Abstract
Objective:The purpose of this study was to assess the microhardness of posterior composite resins at different depths varying the post-irradiation time.Materials and methods:For each composite resin [Solitaire 2 (SO) - Heraus Kulzer, P60 (P) - 3M, Prodigy Condesable (PC) - Kerr, Surefil (S) - Dentsply and Alert (A) - Pentron], 6 specimens (3 mm in diameter; 4mm high) were prepared using a black polyurethane cylindrical matrix. The resins were inserted in a bulk increment and light cured for 40 seconds. Microhardness was analyzed at different depths (top, 0.4 mm, 1.0 mm, 2.0mm, 3.0 mm and 4.0 mm) and at two moments (20 minutes and 24 hours after light-curing). Data were analyzed by ANOVA and Tukey's test (p<0.05).Results:Overall, microhardness means decreased significantly with the increase of depth, being lower in the first moment tested. P, S and PC showed the highest microhardness means.Conclusion:It may be concluded that the tested composite resins presented a gradual decrease of microhardness as depth increased and this drop was more accentuated for depths beyond 2 mm. For all materials, higher microhardness means were recorded 24 hours after light activation. P60 yielded the best results at the different depths evaluated.
Highlights
Because of their remarkable evolution and improved physical and chemical properties, the use of composite resins for rehabilitation of posterior teeth has increased considerably[14]
The matrix cavity was filled with a single increment of the following composite resins: Solitaire 2 (SO) - Heraus Kulzer; P60 (P) - 3M; Prodigy Condensable (PC) - Kerr; Surefil (S) Dentsply and Alert (A) - Pentron
Vickers microhardness means (±SD) recorded at the different depths as a function of the post-irradiation time for all tested materials are displayed on Table 2
Summary
Because of their remarkable evolution and improved physical and chemical properties, the use of composite resins for rehabilitation of posterior teeth has increased considerably[14]. The improvements in the currently available composite materials include the increase of filler content, variations in size, type[14] and morphology of the particles, in addition to changes in the organic matrix[20]. Polymerization of the core of the restoration is directly related to the material’s chemical composition, the organic (type of matrix) or inorganic portion, type, morphology and filler contents[11]. It is influenced by the thickness of the increment inserted into the cavity[10], intensity and irradiation time, light spectrum[23] and distance of the tip of the light-curing unit to the material to be activated[7]
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