Fracture Resistance Of Premolar Teeth Treated With Different Root Canal Instrumentation And Restored With Three Restorations

Objective: The fracture resistance of endodontically treated teeth was important to the teeth survival rate.The purpose of this study was to compare the fracture resistance of endodontically treated human premolar teeth with three restorations and the effect of different root canal instrumentation.Methods:135 extracted human mandibular premolars with single canal were selected between January 2015 to October 2016 and randomly divided into two parts.The first part of 75 premolars were randomly divided into five groups(A,B,C,D,E),which were prepared by #25 0.04 taper;#25 0.06 taper;#30 0.04 taper and #30 0.06 taper rotary instruments separately,and E group were prepared by #30 0.06 taper rotary instruments with CBCT reconstruction and mini-invasive technology;Then a compressive strength testing by the universal testing machine was applied to each tooth.The peak compressive strength was recorded when each vertical tooth fracture noticed.The second part of 60 premolars were 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 were restored with composite resin,Group C were restored with glass-fiber post and ceramic inlay,Group D were restored with Ever Stick 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: The first part : No significant differences were obtained either between Group A(153.26 ± 56.31 N)and Group B(143.18 ±46.26 N)or between Group C(91.26± 29.43 N)and Group D(83.17 ± 26.32 N)(P > 0.05).However,there were significant differences between Group E(310.28 ± 38.87 N)and Group ABCD,Group A and Group C as well as Group B and Group D(P < 0.05 =.The second part: Group C(961.05±101.45N)and group D(1024.66±78.56N)was significantly higher than that in the Group B(796.57±118.85N)and the group A(1413.91±95.93N)(p<0.05).Conclusion: Increased taper and size of file tip of root canal instrumentation would decrease root strength.By CBCT and mini-invasive technology,the root canal treatment with pulp chamber top reserved was better than other treatment.The use of Ever Stick high-strength fiber composite resin in premolar teeth with standardized MO cavities can significantly increase the fracture resistance.