Continuing with the dimensional validation of our TECHFIT products, in this article we will discuss the dimensional accuracy for TECHFIT Orthognathic Surgical Guides.
TECHFIT Orthognathic Surgical Guides are patient-specific devices that are manufactured by rapid prototyping from Biocompatible Clear Resin. These guides are intended to assist the surgeon in the transfer of the pre-surgical plan to the operating room.
The Orthognathic Surgical Guides include Surgical Guides and Splints used for orthognathic surgery.
Surgical Guides help guide osteotomies through slots and perforations by drilling holes using surgical tools, as well as guide the correct positioning of bones and implants.
Splints, on the other hand, are optional templates used to guide the correct teeth positioning and to validate the patient’s final occlusion.
The evaluation of the dimensional accuracy of the original Orthognathic Surgical Guide design to the printed guide, both pre and post-sterilization, is critical to ensuring optimal surgical planning. This is because the surgeon must ensure that the cuts and perforations are compatible with bone movements and plate fixation, to obtain satisfactory aesthetic and functional changes. Thus, a meticulous assessment of the dimensional congruence between the two versions is indispensable to maintain the original surgical plan.
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The different types of Orthognathic Surgical Guides (Le Fort Surgical Guide, Genioplasty Surgical Guide, and splints) were manufactured following our manufacturing process, taking into account the full range of design specifications.
Subsequently, each 3D-printed surgical guide and splint were scanned before and after sterilization and compared to their original design to determine the dimensional error. The original design and scanned images were digitally aligned and overlapped. Then, the dimensional error was estimated by comparing the difference between the overlapped images on a point-by-point basis using the Analyze toolbox of the Mimics Innovation Suite.
The numerical data was exported and analyzed by an expert Statistically Epidemiologist. Each model was analyzed and graphed, showing the histogram of the mean dimensional error in the alignment of STL files, of the 3D-printed Orthognathic Surgical Guides and original design. Most histograms showed a narrow concentration of data without many extreme differences.
The acceptance criterion for Orthognathic Surgical Guides was set at ± 1.0 mm according to Goulart et al. [1] and the proprietary published data from TECHFIT [2].
In this test, the dimensional error between the original design and the 3D-printed Orthognathic Surgical Guides before sterilization was -0.0465 ± 0.176 mm, and between the original design and the sterilized Orthognathic Surgical Guides was -0.0459 ± 0.246 mm, showing compliance with the acceptance criteria by resulting in much lower error than ± 1 mm.
In the following images, you can see the macro-dimensional comparison between the different comparisons:
Likewise, the resulting dimensional error (mean difference) of comparing the 3D-printed Orthognathic Surgical Guides before and after sterilization was considerably low (-0.0147 ± 0.203 mm), indicating the dimensional stability of the Orthognathic Surgical Guides after the sterilization process. Additionally, the plotted mean differences of each Orthognathic Surgical Guide showed that even when 2 standard deviations from the mean are considered, the dimensional error does not come close to the acceptance criteria, being considerably lower.
The Orthognathic Surgical Guides displayed high consistency with a narrow 95% CI of their dimensional errors, demonstrating that the printed Surgical Guide’s fidelity to the original design even if sterilized is maintained.
The results indicate that the proportions and dimensions of the original digital design are maintained in 3D printed non-sterilized Orthognathic Surgical guides, demonstrating that the TECHFIT 3D printing process preserves the accuracy of the guides and splints.
Similarly, 3D printed sterilized Orthognathic Surgical guides are not affected dimensionally by the sterilization process and maintain accuracy and fidelity to the original digital design and the patient's anatomy.
References
[1] Goulart MEP, Biegelmeyer TC, Moreira-Souza L, Adami CR, Deon F, Flores IL, et al. What is the accuracy of the surgical guide in the planning of orthognathic surgeries? A systematic review. Med Oral Patol Oral y Cir Bucal 2022;27:e125–34. https://doi.org/10.4317/medoral.25042.
[2] Toro M, Cardona A, Restrepo D, Buitrago L. Does vaporized hydrogen peroxide sterilization affect the geometrical properties of anatomic models and guides 3D printed from computed tomography images? 3D Print Med 2021;7:1–10. https://doi.org/10.1186/s41205-021-00120-w