Degree of conversion of dual-cured resin cement light-cured through three fibre posts within human root canals: an ex vivo study

Aim  To evaluate the degree of conversion of one dual-cured resin cement light-cured through three fibre posts within extracted human teeth.
Methodology  Fifteen mandibular premolars were root filled and then divided into three groups. Variolink II was light-cured through the posts (LP, D.T. Light-Post; PP, FRC Postec Plus; SP, Snowpost) within the root canal. The degree of conversion was obtained at 1 mm intervals in 9 mm-deep longitudinally sectioned root canals using an optical microscope connected to an FTIR spectrophotometer ( n  =   10). The light transmission of each post tested was also examined using UV–Vis spectroscopy. Data were analysed using anova and Tukey's test ( α  = 0.05).
Results  The LP and PP posts revealed a light transmission of 10.2% and 7.7%, respectively, whereas the SP post exhibited a significantly lower value of 0.5%. The degree of conversion mean value ranged from 32.78% to 69.73% depending on the depth and type of post. For all the groups, there were significant decreases in the degree of conversion values for the middle region when compared with those for the cervical region ( P  <   0.05). Except at a depth of 1 mm, the SP group consistently exhibited significantly lower degree of conversion values than the other groups ( P  <   0.05). The linear regression analysis revealed a strong correlation between the light transmission of the posts and the overall degree of conversion value for each group ( R ² = 0.9888).
Conclusions  The decrease in the degree of conversion for Variolink II relative to the depth was dependent on the light transmission capacity of the posts tested.