Influence of Geometrical Configuration of a Translucent Fiberglass Post on the Polymerization of a Dual Cure Resin Cement Analyzed by EPR Spectroscopy

Abstract

This research aimed to study the influence of the geometrical configuration of a translucent fiberglass post on the dual cure resin cement polymerization by electron paramagnetic resonance (EPR) spectroscopy. A 20-mm long, White Post DC no. 1 fiberglass post (FGM, Joinvile, SC, Brazil) was sectioned in half to obtain two different groups of posts: cylindrical and conical. Each post was cemented with AllCem A1 dual cure resin cement (FGM, Joinvile, SC, Brazil) using a root canal model and light cured for 40 s. Following cementation, the post was removed and sectioned to obtain 2 mm samples at different depth of cementation. EPR spectra were obtained 10 min and 24 h after cementation to determine the concentration of free radicals (FR) in the surrounding hardened (cured) dental cement, once the concentration of FR is proportional to the light intensity at the restoration point. No significant decrease was observed in light transmission through the cylindrical post that affected the FR concentration, at depths up to 5.5 mm. In contrast, a decrease was verified for all samples conical geometry. The light conduction was effective up to 5.5 mm of curing depth when a cylindrical post was used. The cylindrical configuration was more efficient at conducting light to the deepest points of the restoration compared with the conical configuration.

Peroxide-Free and Amine-Free Redox Free Radical Polymerization: Metal Acetylacetonates/Stable Carbonyl Compounds for Highly Efficient Synthesis of Composites

“…First, we focused on Mn­(acac) 3 /Dket1 interaction. Interestingly, in Figure A, the final polymer cured using Mn­(acac) 3 /Dket1 (curve 1) or BPO/4- N , N -TMA (curve 2) shows radicals trapped in the polymer matrix at 3500 ± 50 G (see also Figure B), in line with the literature. − On the contrary, the signal of the polymer is clearly showing six bands typical of Mn­(II) when the Mn­(acac) 3 /Dket1 initiating system is used (Figure A, curve 1); we can therefore clearly expect that some Mn­(II) are trapped in the polymer after reaction. In other words, it strongly suggests the reduction of Mn­(III) to Mn­(II) by Dket1.…”

Polymerization shrinkage and porosity profile of dual cure dental resin cements with different adhesion to dentin mechanisms

“…Self‐cured dental materials polymerizes by the degradation of an initiator (usually the benzoyl peroxide) generating free radicals, whereas in the photo‐cure free radicals are generated by activation of a photoinitiator (camphorquinone). In dual cure resin cements the photo‐cure and self‐cure are associated aiming to ensure complete polymerization of the cement mass even used under opaque and/or thick restorations (Salz, Zimmermann, & Salzer, ), on inside a root canal to retain a translucent fiberglass post (Salomão, Vicentin, Contreras, Hoeppner, & Di Mauro, ; Vicentin, Salomão, Hoeppner, & Di Mauro, ).…”

Microporosity and polymerization contraction as function of depth in dental resin cements by X‐ray computed microtomography

“…In the self‐cure reaction the free radicals are generated by the degradation of an initiator (usually benzoyl peroxide) reacting with a coinitiator (tertiary amine), whereas the photo‐cure is initiated when the camphorquinone molecule absorbs blue visible light from a light‐curing unit (Malkoç, Sevimay, Tatar, & Çelik, 2015; Peutzfeldt, 1997; Salz, Zimmermann, & Salzer, 2005). The combination of the self‐cure and photo‐cure polymerization processes guarantees more effective polymerization of the cement mass at deepest points of the restoration (Salomão, Vicentin, Contreras, Hoeppner, & Di Mauro, 2015; Vicentin, Salomão, Hoeppner, & Di Mauro, 2016), improvement of physical and mechanical properties, diversification of clinical indications and longer longevity of the restoration (Khoroushi, Ghasemi, Abedinzadeh, & Samimi, 2016).…”