In vitro comparison of analog versus digital impressions of the periodontally compromised dentition focused on interdental areas

Aim: For orthodontic aligner treatment, excellent full-arch impressions with correctly displayed interdental areas (IAs) are required. To analyze the ability of impression taking of the IAs in periodontally compromised dentitions, two intraoral scanning systems and one conventional impression technique were investigated in vitro under standardized testing conditions. Materials and methods: A total of 60 impressions of the maxilla and mandible were taken from a periodontally compromised test model (A-PB) with three different techniques (n = 20): One conventional impression (EXA'lence) (CVI) and two digital impressions with the intraoral scanners Trios III (3Shape) (TIO) and True Definition (3M ESPE) (TRU). Standard tessellation language (STL) datasets were generated for TIO and TRU, whereas type IV dental stone casts were manufactured for CVI. The casts were then digitized with a laboratory scanner (ATOS). The percentage of displayed IAs in relation to the complete IA was calculated for each IA using evaluation software (GOM Inspect). Finally, the data were subjected to the median test. Result: TRU showed a significantly higher percentage of displayed IAs compared with the other two methods (P 0.05). Only a few IAs were shown in CVI. TIO showed significantly better results compared with CVI, although the results were not as good as those of TRU. Conclusion: Within the limitations of this in vitro study, intraoral scanners - and especially the one based on active wavefront sampling (AWS) technology (as for TRU) - can be recommended for the reproduction of wide IAs (undercuts) in periodontally compromised patients. Keywords: intraoral scanners, periodontally compromised dentition, full-arch impression, aligner treatment, orthodontics, digital dentistry