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HIGH VISCOSITY BULK-FILL GIOMER AND ORMOCER-BASED RESIN COMPOSITES : AN IN-VITRO COMPARISON OF THEIR MECHANICAL BEHAVIOUR

Table 1 . Materials , Manufacturer , chemical composition of matrix and filler as well as filler content by weight ( wt .) and volume ( vol .) %

Bulk Fill RBCs

Manufacturer , Color , Batch

Resin Matrix Filler Filler wt %/ vol %

Tetric EvoCeram ® Bulk Fill Nano-hybrid RBC

Admira Fusion x-tra Nano-hybrid RBC

X-tra Fil Hybrid RBC

SonicFill™ Nano-hybrid RBC

Beautifil Bulk restorative GIOMER

QuixFil Hybrid RBC

Ivoclar Vivadent IVA , P84129

Voco Universal , 1527519

Voco Universal , 1230323

Kerr A3 , 3851737

Shofu Dental Corporation , Universal , 11402 Dentsply DeTrey Universal , 1209000241

Bis-GMA , UDMA

Organically modified silicic acid

Ba-Al-Si-glass , prepolymer filler ( monomer , glass filler and ytterbium fluoride ), spherical mixed oxide

79-81 ( including 17 % prepolymers )/ 60-61

n . s . 84 / -

Bis-GMA , UDMA , TEGDMA n . s . 86 / 70.1

Bis-GMA , TEGDMA , EBPDMA

Bis-GMA , UDMA , Bis-MPEPP , TEGDMA

Bis-EMA , UDMA , TEGDMA , TMPTMA , TCB-Resin

SiO2 , Glass , oxide 83.5 /

S-PRG filler based on F-B-Al-Si-glass , prepolymer filler

87.0 / 74.5

Sr-Al-Na-F-P-Si-glass 86 / 66

Abbreviations : Bis-GMA , bisphenol-A diglycidyl ether dimethacrylate ; EBPDM / Bis-EMA , ethoxylated Bisphenol-Adimethacrylate ; TEGDMA , Triethyleneglycol dimethacrylate ; UDMA , Urethane dimethacrylate ; TMPTMA , Trimethylolpropan- Trimethacrylat ; TCB resin , butane-1,2,3,4-tetracarboxylic acid , bis-2-hydroxyethyl methacrylate ; Bis-MPEPP , Bisphenol A Polyethoxy-Dimethacrylat n . s ., not specified Data are provided by manufacturers

Table 2 . Influence of the parameters . Filler weight on the mechanical properties . Table contains the partial eta-square values . The higher the partial eta-square , the higher the influence of the selected factor on the measured property ( p < 0.001 )

2 . Materials and Methods

One giomer , one ormocer as well as the first launched high-viscosity bulk-fill RBC were compared with three established high-viscosity bulk-fill resin composites ( Table 1 ) by assessing their mechanical properties at macroscopic ( σ and E flexural

) and microscopic scale ( HM , HV , Y HU and

Creep ).

2.1 Macro-mechanical Characteristics The flexural strength ( σ ) and flexural modulus ( E flexural

) were determined in a three-point-bending test ( n = 20 ). Therefore , specimens were made by compressing the composite material between two glass plates with intermediate Polyacetate sheets , separated by a steel mold having an internal dimension of ( 2 x 2 x 16 ) mm . Irradiation occurred on the top and bottom of the specimens , as specified in ISO 4049:2009 standards ; 20 the duration of the light exposures was 20s , with three light exposures , overlapping one irradiated section no more than 1 mm of the diameter of the light guide ( Elipar tm Freelight 2 , 3M ESPE , Seefeld , Germany , 1,241 mW / cm ²) to prevent multiple polymerizations . After removal from the mold , the specimens were ground with silicon carbide sand paper ( grit size P 1200 / 4000 ( Leco )) to remove protruding edges or bulges , and then stored for 24 h in distilled water at 37 ° C . The specimens were loaded until failure in a universal testing machine ( Z 2.5 , Zwick / Roell , Ulm , Germany ) in a threepoint-bending test device , which was constructed according to the guidelines of NIST No . 4877 with a 12 mm distance between the supports . 21 During testing , the specimens were immersed in distilled water at room temperature . The crosshead speed was 0.5 mm / min . The universal testing machine measured the force during bending as a function of the deflection of the beam . The bending modulus was calculated from the slope of the linear part of the force-deflection diagram .

2.2 Micro-mechanical Characteristics Fragments ( n = 10 ) of the three-point-bending test specimens of each group were used to determine the micro-mechanical properties ( Martens Hardness ( HM ), Vickers hardness ( HV ), indentation modulus ( Y HU

) and creep ) according to DIN 50359-1:1997-10 22 by means of a universalhardness device ( Fischerscope H100C , Fischer , Sindelfingen , Germany ). Prior to testing , the