Shrinkage and Contraction Force of Bulk-filling and Microhybrid Composites

Bulk Filling composites guarantee a layer thickness of at least 4 mm. Because of the higher composite  volume, low shrinkage  and shrinkage force are necessary for a clinical success. Objectives: The purpose of this study was the measurement of the volume shrinkage and the contraction force (CF) in upto 3 different layer thicknesses of different Bulk Filling and Microhybrid composites. Methods: 6 Bulk Filling composites (Tetric EvoCeram Bulk Fill from Ivoclar Vivadent, Sonic Fill from Kerr, Quix Fil from Dentsply, SureFil  SDR flow from Dentsply, Venus Bulk Fill from Heraeus Kulzer, X-tra fil from Voco) and 3 Microhycrid composites (Filtek Supreme XTE, Filtek Z250 from 3MEspe and Herculite XRV Ultra from Kerr) were examined. Shrinkage (60min post-cure) was measured using NIST mercury dilatometer (n=3) for the mouldable composites. The flowable composites were measured (60 min post-cure)  with the Archimedes principle (n= 6). Contraction force was measured using a Bioman shrinkage-stress instrument (Watts, Manchester UK). Specimens (Ø = 10 mm, h = 0.8 mm, 2.0 mm 4.0 mm) were placed between a sand blasted metal rod and a silanated glass plate. CF was continuously monitored from exposure  (10 s Bluephase HIP) to 1800 s (n=3). The data were analyses by ANOVA (p<0.05).                                                                             

Results: (Mean ± SD)

Materials	Shrinkage (%)	Shrinkage Force (N)
		0.8 mm	2.0 mm	4.0 mm
Tetric EvoCeram Bulk Fill	1.96 ±0.03	94.9 ±7	118.8±1.4	110±3.8
Sonic Fill	1.99 ±0.02	108.3±4.6	138.7±12	139.1±4.7
X-tra fil	1.86 ±0.03	91.0±4.8	141.3±8.2	144.0±10
QuixFil	1.99±0.05	98.0±1.1	142.1 ±9	150.0±19
SureFil  SDR flow	3.36 ±0.28	87.2±4.2
Venus Bulk Fill	3.36±0.13	105.5±6.6
Filtek Supreme XTE	2.06 ±0.04	118.5 ±1.6	151.7±13
Filtek Z250	2.07±0.02	95.6±4.5	128.1.±0.5
Herculite XRV Ultra	2.38±0.06	129.8±2.7	125.7±5.2

Conclusions: Polymerization shrinkage and shrinkage forces were different between various resin composites. There is no correlation between shrinkage and shrinkage force. The shrinkage force is different in the layer thickness of the composite. The shrinkage force at 4 mm is not higher than at 2.