Digital versus conventional impression-taking of the ear canal: A comparison of accuracy between a handheld scanner and impression material

Background: The comfort of hearing aids is directly linked to the fitting of the earmolds. Additive manufacturing is now standard practice in the production of earmolds, which is why digitally capturing the ear canal is the critical first step. Traditionally, this is done using silicone impression materials, followed by scanning the impressions. A handheld scanner or ear canal scanner for direct digital capture has recently become available on the market as an alternative. The aim of this study is to evaluate the accuracy of this digital system in comparison with the conventional method. Method: Two ear canal models were produced using 3D-printing technology to serve as reference models. Five users each took three conventional and three digital impressions. The conventional impressions were digitised using a desktop scanner. The scans were compared with the reference model using software-assisted best-fit superimposition. The mean of the deviation and the standard deviation of the deviation were evaluated. Results: Digital impression-taking resulted in a lower mean of the deviation (–0.052 mm) compared with impression materials (Material 1: –0.136 mm; Material 2: –0.118 mm), suggesting slight shrinkage of the impression materials. The standard deviations of the deviation were 0.415 mm for the handheld scanner and between 0.496 mm and 0.546 mm for the conventional methods. The influence of geometry or the user was minimal. Conclusion: Digital impression-taking using a handheld scanner is an equivalent alternative to conventional impression-taking. The advantages lie primarily in the workflow, time savings and the patient experience, whilst the high initial costs are currently limiting its widespread adoption.