Accuracy of Dental Fillings Based on 3D Printing Versus CAD/CAM

Objectives: New restoration materials and techniques are needed in the field of restorative dentistry. The aim was to evaluate the accuracy of 3D printing technology used in fabrication of dental inlay/onlay fillings and to compare their accuracy to those manufactured with CAD/CAM (computer-aided design and computer-aided manufacturing) system, based on in vitro experiment. Applicability of digital impression technique for 3D printing was also evaluated.
Methods: Six inlay/onlay cavities with different shapes and forms were prepared on six extracted and root canal treated human molar teeth. For digital copying, the teeth were inserted in putty blocks. Digital impressions were taken with CEREC AC Omnicam© intraoral scanner to create 3D models for the manufacturing of inlay/onlay fillings. Based on the same impression data, nano-ceramic fillings were milled in CEREC MC XL© milling unit and composite fillings were manufactured with a Multijet printer using Visijet M3 Crystal material and 0.016 mm layer thickness. The accuracy was evaluated by measuring the marginal and internal gaps of the fillings based on x-ray microtomography (micro-CT) 3D imaging scans. The internal fit was also evaluated using a replica technique with A-silicone impressions and weighing.
Results: Fillings manufactured with 3D printing technique showed better marginal and internal fit values. The mean values of internal gap of 3D printed fillings were 40-60% lower as compared to CAD/CAM manufactured fillings, the difference being statistically significant in most of the measuring points (p<0.05, t-test). The largest gaps were seen on the bottom of the approximal cavities.
Conclusions: Concerning the accuracy, the multijet 3D printing technique may be a clinically acceptable alternative to subtractive CAD/CAM milling technique in fabrication of dental inlay/onlay fillings. However, additional investigations are needed to develop the 3D printing process and suitable materials for dental applications.