Background: The most important change in the mechanical properties of endodontically-treated teeth is the reduction of fracture strength. The aim of the present study was to compare the fracture strength of teeth restored with bulk-fill composite, flowable bulk-fill composite and conventional composite resin in the presence or absence of fiber.Materials and Methods: In this laboratory study, 120 intact maxillary first premolar teeth were selected and placed in eight groups. The groups were designed with three types of composites (conventional, bulk-fill, flowable bulk-fill) with and without fiber and two negative control groups and positive, Mesio-occlusal-distal (MOD) cavity was prepared in all groups. After the endodontics, the composite of the same group was used in each group to restore the teeth by incremental method. All restorations were polished, mounted and tested by Universal testing machine. Results: The fracture strength in the fiber-reinforced bulk-fill composite group was significantly higher than the fiber-free group. The teeth restored with fiber-free composites had lower fracture strength. The fracture strength was the same in the samples treated with conventional and bulk-fill composite resins, and it was significantly lower in the samples treated with flowable bulk-fill composite than those treated with conventional and bulk-fill composites. There was a significant difference in fracture strength of fiber-reinforced composites.Conclusion: Tooth restoration reduces fracture strength. Fiber addition has no significant effect on increasing the fracture strength of composites. پرونده مقاله

Background: The present study aimed to use a DIAGNOdetnt unit to compare the effects of casein phosphopeptideamorphous calcium phosphate fluoride (CPP-ACPF), 0.05% sodium fluoride (NaF) mouth rinse, and glass ionomer (GI) on enamel remineralization.Materials and Methods: This in vitro study was performed on 50 intact human premolars in five groups: A (artificial saliva), B (CPP-ACPF), C (NAF), D (GI), and E(GI+NAF). All samples were assessed using a DIGNOdetnt unit before and after demineralization. The teeth in each group were treated (except for the control group) then pH cycled repeatedly for 30 days. After this, the remineralization evaluation was evaluated. Data gathered by DIAGNOdetnt were analyzed by One way analysis of variance. The least significant difference (LSD) test was used for multiple comparisons (α=0.05).Results: After the treatment, the mean DIAGNOdetnt values in groups B(3.6), C(4.7), D (5.1), and E(3.5) were significantly lower than that in group A(P<0.0001). LSD test showed that the mean DIAGNOdetnt value in groups B and E was lower than for groups C and D(P<0.001).Conclusion: Although the repeated application of all the experimental materials was efficient, CPP-ACPF and GI+NAF had more prominent remineralization potential in comparison to NAF and GI alone. پرونده مقاله