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Polymerization stress related to radiant exposure and its effect on microleakage of composite restorations
Fernanda Calabró Calheiros1, Fernanda Tranchesi Sadek, Leticia Cristina Cidreira Boaro
1University of São Paulo, School of Dentistry, Department of Biomaterials and Oral Biochemistry - FOUSP, Av. Prof. Lineu Prestes, 2227 São Paulo, SP 05508-900, Brazil.
Objectives:
Verify the influence of radiant exposure (dose) on polymerization stress and microleakage of composite restorations using two adhesive systems.
Methods:
An experimental composite (1BisGMA:1TEGDMA, 75wt.% filler) was subjected to 3, 6, 12 or 24J/cm(2) under 500mW/cm(2). Stress was measured in 1-mm height specimens placed between two glass rods (Ø=5mm) attached to a testing machine. Microleakage was assessed in cylindrical restorations (Ø=5mm, h=2mm) with enamel margins, using Adper Single Bond 2 (SB) or Adper Prompt (PR). After storage, specimens were subjected to dye penetration (50% AgNO(3)) and sectioned twice, perpendicularly. Microleakage of the 8tooth/composite interfaces was recorded in millimeters. KHN was measured at both surfaces of cylindrical specimens (Ø=5mm, 1 or 2mm height). ANOVA/Tukey test were used (alpha=0.05). KHN top and bottom were compared using paired t-tests.
Results:
Stress increased significantly with dose (3J/cm(2): 1.4+/-0.3(c); 6J/cm(2): 4.3+/-0.5(b); 12J/cm(2): 9.3+/-0.6(a); 24J/cm(2): 9.9+/-0.7(a), in MPa). For both average and maximum microleakage, interactions were not statistically significant (p>0.05). Tooth average microleakage was influenced by the adhesive system (SB
Conclusions:
Stress and microleakage increased significantly with the applied radiant exposure.
