Multibracket appliance: impression defaults and their reduction by blocking-out  —  a three-dimensional study

Objectives This study examines accuracy of dental impressions and following plaster models taken during treatment with fixed appliances. Materials and methods A maxillary typodont was provided with brackets. Three examiners took impressions three times each of the variants: brackets only, archwire fixed by alastics, ligatures or Kobayashi-hooks, and brackets and archwire covered completely or just on the gingival side by protection or impression wax. Casts were scanned using Activity102 ® . Virtual models were compared to the scan of the typodont using Comparison ® . Differences were measured and descriptively analyzed. Estimated means with 95 % confidence intervals were computed. Significance was assessed using linear mixed models. Results While pyramidal reference blocks had a mean difference of 0.019 mm (95 % CI = 0.017–0.021 mm) to the master model, teeth without attachments showed 0.097 mm (95 % CI = 0.082–0.111 mm), and teeth with brackets 0.169 mm (95 % CI = 0.156–0.182 mm) ( p