title: Post-gel shrinkage with different modes of LED and halogen light curing units.
abstract: This study compared the post-gel shrinkage of two LED (light-emitting diodes) lights (Elipar FreeLight [FL], 3M ESPE; GC e-Light [EL], GC), a high intensity (Elipar TriLight [TL], 3M ESPE) and a very high intensity (Astralis 10 [AS], Ivoclar Vivadent) halogen light to a conventional (Max [MX] (control), Dentsply-Caulk) halogen light. Ten light curing regimens were investigated. These included continuous (FL1, EL2, MX, TL1 and AS1), soft-start (FL2, EL4, TL2), pulse activation (EL1) and turbo (EL3) modes. A strain-monitoring device and test configuration was used to measure the linear polymerization shrinkage of a composite restorative (Z100, [3M ESPE]) during and post-light polymerization up to 60 minutes when cured with the different modes. Five specimens were made for each cure mode. Results were analyzed using ANOVA/Scheffe's post-hoc test and independent sample t-tests at significance level 0.05. Shrinkage associated with the various modes of EL was significantly lower than MX immediately after light polymerization and at one-minute post-light polymerization. No significant difference between MX and the various lights/cure modes was observed at 10, 30 and 60-minutes post-light polymerization. At all time intervals, post-gel shrinkage associated with continuous light curing mode was significantly higher than the soft-start light curing mode for FL and TL.
authors.affiliation: Department of Restorative Dentistry, Faculty of Dentistry, National University of Singapore, Republic of Singapore. g0306023@nus.edu.sg
authors.forename: M S
authors.initials: MS
authors.lastname: Soh
authors.forename: Adrian U J
authors.initials: AU
authors.lastname: Yap
authors.forename: K S
authors.initials: KS
authors.lastname: Siow
mesh_terms: D000704:Analysis of Variance; D003188:Composite Resins / Q000528:radiation effects*; D003748:Dental Equipment; D003799:Dental Stress Analysis; D006219:Halogens; D008027:Light; D008422:Materials Testing; D015394:Molecular Structure; D044367:Phase Transition; D011108:Polymers / Q000737:chemistry; D012666:Semiconductors; D012822:Silicon Dioxide / Q000528:radiation effects*; D018709:Statistics, Nonparametric; D013674:Technology, Dental / Q000295:instrumentation*; D015040:Zirconium / Q000528:radiation effects*
chemical_list: D003188:Composite Resins; D006219:Halogens; D011108:Polymers; C083568:Z100 composite resin; D012822:Silicon Dioxide; D015040:Zirconium