Comparative analysis of root surface smear layer removal by different etching modalities or erbium:yttrium-aluminum-garnet laser irradiation. A scanning electron microscopy study

The purpose of this study was to evaluate the effect of erbium:yttrium-aluminum-garnet (Er:YAG) laser (2.94 mu m) irradiation on the removal of root surface smear layer of extracted human teeth and to compare its efficacy with that of citric acid, ethylenediamine tetra-acetic acid (EDTA), or a gel containing a mixture of tetracycline hydrochloride (HCl) and citric acid, using scanning electron microscopy (SEM). Thirty human dentin specimens were randomly divided into six groups: G1 (control group), irrigated with 10 ml of physiologic saline solution; G2, conditioned with 24% citric acid gel; G3, conditioned with 24% EDTA gel; G4, conditioned with a 50% citric acid and tetracycline gel; G5, irradiated with Er:YAG laser (47 mJ/10 Hz/5.8 J/cm(2)/pulse); G6, irradiated with Er:YAG laser (83 mJ/10 Hz/10.3 J/cm(2)/pulse). Electron micrographs were obtained and analyzed according to a rating system. Statistical analysis was conducted with Kruskal-Wallis and Mann-Whitney tests (P < 0.05). G1 was statistically different from all the other groups; no statistically significant differences were observed between the Er:YAG laser groups and those undergoing the other treatment modalities. When the two Er:YAG laser groups were compared, the fluency of G6 was statistically more effective in smear layer removal than the one used in G5 (Mann-Whitney test, P < 0.01). Root surfaces irradiated by Er:YAG laser had more irregular contours than those treated by chemical agents. It can be concluded that all treatment modalities were effective in smear layer removal. The results of our study suggest that the Er:YAG laser can be safely used to condition diseased root surfaces effectively. Furthermore, the effect of Er:YAG laser irradiation on root surfaces should be evaluated in vivo so that its potential to enhance the healing of periodontal tissues can be assessed.

Adhesives bonded to erbium:yttrium-aluminum-garnet laser-irradiated dentin: transmission electron microscopy, scanning electron microscopy and tensile bond strength analyses

The aim of this in vitro study was to investigate the effect of erbium:yttrium-aluminum-garnet (Er:YAG) laser irradiation on dentinal collagen by transmission electron microscopy and to analyze the resin-dentin interface by scanning electron microscopy. A tensile bond strength test was also applied. Specimens from 69 sound human third molars were randomly divided into three groups: control (no laser), and two irradiated groups, laser 250 (250 mJ/2 Hz) and laser 400 (400 mJ/4 Hz). Then, specimens were restored with two adhesive systems, an etch-and-rinse or a self-etch system. Although ultrastructural examination showed a modified surface in the irradiated dentin, there was no statistical difference in bond strength values between the laser groups and controls (P < 0.05). In conclusion, the use of Er:YAG laser for ablating human dentin did not alter the main adhesion parameters when compared with those obtained by conventional methods, thus reinforcing its use in restorative dentistry.

Comparison among four commonly used demineralizing agents for root conditioning: a scanning electron microscopy

Dental roots that have been exposed to the oral cavity and periodontal pocket environment present superficial changes, which can prevent connective tissue reattachment. Demineralizing agents have been used as an adjunct to the periodontal treatment aiming at restoring the biocompatibility of roots. OBJECTIVE: This study compared four commonly used demineralizing agents for their capacity of removing smear layer and opening dentin tubules. METHODS: Fifty fragments of human dental roots previously exposed to periodontal disease were scaled and randomly divided into the following groups of treatment: 1) CA: demineralization with citric acid for 3 min; 2) TC-HCl: demineralization with tetracycline-HCl for 3 min; 3) EDTA: demineralization with EDTA for 3 min; 4) PA: demineralization with 37% phosphoric acid for 3 min; 5) Control: rubbing of saline solution for 3 min. Scanning electron microscopy was used to check for the presence of residual smear layer and for measuring the number and area of exposed dentin tubules. RESULTS: Smear layer was present in 100% of the specimens from the groups PA and control; in 80% from EDTA group; in 33.3% from TC-HCl group and 0% from CA group. The mean numbers of exposed dentin tubules in a standardized area were: TC-HCl=43.8±25.2; CA=39.3±37; PA=12.1±16.3; EDTA=4.4±7.5 and Control=2.3±5.7. The comparison showed significant differences between the following pairs of groups: TC-HCl and Control; TC-HCl and EDTA; CA and Control; and CA and EDTA. The mean percentages of area occupied by exposed dentin tubules were: CA=0.12±0.17%; TC-HCl=0.08±0.06%; PA=0.03±0.05%; EDTA=0.01±0.01% and Control=0±0%. The CA group differed significantly from the others except for the TC-HCl group. CONCLUSION: There was a decreasing ability for smear layer removal and dentin tubule widening as follows: AC>TC-HCl>PA>EDTA. This information can be of value as an extra parameter for choosing one of them for root conditioning.

Physicochemical characterization of two deproteinized bovine xenografts

Calcium phosphate salts, or more specifically hydroxyapatite, are products of great interest in the fields of medical and dental science due to their biocompatibility and osteoconduction property. Deproteinized xenografts are primarily constituted of natural apatites, sintered or not. Variations in the industrial process may affect physicochemical properties and, therefore, the biological outcome. The purpose of this work was to characterize the physical and chemical properties of deproteinized xenogenic biomaterials, Bio-Oss (Geistlich Biomaterials, Wolhuser, Switzerland) and Gen-Ox (Baumer S.A., Brazil), widely used as bone grafts. Scanning electron microscopy, infrared region spectroscopy, X-ray diffraction, thermogravimetry and degradation analysis were conducted. The results show that both materials presented porous granules, composed of crystalline hydroxyapatite without apparent presence of other phases. Bio-Oss presented greater dissolution in Tris-HCl than Gen-Ox in the degradation test, possibly due to the low crystallinity and the presence of organic residues. In conclusion, both commercial materials are hydroxyapatite compounds, Bio-Oss being less crystalline than Gen-Ox and, therefore, more prone to degradation.

Effect of different cleansers on the surface of removable partial denture

Removable partial dentures (RPD) demand specific hygienic cleaning and the combination of brushing with immersion in chemical solutions has been the most recommended method for control of biofilm. However, the effect of the cleansers on metallic components has not been widely investigated. This study evaluated the effect of different cleansers on the surface of RPD. Five disc specimens (12 mm x 3 mm metallic disc centered in a 38 x 18 x 4 mm mould filled with resin) were obtained for each experimental situation: 6 solutions [Periogard (PE), Cepacol (CE), Corega Tabs (CT), Medical Interporous (MI), Polident (PO), 0.05% sodium hypochlorite (NaOCl), and distilled water (DW) control] and 2 Co-Cr alloys [DeguDent (DD) and VeraPDI (VPDI)] were used for each experimental situation. A 180-day immersion was simulated and the measurements of roughness (Ra, µm) of metal and resin were analyzed using 2-way ANOVA and Tukey’s test. The surface changes and tarnishes were examined with a scanning electronic microscopy (SEM). In addition, energy dispersive x-ray spectrometry (EDS) analysis was carried out at representative areas. Visually, NaOCl and MI specimens presented surface tarnishes. The roughness of materials was not affected by the solutions (p>0.05). SEM images showed that NaOCl and MI provided surface changes. EDS analysis revealed the presence of oxygen for specimens in contact with both MI and NaOCl solutions, which might suggest that the two solutions promoted the oxidation of the surfaces, thus leading to spot corrosion. Within the limitations of this study, it may be concluded that the NaOCl and MI may not be suitable for cleaning of RPD.

Mentors, students, and the undergraduate medical course: a virtuous circle

BACKGROUND: Mentoring Programs have been developed in several medical schools, but few studies have investigated the mentors'perspective. PURPOSES: To explore mentors'perceptions regarding their experience. METHODS: Mentors at a medical school were invited to participate in an in-depth interview including questions on satisfaction, difficulties, and perception of changes resulting from the program. RESULTS: Mentors' satisfaction and difficulties are strongly associated with students'involvement in the activity. Mentors believe changes observed in students were more related to life issues; for some mentors, there is no recognition or awareness of the program. However, most of the mentors acknowledged important changes in relation to themselves: as teachers, faculty members, and individuals. CONCLUSION: Attendance is crucial for both the mentoring relationship and strengthening of the program. Students involved in the activity motivate mentors in teaching and curriculum development, thereby creating a virtuous circle and benefiting undergraduate medical education as a whole.

Drag reduction by polyethylene glycol in the tail arterial bed of normotensive and hypertensive rats

This study was designed to evaluate the effect of drag reducer polymers (DRP) on arteries from normotensive (Wistar) and spontaneously hypertensive rats (SHR). Polyethylene glycol (PEG 4000 at 5000 ppm) was perfused in the tail arterial bed with (E+) and without endothelium (E-) from male, adult Wistar (N = 14) and SHR (N = 13) animals under basal conditions (constant flow at 2.5 mL/min). In these preparations, flow-pressure curves (1.5 to 10 mL/min) were constructed before and 1 h after PEG 4000 perfusion. Afterwards, the tail arterial bed was fixed and the internal diameters of the arteries were then measured by microscopy and drag reduction was assessed based on the values of wall shear stress (WSS) by computational simulation. In Wistar and SHR groups, perfusion of PEG 4000 significantly reduced pulsatile pressure (Wistar/E+: 17.5 ± 2.8; SHR/E+: 16.3 ± 2.7%), WSS (Wistar/E+: 36; SHR/E+: 40%) and the flow-pressure response. The E- reduced the effects of PEG 4000 on arteries from both groups, suggesting that endothelial damage decreased the effect of PEG 4000 as a DRP. Moreover, the effects of PEG 4000 were more pronounced in the tail arterial bed from SHR compared to Wistar rats. In conclusion, these data demonstrated for the first time that PEG 4000 was more effective in reducing the pressure-flow response as well as WSS in the tail arterial bed of hypertensive than of normotensive rats and these effects were amplified by, but not dependent on, endothelial integrity. Thus, these results show an additional mechanism of action of this polymer besides its mechanical effect through the release and/or bioavailability of endothelial factors.

Drug consumption among medical students in São Paulo, Brazil: influences of gender and academic year

OBJECTIVE: To analyze alcohol, tobacco and other drug use among medical students. METHOD: Over a five-year period (1996-2001), we evaluated 457 students at the Universidade de São Paulo School of Medicine, located in São Paulo, Brazil. The students participated by filling out an anonymous questionnaire on drug use (lifetime, previous 12 months and previous 30 days). The influence that gender and academic year have on drug use was also analyzed. RESULTS: During the study period, there was an increase in the use of illicit drugs, especially inhalants and amphetamines, among the medical students evaluated. Drug use (except that of marijuana and inhalants) was comparable between the genders, and academic year was an important influencing factor. DISCUSSION: Increased inhalant use was observed among the medical students, especially among males and students in the early undergraduate years. This is suggestive of a specific behavioral pattern among medical students. Our findings corroborate those of previous studies. CONCLUSION: Inhalant use is on the rise among medical students at the Universidade de São Paulo School of Medicine. Because of the negative health effects of illicit drug use, further studies are needed in order to deepen the understanding of this phenomenon and to facilitate the development of preventive measures.

Scanning electron microscopy of the corneal endothelium of ostrich

The aim of this study was to examine the endothelial surface morphology and perform a morphometric analysis of the corneal endothelial cells of ostrich (Struthio camelus) using scanning electron microscopy. Polygonality, mean cell area, cell density and coefficient of variation of mean cell area were analyzed. The normal corneal endothelium consisted of polygonal cells of uniform size and shape with few interdigitations of the cell borders. Microvilli appeared as protusions on the cellular surface. The average cell area was 269±18µm² and the endothelial cell density was 3717±240cells mm-2. The coefficient of variation of the cell area was 0.06, and the percentage of hexagonal cells was 75%. The parameters evaluated did not differ significantly between the right and the left eye from the same ostrich. The results of this study showed that the ostrich corneal endothelial cells appear quite similar to those of the other vertebrates.

Oral Health Promotion Through an Online Training Program for Medical Students

The objective of this study was to compare the impact on knowledge and counseling skills of face-to-face and Internet-based oral health training programs on medical students. Participants consisted of 148 (82 percent) of the 180 invited students attending their fifth academic year at the Faculty of Medicine, University of Sao Paulo, Brasil, in 2007. The interventions took place during a three-month training period in the clinical Center for Health Promotion, which comprised part of a clerkship in Internal Medicine. The students were divided into four groups: 1) Control Group (Control), with basic intervention; 2) Brochure Group (Br), with basic intervention plus complete brochure with oral health themes; 3) Cybertutor Group (Cy), with basic intervention plus access to an Internet-based training program about oral health themes; and 4) Cybertutor + Contact Group (Cy+C), the same as Cy plus brief proactive contact with a tutor. The impact of these interventions on student knowledge was measured with pre- and post assessments, and student skills in asking and counseling about oral health were assessed with an objective structured clinical examination (OSCE). Multivariate logistic regression models were applied to identify the odds ratios of scoring above Control's medians on the final assessment and the OSCE. In the results, Cy+C performed significantly better than Control on both the final assessment (OR 9.4; 95% CI 2.7-32.8) and the OSCE (OR 5.6; 95% CI 1.9-16.3) and outperformed all the other groups. The Cy+C group showed the most significant increase in knowledge and the best skills in asking and counseling about oral health.

The Ultrastructural Study of Tumorigenic Cells Using Nanobiomarkers

Despite recent advances, patients with malignant brain tumors still have a poor prognosis. Glioblastoma (WHO grade 4 astrocytoma), the most malignant brain tumor, represents 50% of all astrocytomas, with a median survival rate of <1 year. It is, therefore, extremely important to search for new diagnostic and therapeutic approaches for patients with glioblastoma. This study describes the application of superparamagnetic nano-particles of iron oxide, as well as monoclonal antibodies, of immunophenotypic significance, conjoined to quantum dots for the ultrastructural assessment of glioblastoma cells. For this proposal, an immunophenotypic study by flow cytometry was carried out, followed by transmission electron microscopy analysis. The process of tumor cell labeling using nanoparticles can successfully contribute to the identification of tumorigenic cells and consequently for better understanding of glioblastoma genesis and recurrence. In addition, this method may help further studies in tumor imaging, diagnosis, and prognostic markers detection.

The characteristics of depressive symptoms in medical students during medical education and training: a cross-sectional study

Background: Medical education and training can contribute to the development of depressive symptoms that might lead to possible academic and professional consequences. We aimed to investigate the characteristics of depressive symptoms among 481 medical students (79.8% of the total who matriculated). Methods: The Beck Depression Inventory (BDI) and cluster analyses were used in order to better describe the characteristics of depressive symptoms. Medical education and training in Brazil is divided into basic (1(st) and 2(nd) years), intermediate (3(rd) and 4(th) years), and internship (5(th) and 6(th) years) periods. The study organized each item from the BDI into the following three clusters: affective, cognitive, and somatic. Statistical analyses were performed using analysis of variance (ANOVA) with post-hoc Tukey corrected for multiple comparisons. Results: There were 184 (38.2%) students with depressive symptoms (BDI > 9). The internship period resulted in the highest BDI scores in comparison to both the basic (p < .001) and intermediate (p < .001) periods. Affective, cognitive, and somatic clusters were significantly higher in the internship period. An exploratory analysis of possible risk factors showed that females (p = .020) not having a parent who practiced medicine (p = .016), and the internship period (p = .001) were factors for the development of depressive symptoms. Conclusion: There is a high prevalence towards depressive symptoms among medical students, particularly females, in the internship level, mainly involving the somatic and affective clusters, and not having a parent who practiced medicine. The active assessment of these students in evaluating their depressive symptoms is important in order to prevent the development of co-morbidities and suicide risk.

Increased myoepithelial cells of bronchial submucosal glands in fatal asthma

Background: Fatal asthma is characterised by enlargement of bronchial mucous glands and tenacious plugs of mucus in the airway lumen. Myoepithelial cells, located within the mucous glands, contain contractile proteins which provide structural support to mucous cells and actively facilitate glandular secretion. Objectives: To determine if myoepithelial cells are increased in the bronchial submucosal glands of patients with fatal asthma. Methods: Autopsied lungs from 12 patients with fatal asthma (FA), 12 patients with asthma dying of non-respiratory causes (NFA) and 12 non-asthma control cases (NAC) were obtained through the Prairie Provinces Asthma Study. Transverse sections of segmental bronchi from three lobes were stained for mucus and smooth muscle actin and the area fractions of mucous plugs, mucous glands and myoepithelial cells determined by point counting. The fine structure of the myoepithelial cells was examined by electron microscopy. Results: FA was characterised by significant increases in mucous gland (p = 0.003), mucous plug (p = 0.004) and myoepithelial cell areas (p = 0.017) compared with NAC. When the ratio of myoepithelial cell area to total gland area was examined, there was a disproportionate and significant increase in FA compared with NAC (p = 0.014). Electron microscopy of FA cases revealed hypertrophy of the myoepithelial cells with increased intracellular myofilaments. The NFA group showed changes in these features that were intermediate between the FA and NAC groups but the differences were not significant. Conclusions: Bronchial mucous glands and mucous gland myoepithelial cell smooth muscle actin are increased in fatal asthma and may contribute to asphyxia due to mucous plugging.

Genetic Background of Patients from a University Medical Center in Manhattan: Implications for Personalized Medicine

Background: The rapid progress currently being made in genomic science has created interest in potential clinical applications; however, formal translational research has been limited thus far. Studies of population genetics have demonstrated substantial variation in allele frequencies and haplotype structure at loci of medical relevance and the genetic background of patient cohorts may often be complex. Methods and Findings: To describe the heterogeneity in an unselected clinical sample we used the Affymetrix 6.0 gene array chip to genotype self-identified European Americans (N = 326), African Americans (N = 324) and Hispanics (N = 327) from the medical practice of Mount Sinai Medical Center in Manhattan, NY. Additional data from US minority groups and Brazil were used for external comparison. Substantial variation in ancestral origin was observed for both African Americans and Hispanics; data from the latter group overlapped with both Mexican Americans and Brazilians in the external data sets. A pooled analysis of the African Americans and Hispanics from NY demonstrated a broad continuum of ancestral origin making classification by race/ethnicity uninformative. Selected loci harboring variants associated with medical traits and drug response confirmed substantial within-and between-group heterogeneity. Conclusion: As a consequence of these complementary levels of heterogeneity group labels offered no guidance at the individual level. These findings demonstrate the complexity involved in clinical translation of the results from genome-wide association studies and suggest that in the genomic era conventional racial/ethnic labels are of little value.

Transmission electron microscopy for characterization of acrosomal damage after Percoll gradient centrifugation of cryopreserved bovine spermatozoa

The objective of this study was to characterize acrosomal ultrastructure following discontinuous Percoll gradient centrifugation of cryopreserved bovine sperm. Semen was collected from six bulls of different breeds and three ejaculates per bull were evaluated. Frozen semen samples were thawed and the acrosomal region of sperm cells was evaluated by transmission electron microscopy (TEM) before (n = 18) and after (n = 18) Percoll centrifugation. The evaluation of 20 sperm heads from each of the 36 samples analyzed ensured that a large number of cells were investigated. The data were subjected to analysis of variance at a level of significance of 5%. Percoll centrifugation reduced the percentage of sperm exhibiting normal acrosomes (from 61.77 to 30.24%), reduced the percentage of sperm presenting atypical acrosome reactions (from 28.38 to 4.84%) and increased the percentage of sperm exhibiting damage in the acrosome (from 6.14 to 64.26%). The percentage of sperm with typical acrosome reactions was not significantly different before (3.70%) and after (0.67%) centrifugation. TEM distinguished four different types of acrosomal status and enabled ultrastructural characterization of acrosomal injuries. The percentage of sperm exhibiting normal acrosomes decreased and damage in the acrosome was the most frequent acrosomal injury with the Percoll gradient centrifugation protocol utilized.