The accuracy of virtual interocclusal registration during intraoral scanning

Statement of problem Evidence on the accuracy and reproducibility of the virtual interocclusal registration procedure and recommendations as to how to make a virtual interocclusal record are lacking. Purpose The purpose of this in vitro study was to assess whether virtual interocclusal registration records made at different locations around the arch affect the alignment of virtual casts, and to assess whether quadrant and complete arch scans have different effects on cast alignment when they are articulated with virtual interocclusal records. Material and methods Three sites of close proximity (SCPs) and 3 sites of clearance (SCs) were identified in each sextant of mounted zirconia master models. The SCPs and SCs were confirmed by using shimstock foil and the transillumination of an interocclusal impression. Complete-arch and quadrant scans of the master models were made with an intraoral scanner and registered with different virtual interocclusal registration records. The SCPs and SCs indicated by the scanner’s software and by independent software were compared according to the sensitivity, specificity, and predictive values of each method. Results Changed locations of SCPs were found depending on the location of the virtual interocclusal registration record. The intraoral scanner’s software contacts had a higher sensitivity of 92.86% and a negative predictive value of 84.21% than the contacts revealed by the independent software that exhibited a sensitivity of 69.05% and a negative predictive value of 70.45%. However, the intraoral scanner software had a lower specificity of 41.03% and a positive predictive value of 62.90% compared with the independent software, which exhibited a specificity of 79.49% and a positive predictive value of 78.38%. The quadrant scans had a higher sensitivity than did the complete-arch scans. Conclusions Different occlusal contacts are obtained from interocclusal registration scans in different segments of the dental arch. The difference is more obvious in complete-arch scans, where a tilting effect toward the site of the interocclusal registration scan was observed. Occlusal contacts obtained from interocclusal registration scans for quadrant scans had a higher sensitivity than did those for complete-arch scans.