Fracture Resistance Of Endodontically Treated Premolars Restored With Three Post-and-Core Materials

Objective:To compare the fracture resistance of endodontically treated teeth with retained coronal dentin restored with three different post-and-core materials through mechanical test for clinical application.Methods:A total of 54 intact single-rooted human maxillary first premolars of similar dimensions were extracted recently from adolescents who were receiving orthodontic treatment.Teeth were randomly divided into nine groups with six each.Teeth in group A were cut off from the point 3mm up the cemento-enamel junction(CEJ) and restored with silver amalgam post-and-core system. Teeth in group B were cut off from the point 4mm up the CEJ and restored with silver amalgam post-and-core system.Teeth in group C were cut off from the point 5mm up the CEJ and restored with silver amalgam post-and-core system.Teeth in group D were cut off from the point 3mm up the CEJ and restored with resin-modified glass ionomer post-and-core system.Teeth in group E were cut off from the point 4mm up the CEJ and restored with resin-modified glass ionomer post-and-core system.Teeth in group F were cut off from the point 5mm up the CEJ and restored with resin-modified glass ionomer post-and-core system.Teeth in group G were cut off from the point 3mm up the CEJ and restored with double-cure composite resin post-and-core system.Teeth in group H were cut off from the point 4mm up the CEJ and restored with double-cure composite resin post-and-core system.Teeth in group I were cut off from the point 5mm up the CEJ and restored with double-cure composite resin post-and-core system.All the specimens with full crown casts were embedded vertically in autopolymerizing acrylic resin from the point 2mm below the CEJ.Then all the specimens were mounted in the universal test machine for fracture resistance test at a crosshead speed of 1mm/min while the load angle was 45 degree to the long axis of the teeth until failure,as the load is pointed to the middle of central groove of occlusal surface.Recorded the top loads and mode of root fracture while the results were analyzed through SPSS13.0 software.Results:Group I has the highest fracture resistance with the value of 896.19±71.42N while group D has the lowest fracture resistance with the value of 307.42±46.68N. There were statistically significant differences(p<0.05).Factorial experiment was used to determine significant differences of the fracture resistance loads among all groups. The results showed the differences were significant with material factor(p<0.05), and the differences were significant with retained dentin factor (p<0.05).There was an interactive relationship between two factors. The fracture mode of three post-and-core systems allowed the possibility of repreparation.Conclusions:Different post-and-core materials had significant difference in fracture resistances.The double-cure composite resin post-and-core system had the highest fracture strength,followed by the silver amalgam post-and-core system and the resin-modified glass ionomer post-and-core system had the lowest fracture strength. Preserve healthy teeth tissue as much as possible increased the fracture resistance of post-and-core systems.Three post-and-core materials can be used to restore partial defect of crown,and showed superiority in remaining teeth protection.