Objective: To measure the fracture resistance of mandibular premolar roots following root canal instrumentation with different sizes.
Methods: A total of 60 human permanent mandibular premolars with a straight single canal were decoronated and assigned to 6 groups (n=6). In the control group, the roots were unistrumented, whereas roots in 5 experimental groups were instrumented to different master apical files (MAF) and tapers (MAF/ taper): 40/0.10, 45/0.10, 45/0.15 50/ 0.05, 55/0.05 .All roots were subjected to vertical loading until fracture.
Results: Fracture load values for instrumented roots were lower than the intact roots of the control group. In 50/0.05, 55/0.05 the fracture load values were significantly lower than the fracture load value for the control group (p<0.05) with a 30% decrease. No significant difference in the fracture modes were detected among the 6 groups (p>0.05)
Conclusion: Mechanical instrumentation adversely affects the fracture resistance of roots. When the roots of mandibular premolars were instrumented to a MAF equal to or larger than 50 with a taper of 0.05 or to a MAF of 45 with a taper of 0.15, the fracture load values suddenly decreased.
Impact Factor
2022: 6.012
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