# Accuracy assessment of digital impressions with varied scanning paths in partially edentulous ridges with mobile abutment teeth: An in vitro comparative study

## TL;DR

Digital impressions are more accurate than conventional ones for partially edentulous cases with mobile teeth, especially when using recommended scanning paths.

## Contribution

This study compares digital and conventional impression accuracy in partially edentulous models with mobile abutment teeth.

## Key findings

- Digital impressions showed significantly higher accuracy than conventional methods.
- Manufacturer-recommended scan path A produced lower deviations than scan path B.
- Models with GII and GIII mobility had clinically unacceptable deviations in conventional impressions.

## Abstract

Periodontal prosthesis or removable partial dentures are essential treatments for partially edentulous dentition with periodontal issues. This study aimed to assess the accuracy of digital impressions obtained through an intra-oral scanner, employing different scanning paths versus conventional impressions in partially edentulous ridges with mobile abutment teeth.

Eight lower Kennedy class I and class III models were employed as test models. The abutment teeth in these models were subjected to various mobility grades, according to the Miller classification. Reference data was generated by scanning the test models using an extra-oral laboratory scanner. An intra-oral scanner (TRIOS 4; V21; 3Shape A/S) was used to obtain ten digital impressions following two different scanning paths (Scan path A and Scan path B). For conventional impressions, two impression materials (Monophase polyether and Polyvinyl siloxane) were used to create ten impressions with a one-step technique. Working stone casts were produced and converted to digital data. Accuracy was assessed by analyzing the deviation between test data (digital and conventional data) and the reference data using 3D software (Geomagic Control X). The data was analysis using sequential tests, including two-way and one-way ANOVA, and paired t-tests (p < 0.05).

Digital impressions obtained through an intra-oral scanner exhibited significantly higher accuracy. Within the digital impression category, those recommended by the manufacturer obtained using scan path A showed lower deviations than those acquired through scan path B. Considering the degree of tooth mobility, models with GII and GIII mobile RPD abutment teeth displayed significantly higher deviations (p < 0.001) than those with G0, GI across all impression techniques. The accuracy of conventional impressions with GII and GIII mobility was clinically unacceptable (deviation >200µm).

For partially edentulous cases with mobile abutment teeth, digital impressions exhibited superior accuracy for G0, GI. Following the manufacturer-recommended scanning protocol in scan path A can improve the accuracy of impressions. Furthermore, if there is persistent mobility, particularly in GII and GIII, the use of final conventional impressions is forbidden.