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.
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.
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).
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.
With the utilized design, the guides fabricated with SLA provided lower dimensional changes as compared to the ones produced by the other printing techniques.