This article has Open Peer Review reports available.
Correction of a severe facial asymmetry with computerized planning and with the use of a rapid prototyped surgical template: a case report/technique article
© Seres et al.; licensee BioMed Central Ltd. 2014
Received: 5 May 2014
Accepted: 6 June 2014
Published: 11 July 2014
Management of significant facial asymmetry presents a challenge due to the geometric complexity of the bony and other facial structures. Manual model surgery is an essential part of treatment planning but it can be complicated, time-consuming and may contain potential errors. Computer-aided surgery has revolutionized the correction of maxillofacial deformities. The aim of this study was to report a case of facial asymmetry when computerised simulation surgery was performed instead of manual model surgery and a virtually planned wafer splint was fabricated. A 26-year-old male was presented with a severe right-sided hemimandibular elongation. Following presurgical orthodontics high-resolution computer tomography scan was performed. The stack images were reformatted into a three-dimensional structure. Virtual Le Fort-I osteotomy was performed and the symmetry of the maxilla was corrected with the help of a three-dimensional planning software. A virtual intermediate surgical wafer was designed and produced with three-dimensional rapid prototyping technology. The mandible was rotated into the correct position following virtual bilateral sagittal split osteotomy to visualize the movements of the osteotomised mandibular segments. The two-jaw procedure was performed according to the virtual plan. The facial symmetry was improved significantly and stable occlusion was achieved. This complex case shows the advantages of computer-aided surgical planning and three-dimensional rapid prototyping for the correction of facial asymmetries.
Correction of severe facial asymmetry is a challenging task due to the geometric complexity of the dentition, the bony structures and the soft tissues. Mandibular asymmetry is usually associated with a unilateral vertical maxillary excess and an occlusal cant, therefore, in most cases the deformity cannot be treated with single-jaw surgery .
Traditional cephalometric analysis is of limited value in interpreting the cause of the asymmetry, because complex three-dimensional (3D) structures are projected onto two-dimensional (2D) planes. Treatment planning of an asymmetric case requires three-dimensional consideration in the sagittal, coronal and horizontal planes. Traditionally, manual model surgery is an essential part of the preoperative workup that involves many time-consuming laboratory based steps. When two-jaw surgery is performed, following the transposition of the maxilla on the stone dental model in the articulator an interocclusal splint is fabricated that serves as an intermediate guide for repositioning the maxilla relative to the intact mandible. The second, or final wafer relates the mobilized mandible to the fixated maxilla.
It is of critical importance that model surgery is based on accurate translation of the theoretical transposition data. Any discrepancy between the plan and the model surgery will lead to an inaccurate interocclusal splint. A poorly designed and/or fabricated wafer can lead to a disastrous outcome even when the most skillful surgical technique is used.
If a symmetric or slightly asymmetric face is operated on, when the jaws are moved mainly in the anteroposterior and vertical direction, traditional, 2D analysis and planning are usually satisfactory. But even in these cases, small errors in each step of model surgery can compound and lead to an inaccurate result [2–4].
Major asymmetry involving both the upper and lower jaws often requires complicated two-jaw surgery. In these cases 3D planning is essential. The problem is twofold: first, how the most precise planning can be achieved and second, how the treatment plan can be transferred to the operating room. Accurate cephalometric analyses and 3D planning based on plain lateral and frontal cephalograms are hardly possible [5–7].
Improved imaging techniques and advances in software engineering have moved 3D computer models from the research and development area into routine clinical application [8–10]. Three-dimensional reconstruction images can be easily rotated and viewed from any angle. Accurate measurements can be performed on the maxillofacial complex and this helps not only to understand the etiology of facial asymmetry but to plan the osteotomies and movements of the segments.
Rapid prototyping is a remarkable, quickly evolving technology that has been revolutionizing the manufacturing process in several fields. With these technologies splints can be made that can guarantee the precise repositioning of the bony segments during surgery [11, 12].
The aim of this study is twofold, first, to investigate whether virtual 3D model surgery is suitable for treatment planning of an asymmetric two-jaw surgery, and second, to examine if rapid prototyping may eliminate the need for manual model surgery and the conventional fabrication of the interocclusal splint in the dental laboratory. A case of a severe facial asymmetry is reported when computer aided surgical planning was performed and the intermediate wafer was designed virtually and was manufactured by a three-dimensional printer.
Case presentation/technique description
When two-jaw surgery is planned for an asymmetric case spatial positioning of the maxilla is considered more critical than the repositioning of the mandible. Intermediate wafers are used more frequently than the final ones . In our case reported, the key point of the procedure was the accurate repositioning of the maxilla. The maxillary segment mobilized via Le Fort I osteotomy showed acceptable intrinsic symmetry, therefore further maxillary osteotomies were not performed. The mobilized unit was placed symmetrically with respect to the sagittal plane. To achieve this it was rotated clockwise until the maxillary occlusal plane was parallel to the interpupillary line. At the same time a further rotation was performed in the horizontal plane to move the posterior part of the maxilla to the right. Amongst others, the complex rotational movement can be one of the sources of inaccuracies in manual model surgery. While with traditional methods treatment planning and model surgery are two separate steps, with virtual surgery these two procedures can be performed at the same time, there is no information loss between the two. The most complicated movements can be made precisely and the most accurate measurements can be calculated simultaneously. The final product of virtual model surgery is a virtual splint that can be materialized by rapid prototyping. This technique relies on the accuracy of the virtual model and the production of the surgical splint to ensure a successful surgery . The intermediate wafer was fabricated with the highest printing accuracy in our case and it proved to be the most reliable tool to transfer virtual surgery into the operating room.
The new position of the mandible was determined by the repositioned maxilla. Virtual surgery showed that the mandible would be brought forward by 8.6 mms on the left side. Manual model surgery focuses on the dentition and the occlusion but changes in the bony structure cannot be displayed. Although final wafer was not used as the mandible was simply placed into maximal intercuspal occlusion, virtual surgery still helped us to understand and visualize the rotational movement of the mandible.
Latest computerized and rapid prototyping technologies let us fully imagine, design and control orthognathic procedures without information loss among the surgeons, orthodontists and dental technicians. Any number of alternative treatment strategies can be investigated simultaneously during the planning phase. Computerised simulation surgery can be extremely useful in severe asymmetric cases when precise treatment planning with traditional methods is hardly possible. With this method manual model surgery and other laboratory steps can be avoided. The surgical wafer splint can be planned virtually and fabricated by a 3D printer.
Written informed consent was obtained from the patient for publication of this Case report and any accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal.
- Cheong YW, Lo LJ: Facial asymmetry: etiology, evaluation, and management. Chang Gung Med J. 2011, 34: 341-351.PubMedGoogle Scholar
- Cevidanes LH, Tucker S, Styner M, Kim H, Chapuis J, Reyes M, Proffit W, Turvey T, Jaskolka M: Three-dimensional surgical simulation. Am J Orthod Dentofacial Orthop. 2010, 138: 361-371.View ArticlePubMedPubMed CentralGoogle Scholar
- Ellis E: Accuracy of model surgery: evaluation of an old technique and introduction of a new one. J Oral Maxillofac Surg. 1990, 48: 1161-1167.View ArticlePubMedGoogle Scholar
- Choi JY, Song KG, Baek SH: Virtual model surgery and wafer fabrication for orthognathic surgery. Int J Oral Maxillofac Surg. 2009, 38: 1306-1310.View ArticlePubMedGoogle Scholar
- Edler R, Wertheim D, Greenhill D: Outcome measurement in the correction of mandibular asymmetry. Am J Orthod Dentofacial Orthop. 2004, 125: 435-443.View ArticlePubMedGoogle Scholar
- Hwang HS, Hwang CH, Lee KH, Kang BC: Maxillofacial 3-dimensional image analysis for the diagnosis of facial asymmetry. Am J Orthod Dentofacial Orthop. 2006, 130: 779-785.View ArticlePubMedGoogle Scholar
- Gateno J, Xia JJ, Teichgraeber JF: A new three-dimensional cephalometric analysis for orthognathic surgery. J Oral Maxillofac Surg. 2011, 69: 606-622.View ArticlePubMedPubMed CentralGoogle Scholar
- Baek SH, Kang SJ, Bell WH, Chu S, Kim HK: Fabricating a surgical wafer splint by three-dimensional virtual model surgery. Distraction Osteogenesis of the Facial Skeleton. Edited by: Bell WH, Guerrero CA. 2006, Hamilton, Ontario: BC Decker, 115-130.Google Scholar
- Swennen GR, Mollemans W, Schutyser F: Three-dimensional treatment planning of orthognathic surgery in the era of virtual imaging. J Oral Maxillofac Surg. 2009, 67: 2080-2092.View ArticlePubMedGoogle Scholar
- Hsu SS, Gateno J, Bell RB, Hirsch DL, Markiewicz MR, Teichgraeber JF, Zhou X, Xia JJ: Accuracy of a computer-aided surgical simulation protocol for orthognathic surgery: a prospective multicenter study. J Oral Maxillofac Surg. 2013, 71: 128-142.View ArticlePubMedGoogle Scholar
- Metzger MC, Hohlweg-Majert B, Schwarz U, Teschner M, Hammer B, Schmelzeisen R: Manufacturing splints for orthognathic surgery using three-dimensional printer. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2008, 105: e1-e7.View ArticlePubMedGoogle Scholar
- Levine JP, Patel A, Saadeh PB, Hirsch DL: Computer-aided design and manufacturing in craniomaxillofacial surgery: the new state of the art. J Craniofac Surg. 2012, 23: 288-293.View ArticlePubMedGoogle Scholar
- Lorensen WE, Cline HE: Marching cubes: A high resolution 3D surface construction algorithm. Comp Graph. 1987, 21: 163-169.View ArticleGoogle Scholar
- Erdőhelyi B, Varga E, Kuba A: Surgical planning tool with biomechanical simulation. Proceedings of the International Conference on Computer Assisted Radiology and Surgery (CARS). Int J Comput Assist Radiol Surg. 2007, 2: S262-S263.Google Scholar
- Parbatani R, Williams AC, Ireland AJ, Sandy J: The process of orthognathic care in an NHS region. Ann R Coll Surg Engl. 2010, 92: 34-39.View ArticlePubMedPubMed CentralGoogle Scholar
- Varga E, Hammer B, Hardy BM, Kamer L: The accuracy of three-dimensional model generation. What makes it accurate to be used for surgical planning?. Int J Oral Maxillofac Surg. 2013, 42: 1159-1166.View ArticlePubMedGoogle Scholar
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.