27 October 2021

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Digital Procedures Compared to Conventional Gypsum Casts: an ex vivo study

Allegra Comba

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Computer-assisted design/manufacturing (CAD/CAM) systems have made single tooth indirect restoration easier, faster, and more predictable. Intraoral scanning and milling devices allow simple and fast digital impressions, thus enabling the projection, customization, and finally, milling of the restorations in the same appointment (chairside protocol), with consequent reduction of costs and patient discomfort. However, The traditional workflow is still frequently used and yet considered by many authors and clinicians the gold standard model for the manufacturing of adhesive restorations. For that reason the group of research of the University of Turin, guided by Prof. Nicola Scotti, conducted an ex vivo study was to compare the trueness of traditional and digital workflows and to analyze the interfacial fit of CAD/CAM restorations on gypsum and 3D-printed casts (3DC). 

Materials and Methods
To conduct the research Dr. Baldi et al. selected forty patients that underwent indirect posterior adhesive restorations. After tooth preparation, both traditional and chairside procedures were followed. Obtained models were scanned to generate STL files of the intraoral impression (IOS), the conventional cast (RS), and the 3D-printed cast (3DCS). Superimposition of the casts was performed to evaluate trueness. Then, for each preparation, two identical CAD/CAM restorations were milled and luted on RS and 3DC. Micro-CT scan was performed to evaluate 3D interfacial fit. 

Results
From the data collected by the Italian research group it could be underlined that surface trueness analysis showed no significant differences among groups (p > 0.05), with average trueness ranging from 11.56 to 17.01 µm. Micro-CT analysis showed significant differences between gypsum casts (average ranging from 135.78 to 212.31 µm) and 3DC (average ranging from 57.63 to 144.55 µm) for both marginal and internal fit. 

Conclusions
Dr Baldi et al. concluded their ex vivo study affirming that in adhesive restorations manufacturing, digital and conventional procedures generate casts that are not significantly different. Marginal fit of adhesive restorations is similar to conventional crown design and clinically acceptable. 

Finally, authors  affirmed that it is assumable that a direct digital workflow could benefit from the usage of 3DC.

(Photocredit: Andrea Baldi)

For further information: Digital Procedures Compared to Conventional Gypsum Casts in the Manufacturing of CAD/CAM Adhesive Restorations: 3D Surface Trueness and Interfacial Adaptation Analysis