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Glass transition and degree of conversion of a light-cured orthodontic composite
Michela M D S Sostena1, Renata A Nogueira, Carlos R Grandini
1Department of Physics and Chemistry, São Paulo State University, Ilha Solteira, Brazil.
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 (35-84 masculineC versus 135 masculineC), 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/cm(2) is necessary to reach adequate conversion level and obtain satisfactory adhesion.
