Accuracy assessment of removable partial denture frameworks fabricated by selective laser melting using two different  workflows. A cross-over  Clinical Study.

Abstract

<title>Abstract</title> <bold>Background: </bold>Rapid advancements in computer-aided design and computer-aided manufacturing (CAD-CAM) have opened new pathways in the fabrication of removable partial dentures (RPDs). Digital impression serves as the first step of (CAD-CAM) technique, which includes two methods for data acquisition: direct intraoral scanning or indirect extraoral scanning. RPD frameworks may be considered the definitive test of accuracy for a digital workflow. This cross-over clinical study aimed to evaluate the overall accuracy of various parts for mandibular metallic RPD frameworks made by selective laser melting (SLM) using fully-digital versus combined analog-digital workflows. <bold>Methods: </bold>This study was carried out on 24 participants with mandibular Kennedy class I arches. Each participant received two RPDs frameworks, one fabricated using a combined analog-digital workflow (Group I) and the other using a fully- digital workflow (Group II). In Group I, the analog steps involved taking physical impressions and creating stone casts followed by scanning the casts with a laboratory scanner to create virtual casts. In Group II, a definitive scan STL file was created using an intraoral digital scanner. Both groups used 3Shape software for digital design of the RPD framework, ensuring consistency by using the same design, and subsequent fabrication using selective laser melting (SLM). To evaluate the accuracy, STL data analysis was performed through intra-oral digital superimposition evaluation, a color map was assessed and overall accuracy and the misfit (distance between each framework component and the reference intra-oral scan STL file) were measured at rest, proximal plate, lingual plate and I-bar retentive clasp terminal areas. The Paired t-test was utilized for statistical analysis of the data. <bold>Results: </bold>In Group I: combined analog-digital workflow color map assessment revealed more gaps particularly in the lingual plate and proximal plate areas, whereas Group II: fully-digital workflow<bold> </bold>showed better accuracy. Regarding the overall accuracy in the rest, proximal plate, lingual plate, and I-bar clasp retentive terminal, Group II <bold> </bold>was significantly superior to Group I <bold> </bold>(P= 0.0125, 0.0019, &lt;0.001, &lt;0.001, and 0.0119, respectively). <bold>Conclusions: </bold>Within the limitations of this study, both workflows resulted in frameworks with clinically acceptable accuracy. However, SLM RPD frameworks fabricated using the fully-digital workflow showed superior accuracy in key areas such as the rest, proximal plate, lingual plate, and I-bar clasp retentive terminal areas, when compared to the combined analog-digital workflow. <bold>Trial registration: </bold>Retrospectively registered (NCT06412159) 03/05/2024.