Structural and mechanical properties of a giomer-based bulk fill restorative in different curing conditions

Abstract

ObjectiveThe main goal of this study was to compare the polymerization degree of bulk-fill giomer resin cured with three different light-curing units (LCUs): a polywave third-generation (Valo); a monowave (DemiUltra: DU); and a second-generation LED (Optima 10: Opt) LCUs by using structural and mechanical properties.Material and methodsGiomer samples of 2 and 4 mm cured with three LCUs were employed in vitro analysis. The degree of curing (DC%) was determined with Fourier-Transform Infrared Spectroscopy (FTIR). Microstructural features were observed with scanning electron microscopy (SEM). Flexural strength (FS), compression strength (CS), elastic modulus and fracturing strain were determined for mechanical properties. Surface microhardness (SMH) values were also measured. Oneway ANOVA, two-way analysis of variance and Tukey multiple comparison tests were used for statistically analyzing the FS and SMH.ResultsDC% values were 58.2, 47.6, and 39.7 for the 2 mm samples cured with DU, Opt., and Valo LCUs, respectively. DC% values of the 4 mm samples were 50.4, 44.6, and 38.2 for DU, Opt, and Valo, respectively. SMH values were Valo, Opt<DU at top of the samples; Valo<DU, Opt at 2 mm, and DU, Valo<Opt at 4 mm depth. Giomer samples cured with Opt and DU exhibited higher FS values than Valo. CS values were similar but compressive modulus and fracturing strain (%) varied depending on the curing protocol.ConclusionsBased on the results, it can be concluded that curing device and protocol strongly affect crosslinking reactions and thus DC%, SMH, compressive modulus and strain at break values. Consequently, it can be deduced that curing protocol is possibly the most important parameter for microstructure formation of highly-filled composite restoratives because it may bring some structural defects and physical frailties on restorations due to lower degree of polymerization.

Structural and mechanical analysis of three orthodontic adhesive composites cured with different light units

“…32 On the other hand, other studies reported better polymerization with darker materials compared to lighter counterparts. [33][34][35] The Grēngloo™ Adhesive is a green paste with a colorchange property that changes its color to a translucent color when the adhesive increases to warmer body temperatures. This feature allows easier removal of excess adhesive flash during bracket bonding before curing and facilitates cleanup of the adhesive remnants after debonding once the adhesive is cooled with air or water.…”

Effect of Polymerization Time and Home Bleaching Agent on the Microhardness and Surface Roughness of Bulk-Fill Composites: A Scanning Electron Microscopy Study

“…This procedure was repeated for four positions (in each quadrant in a clockwise direction) on the same specimen, and the arithmetic mean was obtained from these values. The mean surface roughness values were calculated for each specimen [17]. The roughness measurements were repeated after home bleaching regimens performed for 1 hour × 14 days.…”

Mechanical properties of composites with bioactive technology Giomer: a literature review

“…Instead to what was observed for flexural properties, in some studies the material suffered a reduction in microhardness when submerged in some solutions (Choi et al, 2019;Silva et al, 2019;Tanthanuch et al, 2014;Kooi et al, 2012). In addition, the polymerization protocol influenced the microhardness of the giomer, as well as the supervised whitening at home protocol (Kaya et al, 2018;Kimyai et al, 2017;Gonulol, Ozer, Tunc, 2016).…”

“…Comparing the degree of polymerization of the bulk-fill giomer submitted to three different photopolymerization units, it was possible to associate the third generation Polywave Valo (Ultradent, South Jordan, USA) with the lowest microhardness of the giomer among the units tested. In addition, the polymerization protocol influenced the mechanical performance of the material, thus concluding that the polymerization time may influence the compression strength of the giomer more than the power of the device (Kaya et al, 2018). In addition, another study found that Valo's "extra Power" polymerization mode (Ultradent, South Jordan, USA) resulted in lower Vickers microhardness values in the material samples (Gonulol, Ozer, Tunc, 2016).…”