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Objective To evaluate the impact of ultra-high-molecular-weight polyethylene (UHMWPE)-Ribbond fibers, when combined with different restorative materials, on fracture resistance and marginal adaptation of isolated primary molar defects, to provide a reference for clinical practice. Methods This study was approved by the Ethics Review Committee. A total of 72 extracted primary molars with complete crowns were collected, and 66 primary molars were randomly assigned as experimental groups for the fracture resistance and microleakage tests. The molars were divided into six groups (n = 11) based on the type of restorative materials and the application of Ribbond fibers: Group A1, 3M Filtek Z250 + Ribbond; Group A2, 3M Filtek Z250; Group B1, Beautifil II LS + Ribbond; Group B2, Beautifil II LS; Group C1, 3M Filtek Bulk Fill + Ribbond; and Group C2, 3M Filtek Bulk Fill. Groups A1, B1 and C1 received the fiber-reinforcing technique, whereas Groups A2, B2 and C2 received the direct restorative technique; the remainings were in Group D (blank control group), which did not receive treatment for the fracture resistance test. The fracture resistance test was divided into six experimental groups and one blank control group (n = 6). Primary molar teeth in each experimental group were prepared with Class II cavities and filled. The fracture load of all samples was detected, and the fracture mode was analyzed after thermal cycling. The microleakage test was divided into six experimental groups, with five in each group. Class I cavities with a diameter of 3 mm and depth of 2.5 mm were prepared within the mesial and distal marginal ridges on the occlusal surface and filled for primary molars in each group. Marginal microleakage was assessed after thermal cycling. Results The fracture resistance test results showed that the fracture resistance in groups that received the fiber-reinforcing technique was greater than that in groups that received the direct restorative technique: Group A1>Group A2, Group B1>Group B2, Group C1>Group C2 (PPPP |
