Scanning Electron Microscopy Evaluation of Dental Root Resorption Associated With Granuloma.

The inflammatory resorption of dental root apex (i.e., the process of removal of cementum and/or dentine through the activity of resorbing cells) may show different configurations and damage the apical root structure. As knowing the morphology of resorption areas of human teeth is essential for the success of endodontic treatments, we investigated the apical resorption by scanning electron microscopy, focusing on roots with granulomas. A total of 30 teeth (with penetrating carious lesions and chronic periapical lesions) were examined, the apical third of the roots were removed and analyzed to estimate periforaminal and foraminal resorption, shape and morphology of foramen resorption, centering of the periforaminal resorption area, and diameters of each apical foramen. Periforaminal resorption was present in all samples, whereas foraminal resorption was present in 92% of cases (mainly funnel shaped). Lacunae were observed in the foraminal resorption area with an average diameter of 35±14 µm. The major and minor diameters of the foramina in teeth with resorption were 443 and 313 µm, respectively (higher than in healthy teeth). This result indicates an expansion of the apical diameters caused by the pathology, which could encourage a different clinical instrumentation for these teeth.

Biological, thermal and mechanical characterization of modified glass ionomer cements: The role of nanohydroxyapatite, ciprofloxacin and zinc l-carnosine.

The study evaluated the effects of 4 wt% nanohydroxyapatite (HA), 6 wt% zinc l-carnosine (MDA) and 1.5 wt% Ciprofloxacin (AB) on the mechanical, thermal and biological properties of glass ionomer cements (GIC). Filler and additive concentrations were selected after a previous study had tested single components and different percentages. Specimens included five silicon molds of each GIC cement for all tests. They were stored at room temperature for 24 h from specimen collection to analysis. Mechanical tests, calorimetric analysis, morphological investigation, antibacterial and cell viability assays were conducted. One-way analysis of variance (ANOVA) was used for data analysis with significance set at p < 0.05. Adding HA, MDA and AB to GICs modified their thermal, mechanical and microbiological properties. Polymerization increased. A slight decrease in the compressive strength of modified GICs was observed in dry condition (p < 0.05). Cement extracts affected cell viability in relation to extract dilution. Mechanical behavior improved in modified glass ionomer cements, especially with the powder formulated antibiotic. Overall cytotoxicity was reduced. Therefore adding nanohydroxyapatite, antibiotic and a mucosal defensive agent to conventional glass ionomer cement in special need patients could improve the clinical, preventive and therapeutic performance of the cements, without altering their mechanical properties.

Effect of fibre posts, bone losses and fibre content on the biomechanical behaviour of endodontically treated teeth: 3D-finite element analysis.

The aim of this work was to evaluate the stress distribution inside endodontically treated teeth restored with different posts (glass fibre, carbon fibre and steel posts) under different loading conditions by using a 3D-finite element analysis. The effect of masticatory and impact forces on teeth with different degrees of bone loss was analysed. The model consists of: dentine, post, cement, gutta-percha, core and crown. Four simulations were conducted with two static forces (170N horizontal and 100N oblique) and two sections constrained: 1mm (alveolar bone position in a normal periodontium) and 6mm (middle of root) below the crown. Von Mises and the principal stresses were evaluated and analysed with a 3-way ANOVA and Tukey test (α=0.05) and the effect of fibre percentage analysed. Significant differences were found among the stress values for all conditions (p<0.05). Impact load was always responsible for the most critical situation especially when the bone loss was more evident. The system with steel posts showed the highest principal stresses at the post-cement interface with horizontal load and top constraints (compressive stress of 121MPa and tensile stress of 115MPa). The use of glass posts provides a more homogeneous behaviour of the system with lower stresses. Higher fibre percentages gave higher stress in the posts. Moreover, larger bone losses are responsible for important increase in stress. Thus, this work demonstrated that periodontal disease has an important role in the success of tooth restoration after endodontic therapy, influencing the choice of post material and depth.

Nanomaterials for Tissue Engineering In Dentistry.

The tissue engineering (TE) of dental oral tissue is facing significant changes in clinical treatments in dentistry. TE is based on a stem cell, signaling molecule, and scaffold triad that must be known and calibrated with attention to specific sectors in dentistry. This review article shows a summary of micro- and nanomorphological characteristics of dental tissues, of stem cells available in the oral region, of signaling molecules usable in TE, and of scaffolds available to guide partial or total reconstruction of hard, soft, periodontal, and bone tissues. Some scaffoldless techniques used in TE are also presented. Then actual and future roles of nanotechnologies about TE in dentistry are presented.

A New Phase Change Material Based on Potassium Nitrate with Silica and Alumina Nanoparticles for Thermal Energy Storage.

In this study different nanofluids with phase change behavior were developed by mixing a molten salt base fluid (KNO3 selected as phase change material) with nanoparticles using the direct synthesis method. The thermal properties of the nanofluids obtained were investigated. Following the improvement in the specific heat achieved, these nanofluids can be used in concentrating solar plants with a reduction of storage material. The nanoparticles used (1.0 wt.%) were silica (SiO2), alumina (Al2O3), and a mix of silica-alumina (SiO2-Al2O3) with an average diameter of 7, 13, and 2-200 nm respectively. Each nanofluid was prepared in water solution, sonicated, and evaporated. Measurements of the thermophysical properties were performed by DSC analysis, and the dispersion of the nanoparticles was analyzed by SEM microscopy. The results obtained show that the addition of 1.0 wt.% of nanoparticles to the base salt increases the specific heat of about 5-10 % in solid phase and of 6 % in liquid phase. In particular, this research shows that the addition of silica nanoparticles has significant potential for enhancing the thermal storage characteristics of KNO3. The phase-change temperature of potassium nitrate was lowered up to 3 °C, and the latent heat was increased to 12 % with the addition of silica nanoparticles. These results deviated from the predictions of theoretical simple mixing model used. The stored heat as a function of temperature was evaluated for the base salt, and the nanofluids and the maximum values obtained were 229, 234, 242, and 266 J/g respectively. The maximum total gain (16 %) due to the introduction of the nanoparticles (calculated as the ratio between the total stored heat of the nanofluids and the base salt in the range of temperatures 260-390 °C) was also recorded with the introduction of silica. SEM and EDX analysis showed the presence of aggregates in all nanofluids: with silica nanoparticles they were homogenously present while with alumina and silica-alumina also zones with pure salt could be detected.

Mechanical effect of static loading on endodontically treated teeth restored with fiber-reinforced posts.

The aim of this study was to investigate the mechanical behavior of a dental system built up with fiber-reinforced composite (FRC) endodontic posts with different types of fibers and two cements (the first one used with a primer, the second one without it). Six FRC posts were used. Each system was characterized in terms of structural efficiency under external applied loads similar to masticatory forces. An oblique force was applied and stiffness and maximum load data were obtained. The same test was used for the dentine. The systems were analyzed by scanning electron microscope (SEM) to investigate the surface of the post and inner surface of root canal after failure. The mechanical tests showed that load values in dental systems depend on the post material and used cement. The highest load (281 ± 59 N) was observed for the conical glass fiber posts in the cement without primer. There was a 50 and 85% increase in the maximum load for two of the conical posts with glass fibers and a 229% increase for the carbon fiber posts in the cement without primer as compared with the cement with primer. Moreover, almost all the studied systems showed fracture resistances higher than the typical masticatory loads. The microscopic analysis underlined the good adhesion of the second cement at the interfaces between dentine and post. The mechanical tests confirmed that the strength of the dental systems subjected to masticatory loads was strictly related to the bond at the interface post/cement and cement/dentine.

Effect of nanoparticles on heat capacity of nanofluids based on molten salts as PCM for thermal energy storage.

In this study, different nanofluids with phase change behavior were developed by mixing a molten salt base fluid (selected as phase change material) with nanoparticles using the direct-synthesis method. The thermal properties of the nanofluids obtained were investigated. These nanofluids can be used in concentrating solar plants with a reduction of storage material if an improvement in the specific heat is achieved. The base salt mixture was a NaNO3-KNO3 (60:40 ratio) binary salt. The nanoparticles used were silica (SiO2), alumina (Al2O3), titania (TiO2), and a mix of silica-alumina (SiO2-Al2O3). Three weight fractions were evaluated: 0.5, 1.0, and 1.5 wt.%. Each nanofluid was prepared in water solution, sonicated, and evaporated. Measurements on thermophysical properties were performed by differential scanning calorimetry analysis and the dispersion of the nanoparticles was analyzed by scanning electron microscopy (SEM). The results obtained show that the addition of 1.0 wt.% of nanoparticles to the base salt increases the specific heat of 15% to 57% in the solid phase and of 1% to 22% in the liquid phase. In particular, this research shows that the addition of silica-alumina nanoparticles has a significant potential for enhancing the thermal storage characteristics of the NaNO3-KNO3 binary salt. These results deviated from the predictions of the theoretical model used. SEM suggests a greater interaction between these nanoparticles and the salt.

Compressive and flexural behaviour of fibre reinforced endodontic posts.

OBJECTIVES: The aim of this study was to investigate the mechanical properties of five types of fibre-reinforced composite (FRC) posts and compare them with traditional metal post. METHODS: Five FRC posts and a metallic post having different geometry and type of fibre (glass, carbon or quartz fibre) were loaded to failure in compression and bending. The transverse sections of FRC posts were observed using SEM to evaluate the fracture mode and the percentage of fibres (compared with burn-off test). Densities and voids content were also evaluated. RESULTS: Mechanical results were subjected to a one-way ANOVA and Tukey test (p<0.05). In compression, quartz fibre posts exhibited the greater maximum load and ultimate strength, carbon fibre posts showed a poor compressive behaviour. All posts had similar compressive moduli. Carbon posts showed the highest flexural properties (p<0.0001) while glass posts the greater maximum load. The fracture load values correlated to the diameters of posts showed a parabolic behaviour. The flexural strengths of all posts were four and seven times higher than dentine. The elastic moduli of almost all posts were similar to dentine. The compressive strengths were lower than flexural strengths. The fibre diameters ranged from 5.2 to 26 µm, the volume percentage of fibres was about 64%. The content of voids of some posts lower their mechanical behaviour. CONCLUSIONS: Compressive properties of FRC posts were lower than in bending. The flexural properties of FRC posts were higher than the metal post and similar to dentine. The mechanical behaviour is influenced by voids.