Method: Fifteen human anterior teeth (n=15) (lateral incisor and central incisor) were selected, cleaned and standardized in 15 mm of length. The root canal was prepared in 12 mm with a custom bur of the post system (White Post DC #3) and the fiber posts were cemented using the RelyX U 100 cement. Three slices with 2 mm height were obtained per tooth and submitted to the push-out bond strength test. The area of each disk slice was calculated based on the disk slice dimensions (coronal diameter, apical diameter and height). These dimensions were analyzed by different operators and instruments, as described: G1- Operator A with digital caliper; G2- Operator A with stereomicroscope (30x-magnification); G3-Operator B with digital caliper; G4- Operator B with stereomicroscope (30x-magnification); G5- Operator C with digital caliper; G6- Operator C with stereomicroscope (30x-magnification). The mean of adhered interfacial area and the push-out bond strength, obtained by each operator and instrument, were analyzed by the 2-way ANOVA and Tukey’s test (p=0.05).
Result: The operator (p=0.0395) and the measurement instrument (p=0.0178) showed influence on the area of the disk slices, but did not influence on the push-out bond strength means (p=0.757 and p=0.463, respectively).
Conclusion: Different operators or two measurement instruments of interfacial area do not influence the results of push-out bond strength between fiber post and root dentin. Thus, concerning the analyzed variables, it is possible to compare push-out bond strength values from other similar in vitro studies that used stereomicroscope or digital caliper for interfacial area measurement made by other operator.