# Trueness of Extraoral Digital Impressions for Full-Arch Implant Impressions—In Vitro Study

## TL;DR

This study compares the accuracy of digital impressions made from silicone versus stone casts in full-arch implant cases, finding similar results when using different scanners.

## Contribution

The study provides empirical evidence on the trueness of direct scanning of silicone impressions in full-arch implant rehabilitation.

## Key findings

- Direct scanning of silicone impressions is comparable to scanning stone casts in full-arch implant cases.
- The greatest deviations occurred between the most posterior implants, ranging from 173 to 314 µm.
- No significant differences were found between the two extraoral scanners used in the study.

## Abstract

Direct scanning of silicone impressions is a valid technique. However, studies in implant-supported rehabilitations are lacking. This in vitro study aims to compare the trueness of impressions obtained with two types of silicone and their corresponding stone casts, using two laboratory scanners in a full-arch implant rehabilitation. A master cast with six dental implants was scanned with a 12-megapixel scanner to obtain a digital master cast. Ten implant impressions were made using two silicones (Zhermack and Coltene) with the open-tray technique. The impressions and stone casts were scanned by two extraoral scanners (Identica T500, Medit; and S600 ARTI, Zirkonzhan). Trueness was assessed by comparing linear and angular distances in digital casts with the master cast. A p < 0.05 significance level was considered. The results showed that for the linear measurements, 72% were higher than the master cast measurements, and no consistent pattern was observed in the angular measurements. The greatest deviations were detected between the most posterior implants, with mean values ranging between 173 and 314 µm. No significant differences were found between scanners. However, differences were observed in the distances between silicones (46.7%) and between impressions and stone casts (73.3%). This work demonstrates that the direct scanning of silicone impressions yields results comparable to those obtained from scanning gypsum casts in full-arch implant-supported rehabilitation.