IADR Abstract Archives
Degree of Conversion and Extension of Polymerization of Resin Cements
Objectives: The aim of this study was to evaluate the influence of light incidence positions on the degree of conversion and the extension of polymerization of resin cements for glass fiber post luting.
Methods: The crowns of 27 bovine incisors were sectioned, root pulps were removed and the canals were prepared for glass fiber posts luting (diameter=1.3 mm). The roots were randomly divided into nine groups (n= 3) according to the light incidence positions (Coronal, Middle and Apical) and resin cements. The glass fiber posts were luted with self-cured resin cement C&B™ Cement (Bisco), dual-cured resin cement RelyX™ ARC (3M ESPE) or dual-cured self-adhesive resin cement RelyX™ U200 (3M ESPE). Dual-cured resin cements were light-cured for 30 seconds (1340 mW/cm2, Bluephase, Ivoclar Vivadent). Each root-cement-post set was sectioned to obtain 1mm-specimens from each root third. Additional samples of dual-cured resin cements were prepared with and without photoactivation. The degree of conversion and the extension of polymerization of the cements were determined by FT-Raman spectroscopy and Differential Scanning Calorimetry, respectively. Non-parametric tests were used to evaluate the effects of the variables studied (p≤0.05).
Results: There was no significant effect of light incidence position in the degree of conversion and the extension of polymerization of the cements studied, when the light position varied from Coronal, Middle or Apical (p>0.05). When light incidence was fixed at Coronal, the extension of polymerization of self-adhesive resin cement was higher in the apical third (p=0.05) and the degree of conversion of conventional dual-cured cement was lower in the apical third (p=0.05). There was no significant correlation between degree of conversion and extension of polymerization (p>0.05).
Conclusions: Under the experimental conditions of this study, the light incidence positions did not affect the degree of conversion and the extension of polymerization of dual-cured resin cements. The quality of dual-cured resin cements polymerization was compromised in the deepest portion of the canal.
Methods: The crowns of 27 bovine incisors were sectioned, root pulps were removed and the canals were prepared for glass fiber posts luting (diameter=1.3 mm). The roots were randomly divided into nine groups (n= 3) according to the light incidence positions (Coronal, Middle and Apical) and resin cements. The glass fiber posts were luted with self-cured resin cement C&B™ Cement (Bisco), dual-cured resin cement RelyX™ ARC (3M ESPE) or dual-cured self-adhesive resin cement RelyX™ U200 (3M ESPE). Dual-cured resin cements were light-cured for 30 seconds (1340 mW/cm2, Bluephase, Ivoclar Vivadent). Each root-cement-post set was sectioned to obtain 1mm-specimens from each root third. Additional samples of dual-cured resin cements were prepared with and without photoactivation. The degree of conversion and the extension of polymerization of the cements were determined by FT-Raman spectroscopy and Differential Scanning Calorimetry, respectively. Non-parametric tests were used to evaluate the effects of the variables studied (p≤0.05).
Results: There was no significant effect of light incidence position in the degree of conversion and the extension of polymerization of the cements studied, when the light position varied from Coronal, Middle or Apical (p>0.05). When light incidence was fixed at Coronal, the extension of polymerization of self-adhesive resin cement was higher in the apical third (p=0.05) and the degree of conversion of conventional dual-cured cement was lower in the apical third (p=0.05). There was no significant correlation between degree of conversion and extension of polymerization (p>0.05).
Conclusions: Under the experimental conditions of this study, the light incidence positions did not affect the degree of conversion and the extension of polymerization of dual-cured resin cements. The quality of dual-cured resin cements polymerization was compromised in the deepest portion of the canal.