In vitro evaluation of the post-space depth reading with an intraoral scanner (IOS) compared to a traditional silicon impression

Objectives: The aim of the study was to assess the depth and quality of the post-space reading, using an IOS without scan-post, compared to a traditional silicon technique.

Methods: Six extracted bicuspids were decoronated and endodontically treated. After having prepared the space for the posts, a structure in pink acrylic resin was created with two resin elements. At the center of the structure one sample was put at a time. Digital and traditional impressions were taken for each sample.Digital impressions were developed through the Computer-aided design (CAD) software in order to integrate the scanner results into a three-dimensional grid to make the measurements. A K-file was used to measure the length of the post-space of each sample obtained through the traditional silicon impression and subsequently the measurement results were reported on a millimeter gauge. Furthermore, an assessment of the width of the entrances of the post-spaces was carried out.

Results: The mean reading depth discrepancy expressed in percentages (19.58%) indicates that the digital impression with current technologies fails to impress clearly the post-space. Standard deviation of the data expressed in percentage is 13.89, suggesting that the values were not similar to each other. In two cases the digital technique has achieved less than 10% difference compared to the traditional technique, but there have been also cases in which the variation in depth has reached almost 40%.The samples that showed the minor discrepancy between the two techniques expressed the widest post-space entrance.

Conclusions: In this in vitro study, the application of the IOS for the post-space reading in order to deliver an anatomic post has been proven to be still not reliable, as there are still depth reading limitations for the narrow root channels. In fact, in this type of channels it is difficult to reach with the light beam of the IOS the deepest areas of the post-space, with a consequent incomplete post-space reading.