STOMATOLOGY EDU JOURNAL 2017, Volume 4, Issue 3 SEJ_3-2017_Online - Page 17

characterise the glass phase of the polymerisation process and varied comparatively less with the depth. While parameter “d” was not dependent on specimen thickness, parameter “c” showed a slightly increase, however only at a depth of 6-mm. The maximal rate of polymerisation, Rate max , was, 70 70 60 60 50 50 40 40 Considering the indicated 95% confidence interval, no difference was identified for “a” at 100-µm and 2-mm depths, while “a” decreased subsequently with depth. In contrast, the parameter “b” decreased with increased specimen thickness already in thin layers. Parameters “c” and “d” 30 20 0.1 mm 2 mm 4 mm 6 mm 10 0 0 50 100 150 200 250 30 20 0.1 mm 2 mm 4 mm 6 mm 10 0 300 350 0 5 10 Time, s 15 20 25 30 Time, s Figure 1. Variation in DC in time measured at the bottom of 100-µm, 2-mm, 4-mm and 6-mm increments (mean value of n = 6), left: 300 s recordings; right a close up view of the first 30 s allowing identifying the different start of the C-C double bond conversion as function of specimen thickness). 0.1 mm 2 mm 2 mm 30 30 25 25 20 20 15 15 1 mm 10 10 5 5 0 0 -5 0 20 40 -5 60 0 4 mm 25 20 20 15 15 25 10 60 10 5 5 0 0 40 DC, % 40 6 mm 30 DC, % 60 6 mm 30 20 40 DC, % 4 mm 0 20 DC, % DC, % DC, % -5 Polymerisation kinetics in a fibre reinforced resin-based composite 60 -5 0 20 DC, % DC, % Figure 2. Rate of C-C double bond conversion versus degree of cure (DC) as function of increment thickness. Stomatology Edu Journal 167