Background <p>The objective of this study was to examine the impact of varying taper dimensions and different forms of bioceramic sealers on the fracture resistance of mandibular premolar teeth prepared using single-file Ni-Ti instrumentation systems in vitro.</p> Methods <p>Forty single-rooted mandibular premolars were randomly allocated into four groups (<i>n</i> = 10) according to the taper value and type of sealer used: Group T4-AHBC – 25/0.04 taper with AH Plus BCS (premixed syringe form), Group T6-AHBC – 25/0.06 taper with AH Plus BCS, Group T4-BRCS – 25/0.04 taper with BioRoot RCS (powder-liquid form), and Group T6-BRCS – 25/0.06 taper with BioRoot RCS. Root canals were prepared and then obturated with the designated sealers. Using a universal testing machine at a crosshead speed of 1&#xa0;mm/min, fracture resistance was measured, and the resulting data were analyzed statistically.</p> Results <p>Statistical analysis revealed that there were no significant differences in fracture resistance between the groups (<i>p</i> = 0.188). Neither the taper value nor the bioceramic sealer form had a significant effect on fracture resistance.</p> Conclusions <p>Within the limitations of this in vitro study, variation in taper values and sealer forms did not affect fracture resistance. Both powder-liquid and premixed syringe forms demonstrated similar performance, suggesting that clinicians may choose between them based on handling preference and clinical practicality.</p>