الفهرس 
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Abstract
Background :The destructive nature of tooth preparation has been encountered as the main reason of reduction in the tooth strength. Furthermore pulpotomized procedure, occlusal tooth preparation and mesio-occluso-distal (MOD) cavities are the principal procedures in the tooth weakening and consequently increase the susceptibility of the tooth to fracture. Aim :To evaluatefracture resistance of resin-modified glass-ionomer cement, nanocomposite and compomer versus amalgam restoration for restoring pulpotomized primary molars. Methods : Pulpotomy with class II cavity preparation was performed for one hundred and twenty extracted second primary molars. Teeth were randomly divided into two equal main groups (60 each), according to cusp reduction preparation. group (A) with cusp reduction and group (B) without cusp reduction. Each group is further subdivided into four subgroups (15 teeth each) according to the type of restorative materials. Teeth were restored with four different types of restorative materials according to manufacturer instructions, thermocycled and mounted in self –curing acrylic resin. Fracture resistance was measured using universal testing machine. Data were statistically analyzed using ANOVA and post hoctucky test. Results : In both (A) and (B) groups, the highest resistance to fracture was recorded in composite subgroups (823.02±267.49 & 807.87±257.51) compomer was the restorative material that yielded the lowest fracture resistance in both groups (404.78±170.00 & 397.47±131.35).A highly significant statistically difference (0.001) was revealed when both groups (A, B) were compared regarding the type of fracture in different subgroups. Favorable fractures were observed higher in prepared cavities with cusp reduction, while unfavorable fractures were significantly higher in prepared without cusp reduction. Conclusion : Fracture resistance was higher in pulpotomized teeth restored with composite in comparison with RMGIC, amalgam and comopmer in both groups (A, B). Cusp coverage restorations recorded higher numbers of favorable type of fracture.