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Erschienen in:
01.05.2015 | Original Article
Influence of irradiation time on subsurface degree of conversion and microhardness of high-viscosity bulk-fill resin composites
Erschienen in: Clinical Oral Investigations | Ausgabe 4/2015
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Objectives
To evaluate the influence of irradiation time on degree of conversion (DC) and microhardness of high-viscosity bulk-fill resin composites in depths up to 6 mm.
Materials and methods
Four bulk-fill materials (Tetric EvoCeram Bulk Fill—TECBF; x-tra fil—XF; QuixFil—QF; SonicFill—SF) and one conventional nano-hybrid resin composite (Tetric EvoCeram—TEC) were irradiated for 10, 20, or 30 s at 1,170 mW/cm2. DC and Knoop microhardness (KHN) were recorded after 24-h dark storage at five depths: 0.1, 2, 4, 5, and 6 mm. Data were statistically analyzed using ANOVA and Bonferroni’s post-hoc test (α = 0.05).
Results
With increasing bulk thickness, DC and KHN significantly decreased for TEC. TECBF and SF showed a significant decrease in DC and KHN at 4-mm depth after 10-s irradiation, but no decrease in DC after 30-s irradiation (p > 0.05). XF and QF demonstrated no significant DC decrease at depths up to 6 mm after irradiation of at least 20 s. At 4-mm depth, all materials tested achieved at least 80 % of their maximum DC value, irrespective of irradiation time. However, at the same depth (4 mm), only XF and QF irradiated for 30 s achieved at least 80 % of their maximum KHN value.
Conclusions
Regarding DC, the tested bulk-fill resin composites can be safely used up to at least 4-mm incremental thickness. However, with respect to hardness, only XF and QF achieved acceptable results at 4-mm depth with 30 s of irradiation.
Clinical relevance
Minimum irradiation times stated by the manufacturers cannot be recommended for placement of high-viscosity bulk-fill materials in 4-mm increments.