Degree of conversion and depth of cure of Ivocerin containing photo-polymerized resin luting cement in comparison to conventional luting agents

Abstract

Objective:To evaluate the degree of conversion (DC) and depth (extent) of cure of four resin cements (Variolink E, Calibra, NX3 and Variolink N) using Fourier transform infrared (FTIR) and Vickers Micro hardness (MH).Methods:Ten disks (1mmx2mm) of each resin cement were light cured through a ceramic disk for 40 seconds prior to assessment. The ATR spectra of the uncured resin were collected in absorbance mode from 16 scans at 4 wave number resolutions. Degree of conversion was calculated by estimating the changes in peak height ratio of the absorbance intensities of aliphatic C=C peak at 1638 cm-1 and that of an internal standard peak of aromatic C=C at 1608 cm-1 during polymerization. For Vickers microhardness testing 10 disks of each cement specimen was exposed to 100 grams of load for 15 seconds. Three indentations were made 0.5mm apart and an average Vickers micro-hardness (MH) for each specimen. Two way ANOVA and multiple comparison tests were performed to assess data.Results:The highest degree of conversion by peak area was shown by Variolink-Esthetic [light-cure (87.18±2.90%)]; however the lowest was observed in samples of Variolink-N [Dual cure (44.55±4.33%)]. Similarly, Variolink-Esthetic and NX3 cement showed significantly higher MH as compared to other groups.Conclusion:Ivocerin containing Variolink–E cement showed high degree of conversion and extent of polymerization when compared to conventional light and dual cure luting cements.

Color stability and degree of conversion of a novel dibenzoyl germanium derivative containing photo-polymerized resin luting cement

“…35 The low DC observed for Variolink-N and Calibra compared to Variolink-E and NX3 may also be associated with the instability of these dual cure cements due to the presence of tertiary amines and benzoyl peroxide as initiators. 15,36 To compare the color stability of the four luting cements in the present study, spectrophotometry with the CIE L* a* b* system and a color difference formula was employed. 27,37 Currently, the CIE system is the most reproducible and comparable color measuring system.…”

“…The DC methodology used was adopted from previous studies. 8,15 Resin cement samples were placed into vinyl molds (thickness, 1 mm; inner diameter, 2 mm). Mylar strips (DuPont Mylar 0.002 gauge/60 mm thick) were used to inhibit oxygen polymerization and facilitated placement of the ceramic discs prior to photo-polymerization.…”

“…14 Since tertiary amines are not utilized for chemical activation, the co-initiators in light polymerizing cements are relatively more stable and, thus, cause less color variation over time. 15 Furthermore, accumulating evidence suggests that changes in color stability are also associated with the DC of luting cements. 16,17 The DC of monomer to polymer influences the physical and chemical stability of a material.…”

“…It has been reported that exposure of Ivocerin to light induces the splitting of chemical bonds within the photo-initiator to form a polymerized network. 15,20 Ivocerin has also been found to exhibit increased quantum efficiency and potentially superior optical properties compared to CQ, even in small amounts. 20 Furthermore, initial studies of bulk fill composites have shown that Ivocerin displays an increased DC and reactivity to light (between wavelengths ranging from 370 to 460 nm) compared to other photo-initiators.…”

“…20 Furthermore, initial studies of bulk fill composites have shown that Ivocerin displays an increased DC and reactivity to light (between wavelengths ranging from 370 to 460 nm) compared to other photo-initiators. 15,21,22 To date, inadequate evidence is available regarding the color stability and DC of Variolink-E compared to commonly used luting cements. 23 It is hypothesized that Variolink-E will exhibit better resistance to staining (color stability) and a higher DC compared to conventional luting cements based on its use of a dibenzoyl germanium derivative initiator.…”