Influência da unidade fotoativadora na dureza e densidade de ligações cruzadas de um compósito nanoparticulado

Abstract

The present study aimed to evaluate the effect of type of photo-curing unit (halogen, LED 2nd generation and LED 3nd generation) on Knoop hardness (KHN) and crosslink density (DLC) of nanofilled composite Filtek Z350 XT (3M ESPE), color A2E, XWE and CT, polymerized with three units: Optilux 501 (600 mW/cm2, Demetron Kerr Corp), Radii Cal (800 mW/cm2, SDI) and Bluephase G2 (1000 mW/cm2, Ivoclar Vivadent). Five specimens of each group were made with a white Teflon matrix(ϕ 2,5 mm x h 4 mm), resulting in nine groups: G1- A2E, Radii Cal, polymerized for 30s; G2- A2E, Bluephase G2, 24s; G3- A2E, Optilux 501, 40s; G4- XWE, Radii Cal, 30s; G5- XWE, Bluephase G2, 24s; G6- XWE, Optilux 501, 40s; G7- CT, Radii Cal, 30s; G8- CT, Bluephase G2, 24s; G9- CT, Optilux 501, 40s. Exposure times were calculated for standardizing the radiant exposure to 24 J/cm2. The specimens were stored protected from light, 37ºC, for 24 hours. After including and polishing, Knoop hardness (KHN) was performed, and then the specimens were emerged in absolute ethanol for 24 hours for testing cross-linking density (CD) through softening. Data were evaluated by two-way ANOVA and Duncan multiple comparison test (α = 0.05). The photo-curing unit did not exert significant influence to KHN (p = 0.3422), or for DCL (p = 0.1315). With regard to factor the composite color was significant difference for both KHN (p <0.001) and DLC (p = 0.002), the values of KHN were: A2E [93.49 (1.16)] = XWE [91, 89 (0.78)] > CT [71.46 (1.76)], and DLC, measured by percent reduction of KHN were: A2E [9.1 (1.3)] = XWE [9.6 (1.6)] > CT [11.5 (2.0)]. It was concluded that the unit did not influence the KHN and DLC, but the color of the composite significantly influences these properties, whereas the color CT had lower KHN and DLC.