Effect of Resin Cement Mixing and Insertion Method into the Root Canal on Cement Porosity and Fiberglass Post Bond Strength.

PURPOSE: To evaluate the method of resin cement mixing and insertion into the root canal on resin cement porosity and fiberglass-post push-out bond strength (PBS). MATERIALS AND METHODS: One hundred twenty human single-rooted teeth were sectioned to a length of 15 mm, en-do-dontically filled, and received a fiberglass post cemented with 3 self-adhesive resin cements (RelyX U200, seT, Panavia SA) using 4 mixing methods/insertion techniques (handmix/endodontic file, handmix/Centrix syringe, automix/conventional tip, automix/endo tip). The samples were scanned using micro-CT. Two slices from the cervical, middle, and apical thirds were submitted to push-out bond strength (PBS) testing, and failure modes were classified. The PBS, volume of resin cement, and porosity data were analyzed using ANOVA and Tukey's test. RESULTS: The porosity was lowest in the cervical third and highest in the apical third, irrespective of the resin cement. The porosity was lower in the the automix/endo tip group compared to the handmix/endodontic file group. The use of Centrix or endo tip reduced the porosity and increased the PBS in the apical third compared with the use of endodontic files. The root canal depth reduced the PBS for U200 and seT when handmix/endodontic files were used. U200 and seT using the automix method increased the PBS, thus eliminating the effect of root region, irrespective of the insertion technique. In general, U200 showed higher PBS and Panavia lower PBS. Adhesive failure between root dentin and resin cement was predominant. CONCLUSIONS: Automixing the cement and using an endo tip produces fewer voids and increased the bond strengths.

G6PD deficiency alleles in a malaria-endemic region in the Western Brazilian Amazon.

BACKGROUND: Plasmodium vivax parasites are the predominant cause of malaria infections in the Brazilian Amazon. Infected individuals are treated with primaquine, which can induce haemolytic anaemia in glucose-6-phosphate dehydrogenase (G6PD)-deficient individuals and may lead to severe and fatal complications. This X-linked disorder is distributed globally and is caused by allelic variants with a geographical distribution that closely reflects populations exposed historically to endemic malaria. In Brazil, few studies have reported the frequency of G6PD deficiency (G6PDd) present in malaria-endemic areas. This is particularly important, as G6PDd screening is not currently performed before primaquine treatment. The aim of this study was to determine the prevalence of G6PDd in the region of Alto do Juruá, in the Western Brazilian Amazon, an area characterized by a high prevalence of P. vivax infection. METHODS: Five-hundred and sixteen male volunteers were screened for G6PDd using the fluorescence spot test (Beutler test) and CareStart™ G6PD Biosensor system. Demographic and clinical-epidemiological data were acquired through an individual interview. To assess the genetic basis of G6PDd, 24 SNPs were genotyped using the Kompetitive Allele Specific PCR assay. RESULTS: Twenty-three (4.5%) individuals were G6PDd. No association was found between G6PDd and the number of malaria cases. An increased risk of reported haemolysis symptoms and blood transfusions was evident among the G6PDd individuals. Twenty-two individuals had the G6PDd A(-) variant and one the G6PD A(+) variant. The Mediterranean variant was not present. Apart from one polymorphism, almost all SNPs were monomorphic or with low frequencies (0-0.04%). No differences were detected among ethnic groups. CONCLUSIONS: The data indicates that ~1/23 males from the Alto do Juruá could be G6PD deficient and at risk of haemolytic anaemia if treated with primaquine. G6PD A(-) is the most frequent deficiency allele in this population. These results concur with reported G6PDd in other regions in Brazil. Routine G6PDd screening to personalize primaquine administration should be considered, particularly as complete treatment of patients with vivax malaria using chloroquine and primaquine, is crucial for malaria elimination.

Influence of different post design and composition on stress distribution in maxillary central incisor: Finite element analysis.

BACKGROUND: Post design and material has very important effects on dentinal stress distribution since the post placement can create stresses that lead to root fracture. MATERIALS AND METHODS: In this study we use finite element analysis (FEA) to evaluate stress distribution on endodontically treated maxillary central incisors that have been restored with different prefabricated posts. Six models were generated from the image of anatomical plate: Four metallic posts (ParaPost XH, ParaPost XT, ParaPost XP, and Flexi-Flange) and one fiberglass post (ParaPost Fiber Lux). The sixth model was a control-a sound maxillary central incisor. We used CAD software and exported the models to ANSYS 9.0. All the materials and structures were considered elastic, isotropic, homogeneous, and linear except the fiberglass post which was considered orthotropic. The values for the mechanical properties were obtained by a review of the literature and the model was meshed with 8-node tetrahedral elements. A load of 2N was applied to the lingual surface at an angle of 135 degrees. RESULTS: The stress results were recorded by shear stress and von Mises criteria; it was observed that there was no difference for stress distribution among the titanium posts in the radicular portions and into posts. There was higher stress concentration on the coronary portion with the titanium posts than with the glass fiber post. It seems that the metallic posts' external configuration does not influence the stress distribution. CONCLUSION: Fiber posts show more homogeneous stress distribution than metallic posts. The post material seems to be more relevant for the stress distribution in endodontically treated teeth than the posts' external configuration.

Influence of the endodontic treatment on mechanical properties of root dentin.

This study evaluated the effect of endodontic treatment and storage time on the flexural and ultimate tensile strength of root dentin. Eighty bovine teeth were divided into endodontically treated (ET) and endodontically untreated (NT) teeth. The ET canals were instrumented and irrigated with sodium hypochlorite 1.0%. Roots were filled with gutta-percha and zinc-oxide/eugenol cement by the lateral condensation technique. Tests were performed as follows: t1, immediately; t2, 7 days; t3, 15 days; and t4, 30 days after extraction for NT groups or after extraction and endodontic treatment for ET groups (n= 0). Roots were axially cut into two halves, one half was used to obtain bars for performing the four-bending flexural test and the other half to obtain slices that were trimmed resulting in hourglass-shaped specimens for microtensile testing. Samples were submitted to the tests, and the data were statistically analyzed. Results indicated that endodontic treatment potentiated by time elapsed after endodontic treatment can affect the physical properties of dentin.