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Impact of Autoclaving on the Dimensional Stability of 3D-Printed Guides for Orthodontic Mini-Implant Insertion - An
Samuel David1, Mira Hüfner1, Nicole Rauch2
1Department of Orthodontics, University Hospital of Düsseldorf, Düsseldorf, Germany.
Objectives:
This study aimed to assess the effect of the printing process itself and steam autoclaving on the geometrical stability of 3D-printed guides for mini-implant insertion.
Material And Methods:
Fifty guides (n = 10 per group) were printed with five printer/resin combinations (PRCs) from the same STL file using either digital light processing (DLP/EG, DLP/Next, DLP/Opti), desktop stereolithography (SLA/DSG) or liquid crystal display stereolithography printers (LCD/Amber). Half were sterilized by steam autoclaving with Cycle 1 (121°C, 1 bar, 20.5 min), half with Cycle 2 (134°C, 2 bars, 5.5 min). Before (T0) and after sterilization (T1) the guides were scanned with a structured light 3D scanner, and selected guides also with micro-CT for validation. Linear measurements were performed in three axes on STL, and on T0 and T1 scans. Linear mixed-effects models were used, followed by post-hoc tests in case of significance.
Results:
Measurements at T0 and T1 differed significantly from STL in both x- and y-axis (4 and 3 PRCs, respectively) (p < 0.05); in z-axis only DLP/Next showed significant differences between T0 and STL (p < 0.001). The comparison between T0 and T1 revealed significant differences in x-axis for DLP/Next and DLP/Opti after Cycle 1 and Cycle 2, respectively (p < 0.05), while in the y-axis no intra-group difference was recorded. In the z-axis all PRCs except for SLA/DSG exhibited significant shrinkage (for Cycles 1 or 2). Differences between the two cycles at T1 were registered only in z-axis (DLP/Next and LCD/Amber).
Conclusions:
Compared with the original, all PRCs except for SLA/DSG presented significant changes in their dimensional stability owing to the printing process itself and/or the sterilization. If these changes are of clinical significance, they remain to be verified.
Clinical Relevance:
With the utilized design, the guides fabricated with SLA provided lower dimensional changes as compared to the ones produced by the other printing techniques.
