الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 105 |  |  |
| | | from | 105 | | |
Abstract
Aim of the study: To evaluate the fracture resistance of maxillary premolar teeth with MOD cavities, restored with different bulk fill resin composite systems. Materials and methods: Seventy maxillary first premolars were selected and divided into seven groups (n=10). The first group was left intact and considered as positive control group (In). Standardized class II MOD cavities were prepared in the remaining groups. The second group was left prepared unrestored and considered as negative control group (Un). Five different resin composite systems were used to restore the prepared cavities in the remaining five groups. The first one was incrementally applied resin composite Z350 XT (ZX). The remaining resin composite systems were of bulk fill types, including: Tetric® N Ceram Bulk-Fill (TB), Filtek Bulk Fill (FB), SonicFill2™ (SF) and Reveal® HD Bulk (RV). All the groups were thermocycled for 5000 cycles. Fracture resistance test was performed immediately after thermal cycling process using universal testing machine (Instron 3345, Canton, MA, USA). Fracture patterns were examined under stereomicroscope. Samples from each group were examined under SEM. Data were tabulated then analyzed using One-way analysis of variance (ANOVA) followed by student t-test in order to determine significant differences among groups. Results: There was no statistical significant difference (P≤ 0.05) between FB, SF groups. On the other hand, there was a significant difference between In, Un, ZX, TB, RV groups (p= 0.0001).Additionally, there was a significant difference between (FB, SF) groups and the remaining groups (p= 0.0001). Conclusion: Based on the results of the current study: 1- Extensive MOD cavity preparations greatly deteriorate the fracture resistance of maxillary premolars. 2- Tetric N Ceram Bulk-fill resin composite restorative system is considered the most appropriate tested material to improve fracture resistance of restored premolar teeth. 3- Except Reveal HD Bulk, other types of bulk-fill resin composites showed comparable ability to increase tooth fracture resistance, with incremental-fill resin composite systems. 4- Both incremental-fill and bulk-fill resin composite systems don’t provide fracture resistance near that of sound teeth.