# Accuracy of digitally designed endodontic posts: a micro-computed tomography analysis of intraoral scanner and extraoral scanning techniques

## TL;DR

This study compares digital scanning techniques for making dental posts and finds that using an extraoral scanner with resin impressions gives the best fit.

## Contribution

The study introduces a novel comparison of intraoral and extraoral scanning workflows for endodontic post fabrication using micro-CT analysis.

## Key findings

- Extraoral indirect scanning with Vinyl UXD showed superior canal compatibility compared to other methods.
- Micro-CT analysis revealed statistically significant differences in fit between scanning techniques.
- Resin-based 3D printed posts using the extraoral method are clinically viable.

## Abstract

The digital scanning step represents a critical stage in ensuring an accurate treatment protocol. Due to the challenges associated with intracanal scanning, such as limited direct visualization of the working field and restricted access, the selection of appropriate intracanal digitization techniques for custom post fabrication becomes essential to achieve precise dimensional accuracy.

This study evaluated the fit of three-dimensional-printed posts within root canals, using micro-computed tomography to assess the internal fit and compatibility based on the canal geometry. These canal dimensions were obtained using different digital scanning workflows.

Following root canal shaping, a 7-mm post-cavity preparation was made using human mandibular premolars (N = 35). Specimens were divided into five groups (n = 7) based on the digital scanning method used: direct scan via iTero Element 2, direct scan via Trios 3, indirect scan via iTero Element 2, indirect scan via Trios 3, and indirect scan via Vinyl UXD. Post designs were created using Exocad DentalCAD software and fabricated with the Asiga Max UV 3D printer employing digital light processing. Posts were printed using a resin-based material (Saremco Print Crowntec) and cemented with Panavia SA Cement Plus. Samples were scanned using a high-resolution micro-CT system (85 kV, 118 µA, voxel size 13.68 μm, 180° rotation, 2600 ms exposure). Internal canal compatibility was assessed using the resulting micro-computed tomography data.

Posts fabricated using indirect digital scanning workflow from the Vinyl UXD extraoral scanner demonstrated superior canal compatibility. Micro-computed tomography analysis revealed that this method produced statistically significant differences from those of the other groups (p < 0.05).

Among the evaluated techniques, the extraoral indirect digital scanning workflow, involving the scanning of conventional resin impressions with an extraoral scanner, yielded the highest internal canal compatibility of the fabricated posts. These findings support the potential clinical viability of the permanent resin material used in three-dimensional printing for post fabrication.