Fracture Resistance And Failure Patterns Of Four Different Post-core Systems Restored In Mandibular First Premolar. An In Vitro Study

Objective:To compare the fracture resistance and failure patterns of the cast metal post-core systems and non-metal post-core systems restored in mandibular first premolar. In order to provide the restoration data and reference laboratory for the post-core restoration of clinical residual crown and root.Methods:Fourty orthodontic extracted human single root canal man-dibular first premolars were endodontically treated and the crown of the teeth was sectioned at 2.0mm above the labial cement enamel junction. The teeth were randomly and equally divided in four and restored with Ni-Cr cast metal post-core,40% Au-Pd cast metal post-core, RTD quartz fiber post-core system, and Cosmopost post-core system (zirconium ceramic), respectively, prepared with parallel grinder out of 2mm ferrule and unified form of the core department, casting metal full crown restoration bond. Then all the teeth were embedded in acrylic resin blocks. Loads were measured with the axis of the tooth into a 30-degree angle on the universal load-testing machine, loading speed of 1.0mm/min tip load. Record instantaneous force when destroyed, test the fracture resistance and failure patterns. At last, use SPSS11.0 to statistical analysis.Results:1. Ni-Cr cast metal post-core has the highest flexural strength. It had no statistically significant difference with 40% Au-Pd cast metal post-core (P>0.05), also had no statistically significant difference with Cosmopost post-core system(P>0.05); 40% Au-Pd cast metal post-core and Cosmopost post-core system had no significant differences(P>0.05); The fracture loads of Ni-Cr cast metal post-core,40% Au-Pd cast metal than that of RTD quartz fiber post-core system group (P<0.05).2. The failure patterns of the cast metal post-core systems are significant different from the non-metal post-core systems (P<0.05).Conclusion:1. Ni-Cr cast metal post-core,40% Au-Pd cast metal post-core, RTD quartz fiber post-core system and Cosmopost post-core system (zirconium ceramic) are meeting the clinical needs.2. The fracture of RTD quartz fiber post-core system and Cosmopost post-core system are in the 1/3 of root neck; Ni-Cr cast metal post-core and 40% Au-Pd cast metal post-core are in the 1/3 of root central or the 1/3 of root tip. The non-metal post-core systems may be better in prevention of tooth root from fracture.