Electron spin resonance studies of dental composites: effects of irradiation time, decay over time, pulverization, and temperature variations

Ottaviani, M. Francesca; Fiorini, Anna Lisa; Pn, Mason; Corvaja, C.

doi:10.1016/0109-5641(92)90066-l

Cited by 38 publications

(22 citation statements)

References 12 publications

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“…This would give a lower number of quanta than calculated although the dispersion of light is to some degree included in the ªaº of equations (3) and (4). Further, in an electron spin resonance study it was found that the formation of radicals in 5-mm thick samples of light-cured resin in most cases did not reach a maximum unless the samples were irradiated for times longer than 40 s (17). This seems to indicate that the consumption of camphorquinone was not complete at T = 30 s, as estimated above.…”

Section: E Asmussen and A Peutzfeldtmentioning

confidence: 82%

Direction of shrinkage of light-curing resin composites

Asmussen¹,

Peutzfeldt²

1999

Acta Odontologica Scandinavica

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It is occasionally stated in the dental literature that light-curing resin composites shrink towards the light source. As light travels at the speed of light, this dictum is not obvious. It was the purpose of the present study to investigate the direction of shrinkage of a light-curing resin composite in relation to the attachment and the thickness of the material. The resin composite was applied in cylindrical brass molds in such a manner that a flash, serving as attachment, was produced at one side of the specimens, while the material was flush with the mold at the other side. The specimens were now irradiated from either the flash or the flush side, and the convexity or the concavity of the specimens was measured. At a material thickness of 3 mm, the shrinkage was towards the light source, irrespective of the position of the flash. At 4 and 5 mm thickness of the molds, the direction of shrinkage could be directed towards or away from the light source, depending on the position of the flash. The number of light quanta emitted from the light source and passing through the material was compared with the number of molecules of camphorquinone present in a resin composite of 3, 4, or 5 mm thickness. It was concluded that under the conditions of the present study, the direction of shrinkage was the result of an interplay between the direction of the light, the attachment of the material, and the thickness of the material.

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Section: E Asmussen and A Peutzfeldtmentioning

confidence: 82%

Direction of shrinkage of light-curing resin composites

Asmussen¹,

Peutzfeldt²

1999

Acta Odontologica Scandinavica

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“…EPR spectroscopy is a highly sensitive and nondestructive technique for identifying and quantifying the paramagnetic species in a sample (free radicals in this case) 13 . EPR has been used to study the behavior of methacrylate radicals in numerous situations, including: irradiation at different wave lengths 14 , required polymerization time as a function of resin composition 15 or sample thickness 16 , resin hardness as a function of the relative number of radicals 17,18 , degree of conversion 19 , translucence 13,[20][21][22] , and molecular structure of the generated radicals 23 . As the signal intensity of the EPR spectrum is proportional to the amount of free radicals in a sample, and considering that the translucency of some fiberglass posts provides the 12,24,25 , this current study evaluated the free radical concentration according to the depth into a simulated root canal to characterize the influence of the translucent fiberglass post on the polymerization of resin cement, and then its influence on cementation.…”

Section: Introductionmentioning

confidence: 99%

The Influence of a Translucent Fiberglass Post on the Polymerization of Dual Cure Resin Cement Analyzed by Electron Paramagnetic Resonance

et al. 2015

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Electron Paramagnetic Resonance (EPR) was used as an alternative method to study the conversion degree of dual cure resin cement and verify the influence of prefabricated translucent fiberglass post on the dual cure resin cement polymerization at different restoration points. The post cementation of White Post DC (FGM, Joinville, SC, Brasil) was simulated using the dual cured resin cement Allcem (FGM, Joinville, SC, Brasil) in three different protocols: cement irradiated for 40 s; no light irradiation and cement irradiated with sealed cementation line. 2mm samples were obtained from three post sections and EPR spectra were obtained 10 minutes and 24 hours after mixing the base paste and catalyst of the cement. Results shows that the light curing protocol influenced the concentration of free radicals up to 8mm of the restoration, and the capacity of light transmission of the post was significant for the first 8mm of restoration and is non-existent in the deepest points of a simulated root canal. The cure in the apical part of restoration is exclusively chemical.

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“…In the solid state of TAEI monomer and its mixture with TMPTA or PETA (8:2 and 9:1 ratios, Tables 5 and 6, respectively), the polymerization occurs by propagation through functional groups, which have a very limited mobility. The formation of a supermolecular structure network (polymer structure features observable at a level above that of individual polymer molecules) hinders the movement of propagating free radicals, which are entrapped in the dense network (8,20). The propagation mechanism in the solid state is physically different from polymerization mechanisms in the liquid state, since the latter involve diffusion of polymer macro-radicals and chain segments to bring radicals within a reaction zone before terminating (21).…”

Section: Resultsmentioning

confidence: 97%

Highly cross-linked networks for dental applications obtained by photocuring of tris[2-(acryloyloxy)ethyl]isocyanurate, 2-ethyl-2-(hydroxymethyl)-1,3-propanediol triacrylate, and pentaerythritol triacrylate

Nie

Lindén

Rabek

et al. 1999

Acta Odontologica Scandinavica

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Highly cross-linked networks have been obtained by photoinitiated camphorquinone-amine polymerization of tris[2-(acryloyloxy)ethyl]isocyanurate alone and/or with 2-ethyl-2-(hydroxymethyl)-1,3-propanediol triacrylate or pentaerythritol triacrylate, which can be considered a new class of dental restorative resins. The most effective coinitiators in this system are amines such as ethyl-4-dimethylaminobenzoate, N,N-dimethyl-benzylamine, and 2,4,6-tris(dimethylaminomethyl)phenol. The volume shrinkages of polymerized samples were 8%-13%. The hardness of photocured resins in the presence of an inorganic filler (aluminum/fluoro/silicate glass, Ketac-Fil was slightly less than that of a restorative composite material (Z100 MP).

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Electron spin resonance studies of dental composites: effects of irradiation time, decay over time, pulverization, and temperature variations

Cited by 38 publications

References 12 publications

Direction of shrinkage of light-curing resin composites

Direction of shrinkage of light-curing resin composites

The Influence of a Translucent Fiberglass Post on the Polymerization of Dual Cure Resin Cement Analyzed by Electron Paramagnetic Resonance

Highly cross-linked networks for dental applications obtained by photocuring of tris[2-(acryloyloxy)ethyl]isocyanurate, 2-ethyl-2-(hydroxymethyl)-1,3-propanediol triacrylate, and pentaerythritol triacrylate

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