Accuracy of dental implant impressions is directly associated with the accuracy and fit of the final implant-supported prosthesis (Lee et al., 2008;Papaspyridakos et al., 2014a). Misfitting prostheses may be related to the increased rate of biological and technical complications and affect the long-term success of dental implants and prosthetic reconstructions (Katsoulis et al., 2017).Although conventional implant impressions have served as a standard method for a long time, this workflow has its limitations as it involves a considerable number of separate clinical and laboratory steps, and resulting accuracy dependent on the skills
Computer-guided dynamic navigation systems have elevated dental implant surgery into a more patient-friendly and efficient procedure. However, commercially available systems use displays as an output for guidance. This implies that surgeons have to take their eyes off the surgery site frequently in order to accurately adjust surgical instruments. The solution for such an issue is to use augmented reality (AR) head-mounted devices to showcase all necessary guiding instructions without any distractions. In this work, the implementation of augmented reality in dental surgery using the HoloLens 2 AR headset for the assessment of accuracy is described. The experiments were performed in vitro with two implementation steps, evaluating calibration and perspective of the virtual dental model alignment accuracies using a newly created marker. The calibration results showed overall accuracy and precision surpassing the 1 mm threshold in distance-related measurements. Dependency on the side on which the marker was observed and the movement of the user’s head were considered to be the most influential factors regarding the perspective of the virtual dental model alignment accuracy estimate.
Background : Digital workflow for producing implant-supported restorations involves the usage of intraoral scanners (IOS). From IOS data, 3D printed master model is often fabricated using the selected type of digital analogs. There is a lack of data regarding the effects of IOS, 3D printer, and digital analog type effect on the local and global accuracy of digital analog positions in 3D printed master model. Moreover, errors arising in each step stage should be identified.Aim/Hypothesis : The aim of the study was to estimate the effect of IOS, two 3D printers and 2 digital analog systems on 3D positions of the digital analogs comparing reference, IOS and 3D printed model data sets. The null hypothesis was that there are no statistically significant differences between the data sets.Material and Methods : Two Straumann BLT 4.1 mm RC implants were inserted in the reference model (REF) left quadrant, in the location of second premolar and second molar with 5° angulation. Three calibration spheres of 5 mm in diameter (±1 μm) where placed on the left quadrant at the model base. Scan bodies (3Shape) were attached to the implants and model was scanned with Nikon Altera 10.7.6. industrial scanner (REF-stl). REF model was scanned 10 times with E3 (3Shape) scanner for validation. Ten digital impressions were taken with 3Shape Trios 3 intraoral scanner. The closes to the overall average or IOS impressions STL file (IOS-stl) was selected for 3D printing. Asiga MAX and Next Dent 5100 3D printers, ELOS Print Model Analog and NT-trading DIM-ANALOG were used to produce 4 groups ( n = 10 each) of 3D printed implant models. Later they were scanned with a validated E3 scanner (3D-print-stl). Distance, angulation, rotation, vertical shift measurements were performed using Geomagic Control X 2018 software.Results : Validation procedure of E3 scanner showed the trueness of 26 μm and precision of 16.8 μm. Digital impression procedure with Trios 3 introduced 50 μm distance between the implants error. Local distance measurements showed the best accuracy with a combination of Asiga and Elos (avg = 87.4, SD = 49.2). As for the local vertical shift -most accurate results were achieved with NextDent and Elos group (avg = 50.2 SD = 60.3) Local angulation errors were smallest with Asiga and Elos (0.2 degrees) . Local rotation errors were smallest with a combination Nexdent and Elos (0.2 degrees). Majority of detected differences were statistically significant ( P < 0.05).
Conclusion and ClinicalImplications : Asiga MAX 3D printer performed more accurately than NextDent 5100. ELOS Print Model Analog showed most accurate result both locally and globally than NT trading. Intraoral scanning had significant influence in overall error propagation.Further studies are needed to evaluate other factors.
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