Infrared spectroscopy: a tool for determination of the degree of conversion in dental composites

Moraes, Luciene Gonçalves Palmeira; Rocha, Renata Sanches Ferreira; Menegazzo, Lívia Maluf; Araújo, E. B.; Yukimito, Keizo; Moraes, João Carlos Silos

doi:10.1590/s1678-77572008000200012

Cited by 150 publications

(124 citation statements)

References 15 publications

(22 reference statements)

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“…8,19 The microhardness test can also provide useful information on the conversion as an indirect method. For a single material, a rate of monomer conversion correlates with its microhardness.…”

Section: Discussionmentioning

confidence: 99%

Changes in Degree of Conversion and Microhardness of Dental Resin Cements

Yan

Kim²,

Kim³

et al. 2010

Operative Dentistry

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Resin specimens were prepared for Fourier transform infrared (FTIR) spectroscopy and microhardness testing to determine the DC and Vickers hardness (VH), respectively. The lightcured materials or mixed pastes of the dualcured materials were irradiated with a light-curing unit (Elipar TriLight) through a precured composite overlay for 40 seconds. The FTIR spectra and microhardness readings were taken at specified times: 1, 2, 5, 10, 15, 30 and 60 minutes; 24 hours and after two days and seven days. YL Yan • YK Kim K-H Kim • T-Y Kwon Clinical RelevanceChemical-and dual-cured resin cements, as well as light-cured resin cements, appear to be cured within the first 24 hours post-mix or post-light activation with no further significant changes in the degree of conversion or microhardness.According to the FTIR study, most of the curing reaction of Choice 2 and RelyX Veneer occurred within 10 and 30 minutes, respectively. Multilink, C&B Cement and Calibra exhibited gradual increases in the DC up to 24 hours, with no further statistically significant increase (p>0.05). RelyX ARC attained a DC value within five minutes, similar to that at seven days (p>0.05). Choice 2 and RelyX ARC showed gradual increases in the VH, up to 15 minutes, with no further significant change over the remaining observation time (p>0.05). For RelyX Veneer, Multilink, C&B Cement and Calibra, there were no significant increases in the VH value after 24 hours (p>0.05). The light-cured materials produced significantly higher DC values than the chemicalcured materials (p<0.05). The DC values of the two dual-cured resin cements were significantly different from each other (p<0.001). The results suggest that the significant polymerization reaction was finished within 24 hours post-mix or post-light activation for all resin cements tested.

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Section: Discussionmentioning

confidence: 99%

Changes in Degree of Conversion and Microhardness of Dental Resin Cements

Yan

Kim²,

Kim³

et al. 2010

Operative Dentistry

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“…The degree of conversion (DC%) is determined by the proportion of the remaining concentration of the aliphatic C=C double bonds in a cured sample relative to the total number of C=C bonds in the uncured material [46].…”

Section: Resultsmentioning

confidence: 99%

Continuous and gradual photo-activation methods: influence on degree of conversion and crosslink density of composite resins

Costa

Galvão

Jacomassi

et al. 2010

J Therm Anal Calorim

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Thermal properties and degree of conversion (DC%) of two composite resins (microhybrid and nanocomposite) and two photo-activation methods (continuous and gradual) displayed by the light-emitting diode (LED) light-curing units (LCUs) were investigated in this study. Differential scanning calorimetry (DSC) thermal analysis technique was used to investigate the glass transition temperature (T g ) and degradation temperature. The DC% was determined by Fourier transform infrared spectroscopy (FT-IR). The results showed that the microhybrid composite resin presented the highest T g and degradation temperature values, i.e., the best thermal stability. Gradual photo-activation methods showed higher or similar T g and degradation temperature values when compared to continuous method. The Elipar Freelight 2 TM LCU showed the lowest T g values. With respect to the DC%, the photoactivation method did not influence the final conversion of composite resins. However, Elipar Freelight 2 TM LCU and microhybrid resin showed the lowest DC% values. Thus, the presented results suggest that gradual method photoactivation with LED LCUs provides adequate degree of conversion without promoting changes in the polymer chain of composite resins. However, the thermal properties and final conversion of composite resins can be influenced by the kind of composite resin and LCU.

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“…The composites cured using monomers with high molecular weights, such as Bis-GMA and UDMA, have been found to have a considerable number of remaining double bonds. 28 The limited conversion that occurs in many network polymers is the result of the restricted mobility of radical chain ends, pendant methacrylate, and monomers imposed at a high crosslink density. 29 Photoactivated dental composites typically reach a DC ranging from 43 to 75%, a value which largely depends on composite composition, irradiation intensity, and exposure time.…”

Section: Discussionmentioning

confidence: 99%