Influência da dose de energia sobre o grau de conversão, tensão de polimerização, propriedades mecânicas e microinfiltração in vitro de restaurações em compósito / Influence of the radiant exposure on the degree of conversion, polymerization stress, mechanical properties and in vitro microleakage of composite restorations

Fernanda Calabró Calheiros

Proposition: The aim of this study was to verify the influence of radiant exposure applied to a composite on the degree of conversion (DC), polymerization stress (PS), maximum rate of reaction (Rp max), mechanical properties (flexural strength/FS, elastic modulus/E, Knoop hardness/KHN) and microleakage of in vitro restorations using two adhesive systems. Methods: An experimental composite 1:1 (wt%) of BisGMA and TEGDMA and 75 wt% of inorganic filler was subjected to radiant exposures of 3, 6, 12, 24 and 48 J/cm2 under constant irradiance of 500 mW/cm2. DC and Rp max were monitored for 10 min after photoactivation by FTIR-ATR in 150-?m thick films (simulating the irradiated surface) and at the bottom of 2 mm thick disks. After 48 h dry storage at room temperature, a new set of DC measurements was undertaken. PS was recorded for 10 min in specimens 1 or 2 mm high built between two glass rods (Ø=5 mm) attached to the clamps of an universal testing machine. FS and E were determined by three-point bending test in 10x2x1 mm specimens. Fragments from FS specimens were used to determine KHN (top and bottom) after 48. KHN at 10 min was determined at the top and bottom of specimens 1 or 2 mm thick and 5 mm in diameter. Microleakage was evaluated in cylindrical preparations (Ø=5 mm and 2 mm deep) on the buccal aspect of bovine incisors with enamel margins, restored in bulk. The adhesive systems used were Adper Single Bond 2 (SB) and Adper Prompt (PR). After 48 h storage in water at 37oC, teeth were submitted to the 50% AgNO3 microleakage protocol. Restorations were sectioned in two planes, perpendicular to each other to determine the maximum and mean microleakage (in mm) and the number of surfaces presenting dye penetration at the interface. Results were submitted to one-way ANOVA for all tests, except for microleakage, where a two-way ANOVA was performed. DC and KHN at top and bottom were compared using Student?s t-test. Results: For DC at 10 min, significant differences were found for DC/top, except between 24 and 48J/cm2. For DC/bottom at 10 min there were significant differences among all groups. For DC/top at 48 h, differences were observed among all radiant exposure levels, except between 6 and 12 J/cm2 and between 24 and 48 J/cm2. For the bottom, significant increases in DC were verified among all energy levels. T-test showed statistical differences between top and bottom at all radiant exposure levels for DC at 10 min, while for DC at 48 h no difference was observed between top and bottom in neither of the levels. PS showed differences when the 1 mm specimens were considered, except between 12 and 24 J/cm2. In the 2 mm specimens, significant differences were observed among all energy levels. It was not possible to obtain PS data at 48 J/cm2 due to fracture of the glass rods. Rp max was statistically similar for all groups on the top and bottom of the specimens. T-test did not show differences at the top and bottom for none radiant exposures applied. FS and E showed significant differences among all groups, except between 12 and 24 J/cm2 and between 24 and 48 J/cm2 for FS. KHN at 10 min showed significant differences among groups, except between 3 and 6 J/cm2 on the non-irradiated surface of 2 mm specimens. T-test showed differences for KHN on the top and bottom for 3 and 6 J/cm2. KHN/top at 48 h was significantly different for all groups. For the bottom, 3 and 6 J/cm2 were equivalent. T-test showed statistical difference between top and bottom for 3, 6 and 12 J/cm2. Mean microleakage was influenced by the adhesive system (SB

AUTOR(ES)

DATA DE PUBLICAÇÃO

RESUMO

ASSUNTO(S)

ACESSO AO ARTIGO

Documentos Relacionados