Slavoljub Živković

New nanostructural biomaterials based on active silicate systems and hydroxyapatite: characterization and genotoxicity in human peripheral blood lymphocytes

AIM To characterize and investigate the genotoxic effect of a new endodontic cement based on dicalcium- and tricalcium-silicate (CS) with hydroxyapatite (HA) on human lymphocytes. METHODOLOGY Hydrothermal treatment was applied for synthesis of CS and HA. The final mixture HA-CS, with potential to be used in endodontic practice, is composed of CS (34%) and HA (66%). Human lymphocytes were incubated with HA, HA-CS and CS for 1 h, at 37 °C and 5% CO2. Cell viability was determined using the trypan blue exclusion assay. To evaluate the level of DNA damage comet assay (single cell gel electrophoresis) was performed. For the statistical analysis anova and Duncans Post Hoc Test were used. RESULTS The SEM analysis indicated that CS consisted mostly of agglomerates of several micrometers in size, built up from smaller particles, with dimensions between 117 and 477 nm. This is promising because dimensions of agglomerates are not comparable with channels inside the cell membranes, whereas their nano-elements provide evident activity, important for faster setting of these mixtures compared to MTA. Values of DNA damage obtained in the comet assay indicated low genotoxic risk of the new endodontic materials. CONCLUSIONS The significantly improved setting characteristics and low genotoxic risk of the new material support further research.

Biocompatibility of new nanostructural materials based on active silicate systems and hydroxyapatite: in vitro and in vivo study

AIM To evaluate in vitro cytotoxicity and in vivo inflammatory response to new nanostructural materials based on active calcium silicate systems (CS) and hydroxyapatite (HA-CS). METHODOLOGY Cytotoxicity of eluates of new nanostructural noncommercial materials CS and HA-CS, and MTA (White MTA, Angelus(®) Soluções Odontológicas, Londrina, Brazil) as a control, were tested using the MTT assay on MRC-5 cells. Eluates of set materials were tested in 100% and 50% concentrations, 24 h, 7 days and 21 days post-elution. The pH values were determined for undiluted eluates of set materials. Polyethylene tubes containing the test materials (CS, HA-CS, MTA) were implanted in subcutaneous tissue of Wistar rats. Histopathological examinations were conducted at 7, 15, 30 and 60 days after the implantation. Data were statistically analyzed using three-way and one-way anova Tukeys post hoc test as well as Kruskall-Wallis test with Dunns post hoc test at α = 0.05. RESULTS All materials significantly reduced cell viability; especially when undiluted eluates were used (P < 0.001). After 24 h elution, cell viability was 10 ± 1.8%, 49.5 ± 4.2% and 61 ± 7.4%, for MTA, and HA-CS, respectively. However, CS and HA-CS were significantly less toxic than the control material MTA (P < 0.05). Cytotoxicity could be at least partially attributed to pH kinetics over time. Dilution of eluates of all tested materials resulted in better cell survival. Histopathological examination indicated similar inflammatory reaction, vascular congestion and connective tissue integrity associated with CS, HA-CS and MTA at each observation period (P > 0.05). The only significant difference was found for capsule thickness, that is thicker capsule was associated with HA-CS compared to MTA at 60 days (P = 0.0039). HA-CS induced moderately thick capsules (median score 3, score range 2-3), whereas MTA resulted in thin capsule formation (median score 2, score range 1-3). CONCLUSIONS Evaluation of cytotoxicity and inflammatory response indicated better biocompatibility of CS and HA-CS, in comparison with MTA (White MTA, Angelus(®) Soluções Odontológicas, Londrina, Brazil).

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. Microsc. Res. Tech. 75:1099–1103, 2012.

Mineral trioxide aggregate as material of choice in endodontic therapy

Mineral trioxide aggregate (MTA) is a material with broad indications in endodontics. Currently, this material is used for pulp capping, pulpotomy, as apical barrier in teeth with necrotic pulp and open apex, and in the treatment of various root canal perforations. By comparing the biological response of pulp tissue capped with calcium hydroxide and MTA, the superiority of MTA has been indicated. The bridge of hard tissue formed under MTA prevented the irritation of pulp. Histological studies of pulpotomy in dog teeth have shown after 120 days a hard tissue without necrosis formed under MTA. MTA is also the material of choice for retrograde root canal obturation and lateral perforation. Meta analysis of published papers on MTA in recent years indicated the great clinical success of this material which ensured a good canal seal and superior biocompatibility. It is the only material for retrograde root canal obturation that encourages tissue regeneration. Studies have also shown that MTA has inductive and conductive properties for hard tissue as well as the ability to release ions in a liquid medium. The main disadvantage of MTA is related to its color, the presence of iron and mangan ions, the difficulties in maintaining the characteristics of material during time, absence of solvent for this material and the difficulty for its removal after crosslinking.

Direct pulp capping with novel nanostructural materials based on calcium silicate systems and hydroxyapatite

Summary Introduction Direct pulp capping is an important therapeutic method that has goal to provide formation of dentin bridge and healing process of the pulp. The aim of this study was to investigate the effects of new nanostructural materials based on calcium silicate systems and hydroxyapatite on exposed dental pulp in Vietnamese pigs. Material and Methods The study was conducted on 30 teeth of two Vietnamese pigs (Sus scrofa verus). On buccal surfaces of incisors, canines and first premolars, class V cavities were prepared with a small round bur and pulp horn was exposed. In the first experimental group (10 teeth) the perforation was covered with new nanostructural material based on calcium silicate systems (CS). In the second experimental group, the perforation was covered with compound of calcium silicate systems and hydroxyapatite (HA-CS) (10 teeth). In the control group, exposed pulp was covered with Pro Root MTA® (Dentsply Tulsa Dental, Johnson City, TN, USA) (10 teeth). All cavities were restored with glass ionomer cement (GC Fuji VIII, GC Corporation, Tokyo, Japan). Observation period was 28 days. After sacrificing the animals, histological preparations were done to analyze the presence of dentin bridge, inflammatory reaction of the pulp, pulp tissue reorganization and the presence of bacteria. Results Dentin bridge was observed in all teeth (experimental and control groups). Inflammation of the pulp was mild to moderate in all groups. Neoangiogenesis and many odontoblast like cells responsible for dentin bridge formation were detected. Necrosis was not observed in any case, neither the presence of Gram-positive bacteria in the pulp. Conclusion Histological analysis indicated favorable therapeutic effects of new nanostructural materials based on calcium silicate systems and hydroxyapatite for direct pulp capping in teeth of Vietnamese pigs.

Structural characteristics and mechanisms of fluorapatite mechanochemical synthesis

Abstract This paper analyzes mechanisms of fluorapatite mechanochemical synthesis and its structural characteristics. Several studies of Jokanovic et al. published in appropriate journals and the book “Nanomedicine, the biggest challenge of the 21st century” are the base for this article. Characteristics of obtained materials show numerous biological advantages associated with the specific structural design of material during the process of synthesis. X-ray diffraction (XRD) and infrared spectroscopy with Fourier transform (FTIR) were used for studying the processes of fluorapatite synthesis.

Public health sector workforce in Serbia and world economic crisis

Introduction. Health care, as one of the most important and sensitive fields of human endeavor, has a significant social impact; therefore changes in this area have wide implications on society in general. The latest economic crisis resulted in slow growth of gross domestic product (GDP), high unemployment rates, low living standards, and increased poverty across the globe. This includes decreased capacity of health system, and reduced quality and supply of health services. The aim of the study was to explore possible impact of the current world economic crisis on the public health sector workforce in Serbia. Materials and Methods. The study was conducted as retrospective analyses of the Public Health Institute (PHI) human resource data, the Republic Statistical Office publications and database, the Republic Development Bureau report, as well as the analysis of healthcare expenditures obtained from the Chamber of Health Institutions reports. The comparative analytical method was used for the assessment of socio-economic and human resource indicators over the period of five years, 2006 to 2010. Results. Results showed that the world economic crisis discontinued steady economic growth in Serbia. Between 2006 and 2008, the real GDP growth rate has been fluctuating between 3.6% and 5.4 %, while in 2009 it had negative growth rate of -3.1 % and slight increase in 2010 of 1.0%. In 2006, the GDP per capita was US

Canal wall thickness after preparation with NiTi rotary files

3,943, and by 2008 it almost doubled reaching US

Subchronic Systemic Toxicity of New Endodontic Material Based on Calcium Hydroxyapatite and Calcium Silicates

6,498, while in 2009 it fell down to US

Bioactive Glasses in Bone Tissue Engineering/ Bioaktivna stakla u inženjerstvu koštanih tkiva

5,499, and continued decrease in 2010 to US