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Table 2 Mean force (kN) required to fracture the tooth roots and the root fracture sites, in each group

From: An in vitro study evaluating the effect of ferrule design on the fracture resistance of endodontically treated mandibular premolars after simulated crown lengthening or forced eruption methods

Groups Fatigue testing Fracture strength (kN)a Root fracture sitesb
At or above cervical 1/3 Below cervical 1/3
F0 0/8 1.01(0.26) 7 1
CL/F1 0/8 0.91 (0.29) 6 2
CL/F2 0/8 0.73 (0.19) 8 0
OE/F1 0/8 0.96 (0.25) 6 2
OE/F2 0/8 0.76 (0.20) 7 1
  1. Group codes are defined in Table 1
  2. aMean (Standard Deviation)
  3. bFailed roots were classified repairable (the fracture sites located at or above cervical one-third), and irrepairable (the fracture sites below cervical one-third)