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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.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Materials and methods<\/jats:title>\n                    <jats:p>\n                      Forty-eight maxillary first premolar roots were randomly assigned to 4 groups (\n                      <jats:italic>n<\/jats:italic>\n                      \u2009=\u200912); 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 &amp; 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) (\u03b1\u2009=\u20090.05).\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>\n                      The fracture resistance of G1-NC (942.92\u2009\u00b1\u200924.73\u00a0N) had significantly higher values compared to all other groups. Fracture values for the G2-PC (829.62\u2009\u00b1\u200971.55\u00a0N) and the G3-RETY (818.29\u2009\u00b1\u200973.14\u00a0N) did not significantly differ from each other (\n                      <jats:italic>p<\/jats:italic>\n                      \u2009=\u20091.000), but both were significantly higher than the G4-XPER (489.37\u2009\u00b1\u200933.47\u00a0N). The total time of retreatment was significantly reduced when using the G3-RETY (3.89\u2009\u00b1\u20090.84\u00a0min) compared to the G4-XPER (13.30\u2009\u00b1\u20092.05\u00a0min),\n                      <jats:italic>p<\/jats:italic>\n                      &lt; .001.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>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.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1186\/s12903-026-09151-3","type":"journal-article","created":{"date-parts":[[2026,7,14]],"date-time":"2026-07-14T01:16:36Z","timestamp":1783991796000},"update-policy":"https:\/\/doi.org\/10.1007\/springer_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Evaluation of radicular fracture resistance of maxillary premolars following non-surgical retreatment using two novel retreatment kits"],"prefix":"10.1186","volume":"26","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-3115-0103","authenticated-orcid":false,"given":"Fatma M. 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