Investigations on the Degradation Behavior of Processed FeMnSi-xCu Shape Memory Alloys.

A new functional Fe-30Mn-5Si-xCu (x = 1.5 and 2 wt%) biomaterial was obtained from the levitation induction melting process and evaluated as a biodegradable material. The degradation characteristics were assessed in vitro using immersion tests in simulated body fluid (SBF) at 37 ± 1 °C, evaluating mass loss, pH variation that occurred in the solution, open circuit potential (OCP), linear and cyclic potentiometry (LP and CP), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and nano-FTIR. To obtain plates as samples, the cast materials were thermo-mechanically processed by hot rolling. Dynamic mechanical analysis (DMA) was employed to evaluate the thermal properties of the smart material. Atomic force microscopy (AFM) was used to show the nanometric and microstructural changes during the hot rolling process and DMA solicitations. The type of corrosion identified was generalized corrosion, and over the first 3-5 days, an increase in mass was observed, caused by the compounds formed at the metal-solution interface. The formed compounds were identified mainly as oxides that passed into the immersion liquid. The degradation rate (DR) was obtained as a function of mass loss, sample surface area and immersion duration. The dynamic mechanical behavior and dimensions of the sample were evaluated after 14 days of immersion. The nanocompounds found on the surface after atmospheric corrosion and immersion in SBF were investigated with the Neaspec system using the nano-FTIR technique.

Development and Functionalization of a Novel Chitosan-Based Nanosystem for Enhanced Drug Delivery.

Nowadays, infection diseases are one of the most significant threats to humans all around the world. An encouraging strategy for solving this issue and fighting resistant microorganisms is to develop drug carriers for a prolonged release of the antibiotic to the target site. The purpose of this work was to obtain metronidazole-encapsulated chitosan nanoparticles using an ion gelation route and to evaluate their properties. Due to the advantages of the ionic gelation method, the synthesized polymeric nanoparticles can be applied in various fields, especially pharmaceutical and medical. Loading capacity and encapsulation efficiency varFied depending on the amount of antibiotic in each formulation. Physicochemical characterization using scanning electron microscopy revealed a narrow particle size distribution where 90% of chitosan particles were 163.7 nm in size and chitosan-loaded metronidazole nanoparticles were 201.3 nm in size, with a zeta potential value of 36.5 mV. IR spectra revealed characteristic peaks of the drug and polymer nanoparticles. Cell viability assessment revealed that samples have no significant impact on tested cells. Release analysis showed that metronidazole was released from the chitosan matrix for 24 h in a prolonged course, implying that antibiotic-encapsulated polymer nanostructures are a promising drug delivery system to prevent or to treat various diseases. It is desirable to obtain new formulations based on drugs encapsulated in nanoparticles through different preparation methods, with reduced cytotoxic potential, in order to improve the therapeutic effect through sustained and prolonged release mechanisms of the drug correlated with the reduction of adverse effects.

Influence of Dynamic Strain Sweep on the Degradation Behavior of FeMnSi-Ag Shape Memory Alloys.

Iron-based SMAs can be used in the medical field for both their shape memory effect (SME) and biodegradability after a specific period, solving complicated chirurgical problems that are partially now addressed with shape-memory polymers or biodegradable polymers. Iron-based materials with (28-32 wt %) Mn and (4-6 wt %) Si with the addition of 1 and 2 wt % Ag were obtained using levitation induction melting equipment. Addition of silver to the FeMnSi alloy was proposed in order to enhance its antiseptic property. Structural and chemical composition analyses of the newly obtained alloys were performed by X-ray diffraction (confirming the presence of ε phase), scanning electron microscopy (SEM) and energy-dispersive spectroscopy. The corrosion resistance was evaluated through immersion tests and electrolyte pH solution variation. Dynamic mechanical solicitations were performed with amplitude sweep performed on the FeMnSi-1Ag and FeMnSi-2Ag samples, including five deformation cycles at 40 °C, with a frequency of 1 Hz, 5 Hz and 20 Hz. These experiments were meant to simulate the usual behavior of some metallic implants subjected to repetitive mechanical loading. Atomic force microscopy was used to analyze the surface roughness before and after the dynamic mechanical analysis test followed by the characterization of the surface profile change by varying dynamic mechanical stress. Differential scanning calorimetry was performed in order to analyze the thermal behavior of the material in the range of -50-+200 °C. X-ray diffraction and Fourier transform infrared spectroscopy (FTIR) along with Neaspec nano-FTIR experiments were performed to identify and confirm the corrosion compounds (oxides, hydroxides or carbonates) formed on the surface.

Analysis of Degradation Products of Biodegradable ZnMgY Alloy.

Biodegradable metallic materials are increasingly gaining ground in medical applications. Zn-based alloys show a degradation rate between those recorded for Mg-based materials with the fastest degradation rate and Fe-based materials with the slowest degradation rate. From the perspective of medical complications, it is essential to understand the size and nature of the degradation products developed from biodegradable materials, as well as the stage at which these residues are eliminated from the body. This paper presents investigations conducted on the corrosion/degradation products of an experimental material (ZnMgY alloy in cast and homogenized state) after immersion tests in three physiological solutions (Dulbecco's, Ringer's and simulated body fluid (SBF)). Scanning electron microscopy (SEM) was used to highlight the macroscopic and microscopic aspects of corrosion products and their effects on the surface. An X-ray energy dispersive detector (EDS), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) provided general information about the compounds based on their non-metallic character. The pH of the electrolyte solution was recorded for 72 h during immersion. The pH variation of the solution confirmed the main reactions proposed for the corrosion of ZnMg. The agglomerations of corrosion products were on the micrometer scale, mainly oxides, hydroxides and carbonates or phosphates. The corrosion effects on the surface were homogeneously spread, with a tendency to connect and form cracks or larger corrosion zones, transforming the pitting corrosion pattern into a generalized one. It was noticed that the alloy's microstructure strongly influences the corrosion characteristics.

In-Vitro Analysis of FeMn-Si Smart Biodegradable Alloy.

Special materials are required in many applications to fulfill specific medical or industrial necessities. Biodegradable metallic materials present many attractive properties, especially mechanical ones correlated with good biocompatibility with vivant bodies. A biodegradable iron-based material was realized through electric arc-melting and induction furnace homogenization. The new chemical composition obtained presented a special property named SME (shape memory effect) based on the martensite transformation. Preliminary results about this special biodegradable material with a new chemical composition were realized for the chemical composition and structural and thermal characterization. Corrosion resistance was evaluated in Ringer's solution through immersion tests for 1, 3, and 7 days, the solution pH was measured in time for 3 days with values for each minute, and electro-corrosion was measured using a potentiostat and a three electrode cell. The mass loss of the samples during immersion and electro-corrosion was evaluated and the surface condition was studied by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). SME was highlighted with differential scanning calorimetry (DSC). The results confirm the possibility of a memory effect of the materials in the wrought case and a generalized corrosion (Tafel and cyclic potentiometry and EIS) with the formation of iron oxides and a corrosion rate favorable for applications that require a longer implantation period.

New Zn3Mg-xY Alloys: Characteristics, Microstructural Evolution and Corrosion Behavior.

Zinc biodegradable alloys attracted an increased interest in the last few years in the medical field among Mg and Fe-based materials. Knowing that the Mg element has a strengthening influence on Zn alloys, we analyze the effect of the third element, namely, Y with expected results in mechanical properties improvement. Ternary ZnMgY samples were obtained through induction melting in Argon atmosphere from high purity (Zn, Mg, and Y) materials and MgY (70/30 wt%) master alloys with different percentages of Y and keeping the same percentage of Mg (3 wt%). The corrosion resistance and microhardness of ZnMgY alloys were compared with those of pure Zn and ZnMg binary alloy. Materials were characterized using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), linear and cyclic potentiometry, and immersion tests. All samples present generalized corrosion after immersion and electro-corrosion experiments in Dulbecco solution. The experimental results show an increase in microhardness and indentation Young Modulus following the addition of Y. The formation of YZn12 intermetallic phase elements with a more noble potential than pure Zinc is established. A correlation is obtained between the appearance of new Y phases and aggressive galvanic corrosion.

The study of the Association of Decay Risk With Malocclusions in Mixed Dentition at Children From Northeast Romania. A Transversal Retrospective Study.

Aim: The purpose of this study was to investigate if high values of DMFT/dmft indices constitute risk factors for installation in various types of malocclusions in mixed dentition. Material and Methods: The study consisted of 600 study-cast with mixed dentitions coming from the children in northeastern Romania. WHO (World Health Organization) dental caries criteria were applied to both groups. The existence of an increased caries risk was deducted from the dmft (decay, missed, filled temporary teeth) and DMFT (Decay, Missed, Filled Teeth) indices related to age. Malocclusion was classified in the three planes in accordance with the major symptom. The statistical study was conducted in SPSS 16.0 for Windows. The risk factors we have identified through calculating the odds ratio and relative risk. Results: Mean value dmft/DMFT (index in mixed dentition was found 3.64±2.686. The highest values of the dmft/DMFT indices were found in patients with normal overjet (4.73± 2.892) and normal overbite (4.04±2.781). In the transverse plane, the lowest value of DMFT/dmft index was recorded in patients with spacing (2.63±1.915), and the highest values were observed in patients with the combined diagnosis of crowding and lateral cross bite (4.97±3.010) respectively of crowding and spacing (4.65 ±2.792).The presence of malocclusions in the three plans is not influenced by increased DMFT/dmft index (DMFT/dmft>5) unless combined diagnoses of crowding and lateral cross bite, and crowding and spacing where the relative risks are over 2.5. Conclusions: The present study concluded that the prevalence of dental caries in children with mixed dentition is higher in patients with normal overjet and overbite. In terms of the risk of developing a certain malocclusion with dental crowding associate with lateral cross bite, respectively dental crowding associate false spacing are present under a high caries activities.

RISK FACTORS AND PREDICTORS OF CROSSBITE AT CHILDREN.

AIM: was to determine the etiological risk factors and predictors of crossbite' treatment at children. MATERIAL AND METHODS: 270 cases with crossbites and 255 controls with other malocclusions were uniformly evaluated. The crossbites cases were divided in group I (anterior crossbite), group II (posterior crossbite) and group III (anterior and posterior crossbites) and were compared between them per Angle Class malocclusions, dysfunctional and dental causes, associations with other discrepancies, as well by need and types of treatment. Binary logistic regression was used to find risk factors and predictors. RESULTS: The mean age of cases was 10.25?2.770 years. There were found significant differences between the groups of crossbites cases (p<0.05). There were identified risk factors (non-attrition of deciduous teeth, Angle Class II malocclusion and permanent teeth extraction) and protective factors of the crossbite (the tooth decay of deciduous teeth, eruption anomalies and tongue-thrust swallowing). There were found predictors for early corrective treatment (sucking habit, non-attrition and buds crowding) with a precision of 78.5%; for normal treatment (mouth breathing and buds crowding) with a precision of 71.5%; for late treatment (Angle Class III malocclusion, dental crowding and TMJ disorders) with a precision of 83.0%; for maxillary expansion (eruption anomalies and buds crowding) with a precision of 77.0%; for oral associated surgery (macrodontia and TMJ disorders) with a precision of 75.9% (HL test, p > 0.05). CONCLUSION: The risk factors were dental furthermore; the predictors of treatment were adequate with dentition, etiology and disorders at age identification, suggesting the contribution of practitioners in intercepting this orthodontic emergency.

CEPHALOMETRIC FEATURES OF CLASS III MALOCCLUSION.

AIM: The study aimed to identify quantitative and relational characteristics of bone, dental and soft tissue structures for Class III malocclusion, according to gender and age range. MATERIAL AND METHODS: 60 conventional lateral cephalograms were divided into two groups according to ANB angle: the group of cases with skeletal Class III (n = 36) and a control group with skeletal Class I (n = 24). There were performed 53 digital cephalometric measurements according to Steiner, Tweed and Jarabak analyzes. The Kolmogorov-Smirnov, t-student and Levene tests were used to find the characteristics of Class III, using SPSS 16.0 for Windows. RESUITS: We found 14 parameters that distinguished the two classes disorders (the angles SNB, SND, FMA, IMPA, MeGoOcP, Mand 1-MeGo, NSAr, ArGoMe, NGoMe and SNPog; the distances Ao-Bo and lu-NPog; Holdaway and AFH ratios) and 3 parameters for the Class III age ranges (NGoAr angle, Ls-NsPog' distance and S-Ar:Ar-Go ratio) (p ≤ 0.05). There were found no significant differences between genders for skeletal Class III. CONCLUSION: Emphasizing the cephalometric characteristics of Class III malocclusion, with the overall growth together with dental and occlusion development, requires early orthodontic therapy.

Craniofacial morphological changes of familial bilateral hypodontia of maxillary premolars.

The hypodontia of a permanent tooth from a dental group represents a normal evolution in human dentition morphology. Nevertheless, the hypodontia of two teeth within a dental group is a rare developmental anomaly when not associated to a systemic syndrome. The aim of this study was to report two rare cases of four maxillary premolars hypodontia, not including the third molar, of two white women from the same family. There were presented clinical, radiological and genetic findings. These cases are of interest to practitioners for four aspects: the atypical phenotype of hypodontia, the complexity of craniofacial morphological changes, the autosomal dominant familial inheritance with variable expressivity and the difficult classification of diagnosis.

[The characteristics of orofacial clefts in small communities]. / Caracteristicile despicaturilor oro-faciale în colectivitati închise.

AIM: Establishing the prevalence of orofacial clefts in a community of institutionalized children and the correlations with sex, weight at birth, life environment, maternal age and children's associated diseases. MATERIAL AND METHODS: The study was conducted on a batch of 37 living newly-born (15 boys and 22 girls) from 1987 to 1997, with orofacial clefts, institutionalized in placement centers from Iasi, who survived and were treated medical and surgical. The data were collected from the records found in the archives of these centers and were statistically processed with the EpiInfo 3.4.3. software a Center for Disease Control and Prevention C.D.C. (U.S.A.). RESULTS: In 1987, children with orofacial clefts represented 7.42% and in 1997, 2.18% from the total of all children institutionalized. The average rate of prevalence of live births with orofacial clefts was 3.7/year. The frequency of clefts lip and palate in children who survived was 54.06%, clefts lip was 37.84% and clefts palate of 8.10%. Statistically significant correlations were found between the types of orofacial clefts and sex, weight at birth, life environment, maternal age and children's associated diseases (Fcalculat > F(Fisher)). CONCLUSIONS: The results confirm the decreased incidence of children with orofacial clefts, the high prevalence of clefts lip and palate the existence of orofacial cleft complications and the need for orthodontic treatment.

Surface characteristics of retrieved coated and nickel-titanium orthodontic archwires.

OBJECTIVE: The purpose of this study was to investigate the effects of oral fluids and archwire-bracket friction on the surface characteristics of NiTi alloy orthodontic archwires with/without aesthetic coating, in vivo for 2-3 months. MATERIALS AND METHODS: Different cross-sections of NiTi Archwires (DENTSPLY GAC International) and Titanol Cosmetic Archwires (FORESTADENT® USA Inc.) were examined by electron microscopy with dual-beam and spectroscopy analysis, before and after a collecting protocol from patients with multi-technique. RESULTS: Initially, the orthodontic archwires showed microscopic manufacturing and coating defects in the physiognomic layer. After intra-oral exposure, amorphous organic matter deposits were observed on the surface of the NiTi Archwires and the wire coating presented exfoliation on the oral areas of friction with brackets. X-ray microanalysis revealed changes in all atomic and mass percentages of chemical elements from the surface of all retrieved dental archwires, nickel and titanium ion depletion and the occurrence of additional elements due to interactions with saliva. CONCLUSIONS: Intra-oral exposure of NiTi Archwires and the archwire-bracket friction of coated wire altered the morphology and changed the elemental composition of the surface due to the process of corrosion, adhesion of organic matters and ionic exchange with oral fluids.