Evaluation of volumetric changes of 3D printed implant surgical guides after sterilization process

ALYEB ePOSTER BASIC RESEARCH

Background: The placement of osseointegrated implants is a part of the daily clinical practice. Today, with the evolution of digital technology and guided implant surgery, dentistry has become more predictable and accurate. However, the accuracy of this procedure can depend on many factors related to pre-operative stages. One of these factors is the management of the surgical guide and the possible volumetric and morphological changes when attempting to sterilize it.

Aim/Hypothesis: The aim of this study was to investigate the effect of steam heat sterilization on the volumetric and morphological stability of 3D printed surgical guides. Our study tries to explore if this sterilization method could lead to an error during guided implant surgery and can affect the final outcome.

Materials and Methods: A surgical guide was designed by MIS Implant company (MIS Guided) for the purpose of the tests and was given to us in an STL file format. Then, five identical guide templates were produced for each of two different groups of materials (MED610-Stratasys and Visijet M3 Crystal), using a 3D printer. These two groups, of the total ten printed templates and 30 implant sites, were digitally scanned by using an intraoral scanner(3Shape TRIOS) before and after steam heat sterilization at 121°C for 20 minutes. The scan data were saved in STL files and were compared, using the Rhino 6 SR22 and CloudCompare software. Volumetric and morphological evaluation was performed, measuring the span and diameter of each template and comparing the deformation of both materials. Statistical analysis was performed for all parameters.

Results: Statistical analysis (ANOVA) showed no significant differences between the mean deviations of surgical guides for MED610 (P = 0.761757, F-Ratio = 0.09842). The change in volume ranged from 0.5% to 2.06%. On the other hand, for Visijet M3 Crystal the difference between the averages of some groups was large enough to be statistically significant (P = 0.036202, F-Ratio = 6.31508). The volume change ranged from 0.51% to 2.98%. The confidence interval with 95% probability for the mean of the difference before and after was for MED610 [-49.755227, 106.480843] and for Visijet M3 Crystal [-153.375861, -17.329587]. The visualizations of the data showed that morphological changes were noticed mainly in cervical section of the templates and in the area of drill sleeves [Root Mean Square Error(RMSE) = 0.020 ± 0.005].

Conclusions and Clinical Implications: The study concluded that the steam sterilization at 121°C has no significant effects on volumetric changes of the MED610 tested drill templates. Larger differences were observed with Visijet M3 Crystal surgical guides, making it less suitable for steam sterilization. The results also show a larger deformation of the surgical guides in the cervical and drill-sleeve areas. Further investigations are required, to analyse the effect of steam sterilization for 3D printed surgical guides.

Acknowledgements: We would like to express our great thanks to Smile Clinic in Thessaloniki for its contribution to this research project.

Keywords: 3d printing, guided implant surgery, surgical template, steam heat sterilisation, accuracy