Étude in vitro de la variation dans le temps du taux de la densité optique de quatre types de matériaux pour prothèses provisoires

Abstract

The stability of the color of the provisional crowns is particularly important when the treatment plan requires temporary restorations. This stability depends on the capacity of the material to resist absorption and crumbling in solutions. The aim of this article was to evaluate, in vitro, the variation of the rate of the optical density during 15 days of four types of provisional materials soaked in two solutions. Four types of provisional materials available on the Lebanese market: two polymethyl methacrylates (PMMA: Jet®, Tab2000®) and two composite resins (Integrity® and Tempspan®) were evaluated after 1,7 and 15 days of immersion in two solutions (distilled water and Pepsi Cola®). Measurements of the variation of the optical density were obtained with the spectrophotometer (Jenway 6300). The data were analyzed with a 3-way analysis of variance with repeated measurements (ANOVA) followed by different tests and multiple comparisons of Bonferroni (p≤0.05). A significant effect of interaction exists between the factors time, materials and solutions, as shown by the statistical test ANOVA (p< 0.0001). This means that the optical density variation, according to time, is different between materials for each solution on one hand, and on the other hand, between solutions for each material. In distilled water, the four materials behaved in an almost similar way, whereas in Pepsi Cola®, the PMMA resisted better to absorption and crumbling than the composite resins. The tests showed that the rate of the variation of the optical density of the four materials was always lower when they were immersed in distilled water, compared to Pepsi Cola®. The time of immersion is a critical factor in the stability of materials for provisional restorations. The more this time increases and the more faded the material is, because of the absorption of the solution followed by the crumbling.