Restor Dent Endod.  2015 May;40(2):128-135. 10.5395/rde.2015.40.2.128.

Effect of resin thickness on the microhardness and optical properties of bulk-fill resin composites

  • 1Department of Conservative Dentistry, School of Dentistry, Pusan National University, Yangsan, Korea.
  • 2Department of Dental Materials, School of Dentistry, Pusan National University, Yangsan, Korea.


This study evaluated the effects of the resin thickness on the microhardness and optical properties of bulk-fill resin composites.
Four bulk-fill (Venus Bulk Fill, Heraeus Kulzer; SDR, Dentsply Caulk; Tetric N-Ceram Bulk Fill, Ivoclar vivadent; SonicFill, Kerr) and two regular resin composites (Charisma flow, Heraeus Kulzer; Tetric N-Ceram, Ivoclar vivadent) were used. Sixty acrylic cylindrical molds were prepared for each thickness (2, 3 and 4 mm). The molds were divided into six groups for resin composites. The microhardness was measured on the top and bottom surfaces, and the colors were measured using Commission Internationale d'Eclairage (CIE) L*a*b* system. Color differences according to the thickness and translucency parameters and the correlations between the microhardness and translucency parameter were analyzed. The microhardness and color differences were analyzed by ANOVA and Scheffe's post hoc test, and a student t-test, respectively. The level of significance was set to alpha = 0.05.
The microhardness decreased with increasing resin thickness. The bulk-fill resin composites showed a bottom/top hardness ratio of almost 80% or more in 4 mm thick specimens. The highest translucency parameter was observed in Venus Bulk Fill. All resin composites used in this study except for Venus Bulk Fill showed linear correlations between the microhardness and translucency parameter according to the thickness.
Within the limitations of this study, the bulk-fill resin composites used in this study can be placed and cured properly in the 4 mm bulk.


Bulk-fill resin composite; Microhardness; Thickness; Translucency parameter

MeSH Terms



  • Figure 1 Comparison of microhardness among different thicknesses. Inverted triangle (▾) indicates no significant difference. VB, Venus Bulk Fill; SR, SDR; CF, Charisma flow; TB, Tetric N-Ceram Bulk Fill; SO, SonicFill; TN, Tetric N-Ceram.

  • Figure 2 Translucency parameter (TP) and ΔTP of each group. ΔTP23 means the difference between TP2mm and TP3mm, and ΔTP24 means the difference between TP2mm and TP4mm. VB, Venus Bulk Fill; SR, SDR; CF, Charisma flow; TB, Tetric N-Ceram Bulk Fill; SO, SonicFill; TN, Tetric N-Ceram.

  • Figure 3 Correlation between microhardness and TP according to resin thickness. VB, Venus Bulk Fill; SR, SDR; CF, Charisma flow; TB, Tetric N-Ceram Bulk Fill; SO, SonicFill; TN, Tetric N-Ceram.

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