04 March 2024

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Comparative analysis of accuracy in digital and conventional implant impressions: an in vitro study

Lorenzo Breschi

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Introduction

Intraoral scanners (IOSs) have revolutionized contemporary restorative and prosthetic workflows. Current evidence suggests that digital implant scanning technique can be a clinically viable alternative to traditional implant impression with the potential to minimize errors associated with conventional workflow, which involve multiple materials and steps. However, the accuracy of the IOs, especially in completely edentulous patients, can be influenced by various factors including the type of scanner, scanning technique and scan body material. Despite the promising outcomes of laboratories studies, more evidence is needed to validate the clinical application of these techniques.

In this context, Conejo et al. have conducted an in vitro study to measure and compare the accuracy of complete arch conventional pick-up implant impressions, complete arch digital implant scans with IOS and 3D printed casts from digital scans.

Materials and method

Six implants were placed in a type 2 density mandibular model. Dual functioning scannable pick-up impression copings were inserted in the implants, scanned with a reference scanner, and exported in a Standard Tessellation Language format (Group Control). Two conventional impression techniques (n=5), splinted open-tray pick-up impressions (Group OT) and closed-tray pick-up impressions (Group CT), were performed and stone casts were fabricated. Successively, digital scans (Group DS, n=5) were made with an IOS (Primescan; Dentsply Sirona) by a single experienced operator, and the STL files were exported to fabricate 3D-printed casts (Group STL, n=5).

All casts were digitized following the same protocol: scannable pick-up impression copings were inserted in the dental implant analogs in Groups OT, CT, and STL and scanned with the reference scanner. Using a 3D inspection software program, the digitized casts from the different impression techniques were superimposed and compared with the control. Accuracy was assessed using the root mean square (RMS) values, while precision was determined based on the mean of standard deviation of each scanner cross-compared. All data were statistically analysed at a 95% confidence interval (p<0.05).

Results

Regarding the accuracy, significant differences in RMS values were found from the superimposed files between different techniques (p<0.05). In particular, Group DS (P<0.05) showed the lowest mean dimensional difference when superimposed with Group Control, while no significant difference in RMS values was found among Groups CT, OT, and STL (p>0.05). Similarly, Group DS showed the lowest precision values, differing significantly from Group CT and Group STL (p<0.05), while Group CT performed better overall.

Conclusion

Based on the findings of this in vitro study, the authors concluded that, in complete arch implant cases, 3D printed casts from digital scans have similar accuracy to stone casts from conventional impressions. In particular, intraoral scans showed the highest accuracy making digital scans with IOS recommended.

For more information: Conejo J, Yoo TH, Atria PJ, Fraiman H, Blatz MB. In vitro comparative study between complete arch conventional implant impressions and digital implant scans with scannable pick-up impression copings. J Prosthet Dent. 2024 Jan 4:S0022-3913(23)00828-4. doi: 10.1016/j.prosdent.2023.12.012. Epub ahead of print. PMID: 38182453.