## 4 Discussion  
The present study showed that the guided endodontics technique allowed the complete removal of fiberglass posts. The results indicate that the mean deviation in guided accesses is in accordance with previous studies [17; 22]. [PERSON] et al. [14], in an in vitro study, reported a mean deviation of 1.81\({}^{\circ}\) with the guided technique, and this was corroborated by our findings, with a mean deviation of 1.55\({}^{\circ}\) for the EX group. Therefore, the first null hypothesis of the present study was verified, confirming that guided endodontics promotes minimal deviations from planned trajectories and complete removal of intraradicular fiberglass posts. Teeth were kept in a thymol solution (0.1%) to preserve their microhardness until further processing [21]. Although using 3D-printed teeth could be more practical in terms of sample standardization, as they were used in a study by [PERSON] et al. [9], dental hardness is bound to influence the trajectory of the drill since the dental material resistance could lead the operator to use more or less strength to remove the dental structure. This could explain the difference in results presented by [PERSON] et al. [9] and by the present study, as there is a significant difference between experienced and inexperienced operators. This leads to the rejection of the second null hypothesis. Despite the implementation of natural teeth and individualized ceramic crowns, the samples generated in this study demonstrated a significant level of homogeneity. This was achieved through the use of reproducible printed study models, which ensured consistency between the samples. It is important to note that the in vitro nature of this study allowed for greater stability in the study models compared to those found in the oral cavity, and clinicians must be aware of this difference when interpreting the results. In the guided endodontics technique, the sleeve keeps the angulation of the drill precisely on the planned axis. Possible inaccuracies are partially related to the adjustment between the drill and sleeve--necessary to prevent heat from being generated or the drill bit from getting stuck during the access cavity preparation. The tolerance gap, as well as the operator's inexperience, can lead to a deviation in angulation, which would explain the differences found between the two sample groups tested. As shown in the study by [PERSON] et al. [23], eccentric forces exerted by the operator in a guided system will impact the accuracy of the procedure. Despite the statistically significant differences between the two operators, their difference in deviation was only 1\({}^{\circ}\), and both removed the posts successfully. However, it seems that operators need training in the guided technique in order to achieve higher accuracy. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Inexperienced Operator (IN)** & **Experienced Operator (Ex)** & **Difference** & \(p\) * \\ \hline \multirow{5}{*}{Angle} & **Mean (SD)** & **Mean (SD)** & **Mean [CI 95\%]** & \\  & **Median [min-max]** & **Median [min-max]** & & \\ \hline \multirow{2}{*}{3D deviation} & 2.54\({}^{\circ}\) (1.37) & 1.55\({}^{\circ}\) (0.791) & 0.998 & \\  & 2.7\({}^{\circ}\) (0-5.85) & 1.82 [0–2.85] & [0.281–1.714] & \\ \multirow{2}{*}{3D deviation} & 0.44 mm (0.174) & 0.33 mm (0.178) & 0.113 & \\  & 0.45 mm [0.14–0.73] & 0.31 mm [0.11–0.76] & [0.001–0.226] & \\ \hline \hline \end{tabular} SD = standard deviation; CI = confidence interval; * \(t\)-test for independent samples.  
\end{table} 
Table 1: Comparison of the means of the variables studied. In a guided in vivo approach, [PERSON] et al. [20] demonstrated the complete removal of a fiberglass post from an upper central incisor. [PERSON] et al. [24] have also demonstrated the feasibility of the technique in the posterior segment, where the volume of the guide and limitation of mouth opening would seem to be disadvantages.