Pre-heating mitigates composite degradation

Dental composites cured at high temperatures show improved properties and higher degrees of conversion; however,there is no information available about the effect of pre-heating on material degradation. objectives: this study evaluated the effect of pre­heating on the degradation of composites,based on the analysis of radiopacity and silver penetration using scanning electron microscopy/energy-dispersive x-ray spectroscopy (sem/eds). material and methods: thirty specimens were fabricated using a metallic matri× (2×8 mm) and the composites durafill vs (heraeus kulzer),z-250 (3m/espe),and z-350 (3m/espe),cured at 25°c (no pre-heating) or 60°c (pre-heating). specimens were stored sequentially in the following solutions: 1) water for 7 days (60°c),plus 0.1 n sodium hydroxide (naoh) for 14 days (60°c); 2) 50% silver nitrate (agno3) for 10 days (60°c). specimens were radiographed at baseline and after each storage time,and the images were evaluated in gray scale. after the storage protocol,samples were analyzed using sem/eds to check the depth of silver penetration. radiopacity and silver penetration data were analyzed using anova and tukey’s tests (α=5%). results: radiopacity levels were as follows: durafill vs<z-350<z-250 (p<0.05). the depth of silver penetration into the composites ranked as follows: durafill vs>z-350>z-250 (p<0.05). after storage in water/ naoh,pre-heated specimens presented higher radiopacity values than non-pre-heated specimens (p<0.05). there was a lower penetration of silver in pre-heated specimens (p<0.05). conclusions: pre-heating at 60°c mitigated the degradation of composites based on analysis of radiopacity and silver penetration depth. © 2015,faculdade de odontologia de bauru. all rights reserved.