Accuracy of full-arch digital implant impressions taken using intraoral scanners and related variables: A systematic review

Purpose: To evaluate the accuracy of full-arch digital implant impressions taken using intraoral scanners and analyse the related variables.
Materials and methods: An electronic search of studies on the accuracy of digital implant impressions in fully edentulous arches from 1 January 2012 to 29 February 2020 was conducted in PubMed, EMBASE and the Cochrane Library. Only peer-reviewed experimental or clinical studies written in English were included. Studies assessing the accuracy of restorations, case reports, clinical reports, technical reports and reviews were excluded. The literature screening, article reading and assessment of risk of bias were carried out by two reviewers. The data on the study characteristics, accuracy outcomes and investigated variables were extracted.
Results: After removal of duplicates, a total of 166 studies were identified, of which 42 were initially selected for full-text reading and 30 were included in the final analysis (29 in vitro studies and one in vivo study). The trueness of digital implant impressions ranged from 7.6 to 731.7 μm, and the precision ranged from 15.2 to 204.2 μm. Angular deviations were between 0.13 and 10.01 degrees. Considering 100 μm and 0.4 degrees as clinically acceptable levels of deviation, 18 studies reported linear/distance/3D deviations larger than 100 μm and only two studies reported angular deviations below 0.4 degrees. The effect of interimplant distance/length of the arch scanned/scanning sequence/scanning range/implant position (nine studies), implant angulation (ten studies), implant depth (five studies), implant connection (two studies), operator experience (six studies), scan body type (three studies), intraoral scanner type (six studies), scanning strategy (two studies) and modification technique (three studies) was investigated.
Conclusions: Based on the results of the included studies, full-arch digital implant impressions taken using intraoral scanners are not sufficiently accurate for clinical application. Accuracy varies greatly with interimplant distance, scan body type, intraoral scanner type and operator experience, whereas implant angulation, implant connections and implant depth have no effect. The effects of scanning strategy and modification technique need further investigation.