osmium tetroxide (OsO4), ruthenium red (RR), tannic acid (TA) staining, and ionic liquid (IL) treatment is unrivalled for its image quality, magnification, resolution, minimal sample loss, and actual sample structure preserva- tion. The combined use of innovative SEM protocols and 3-D image analysis software will allow for quantitative data from SEM images to be extracted; in this way, data from images of samples that have undergone different antibiofilm treatments can be compared

SiO2 nanoparticles as new repairing treatments toward the Pietraforte sandstone in Florence renaissance buildings

In this work, the consolidation efficiency of SiO2 nanoparticles (synthesized in the Chemistry laboratories at the Tor Vergata University of Roma) was tested on Pietraforte sandstone surfaces belonging to the bell tower of San Lorenzo (Florence, Italy) and was fully investigated. Nanoparticles (synthesized in large-scale mass production) have been characterized by XRD—X-Ray Diffraction; Raman and FTIR—Fourier Transform Infrared spectroscopy; SEM—Scanning Electron Microscopy; while the Pietraforte sandstone morphology was examined by Porosimetry, capillary absorption test, surface hardness test, drilling resistance and tensile strength. The colorimetric measurements were also performed to characterize the optical modification exhibited by Pietraforte sandstones, especially after the SiO2 treatments. Our results show that applying to the Pietraforte, the new consolidating agent based on SiO2 nanoparticles, has several advantages, as they are more resistant to perforation, wear, and abrasion even long range (for long times of exposure and consolidating exercise against Florentine sandstone), compared to the CaCO3 nanoparticles (tested in our previous paper), which instead show excellent performance but only close to their first application. This means that over time, their resistance to drilling decreases, they wear much more easily (compared to SiO2 -treated sandstone), and tend to exhibit quite a significant surface abrasion phenomena. The experimental results highlight that the SiO2 consolidation efficiency on this kind of Florentine Pietraforte sandstone (having low porosity and a specific calcitic texture) seems to be higher in terms of water penetration protection, superficial cohesion forces, and an increase in surface resistance. Comparing the performance of SiO2 nanoparticles with commercial consolidants in solvents such as Estel 1000 (tested here), we demonstrate that: (A) the restorative effects are obtained with a consolidation time over one week, significantly shorter when compared to the times of Estel 1000, exceeding 21 days; (B) SiO2 nanoparticles perform better than Estel 1000 in terms of cohesion forces, also ensuring excellent preservation of the optical and color properties of the parent rock (without altering it after application)

Essential oils biofilm modulation activity, chemical and machine learning analysis. Application on staphylococcus aureus isolates from cystic fibrosis patients

Bacterial biofilm plays a pivotal role in chronic Staphylococcus aureus (S. aureus) infection and its inhibition may represent an important strategy to develop novel therapeutic agents. The scientific community is continuously searching for natural and “green alternatives” to chemotherapeutic drugs, including essential oils (EOs), assuming the latter not able to select resistant strains, likely due to their multicomponent nature and, hence, multitarget action. Here it is reported the biofilm production modulation exerted by 61 EOs, also investigated for their antibacterial activity on S. aureus strains, including reference and cystic fibrosis patients’ isolated strains. The EOs biofilm modulation was assessed by Christensen method on five S. aureus strains. Chemical composition, investigated by GC/MS analysis, of the tested EOs allowed a correlation between biofilm modulation potency and putative active components by means of machine learning algorithms application. Some EOs inhibited biofilm growth at 1.00% concentration, although lower concentrations revealed dierent biological profile. Experimental data led to select antibiofilm EOs based on their ability to inhibit S. aureus biofilm growth, which were characterized for their ability to alter the biofilm organization by means of SEM studies

Effect of ciprofloxacin-loaded niosomes on escherichia coli and staphylococcus aureus biofilm formation

Infections caused by bacterial biofilms represent a global health problem, causing considerable patient morbidity and mortality in addition to an economic burden. Escherichia coli, Staphylococcus aureus, and other medically relevant bacterial strains colonize clinical surfaces and medical devices via biofilm in which bacterial cells are protected from the action of the immune system, disinfectants, and antibiotics. Several approaches have been investigated to inhibit and disperse bacterial biofilms, and the use of drug delivery could represent a fascinating strategy. Ciprofloxacin (CIP), which belongs to the class of fluoroquinolones, has been extensively used against various bacterial infections, and its loading in nanocarriers, such as niosomes, could support the CIP antibiofilm activity. Niosomes, composed of two surfactants (Tween 85 and Span 80) without the presence of cholesterol, are prepared and characterized considering the following features: hydrodynamic diameter, ζ-potential, morphology, vesicle bilayer characteristics, physical-chemical stability, and biological efficacy. The obtained results suggest that: (i) niosomes by surfactants in the absence of cholesterol are formed, can entrap CIP, and are stable over time and in artificial biological media; (ii) the CIP inclusion in nanocarriers increase its stability, with respect to free drug; (iii) niosomes preparations were able to induce a relevant inhibition of biofilm formation