Comparação de duas técnicas de fotopolimerização nas propriedades de contração e temperatura de polimerização de uma resina de incremento único por meio das redes de Bragg

Abstract

The objective of this study was to evaluate the influence of Continuous and Ramp photoactivation modes on the shrinkage polymerization, and thermal change properties of a Filtek™ Bulk Fill Flow composite. 30 third molar teeth were selected. An occlusal Class I cavity (4 mm length x 4 mm wide x 4 mm depth) was prepared.For the positioning of the Bragg sensors, a sensor was positioned in the mesio-distal direction directly in contact with the composite that measured the shrinkage deformation, and another sensor inside a hypodermic needle in the lingual-lingual direction that measured only the temperature. The teeth were restored with Filtek™Bulk Fill Flow resin according to the manufacturer's recommendations. Subsequently, was used a formula to obtain the pure deformation value of the material in μstrain. Statistical analysis was obtained through analysis of variance and Student's t-test. The results showed no significant statistical differences for the shrinkage values between the two photoactivation protocols (Continuous and Ramp) and among 500s, 1500s, 2500s and 3500s times. At the end of 3500s a tendency to stabilize the curves for both modes of photoactivation was observed. The Ramp photoactivation revealed a higher value of temperature variation (16.32°C) when compared to Continuous photoactivation (7.8 °C). The Bragg sensors were able to measure the shrinkage, and the thermal variation. Continuous photoactivation took longer to return to the initial temperature value (2.85 min) than ramp (1.65 min). Future studies should monitor the shrinkage of polymerization for a longer period of time necessary for the total stabilization of the curve.