Effect of implant angulation, intraoral scanning mode, additive manufacturing, and digital implant analog system on the precision of defintive implant casts – Part 2
Authors: Rutkūnas Vygandas , Jegelevičius Darius , Revilla-León Marta , Pletkus Justinas , Akulauskas Mykolas , Özcan Mutlu , Husain Nadin Al-Haj , Auškalnis Liudas 
Published: April 2023

Abstract
Objectives
The accuracy, especially precision of intraoral scans of various intraoral scanning devices using various implant systems, positions and additive manufacturing methods has not been studied sufficiently yet. This in-vitro study evaluated the accumulative effect of intraoral scanning (IOS), additive manufacturing (AM), implant angulation, and implant analog system on the precision of definitive implant cast.
Materials and Methods
A partially edentulous reference (Ref) cast presenting a case of a 3-unit implant supported (BLT RC, Straumann) fixed dental prosthesis in the posterior region was selected. The cast base was prepared using 5 precision spheres and the cast fitted using titanium implant scan bodies (3Shape) and scanned using a laser scanning head device (ALTERA; Nikon) producing a reference Ni data set (n = 1). A second reference data set (T4, n = 10) was prepared using digital scan of the Ref cast using an intraoral scanner (Trios 4, 3Shape A/S). Test quadrant cast were produced out of the digital scans using three different additive manufacturing (AM) devices (MAX UV385 (Asiga), PRO 4K65 UV (Asiga) and NextDent 5100 (3D Systems)) and 3 implant analog systems (Accurate Analog for Printed Models (Elos Medtech), DIM-ANALOG (nt-trading), and RC Repositionable Implant Analog (Straumann)) (n = 90). Open-tray splinted vinyl polysiloxane impressions (n = 10) were made of the Ref cast and control casts poured using Type IV dental stone. Stone and AM casts were thereafter digitized using a laboratory scanner (E4; 3Shape A/S). Implant local and global precision (3D distance, angulation) was assessed comparing reference (Ni, T4), test (AM), and control (stone) groups with a metrology software (Geomagic Control X; 3D Systems). Shapiro-Wilk and Leven’s tests were used to evaluate data normality and homogeneity of variance respectively. Student’s t-test, two-way, and three-way ANOVA models as well as Post hoc Tukey-HSD tests were used (α ≤ .05).
Results
Digital scans made with Trios 4 (3Shape A/S) showed mostly similar precision to stone casts. However, IOS was significantly more precise in capturing angulation between the implants than control stone casts (P = .05). Both groups showed clinically significant global angulation precision (> 0.40°). Global angulation precision of the distal implant was significantly better in AM models rather than IOS (P ≤ .05, ∆≥0.26°). All local measurements showed a similar precision between test AM and control stone models (P > .05). However, global angulation precision of both implants was mostly better in AM models rather than in the control group (P ≤ 0.05, ∆≥0.21°). The AM device MAX UV385 (Asiga) had a significantly higher precision than NextDent 5100 (3D Systems) (P = .05). The implant analog system DIM-ANALOG (nt-trading) provided significantly less local angulation precision than Repositionable Implant Analog (Straumann) (P = .01).
Conclusions
Digital scans reproduce similar distance but higher angulation precision between implants compared to stone casts.
Clinical Relevance:
AM device and implant analog system choice has a significant effect on the precision of AM models.