Effect of implant angulation, intraoral scanning mode, additive manufacturing, and digital implant analog system on the trueness of implant casts – Part 1
Authors: Rutkūnas Vygandas , Jegelevičius Darius , Gedrimienė Agnė , Revilla-León Marta , Akulauskas Mykolas , Özcan Mutlu , Husain Nadin Al-Haj , Auškalnis Liudas 
Published: April 2023

Abstract
Objectives
The accuracy of intraoral digital scans using various intraoral scanning devices regarding additive manufacturing and implant position and system is not evaluated sufficiently yet. To evaluate in-vitro the accumulative effect of intraoral scanning (IOS), additive manufacturing (AM), implant angulation, and implant analog system on the trueness of the definitive implant cast.
Materials and Methods
A case of a three-unit implant-supported (BLT RC, Straumann) fixed dental prosthesis in a posterior region was simulated on the reference (Ref) cast. 5 precision spheres were placed on the cast base. Ref cast was fitted with titanium implant scan bodies (3Shape A/S) and scanned with a coordinate measurement machine equipped with a laser scanning head (ALTERA; Nikon) producing a reference Ni data set (n = 1). Digital scans of the Ref cast were taken with Trios 4 (3Shape A/S) which served as a second reference data set (T4, n = 10). Each digital scan was used to produce physical test quadrant cast with 3 AM machines for 3 implant analog systems (n = 90). Tested implant analog systems: Accurate Analog for Printed Models (Elos Medtech), DIM-ANALOG (nt-trading), and RC Repositionable Implant Analog (Straumann). Tested additive manufacturing (AM) devices: MAX UV385 (Asiga), PRO 4K65 UV (Asiga), and NextDent 5100 (3D Systems). Conventional open-tray splinted vinyl polysiloxane impressions (n = 10) were made of the Ref cast and control casts were poured with Type IV dental stone. Stone and AM casts were fitted with the same titanium implant scan bodies (3Shape A/S) and digitized using a laboratory scanner (E4; 3Shape A/S). Implant local and global trueness (3D distance, angulation) was assessed comparing reference (Ni, T4), test (AM), and control (stone) groups with metrology software (Geomagic Control X; 3D Systems). To assess data normality and homogeneity of variance Shapiro-Wilk and Leven’s tests were used respectively. Student’s t-test, two-way, and three-way ANOVA models were used for statistically significant differences between data groups estimation. A Post hoc Tukey-HSD test for further ANOVA analysis was used. For all tests and models, α was assigned to be less than 0.05.
Results
Digital scans showed higher 3D distance trueness between implants compared to stone casts (P = .00). The trueness of additively manufactured casts was mostly similar to or lower than IOS scans (P ≤ .05). Only in a few instances did the AM casts produced with PRO (Asiga) and Nextdent 5100 (3D Systems) and equipped with Nt-trading and Elos implant analogs showed higher angulation trueness than digital scans (P < .05). AM casts showed better 3D distance and lower angular trueness than stone casts (P < .05). Higher 3D distance deviations were introduced by Nextdent 5100 (3D Systems) AM device and Nt-trading system (P < .05). Implant angulation influence on trueness was non-significant (P > .05).
Conclusions
Within the limitations of this in vitro study, digital scans and additively manufactured casts reproduced the distance between the implants with higher trueness compared to stone casts. All test and control groups had clinically significant angulation deviations.
Clinical Relevance:
AM device and implant analog system have a significant effect on the trueness of AM models.