Objectives: Tooth fracture is a common complication following MOD restorations. This study sought to assess the effect of bulk fill flowable composite reinforced with short fibers on fracture resistance of maxillary premolar teeth that have extensively restored MOD cavities. Materials and Methods: In this invitro experimental study, 60 human maxillary sound premolar teeth were chosen and stored in chloramine solution. The teeth were then mounted into acrylic blocks 1mm below the CEJ. The teeth were randomly divided into 4 groups of 15 each. Group A, Teeth were intact without any cavity (negative control). Wide MOD cavities were prepared using cylindrical bur with high-speed handpiece for the 3 other groups. Group B, the teeth with MOD cavities without any restoration (positive control); Group C, the teeth were restored with bulkfill flowable composite Tetric N flow bulk fill (Ivoclar Vivadent); and group D, the teeth were restored with short fibers reinforced bulkfill flowable composite ever X Flow(GC). The teeth were then stored in water at 37°C for 24h and their fracture resistance was assessed using (INSTRON). The load at fracture was recorded in N, fracture mode was observed. Data were analyzed using one-way ANOVA and Tukey's test with 95% CI. Results: The mean fracture strength was 1216 ± 352 N in group A, 330 ± 201 N in group B, 1013 ± 389 N in group C and 1019 ± 164 N in group D. Conclusion: Extensive MOD cavities restored with bulk fill flowable composite having short fiber reinforcement, increased the fracture strength of teeth against compressive forces, with no difference than did the other bulk fill flowable composite. Large direct restorations present several challenges especially in the posterior dentition. Mastering of shape, contours, occlusal anatomy and function requires particular skills. One must be aware of the KEYWORDS

Post-operative hypersensitivity still occurs although the improvements in adhesive systems and their techniques, so the current study was conducted to evaluate the efficacy of two desensitizing systems. Materials and methods:  A total No. of 48 patients were randomly divided into 3 groups (n=16); Gluma group, SAD group, and control group. Class I cavity preparation and self-etch bonding technique was used by Universal bonding system in the control group, before that desensitizing agent was applied in the two desensitizing tested groups, light cured and composite placement incrementally (Tetric N-ceram) and light cured, finishing, and polishing of composite restorations, then VAS system was used to record post-operative hypersensitivity by patients, and after 1 day,1 week and 1 month the data collected and statistically analyzed. Results: Total number of patients who suffered from post-operative hypersensitivity was 15 patients (31.25 %) after one day of treatment, the total number decreased to 9 patients (18.75 %) after one week postoperatively, and after one month the total number decreased again to 4 patients (8.33 %). In all the tested groups 1 day gave a significant difference than one week ( P= 0.011*),,,