Influence Of Different Restorations On The Fracture Resistance Of Endodontically Treated Premolars With Minor Loss Of Dental Defect

Objective:To evaluate the influence of three different restorations on the fracture resistance of endodontically treated premolars with minor loss of dental defect in order to provide experimental basis for selecting the proper restoration in clinics. Methods:Seventy-two intact and single-rooted human mandibular premolars,extracted recently for orthodontic reasons, were selected for this expriment and then these samples were assigned into three groups(Group A/B/C,n=24).Each group was respectively prepared into 1/3 defect of occlusal surface(Group A),1/2 defect of occlusal surface(Group B),1/3 defect of proximal-occlusal surface model(Group C).Then each group was divided into three subgroups,which one was restored with a light-curing composite resin(Subgroup A1/B1/C1,n=8),one was restored with cast metal full crowns following a light-curing composite resin(Subgroup A2/B2/C2,n=8) and one was restored with fiber post-cores and metal full crowns(Subgroup A3/B3/C3,n=8).Specimens then were embedded vertically in autopolymerizing acrylic resin,which had a flat surface 2mm below the cemento-enamel junction.Each specimen was fixed in the electronic universal load-testing machine with the use of a device that allowed loading below 0.5mm of the tooth buccal cusp at 30 degrees to the long axis of the tooth at a crosshead speed of 1mm/min until fracture occurred. The magnitude of the force causing fracture and fracture patterns were inspected.All the data was analyzed using the SPSS17.0 software package. Results:The fracture resistance of subgroup A2 was statistically significant when compared with the subgroup A1 and subgroup A3.In group B and C,the fracture strength of samples in subgroup B2/B3 and C2/C3 was higher than in subgroup B1 and C1,and there was significant difference between them.There were no statistically significant difference in the fracture mode of three restorations in group A、B and C. Conclusions:A composite resin combined with cast metal full crowns could be used as the first choice to restore the occlusal 1/3 defect of premolar.A composite resin combined with metal full crowns or fiber post-core and metal full crowns was the suitable restoration for the occlusal 1/2 defect and the proximal-occlusal 1/3 defect of premolar.