الفهرس 
Fracture Resistance of Posterior Bulk Fill Flowable Composite Restoring MOD Cavities in Premolars
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Abstract
Aim of the study :
The aim of this study was to evaluate the fracture resistance of bulk fill flowable resin composite restoring MOD cavities in upper premolars compared to incrementally packed nanofilled resin composite using two different bonding approaches self-etch and etch and rinse.
Materials and methods:
A set of 70 sound non- cavitated human upper premolar teeth indicated for extraction were randomly collected. All teeth were free of caries, cracks or restorations. Teeth were put into main 14 main groups (n=5) by the researcher.
group I: sound premolars. group II: unrestored premolars with MOD cavity preparation. group III: premolars with MOD cavity preparation restored by 4mm bulk fill flowable resin composite (Xtra-baseR, VocoTM, Germany) bonded by etch and rinse adhesive system SoloBond M (VocoTM, Germany) without thermocycling. group IV: premolars with MOD cavity preparation restored by 4mm bulk fill flowable resin composite (Xtra-baseR, VocoTM, Germany) bonded by self-etch approach Futura DC (Voco, Germany) without thermocycling. group V: premolars with MOD cavity preparation restored by 4mm bulk fill flowable composite (Xtra-baseR, VocoTM, Germany) bonded by SoloBond M (VocoTM, Germany) with thermocycling. group VI: premolars with MOD cavity preparation restored by 4mm bulk fill composite (Xtra-baseR, VocoTM, Germany) bonded by Futura DC (Voco, Germany) with thermocycling. group VII: premolars with MOD cavity preparation restored by 2mm bulk fill flowable composite followed by 2mm incrementally packed nanohybrid resin composite (Grandio, Voco, Germany) bonded by SoloBond M without thermocycling. group VIII: premolars with MOD cavity preparation restored by 2mm bulk fill flowable composite followed by 2mm incrementally packed nanohybrid resin composite (Grandio, Voco, Germany) bonded by Futura DC without thermocycling. group IX: premolars with MOD cavity preparation restored by 2mm bulk fill flowable composite followed by 2mm incrementally packed nanohybrid resin composite (Grandio, Voco, Germany) bonded by SoloBond M with thermocycling. group X: premolars with MOD cavity preparation restored by 2mm bulk fill flowable composite followed by 2mm incrementally packed nanohybrid resin composite (Grandio, Voco, Germany) bonded by Futura DC with thermocycling. group XI: premolars with MOD cavity preparation restored by 4mm incrementallypacked nanohybrid resin composite (Grandio, Voco, Germany) bonded by SoloBond M without thermocycling. group XII: premolars with MOD cavity preparation restored by 4mm incrementally packed nanohybrid resin composite (Grandio, Voco, Germany) bonded by Futura DC without thermocycling. group XIII: premolars with MOD cavity preparation restored by 4mm incrementally packed nanohybrid resin composite (Grandio, Voco, Germany) bonded by SoloBond M with thermocycling. group XIV: premolars with MOD cavity preparation restored by 4mm incrementally packed nanohybrid resin composite (Grandio, Voco, Germany) bonded by Futura DC with thermocycling. All prepared teeth received restorations except group II “Cavity preparation without restorations” to act as the negative control. After adhesive application, a matrix retainer system, a holder and a metal matrix, (Tofflemire, Miltex Inc, York, PA, USA) was used to simulate the clinical conditions. The specimens were blinded from the assessing personnel by placing them in sequentially numbered sealed light proof containers. Thermocycling were done to half of the specimen, then load was applied on all specimens using universal testing machine with crosshead speed 1 mm/minute applied on the inclined planes of buccal and lingual cusps of the tested teeth till fracture. The outcome is the load at which the specimen was fractured in Newton. The fracture mode was determined either favorable or unfavorable and then assigned either for adhesive, cohesive or mixed fracture mode.
Results:
The analysis of the One Way ANOVA test and the Tukay’s post-hoc test revealed that:
Effect of different resin composite (M) regardless of other variables When Compared to control: Sound teeth (positive control) showed the highest mean Fracture resistance. This result is statistically significant, followed by combined bulk fill and incrementally packed nanohybrid composite and then incrementally packed nanohybrid resin composite then bulk fill flowable resin composite with a significant statistical difference between them; followed by Cavity preparation only (negative control). But without control: Incrementally packed nanohybrid composite covering 2mm bulk fill flowable resin composite showed the highest mean Fracture resistance. This result is statistically significant, followed by the incrementally packed nanohybrid resin