Ultrasonic Filling Technique Improve the Bond Strength of Bulk-fill Resins

Objectives: The purpose of this study was to evaluate the shear bond strength (SBS) of bulk-fill resins to dentin with and without the ultrasonic filling technique.
Methods: 60 prepared bovine teeth divided into six groups for SBS testing (n=10). Each of groups was treated with the universal adhesive (the Optibond Versa, Kerr) and one of the bulk-fill composite resins (A: SonicFill, Kerr. B: Filtek Bulk Fill, 3M ESPE. C: Filtek Bulk Flowable Fill, 3M ESPE). Three groups of teeth were filled with ultrasonic filling technique, in which after the adhesive used, the resin cylinder of 4mm was constructed with the ultrasonic filling device (Compothixo, Kerr). Other three groups of teeth were filled without ultrasonic filling technique, in which after the adhesive used, the resin cylinder of 4mm was constructed with the ordinary filling device. For all the groups, the resin thickness of 4mm bulk-placement was achieved at one-step filling. All the bonded assemblies were immersed in water at 37^OC for 24h, and used for SBS test with universal testing machine at a crosshead speed of (1.0 ± 0.1) mm/min.
Results: Ultrasonic filling technique demonstrated that significantly higher bond strength can be obtained for the three bulk-fill resins compared with ordinary filling technique (p<0.05). The bond strength of the flowable bulk fill resin had more increse with the ultrasonic-filling technique compared to the convention-filling technique (p<0.05).
Conclusions: Significant differences in bond strength were found between the ultrasonic filling technique and the conventional filling technique. And the bond strength of flowable bulk-fill resin had more increase with the ultrasonic-filling technique.