From facial surface acquisition to digital orthopedic support
Biomechanical rationale, clinical proof-of-concept, and validation agenda for a patient-specific Digital Sky Hook
DOI:
https://doi.org/10.67463/d329dc10Keywords:
CAD/CAM, facial photogrammetry, Class III malocclusion, maxillary protraction, additive manufacturing, patient-specific device, digital orthodontics, orthopedic applianceAbstract
Objective: To document the clinical-technical proof-of-concept of a patient-specific Digital Sky Hook for maxillary protraction, emphasizing how non-contact facial acquisition and additive manufacturing may stabilize the extraoral support interface for classical chin-supported mechanics.
Methods: Two clinical-technical applications were considered. The index case, a growing female patient with skeletal Class III malocclusion and maxillary deficiency, was described in detail because complete acquisition, design, fabrication, delivery, seating assessment, and follow-up documentation were available. A second ongoing-use application documented procedural repeatability without statistical or comparative outcome claims.
Results: Three design and printing iterations were required before standardizing the index appliance. The finalized framework showed passive seating, required no hydrocolloid foam or compensatory lining, and was used for 12 to 14 hours per day over an 8-month period without clinically relevant soft-tissue adverse events. Exploratory comparison with a conventional support showed border discrepancies of approximately 2.0 mm superiorly and 2.5 mm inferiorly. The workflow was reproduced in a second patient who received the appliance and remained in active use.
Conclusion: This Methods / Technical Note / Validation Study establishes the feasibility and procedural repeatability of a scan-derived, patient-specific chin-support interface for a classical Sky Hook-type maxillary protraction system. The workflow reduced dependence on facial molding, enabled passive seating without compensatory lining in the index case, and provides a traceable platform for metrological, mechanical, pressure-distribution, and prospective clinical validation
References
Haas AJ. Palatal expansion: just the beginning of dentofacial orthopedics. Am J Orthod. 1970;57(3):219-55. doi:10.1016/0002-9416(70)90028-4. DOI: https://doi.org/10.1016/0002-9416(70)90241-1
Hickham JH, inventor. Orthodontic anterior traction appliance. United States patent US 3,401,457. 1968 Sep 17.
Hickham JH. The skyhook appliance. Am J Orthod. 1972;62(1):29-41. doi:10.1016/0002-9416(72)90122-8.
Hickham JH. Maxillary protraction therapy: diagnosis and treatment. J Clin Orthod. 1991;25(2):102-13.
Furquim LZ. Confecção e instalação do Sky Hook. R Clín Ortodon Dental Press. 2002;1(4):5-13.
Gonçalves L, Furquim LZ, Furquim BD, Terada HH. Digital Sky Hook. Clin Orthod. 2023 Dec-2024 Jan;22(6):84-94. doi:10.14436/2675-486X.22.6.084-094.art. DOI: https://doi.org/10.14436/2675-486X.22.6.084-094.art
Franchi L, Vichi A, Marti P, Lampus F, Guercio S, Recupero A, et al. 3D printed customized facemask for maxillary protraction in the early treatment of a Class III malocclusion: proof-of-concept clinical case. Materials (Basel). 2022;15(11):3747. doi:10.3390/ma15113747. DOI: https://doi.org/10.3390/ma15113747
Kim H, Kim JS, Kim CS, Becker-Weimann S, Cha JY, Choi SH. Skin irritation in children undergoing orthodontic facemask therapy. Sci Rep. 2023;13(1):2200. doi:10.1038/s41598-023-29253-0. DOI: https://doi.org/10.1038/s41598-023-29253-0
Thurzo A, Kosnáčová HS, Kurilová V, Surovková J, Moravčíková R, Kováč P, et al. Smartphone-based facial scanning as a viable tool for facially driven orthodontics? Sensors (Basel). 2022;22(20):7752. doi:10.3390/s22207752. DOI: https://doi.org/10.3390/s22207752
Jindanil T, Zhang B, Seneviratne R, Gredes T, Jamilian A, Volchkevich D, et al. Smartphone applications for facial scanning: a technical and scoping review. Orthod Craniofac Res. 2024;27 Suppl 2:65-87. doi:10.1111/ocr.12821. DOI: https://doi.org/10.1111/ocr.12821
Kouhi M, de Souza Araújo IJ, Asa'ad F, Zeenat L, Bojedla SSR, Pati F, et al. Recent advances in additive manufacturing of patient-specific devices for dental and maxillofacial rehabilitation. Dent Mater. 2024;40(4):700-15. doi:10.1016/j.dental.2024.02.006. DOI: https://doi.org/10.1016/j.dental.2024.02.006
Burns NR, Musich DR, Martin C, Razmus T, Gunel E, Ngan P. Class III camouflage treatment: what are the limits? Am J Orthod Dentofacial Orthop. 2010;137(1):9.e1-9.e13. doi:10.1016/j.ajodo.2009.05.017. DOI: https://doi.org/10.1016/j.ajodo.2009.05.017
Miethke R. John H. Hickham, 1935-2004. Am J Orthod Dentofacial Orthop. 2005;127(1):94. doi:10.1016/j.ajodo.2004.11.022. DOI: https://doi.org/10.1016/j.ajodo.2004.11.022
Published
Issue
Section
License
Copyright (c) 2026 Lisandro Gonçalves, Hélio Terada
This work is licensed under a Creative Commons Attribution 4.0 International License.
This journal publishes articles under the Creative Commons Attribution 4.0 International License (CC BY 4.0). Authors retain copyright and grant the journal the right of first publication. This license permits use, distribution, reproduction, and adaptation in any medium, provided the original author and source are properly credited.
