Effect of high intensity vs. soft-start halogen irradiation on light-cured resin-based composites. Part II: Hardness and solubility.
OBJECTIVE
To determine hardness and solubility of light-cured resin-based composites after high intensity vs. soft-start quartz tungsten halogen irradiation.


METHODS
Knoop hardness of resin-based composite specimens was measured at 1.5 mm depth after dry storage for 24 hours at 37 degrees C so as to indirectly evaluate degree of cure. Solubility was determined gravimetrically by extraction of post-cured (24 hours, 37 degrees C) specimens in 50 wt% methanol for 72 hours. Four hybrid (Filtek Z250, Herculite, Solitaire 2, Tetric Ceram), an inhomogeneously filled hybrid (InTen-S) and a microfilled (Filtek A110, formerly Silux Plus) composite were cured using the quartz tungsten halogen units Astralis 10 and Optilux 501 in the high intensity (Astralis 10 High Power: 10 seconds @ 1300 mW/cm2; Optilux Boost: 10 seconds @ 1140 mW/cm2) or soft-start modes (Astralis 10 Pulse: increase to 700 mW/cm2 within 10 seconds, three periods of 2 seconds @ 1300 mW/cm2 alternating with two periods of 2 seconds @ 700 mW/cm2; Optilux Ramp: exponential increase within 10 seconds, followed by 10 seconds @ 1140mW/cm2).


RESULTS
For the fast curing composites Z250, Tetric Ceram and InTen-S, equivalent hardness was observed after 10 seconds of high intensity and 20 seconds of soft-start irradiation. For the slower curing composites Herculite, Solitaire 2 and A110, the soft-start protocols produced higher hardness values. Regarding solubility however, the superiority of soft-start irradiation was also seen for Tetric Ceram and InTen-S. The lowest solubility was observed for InTen-S, followed by Z250, whereas Herculite and Solitaire 2 scored highest for this parameter.
Hofmann
Norbert
N
Department of Operative Dentistry and Periodontology, Julius-Maximilians-University of Würzburg, Pleicherwall 2, D-97070 Würzburg, Germany. Norbert.Hofmann@mail.uni-wuerzburg.de
Markert
Tanja
T
Hugo
Burkard
B
Klaiber
Bernd
B
D000704:Analysis of Variance; D003188:Composite Resins / Q000528:radiation effects*; D003748:Dental Equipment; D003799:Dental Stress Analysis; D006219:Halogens; D006244:Hardness / Q000528:radiation effects; D008027:Light; D008422:Materials Testing; D015394:Molecular Structure; D044367:Phase Transition; D019279:Resin Cements / Q000528:radiation effects; D012995:Solubility / Q000528:radiation effects
D003188:Composite Resins; C452225:Filtek A110 composite resin; C444701:Filtek Z250; D006219:Halogens; C477684:In Ten-S composite resin; D019279:Resin Cements; C469658:Solitaire 2 composite resin; C121818:Tetric ceram; C065770:Herculite XR