Clinical Evaluation of Intraoral, In-Lab Scanners and PVS Impression Materials Using STL Superimposition

Background/Objective. The objective of this study is to test the hypothesis that there is no significant difference between intraoral scanners and in-lab scanners. An additional objective is to test the hypothesis that there is no significant difference between the accuracy of two types of polyvinyl siloxane PVS impression materials and between PVS impression materials and intraoral scanners. Material and Methods. Fourteen subjects received a set of maxillary and mandibular removable complete dentures [RCD]. Impressions of each RCD were obtained using two PVS impression materials (heavy [H] or medium [M] body with light [L] body). Each RCD was then scanned utilizing two intraoral scanners, Trios [TR] and Omnicam [OM]. The PVS impressions were sent to the lab to be further scanned by an in-lab scanner. STL files of the intraoral and in-lab scans were obtained and trimmed using the GeoMagic X Software. The files were merged [TR vs. OM] and [TR vs. in Lab], [HL vs. ML], [HL vs. TR] and [ML vs. TR] and the gap was measured in sixty points for each merged file. Results. There was no significant difference between [TR vs. OM] with a mean of 44 ± 10 μm. There was a statistically significant difference between [TR vs. In lab] with a mean of 62 ± 21 μm and [ML vs. TR] and [HL vs. ML] with means of 66 ± 24 μm and 50 ± 21 μm, respectively. There was no significant difference between [HL vs. TR] with a mean of 37 ± 10 μm. Conclusions. Intraoral scanners provide a similar quality of scans. The lab scanner depends on the impression materials used. The first null hypothesis was rejected. Using a heavy and light body PVS impression material provides more accurate and dimensionally stable impressions, particularly in full-arch applications, and is comparable to intraoral scanners. The second null hypothesis was rejected, there were significant differences between the PVS groups. These findings guide clinicians in selecting impression methods for complete dentures.