Objective: In this study, it is aimed to determine the effect of post diameter and tooth wall number on fracture formation values during the placement of prefabricated posts on teeth.

Material and Method: One hundred extracted mandibular premolar human teeth with single canal were included in the study. The number of samples was determined as 10 and a total of 10 groups were formed. Root canal treatment was applied to teeth and kept in physiological saline for 1 week. The preparation was designed in such a way that (n =20); in group A all walls are removed, in group B only one wall will be preserved (lingual), in group C two walls will be preserved (buccal and lingual), in group D only distal wall will be removed and that all the walls will be preserved in group E. In subgroups of these groups (1 and 2) (n =10), the root canal space was enlarged to be compatible with the thickness of the posts (1-1.25 mm) to be used in the work with piezo reamer drills. Afterwards, torque force was applied to the specimens and fracture force values were statistically analyzed.

Results: The group with the lowest mean of fracture results was determined as B-2, and the group with the highest number was determined as D-1. There was no statistically significant difference between the fracture values of the teeth according to the number of walls (p >0.05). A significant difference was found between post diameters and fracture values (p <0.05).

Conclusion: While increasing post diameter increased fractures, the number of remaining intact tooth walls had not any effect.