Luiz Carlos Pardini

Radiopacity Evaluation of Calcium Aluminate Cement Containing Different Radiopacifying Agents

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.

Evaluation of radiopacity and microhardness of composites submitted to artificial aging

The purpose of this study was to assess the radiopacity and microhardness of different types of resin-based composites (RBC - hybrid; microhybrid; flowable; cement and polyacid modified) before and after being submitted to artificial accelerated aging. Fifty specimens (7 mm in diameter and 2 mm thick) were fabricated, 10 for each material. The specimens were light-cured and submitted to radiopacity and microhardness tests. After obtaining initial radiopacity and microhardness values, the specimens were taken to the artificial accelerated aging, and new measurement of radiopacity and microhardness of the samples was performed. Data were submitted to statistical analysis (Students t-test - p < 0.05). None of the materials studied showed changes in radiopacity after artificial accelerated aging. There was a significant decrease in microhardness for the microhybrid and polyacid-modified RBC´s. This study suggests that radiopacity remains unaltered after materials are submitted to artificial accelerated aging. Microhardness, however, may vary due to plasticization of the aged RBC matrix.

In vitro comparison of the radiopacity of cavity lining materials with human dental structures

Aim: To compare the optical densities (OD) of calcium hydroxide (CH) and glass ionomer cement with the same thicknesses of the dental structures. Materials and Methods: Eighteen specimens of each material, with thicknesses of 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 mm were made in a Teflon matrix. To compare the radiopacity of the materials with the dental structures, dental cuts of the first molars, increasing in thickness from 0.5 to 3.0 mm, were obtained. To standardize the radiographs, a transparent acrylic matrix (Standardizing Device) was developed and used. Thirty radiographs were taken, five for each tested material. Results: Statistical analysis (Two-way ANOVA - Bonferroni, P < 0.05) demonstrated that when the materials were compared, there was statistically significant difference between the ODs, only for the thickness of 1.0 mm (P < 0.05). Conclusion: The thickness of the material contributed to its radiopacity, and these materials had to be used in a thickness between 1.5 and 2.0 mm.

A Singular Method to Compare Dental Radiographic Films Used to Study Maxillofacial Structures

El objetivo de este articulo es presentar un metodo singular y practico para comparar roentgenogramas, referentes a la densidad optica y al contraste. Este metodo se indica especificamente para la investigacion con el penetrometro stepwedge y el fotodensitometro

Growth of cell populations of the intralobular duct in the submandibular gland of the mouse during postnatal development

The growth of cell populations of intercalated ducts (ID), striated ducts (SD) and convoluted granular tubules (CGT) of the submandibular gland of the mouse was analyzed, during the period of 14 to 84 days of postnatal life, by means of morphometric methods. The absolute number of cells in each type of duct was submitted to curve fitting by means of linear regression analysis, and the obtained equations were: y = 13.22 + 0.87x for ID cells in the growth period of 14 to 84 days; y = -18.82 + 3.69x and y = 176.03 - 1.93x for SD cells in the periods of growth and decay of cells, from 14 to 35 and 35 to 84 days, respectively; and y = 90.59 + 4.60x for CGT cells in the growth period of 28 to 84 days. Based on these equations, the daily accumulation (growth rate) or loss (decaying rate) of cells in the period covered by each equation was calculated. Thus, the rate of growth of ID cells was 0.87 x 10(5) cells/day; the growth and decline rates of SD cells were 3.69 x 10(5) cells/day and -1.93 x 10(5) cells/day, respectively; and the growth rate of CGT cells was 4.60 x 10(5) cells/day. The analysis of the accumulation or loss of cells and the balance of cell populations in the various types of ducts revealed that SD cells were transformed into CGT cells and that the growth of these cells population also depends on the formation of new cells through proliferative activity, probably in the intercalated ducts.