Aim: To compare the application of silane in the bond strength of fiberglass posts in different thirds of the cemented root with a self-adhesive system in an ex vivo study. Materials and methods: Freshly extracted teeth were collected, which had indication of extraction for periodontal or orthodontic reasons. The study evaluated n = 42 specimens that were divided into two large groups: I (control, without silane) and II (with silane); the resistance to adhesion in the respective thirds of the root (cervical, middle, and apical) was also evaluated. The prefabricated fiberglass posts were cemented with and without silane according to the manufacturer's instructions and were cemented with a resin-based cementing agent. The adhesion strength test was evaluated by the universal testing machine. Results: According to the results of this experimental trial, the fiberglass posts that did not receive silane had the highest adhesion strength of 26.5 ± 10.6 MPa, while silane-cemented posts only had 21.7 ± 8.1 MPa. The statistical analysis was performed using the Kruskal-Wallis test and work with a level of significance of p < 0.05. Conclusion: The use of silane as part of the cementing protocol in fiberglass posts does not influence the adhesion strength between the surfaces of the posts and the resin cement because there were statistically significant differences between both adhesion protocols. Clinical significance: This study has a great impact because according to the results, clinical decisions can be made when cementing the fiberglass posts through the application of silane or not.