RESUMO
AIM: To evaluate the influence of radiation on root canal sealer push-out bond strength to dentine and sealer/dentine interface in teeth filled with AH Plus (Dentsply Ind. Com. Ltda, Petrópolis, RJ, Brazil) and MTA Fillapex (Angelus Ind. Prod. Odontológicos S/A, Londrina, PR, Brazil). METHODOLOGY: Thirty-two maxillary canines were selected and randomly assigned to 2 groups (n = 16): one group was not irradiated, and the other was subjected to a cumulative radiation dose of 60 Gy. Root canals were prepared with the Reciproc system (VDW GmbH, Munich, Germany), and each group was divided into 2 subgroups (n = 8) according to the sealer - AH Plus or MTA Fillapex - using the single-cone filling technique. Then, 1-mm-thick dentine slices were obtained from each root third for the push-out test to evaluate sealer bond strength to dentine and for scanning electron microscopy (SEM) to examine the sealer/dentine interface. Failure mode after debonding was determined with a stereomicroscope at ×25 magnification. Bond strength data were analysed by two-way anova with a split-plot design and post hoc Tukey's test (α = 0.05). RESULTS: Significantly lower bond strength (P < 0.0001) was obtained after irradiation (0.71 ± 0.20 versus 0.97 ± 0.29 MPa) and in specimens filled with MTA Fillapex (0.70 ± 0.18 MPa) compared with AH Plus (1.00 ± 0.27 MPa). Percentage of adhesive failures increased after radiation in all root thirds in the teeth filled with AH Plus. SEM revealed more gap-containing regions and fewer tags at the sealer/dentine interface in irradiated specimens, with more tag formation and fewer gaps with AH Plus sealer. CONCLUSIONS: Radiation was associated with a decrease in the push-out bond strength of sealers to intraradicular dentine and formation of more gaps and fewer tags at the sealer/dentine interface regardless of the sealer.
Assuntos
Compostos de Alumínio/efeitos da radiação , Compostos de Cálcio/efeitos da radiação , Dentina/efeitos da radiação , Resinas Epóxi/efeitos da radiação , Óxidos/efeitos da radiação , Materiais Restauradores do Canal Radicular/efeitos da radiação , Silicatos/efeitos da radiação , Dente Canino , Colagem Dentária , Falha de Restauração Dentária , Análise do Estresse Dentário , Fracionamento da Dose de Radiação , Combinação de Medicamentos , Neoplasias de Cabeça e Pescoço/radioterapia , Humanos , Teste de Materiais , MaxilaRESUMO
We studied the layered, hexagonal, semi-metal CaAl(2)Si(2) by magnetization, specific heat and resistivity measurements over a wide range of temperature, pressure and magnetic field. Both the Sommerfeld coefficient (γ = 1 mJ mol(-1) K(-2)) and the Debye temperature (θ(D) = 288 K) are in agreement with the values obtained from the band structure calculation. The resistivity shows a metallic character up to 200 K, followed by saturation and, afterwards, a weak decrease up to 840 K, at which it sharply rises reaching a local maximum at 847 ± 5 K. While the low-temperature thermal evolution was accounted for in terms of intrinsic and extrinsic effects, the additional high-temperature scattering was attributed, based on differential thermal analysis, to a first-order thermal event. No appreciable magnetoresistivity was observed at liquid helium temperatures even for fields up to 90 kOe, indicating an absence of coupling between the electronic and magnetic degrees of freedom. Finally, an externally applied pressure was found to induce a strong reduction in the resistivity following a second-order polynomial: this effect will be discussed in terms of the influence of pressure on the effective mobility and concentration of charge carriers.
Assuntos
Compostos de Alumínio/química , Compostos de Alumínio/efeitos da radiação , Silicatos de Alumínio/química , Silicatos de Alumínio/efeitos da radiação , Compostos de Cálcio/química , Compostos de Cálcio/efeitos da radiação , Impedância Elétrica , Campos Eletromagnéticos , Pressão , TemperaturaRESUMO
INTRODUCTION: The aim of this study was to evaluate the radiopacity of calcium aluminate cement (EndoBinder) with 3 different radiopacifiers (bismuth oxide, zinc oxide, or zirconium oxide) in comparison with gray mineral trioxide aggregate (GMTA), white MTA, and dental structures (enamel and dentin). METHODS: Eighteen test specimens of each cement with thicknesses of 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 mm (n = 3) were made by using a stainless steel matrix and were adapted to a standardizing device (8 × 7 cm) with a graduated aluminum stepwedge varying from 2.0-16.0 mm in thickness. To compare the radiopacity of the cements with that of dental structures, slices of first molars with a thickness increasing from 0.5-3.0 mm were obtained and placed on the standardizing device. One occlusal radiograph for each tested cement was taken, with exposure time of 0.1 seconds and focus-film distance of 20 cm. Films were processed in an automatic device, and the mean radiopacity values were obtained by using a photodensitometer. RESULTS: Mean values showed that the thicker the specimen was, the greater was its radiopacity. Only EndoBinder + bismuth oxide (EBBO) and GMTA demonstrated radiopacity values greater than 3.0 mm of the aluminum scale for all thicknesses. When zinc oxide was used as radiopacifier agent, EndoBinder only reached the desired radiopacity with a thickness of 2.0 mm, and with zirconium oxide it was 2.5 mm. CONCLUSIONS: Bismuth oxide was the most efficient radiopacifier for EndoBinder, providing adequate radiopacity in all studied thicknesses, as recommended by ISO 6876, being similar to GMTA.