Evaluation of radicular fracture resistance of maxillary premolars following non-surgical retreatment using two novel retreatment kits

BACKGROUND: The structural integrity of teeth after endodontic retreatment depends on the amount of remaining dentin. Excessive instrumentation can weaken roots and predispose them to fracture. This study evaluated the fracture resistance of maxillary premolars following non-surgical retreatment (NS-ReT) with Retreaty and XP-endo Rise systems. MATERIALS AND METHODS: Forty-eight maxillary first premolar roots were randomly assigned to 4 groups (n = 12); G1-NC (Negative control, non-instrumented), G2-PC (Positive control, instrumented, not obturated), G3-RETY (Retreaty), and G4-XPER (XP-endo Rise). G2, G3 and G4 groups were prepared using the iRace system. Groups G3 and G4 were obturated with gutta-percha and resin sealer. Gutta percha removal was performed using Retreaty (G3-RETY) and XP-endo Rise retreatment files (G4-XPER). All samples were subjected to fracture testing using a universal testing machine & the maximum fracture load (N) was recorded. Gutta percha removal times (Tf) and total time of retreatment were also measured. Statistical analysis was performed using a mixed-model analysis of variance (ANOVA) (α = 0.05). RESULTS: The fracture resistance of G1-NC (942.92 ± 24.73 N) had significantly higher values compared to all other groups. Fracture values for the G2-PC (829.62 ± 71.55 N) and the G3-RETY (818.29 ± 73.14 N) did not significantly differ from each other (p = 1.000), but both were significantly higher than the G4-XPER (489.37 ± 33.47 N). The total time of retreatment was significantly reduced when using the G3-RETY (3.89 ± 0.84 min) compared to the G4-XPER (13.30 ± 2.05 min), p < .001. CONCLUSIONS: Teeth retreated using the Retreaty instruments demonstrated superior fracture resistance compared to XP-endo Rise and their values were comparable to the positive control group. Moreover, Retreaty file system showed faster gutta-percha removal and canal preparation during retreatments.