0119 Monomer conversion in dual-cured core build-up materials
N. KOURNETAS, S. GIANNIKOU, and G. ELIADES, University of Athens (EKPA), Greece

Objective: To test the hypothesis that the chemically-curing mechanism of dual-cured core build-up materials is equally effective to visible light-curing, during the early setting stages.

Methods: The materials tested were Clearfil DC Core Automix (CD), Cosmecore DC (CM), LuxaCore DC (LX) and  MultiCore DC Flow (MC). Clearfil Core New Bond (CN, chemically-cured) and Clearfil Photo Core (CP, light-cured) were used as a control. Specimens (Ø: 4mm, d: 1mm, n=4 ) prepared without light-exposure were tested after 10, 20, 30min and 1h storage in dark and dry conditions (37oC). Specimens light-cured immediately after mixing  (700mW/cm2 intensity, 20s exp) served as reference. The amount of remaining C=C bonds (%RDB) was measured on bottom surfaces by ATR-FTIR spectroscopy. Two-way ANOVA and multiple comparison tests were used to evaluate the statistically significant differences (a: 0.05).   

Results: The %RDB values (mean/SD) are given below (same superscripts indicate mean values with no statistically differences, p<0.05):  

TIME

CD

CM

LX

MC

10 min

97.52 (1.55)

92.46 (0.75)

56.11 (0.75)b

59.92 (0.43)

20 min

64.27 (1.50)

79.15 (1.14)

53.73 (1.32)b,c,1

55.91 (0.26)e,f,1

30 min

51.69 (0.97)a,2

67.60 (1.46)

51.34 (1.70)c,d,2

54.64 (0.65)e,f,2

1 h

49.73 (1.32)a,3

63.37 (0.95)

50.04 (1.05)d,3

51.92 (1.05)f,3

LC

50.57 (0.68)a,4

51.53 (0.39)4

48.17 (0.51)

56.03 (0.33)e

  The values of the control groups were: CN: 56.74 (0.28) and CP: 43.04 (0.39). A strong interaction was found between material and time. LX and MC showed better dark conversion during the initial 20 min period. After 1h the values of CM were still above 60%, whereas in

CD and LX reached the level of irradiated specimens.  

Conclusions: Some dual-cured core build-up materials demonstrate a very slow chemically initiation mechanism, that leads to low conversion at areas distal to the activating light, providing thus a weak core structure during the early setting stages.      

Seq #15 - Polymer Materials
4:00 PM-5:30 PM, Thursday, September 27, 2007 Ioannis Vellidis Congress Centre Hall 1 "Thessaloniki"

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