Journal of Applied Oral Science (Dec 2009)

Glass transition and degree of conversion of a light-cured orthodontic composite

  • Michela M. D. S. Sostena,
  • Renata A. Nogueira,
  • Carlos R. Grandini,
  • João Carlos Silos Moraes

DOI
https://doi.org/10.1590/S1678-77572009000600006
Journal volume & issue
Vol. 17, no. 6
pp. 570 – 573

Abstract

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OBJECTIVE: This study evaluated the glass transition temperature (Tg) and degree of conversion (DC) of a light-cured (Fill Magic) versus a chemically cured (Concise) orthodontic composite. MATERIAL AND METHODS: Anelastic relaxation spectroscopy was used for the first time to determine the Tg of a dental composite, while the DC was evaluated by infrared spectroscopy. The light-cured composite specimens were irradiated with a commercial LED light-curing unit using different exposure times (40, 90 and 120 s). RESULTS: Fill Magic presented lower Tg than Concise (35-84ºC versus 135ºC), but reached a higher DC. CONCLUSIONS: The results of this study suggest that Fill Magic has lower Tg than Concise due to its higher organic phase content, and that when this light-cured composite is used to bond orthodontic brackets, a minimum energy density of 7.8 J/cm² is necessary to reach adequate conversion level and obtain satisfactory adhesion.

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