Effect of Print Orientation, Storage Conditions, and Time on the Intaglio Surface Accuracy of Additively Manufactured Implant Surgical Guides

Abstract

Statement of problem. The accuracy of additively manufactured (AM) implant surgical guides can be affected by several factors that negatively impact the pre-planned implant position. How the print orientation and storage time and conditions influence manufacturing accuracy remains uncertain.

Purpose. The purpose of the present in vitro study was to evaluate the influence of the print orientation, storage time, and storage conditions on the accuracy of AM surgical guide manufactured by using a stereolithography (SLA) 3D printer.

Material and methods. A power analysis was performed in order to determine the adequate sample size. A tooth-supported maxillary implant surgical guide design was used to fabricate forty specimens (n=10). Four groups were created based on the print orientation used: 0 (Group 0), 45 (Group 45), 70 (Group 70), and 90 (Group 90). The specimens were fabricated using a desktop SLA 3D printer (Form 3B+) and biocompatible dental resin (Surgical Guide Resin V1) following the manufacturer’s recommended protocol. Each group was further divided into 2 subgroups based on the storage conditions: light (L subgroup) and dark (D subgroup) settings. Each group of specimens were digitized using a desktop scanner (Medit T710) at days 0, 1, 7, and 14 and stored at 20 degrees Celsius. The STL files of the scanned surgical templates were superimposed using the master design file using the best-fit alignment in a surface matching software program (Control X). The dimensional differences between the specimens STL files and the master STL file at the intaglio surface of the specimens was computed and analyzed. A single individual performed the data collection. For statistical tests, non-parametric tests for all samples were used Wilcoxon signed rank tests for angulation and storing time within groups, and Mann-Whitney U test for the storing conditions between groups.

Results. Root mean square error (RMSE) values demonstrated that the 0-degree group had the highest accuracy. Statistically significant differences were observed between the 0-degree and 45-degree groups (p<0.001), the 0-degree and 90-degree groups (p<0.001), the 45-degree and70-degree groups (p<0.001), and the 70-degree and 90-degree groups (p<0.001). The comparison between light versus dark storage condition was not statistically significant (p-value=0.161). The difference between the specimens over time (day 0, 3, 7, and 14) were analyzed and did not reveal any statistical significance.

Conclusion. The accuracy of surgical guides on the intaglio surface is affected in a statistically significant manner by the print orientation but not by the storage conditions over time. The present study suggests the zero-degree print orientation produces the most accurate surgical guides and the 45-degree print angulation the least accurate. Also, the assessed storage conditions (dark vs light) over the evaluated 14-day time period do not affect accuracy in a statistically relevant manner.