Property Evaluation of Self-Etch Flowable Composites

Objectives: To evaluate several properties of an experimental self-etching flowable composite (Exp.SEF), comparing the properties with commercial flowable composites.  Materials and Methods: an Exp. SEF (Pentron) and a self-adhesive flowable composite Embrace™ Wetbond™ Class V (Pulpdent) were tested. A conventional Flow-It™ (Pentron) was used as a control. For bonding, the Exp. SEF and Embrace were applied to dentin and enamel (n=6) and light cured 10s and 20s, respectively, following instructions.  Simile™ (Pentron) was used for the button build-up followed by 40” light curing using the Ultradent bonding device.  The samples were then stored at 37 °C in H₂O for 24 hours before test. Shear bond strengths (SBS) was tested on an ATS Universal Testing Machine. Flexural strength (FS), water absorption (WA) and solubility (WS) of the three flowable composites were tested according to ISO 4049. Vicker's Hardness (VH) sample (3x10mm cylinder) was light cured 20s and tested on Clark Instrument. Results: SBS, FS, VH, WA and WS test results are listed in the table below. One-Way ANOVA showed statistical difference among the testing groups.

Flowable Composite	Exp. SEF	Embrace	Flow-It
Application	No adhesive	No adhesive	Need adhesive
SBS (MPa)              Dentin              Enamel	24.5 (5.6) 22.7 (7.0)	6.45(5.64) 6.9 (4.4)	N/A
FS (MPa)	143(24)	69(11)	133(12)
VH (Kg/mm2)	36	28	32
WA (mg/mm3/wk)	30	84	14
WS (mg/mm3/wk)	6	21	2

Conclusion: Exp. SEF has better dentin and enamel bonding strengths than Embrace. The mechanical properties of Exp. SEF are better than Embrace and comparable with Flow-It.  Exp. SEF has lower water absorption and solubility than Embrace, although both WA and WL are higher than Flow-it due to the acidic and more hydrophilic nature of self-etching composites.