Abstract: Objective To explore the influence factors of three restoration methods on the fracture resistance of endodontically treated human premolar teeth. Methods 60 extracted human mandibular premolars with single canal were selected and randomly divided into 4 groups ( A，B，C，D)，Group A remained untreated and served as a control group. The other three groups were endodontically treated and a standardized MO cavity was prepared on each tooth. Over the standardized MO cavity, Group B was restored with composite resin, Group C with ceramicinlay，Group D with EverStick fiber and composite resin. The loading force under the direction at 135 degree to the long axis with crosshead speed of 1mm/min was applied to each tooth until the first sign of failure was noted. Data were recorded and analyzed statistically by SPSS 17.0 software. Results The median values of the samples were as follows: Group A(1413.91±95.93N) and Group D (1324.66±88.56N) were significantly higher than Group B(796.57±118.85N) and Group C(961.05±101.45N) (p<0.05). The incidences of repairable fracture mode were: A(80%), B(73.3%), C(73.3%), D(100%). Conclusion The use of EverStick high-strength fiber composite resin in premolar teeth with standardized MO cavities can significantly increase the fracture resistance and the fracture mode also has more advantages .

Key words: root canal treatment, high-strength fiber,fracture resistance