Spherical Sub-micron Bioactive Glass Particles and Their Interaction with Cells In Vitro

Sub-micron bioactive glass particles (SMBGs) with composition 85 mol% SiO2 and 15 mol% CaO were synthesised and characterised. Bioactivity was demonstrated by the formation of calcium apatite following 5 days immersion in simulated body fluid (SBF). The effect of a 24 h exposure of human mesenchymal stem cells (hMSCs) to SMBGs at concentrations of 100, 150 and 200 μgml-1 on cell viability, metabolic activity and proliferation was determined using the LIVE/DEAD, MTT, total DNA and LDH assays after 1, 4 and 7 days of culture. None of the SMBG concentrations caused significant cytotoxicity, except the highest doses of 150 and 200 μgml-1 which significantly decreased hMSC metabolic activity after 7 days of culture. Cell proliferation decreased as SMBG concentration increased; however none of the SMBGs tested had a significant effect on DNA quantity compared to the control. Confocal microscopy confirmed cellular uptake and localisation of the SMBGs in the hMSC cytoskeleton. Transmission electron microscopy revealed that the SMBGs localised inside the cell cytoplasm and cell endosomes. To correlate the physiochemical properties (agglomerated versus non-agglomerated) of SMBGs with cellular behaviour, mono-dispersed bioactive glass particles (mono-SMBGs) of 80 mol% SiO2, 20 mol% CaO were synthesised with the diameters of 215 ± 20 nm. The effect of mono-SMBGs on both hMSCs and adipose stem cells (ADSC) were investigated using a range of cytotoxicity assays (LIVE/DEAD, MTT, Alamabar blue and Cyquant). Cytotoxicity data revealed that mono-SMBGs were non-cytotoxic to hMSCs or ADSC. TEM imaging techniques were applied to confirm the internalisation of the particles by the MSCs and ADSCs. It was shown, through confocal imaging, that mono-SMBGs were taken up readily by the cells through a clathrin and caveolae independent endocytosis process. In addition, the differentiation of the stem cells was investigated but the cells maintained their phenotype. Overall, the results presented in this thesis are of great importance for assessing the toxicity of sub-micron bioactive glass particles that may either be used as injectables, generated by wear or degradation of bioactive glass scaffolds or be used for other medical applications such as drug delivery or stem cell tracking

Polymeric Nanocomposite Structures Based on Functionalized Graphene with Tunable Properties for Nervous Tissue Replacement

Electroconductive scaffolds can be a promising approach to repair conductive tissues when natural healing fails. Recently, nerve tissue engineering constructs have been widely investigated due to the challenges in creating a structure with optimized physiochemical and mechanical properties close to the native tissue. The goal of the current study was to fabricate graphene-containing polycaprolactone/gelatin/polypyrrole (PCL/gelatin/PPy) and polycaprolactone/polyglycerol-sebacate/polypyrrole (PCL/PGS/PPy) with intrinsic electrical properties through an electrospinning process. The effect of graphene on the properties of PCL/gelatin/PPy and PCL/PGS/PPy were investigated. Results demonstrated that graphene incorporation remarkably modulated the physical and mechanical properties of the scaffolds such that the electrical conductivity increased from 0.1 to 3.9 ± 0.3 S m–1 (from 0 to 3 wt % graphene) and toughness was found to be 76 MPa (PCL/gelatin/PPy 3 wt % graphene) and 143.4 MPa (PCL/PGS/PPy 3 wt % graphene). Also, the elastic moduli of the scaffolds with 0, 1, and 2 wt % graphene were reported as 210, 300, and 340 kPa in the PCL/gelatin/PPy system and 72, 85, and 92 kPa for the PCL/PGS/PPy system. A cell viability study demonstrated the noncytotoxic nature of the resultant scaffolds. The sum of the results presented in this study suggests that both PCL/gelatin/PPy/graphene and PCL/PGS/PPy/graphene compositions could be promising biomaterials for a range of conductive tissue replacement or regeneration applications

Apical Extrusion of Debris after Canal Preparation with Hand-Files Used Manually or Installed on Reciprocating Air-Driven Handpiece in Straight and Curved Canals

Introduction: Apical debris extrusion (DE) subsequent to root canal instrumentation, is one of the most important causes of endodontic flare-ups. The aim of this study was to compare the amount of DE after root canal instrumentation using nickel-titanium (NiTi) hand files with step-back manual technique or installed on reciprocating handpiece. Methods and Materials: This study was conducted on mesiobuccal (MB) roots of extracted maxillary first molars (n=20) and roots of mandibular premolars (n=20) that were randomly divided into two groups (n=20) according to the armamentarium used for canal preparation (air-driven reciprocating handpiece or hand instrumentation). In each group, the MB and premolar roots were prepared with the main apical sizes of 35 and 40, respectively. The extruded debris were collected and weighed. Finally, the mean dry weights were compared using ANOVA and t-test, and Tukey’s Multiple Comparisons Procedures were used to determine the significant differences in amounts of DE. The level of significance was set at 0.05. Results: Regardless of the type of teeth, the mean values of DE, were significantly lower in the handpiece group (P<0.0001). In addition, significantly lower amounts of DE was observed in premolars in similar group (P<0.001). However, this difference was not significant in MB roots of molars (P=0.20). Conclusion: Root canal preparation with reciprocating handpiece can lead to significantly lower debris extrusion than the manual step-back technique. In handpiece-prepared canals, the amount of extruded debris was significantly lower in premolar teeth.Keywords: Apical; Apical Extrusion; Debris Extrusion; NiTi Files; Reciprocation; Step-Back Techniqu

Readiness of Iran Universities of Medical Sciences for Conducting Total Quality Management (TQM) according to Educational Managers’ Point of View

Background & Objective : Total Quality Management (TQM) is a new approach to management which must be implemented gradually during some stages. The first step is to create readiness for change conducting quality management is not possible before acquiring enough readiness. This study was conducted to evaluate the readiness of Iran Universities of Medical Sciences for conducting Total Quality Management (TQM) according to educational managers’ point of view. Methods : In this descriptive study, the participants were all educational managers of 34 Universities of Medical Sciences including 314 vice chancellors for educational affairs, heads of Medical Education Development Centers, deans and pro-vice chancellors for education. Data was collected using a researcher-made questionnaire containing 27 questions about 11 signs of readiness. Results : The results of this study revealed that, considering readiness for conducting Total Quality Management, 9% of the universities were moderate (50 to 59% of the score), 79% were approximately good (60 to 69% of the score) and 12% were good (70 to 73% of the score ). The mean score for universities’ readiness was 64.5%. Readiness for applying TQM philosophy in behavior had the highest score while readiness for allocating resources had the lowest score (78% and 47.86% respectively). Conclusion : The results imply that the universities have had an improving trend and an appropriate atmosphere is ready for conducting Total Quality Management. Keywords: Total Quality Management, Management approach, Quality management philosophy, University of Medical Sciences

Microtensile Bond Strength of Three Restorative Core Materials with IPS E.max Press Ceramic by Two Resin Cements

Objectives: The aim of this study was to compare the microtensile bond strengths (µ TBS) of three core materials with one lithium disilicate reinforced ceramic using two resin cements.Methods: Three core materials (Nulite F® (Biodental Technologies), Filtek Z250® (3M-ESPE), Prettau-Anterior® (Zirkonzhan, Germany)) were prepared as blocks (10×10×4 mm3) according to the manufacturer’s instructions. Lithium disilicate ceramic blocks were also constructed and bonded to core specimens with two dual curing luting resin cements (Duo-Link® (Schaumburg, IL), Bifix QM® (VOCO, Cuxhaven, Germany)). Micro-bar specimens were prepared and loaded in tension to determine the µ TBS Failure modes were classified by scanning electron microscope (SEM). Data were analysed using two-way ANOVA and Tukey HSD test.Results: The µ TBS varied significantly depending on the core materials and resin cements used (P< 0.05). The µ TBS of Bifix QM was significantly higher than of Duo-Link in all core materials. The µ TBS of zirconia core was significantly higher than of both composite cores with both resin cements. There were no statistically significant differences among Nulite F and Filtek Z250 (P> 0.05). The highest bond strength was obtained between zirconia core and Bifix QM (45.3 ± 6.7 MPa).Conclusion: In vitro µ TBS of glass ceramic blocks bonded to zirconia core material showed higher bond strength values than resin-based core material, regardless of the resin cement type used

Negotiation, Centering Ability and Transportation of Three Glide Path Files in Second Mesiobuccal Canals of Maxillary Molars: A CBCT Assessment

Introduction: The aim of this study was to compare negotiation, centering ability and transportation of three path finder rotary instruments (ProGlider, ScoutRace and M3 Pro-Gold Path File) to create glide path in second mesiobuccal (MB2) canals of maxillary molars with cone-beam computed tomography (CBCT). Methods and Materials:  In this in vitro study, 66 maxillary molars with separate second MB2 canals were selected with the following criteria: having 18-21 mm root length, without any resorption or calcification in radiography, without previous treatment and 20-40ºcurve according to Schneider’s method. Then MB2 canals were randomly divided into three groups (n=22). CBCT scan before and after root canal negotiation was taken. A #10 K-file for determination of working length was inserted into all canals. In group1; ProGlider file, group2; ScoutRace file and in group 3; M3 Pro-Gold Path file was implemented. The calculated data from CBCT based on reaching full working length (RFWL) or not (NRFWL) were analyzed using the Pearson Chi-square test. Centering ability was calculated by Fisher’s exact test and amount of transportation was determined with the Pearson Chi-square test in SPSS software. Results: ProGlider file had the least RFWL and ScoutRace was the best, but the results were not statistically significant (P>0.05). Regarding the centering ability and transportation, all 3 groups showed no significant differences (P>0.05), except at level of 2 mm from the apex in buccopalatal direction for ProGlider and ScoutRace files (P<0.05). Conclusion: In spite of insignificantly different results, ScoutRace file was better than other groups in negotiating and centering ability in mesiodistal direction of the MB2 canal in maxillary molars. Also, ProGlider file was significantly better than ScoutRace regarding transportation at level of 2 mm from apex in buccopalatal direction.Keywords: Centering Ability; Cone-Beam Computed Tomography; ProGlider; Second Mesiobuccal Canal; Transportation

Sol-gel synthesis of (Ca-Ba)TiO3 nanoparticles for bone tissue engineering

Piezoelectric materials are the group of smart materials which have been recently developed for biomedical applications, such as bone tissue engineering. These materials could provide electrical signals with no external source power making them effective for bone remodeling. Between various types of materials, BaTiO3 and CaTiO3 are nontoxic piezoelectric ceramics, which recently have been introduced for bone tissue engineering. It is expected that, the combination of these two ceramics could provide suitable piezoelectricity, bioactivity and biocompatibility for bone tissue engineering applications. The aim of this research is to synthesize (BaxCa1-x)TiO3 (x= 0, 0.6, 0.8, 0.9 and 1) nanopowder using sol-gel method. Moreover, the incorporation of Ca+2 ions in the structure of (BaxCa1-x)TiO3 nanoparticles was chemically, structurally and biologically studied. X-ray diffraction (XRD) and scanning electron microscopy (SEM) studies confirmed the role of substituted Ca content on the chemical properties and morphology of particles. Indeed, increasing the amounts of Ca+2 ions resulted in the reduced crystallite size. While incorporation of more than 20 at.% Ca resulted in the formation of a biphasic structure, monophasic solid solution without any secondary phase was detected at less Ca content. Moreover, SEM images revealed that Ca substitution reduced particle size from 70.5 ±12 nm to 52.4 ±9 nm, while the morphology of synthesized powders did not significacntly change. Furthermore, incorporation of upon 10 at.% Ca content within (BaxCa1-x)TiO3 significantly promoted MG63 proliferation compared to pure CaTiO3

Biocompatibility of Portland Cement Modified with Titanium Oxide and Calcium Chloride in a Rat Model

Introduction: The aim of the present study was to evaluate the biocompatibility of two modified formulations of Portland cement (PC) mixed with either titanium oxide or both titanium oxide and calcium chloride. Methods and Materials: Polyethylene tubes were filled with modified PCs or Angelus MTA as the control; the tubes were then implanted in 28 Wistar rats subcutaneously. One tube was left empty as a negative control in each rat. Histologic samples were taken after 7, 15, 30 and 60 days. Sections were assessed histologically for inflammatory responses and presence of fibrous capsule and granulation tissue formation. Data were analyzed using the Fisher’s exact and Kruskal-Wallis tests. Result: PC mixed with titanium oxide showed the highest mean scores of inflammation compared with others. There was no statistically significant difference in the mean inflammatory grades between all groups in each of the understudy time intervals. Conclusion: The results showed favorable biocompatibility of these modified PC mixed with calcium chloride and titanium oxide.Keywords: Biocompatibility; Mineral Trioxide Aggregate; Portland Cemen

Canal Transportation and Centering after Using PathFile and R-Pilot in Mesiobuccal Canals of Maxillary Molars Using Cone-Beam Computed Tomography

Introduction: This study aimed to compare the changes in root canal anatomy following the use of PathFile and R-Pilot using cone-beam computed tomography (CBCT). Methods and Materials: In this in vitro, experimental study, 60 extracted maxillary first and second molars with 20 to 40° mesiobuccal root curvature, minimum of 19 mm of root length, no calcified root canals and no history of previous treatment were divided into two groups (n=30). CBCT scans were taken before and after the treatment, and sections at 1, 2 and 3 mm from the apex were compared. Pairwise comparisons were carried out using the Mann Whitney-U test. The centering ratio data were analyzed using the Chi-square test and Fisher’s exact test. All statistical analyses were carried out using Sigma Stat 4 software. Results: The difference between PathFile and R-Pilot in canal transportation in mesiodistal direction was significant at 1 and 2 mm from the apex (P<0.01). The R-Pilot file was significantly superior to PathFile in centering ability in mesiodistal direction at 1 mm from the apex (P<0.05). Canal transportation direction was towards the mesiolingual and distobuccal in R-Pilot and PathFile groups, respectively. Conclusion: Within the limitations of this study, the results showed that R-Pilot with reciprocal movement is a safe and easy to use instrument for creating a glide path.Keywords: Canal Transportation; Cone-Beam Computed Tomography; Glide Path; PathFile; R-Pilo