Accuracy of inlay and onlay restorations based on 3D printing or milling technique-a pilot study

Purpose: To evaluate and compare the accuracy of 3D printing versus CAD/CAM milling in the fabrication of intay/onlay restorations based on pilot experiments. Material and methods: Different shaped inlay/onlay cavities were prepared on six extracted and root canal treated human molar teeth. Digital impressions were taken with a CEREC AC Omnicam(C) intraoral scanner. Based on the same impression data, nano-ceramic restorations were performed using milling (M group) and composite restorations (from material not for clinical use) using Multijet 3D printing technology (3D group). The accuracy was evaluated by measuring the marginal and internal gaps based on x-ray microtomography 3D imaging scans. The internal fit was evaluated using a replica technique with A-silicone impressions and weighing. Results: The 3D group restorations showed better marginal and internal tit values. The mean internal gap values of the 3D group restorations were 40-60% lower compared to the M group restorations. the difference being statistically significant at most measuring points (p<0.05, t-test). Conclusions: The accuracy of the Multijet 3D printing is at least at the same level as the milling technique in the fabrication of dental inlay/onlay restorations. Additional investigations are needed to develop the 3D printing process and suitable materials for dental applications