engleski

Holographic Interferometry Assesment of Cohesive Fractures in Enamel

Objectives: Disadvantage of composite materials is polymerization shrinkage. We tried to detect the resulting internal stress, manifested as deformations and fractures in dental hard tissues or in the composite material, using double-exposure holographic interferometry. Holography enables us to record the phase and the amplitude of the light waves from an object of recording. Double-exposure interferometry can record two holograms on the same photographic plate, one of the object in its original state, and the other of the deformed object. Interferometric techniques can be used to compare two wave fronts which are originally separated in time or space. Methods: Ten intact human permanent premolars, extracted for orthodontic reasons were used. On a proximal side of each crown direct class II cavity was prepared, followed by composite restoration for which Tetric Ceram (Vivadent) was used. Cavities were treated with self-etching adhesive Clearfill SE Bond. Five of them were restored with and five without Tetric Flow (Vivadent) as elastic layer. To achieve maximal shrinkage composite fillings were cured with high intensity ECS mode of Astralis 10 (Vivadent). The samples were illuminated by helium-neon laser beam and recorded with double-exposure interferometry method on the photographic plate. Recorded hologram was again illuminated with the laser and photographed with CCD camera. Signal captured with camera was converted to 8-bit two-dimensional data and assessed on computer. The strain analysis and surface displacement can be marked as fringe pattern. Distribution and density of fringes inform us about location and amount of deformation. Results: All samples showed certain tension and deformation of the enamel surface. Density of interferometric fringe patterns were greater in the samples treated without flowable composite. Conclusion: The flowable composite acts as stress absorber. Location and size of fractures can be found with great precision.

holographic interferometry; cohesive fractures; composite resins

nije evidentirano