Effect of Different Cements on the Biomechanical Behavior of Teeth Restored with Cast Dowel‐and‐Cores—In Vitro and FEA Analysis

Purpose: To test the hypothesis that the type of cement used for fixation of cast dowel‐and‐cores might influence fracture resistance, fracture mode, and stress distribution of single‐rooted teeth restored with this class of metallic dowels. Materials and Methods: The coronal portion was removed from 40 bovine incisors, leaving a 15 mm root. After endodontic treatment and standardized root canal relief at 10 mm, specimens were embedded in polystyrene resin, and the periodontal ligament was simulated with polyether impression material. The specimens were randomly divided into four groups (n = 10), and restored with Cu–Al cast dowel‐and‐cores cemented with one of four options: conventional glass ionomer cement (GI); resin‐modified glass ionomer cement (GR); dual‐cure resin cement (RC); or zinc‐phosphate cement (ZP). Sequentially, fracture resistance of the specimens was tested with a tangential load at a 135° angle with a 0.5 mm/min crosshead speed. Data were analyzed using one‐way analysis of variance (ANOVA) and the Fisher test. Two‐dimensional finite element analysis (2D‐FEA) was then performed with representative models of each group simulating a 100 μm cement layer. Results were analyzed based on von Mises stress distribution criteria. Results: The mean fracture resistance values were (in N): RC, 838.2 ± 135.9; GI, 772.4 ± 169.8; GR, 613.4 ± 157.5; ZP, 643.6 ± 106.7. FEA revealed that RC and GR presented lower stress values than ZP and GI. The higher stress concentration was coincident with more catastrophic failures, and consequently, with lower fracture resistance values. Conclusions: The type of cement influenced fracture resistance, failure mode, and stress distribution on teeth restored with cast dowel‐and‐cores.     

Clinical evaluation of the alar base width of patients submitted to surgically assisted maxillary expansion

Proposition

The aim of this study was to evaluate both the presence and magnitude of the modifications occurred in the alar base width, in patients submitted to surgically assisted maxillary expansion (SAME).

Methods

The alar base width of 13 patients submitted to SAME followed by alar base suture and simple V-Y suture was measured by using direct measuring with digital paquimeter during regular periods: pre-operative and 2, 6, 24, and 36 months post-operative. Data were submitted to statistical analysis by using ANOVA and Tukey’s test with level of significance of 5%.

Results

There was a statistically significant increase (P?<?0.05) of the alar base width in the comparison between the pre-operative and the 6-, 24-, and 36-month post-operative periods.

Conclusion

SAME procedure increased the alar base width even performing the alar bases sutures; however, despite the widening of 1.6 mm, the clinical result was not compromised and better than without the technique.     

Trypanosoma cruzi Lineages Detected in Congenitally Infected Infants and Triatoma infestans from the Same Disease-Endemic Region under Entomologic Surveillance in Paraguay

Trypanosoma cruzi II is associated with Chagas disease in the southern part of South America. We analyzed T. cruzi variants in field-collected triatomines and congenitally infected infants living in the same disease-endemic region in Paraguay. Results of polymerase chain reactions for T. cruzi kinetoplast DNA and satellite DNA were positive in 83 triatomine feces samples and 58 infant blood samples. However, lineages were detected in 33 and 38 samples, respectively. Trypanosoma cruzi genotypes were determined in 56 (97%) blood samples after hybridization by using specific probes. The Tc I genotype was not detected. The prevalent sublineage was Tc IId in triatomines (27 of 33) and infant blood (36 of 58) as assessed by amplification of the 24Sα ribosomal RNA and the mini-exon region genes. The Tc IIc genotype was detected in 20 infant blood samples and in 1 triatomine. This study shows T. cruzi II is the predominant lineage circulating in triatomines and humans in endemic areas of eastern region of Paraguay.     

Naturally Acquired Antibodies to Plasmodium vivax Duffy Binding Protein (DBP) in Rural Brazilian Amazon

Duffy binding protein (DBP), a leading malaria vaccine candidate, plays a critical role in Plasmodium vivax erythrocyte invasion. Sixty-eight of 366 (18.6%) subjects had IgG anti-DBP antibodies by enzyme-linked immunosorbent assay (ELISA) in a community-based cross-sectional survey in the Brazilian Amazon Basin. Despite continuous exposure to low-level malaria transmission, the overall seroprevalence decreased to 9.0% when the population was reexamined 12 months later. Antibodies from 16 of 50 (36.0%) subjects who were ELISA-positive at the baseline were able to inhibit erythrocyte binding to at least one of two DBP variants tested. Most (13 of 16) of these subjects still had inhibitory antibodies when reevaluated 12 months later. Cumulative exposure to malaria was the strongest predictor of DBP seropositivity identified by multiple logistic regression models in this population. The poor antibody recognition of DBP elicited by natural exposure to P. vivax in Amazonian populations represents a challenge to be addressed by vaccine development strategies.     

Increased adhesive properties of platelets in sickle cell disease: roles for αIIbβ3‐mediated ligand binding,diminished cAMP signalling and increased phosphodiesterase 3A activity

Whilst high pro‐coagulant activity is reported in sickle cell disease (SCD), the precise role of platelets (PLTs) in SCD inflammatory and vaso‐occlusive processes is unclear. Adhesion of PLTs from healthy controls (CON), SCD individuals (SCD) and SCD patients on hydroxycarbamide (SCDHC) to fibrinogen (FB) was compared using static adhesion assays. PLT adhesion molecules and intraplatelet cyclic adenosine monophosphate (icAMP) were observed by flow cytometry and enzyme‐linked immunosorbent assay. SCD‐PLTs demonstrated significantly greater adhesion than CON‐PLTs to FB. Participation of the α_IIbβ₃‐integrin in SCD‐PLT adhesion was implicated by increased α_IIbβ₃ activation and data showing that an α_IIbβ₃‐function‐inhibiting antibody significantly diminished SCD‐PLT adhesion to FB. Platelet activation was potentated by reductions in icAMP; cAMP levels were decreased in SCD‐PLTs, being comparable to those of thrombin‐stimulated CON‐PLTs. Furthermore, SCD‐PLT adhesion to FB was significantly reduced by cilostazol, an inhibitor of cAMP‐hydrolyzing phosphodiesterase 3A (PDE3A). Both α_IIbβ₃‐integrin activation and icAMP correlated significantly with fetal haemoglobin in SCD. Accordingly, hydroxycarbamide therapy was associated with lower PLT adhesion and higher icAMP. SCD‐PLTs may be capable of adhering to proteins encountered on the inflamed vascular wall and, potentially, participate in vaso‐occlusive processes. Hydroxycarbamide and, speculatively, nitric oxide donor or cyclic‐nucleotide‐targeted therapies may aid in the reversal of PLT adhesive properties in SCD.