The surgical management of dentoskeletal deformities is a core part of oral and maxillofacial surgery. Traditional orthognathic surgery relies on presurgical orthodontic set up (traditional orthodontics), planning, occlusal splint fabrication, and fixation with stock titanium plates. However, technological advances such as in-office cone-beam computed tomography (CBCT), 3D printing, and intraoral scanning have allowed for orthognathic virtual surgical planning (VSP), as well as the development of patient specific osteosynthesis implants.1Heufelder M Wilde F Pietzka S et al.Clinical accuracy of waferless maxillary positioning using custom surgical guides and patient specific osteosynthesis in bimaxillary orthognathic surgery. Just as advances in virtual surgical planning and custom fixation plates have facilitated the evolution of surgical therapies offered by oral and maxillofacial surgeons, surgery-first approaches and clear aligner technology are becoming popular therapies in the orthodontic armamentarium. All these technological advances have been successfully incorporated at our institution; modifications such as the use of clear aligner orthognathic splints (CAOS)2Clear aligner orthognathic splints. in combination with custom maxillary fixation plates have been applied for surgery-first and surgery-only patients. The aim of the following step-by-step discussion is to present our institution's workflow using this technical modification of the use of CAOS and custom maxillary fixation plates.Preoperative Workflow

Step 1: During the preoperative visit, a final comprehensive facial analysis and intraoral assessment is completed in standard fashion.

Step 2: A full face CBCT is obtained and critically reviewed to assure its quality. The CBCT needs to be taken without the patient moving to avoid unwelcome artifacts that will affect the accuracy of 3D printed parts.

Step 3: Digital intraoral scanning is done to record the dentition and current occlusion. These records are used to digitally set up the final occlusion in cases of minimal occlusal changes (patients who previously had braces) or cases with no planned occlusal changes (patients undergoing maxillomandibular advancements). Cases with segmentation of the maxilla or cases with significant changes of occlusion will benefit from 3D printing of dental models to set the final occlusion in combination with the orthodontist.

Step 4: The following records are sent to a corporate vendor for virtual surgical planning: 1) full face CBCT, 2) STL files of the intraoral scan capturing the maxillary and mandibular dentition, and if necessary 3) STL files capturing the recorded postoperative bite digitized from the 3D printed dental models.

Step 5: A VSP session is completed following corporate vendor protocol.

Note: As the surgical workflow utilizes custom maxillary fixation plates, cases are planned as maxilla first without the use of an intermediate splint.

Regarding CAOS:1.One of the advantages of using CAOS is that arch bars are not necessary to establish intermaxillary fixation (IMF). Instead IMF is established with the use of IMF screws, orthodontic temporary anchor devices (TADs), or 2.0 fixation screws. To avoid trauma to dental roots, IMF screws guides are planned as a component of the VSP session (Fig 1).

FIGURE 1Virtual surgical planning for IMF screw guide.

Regarding custom maxillary fixation plates:1.Heat mapping is utilized to determine the most favorable bone for ultimate custom plate fixation, and this is incorporated into the predictive screw holes on the cutting guide (Fig 2).

FIGURE 2Maxillary thickness map showing areas of greatest bone stock and its correlation with the planning of the custom maxillary fixation plate.

2.The use of a maxillary custom plate requires a cutting guide designed by the corporate engineers. The cutting guide includes necessary osteotomy angulation and predictive holes where the final custom plate will reside. To facilitate stabilization and confirm proper position intraoperatively of the cutting guide, the engineers can create retentive components which engage the piriform rim, zygomaticomaxillary buttress, and the maxillary dentition (Fig 3).

FIGURE 3Virtual surgical planning for maxillary cutting guide.

3.

Importantly, the design of the Le Fort I cutting guide and final patient specific fixation plate is completed “offline” by the engineers.

Step 6: A proposed final surgical plan and maxillary custom fixation plate and cutting guide designs are sent to the surgeon for final approval before manufacturing.

Step 7: All supplies needed intra-operatively are fabricated and shipped to the medical center. These include IMF screw guides, maxillary cutting guides, patient specific fixation plates, verification models, clear aligner orthognathic splints, and a final palatal splint for maxillary segmental cases (Fig 4).

FIGURE 43D printed devices used intraoperatively. A. IMF screw guide. B. Maxillary cutting guide. C. Custom maxillary fixation plates. D. Pre- and postoperative verification models. E. Final, intermediate, and palatal splints (palatal splints for segmental cases only).

Step 8: The patient returns to clinic for a final preoperative review of surgical plans, postoperative expectations, and home care instructions.

Intraoperative Workflow

Step 1: Nasal intubation completed.

Step 2: Local anesthesia infiltration completed to the maxilla and mandible.

Step 3: IMF screws are placed in the maxilla and mandible using the IMF screw guide, ensuring it is properly seated. Additional midline IMF screws are incorporated in the case of a 3-piece segmental maxilla (Fig 5).

FIGURE 5IMF screw guide. A. Intraoperative photograph demonstrating the placement of the MMF screw guide. B. IMF screws in place.

Step 4: The mandibular osteotomies are completed but the splits are not finalized. The surgical sites are packed and attention turned to the maxilla.

Step 5: A traditional circumvestibular incision is completed and the maxilla is exposed. It is important to consider that the use of custom cutting guides often requires a larger degree of exposure most notably at the zygomaticomaxillary buttresses to allow for full seating of the guide.

Step 6: The floor of the nose is elevated and protected.

Step 7: The custom cutting guide is placed. It is crucial to confirm proper seating of the guide which is facilitated by confirming adaptation of the guide to the previously established anatomical reference points (ie piriform rim, zygomaticomaxillary buttress, and maxillary dentition) (Fig 6).

FIGURE 6Cutting guide. Intraoperative photograph showing the cutting guide in place.

Step 8: Fixation screws are placed to firmly secure the cutting guide in place.

Step 9: Predictive screw holes are drilled.

Step 10: A reciprocating saw is utilized to create the Le Fort I osteotomy using the custom cutting guide slot.

Step 11: If segmental maxillary surgery is planned, a piezoelectric system is used to initiate the segmental osteotomies at the planned interdental sites.

Step 12: The custom cutting guide is removed and the Le Fort I osteotomy is retraced with an emphasis on the posterolateral aspect of the osteotomies which is not included in the guide.

Step 13: The nasal septum, lateral nasal walls, and pterygoid plates are osteotomized and the maxilla is downfractured.

Step 14: The maxilla is gently mobilized in all 3 planes of space to facilitate passive positioning per the virtual surgical plan.

Step 15: Any potential bony interferences are eliminated and any tears in the nasal floor are repaired.

Step 16: If segmental surgery is to be completed, a piezoelectric handpiece is utilized to finalize the palatal osteotomies. Upon completion of the osteotomy, the segmental components are then carefully mobilized.

Step 17: The custom maxillary fixation plates are then secured to the tooth-bearing maxilla utilizing 5 mm screws in predrilled holes.

Step 18: The maxilla is then manipulated and passively secured into the predictive holes previously drilled before mobilization (Fig 7). In the case of segmental osteotomies, the final CAOS splint can be used to help position each segment into the custom maxillary plate.

FIGURE 7Custom maxillary fixation plate. Intraoperative photograph showing the custom maxillary fixation plate securing the maxilla.

Step 19: Attention is then returned to the mandible to complete the mandibular splits.

Step 20: The mandible is manipulated into the final CAOS splint and IMF is established (Fig 8).

FIGURE 8IMF with a clear aligner orthognathic splint (CAOS) in place.

Step 21: The proximal segments are passively seated, and any additional interferences are eliminated. Fixation is achieved with 1 plate in most of the cases or 2 plates in cases with large mandibular advancements. Note: At this time, we are not employing custom mandibular plates due to the difficulties involved with obtaining an accurate and reproducible record of the condylar seating.

Step 22: Once the maxilla and mandible have been secured, a modified horseshoe final palatal splint (without covering the occlusal surface of the maxillary teeth) is then wired in place to the posterior aspect of the maxillary dentition (Fig 9).

FIGURE 9Final palatal splint. Intraoperative photograph showing the final palatal splint secured to the segmented maxilla.

Step 23: All wounds are irrigated, and soft tissue is closed in standard fashion including an alar cinch suture and V-Y mucosal closure.

Step 24: The patient is extubated in routine fashion with transition to PACU care.

Step 25: IMF screws are left in place for the purposes of postoperative jaw manipulation with elastics. They are then removed in clinic 4 weeks postoperatively.

Step 26: In the case of segmental maxillary surgery, the palatal splint is left in place for 8 weeks before removal in clinic.

DiscussionClear aligner orthognathic splints (CAOS) were described in 2019 by Caminiti and Lou as a repositioning and fixation device for performing orthognathic surgery in patients on clear aligner therapy.1Heufelder M Wilde F Pietzka S et al.Clinical accuracy of waferless maxillary positioning using custom surgical guides and patient specific osteosynthesis in bimaxillary orthognathic surgery. In comparison to traditional splints that only contact incisal edges and cusp tips (mostly a limitation because of the position of orthodontic brackets), CAOS fully cover the dental crowns. This characteristic allows for an accurate, precise and easy seating of the entire dentition. This is especially helpful in cases of maxillary segmentation as less manipulation and more control is obtained when seating the complete crowns of the maxillary segment dentition. When fully seated in the maxillary and mandibular dentition, CAOS provides an initial IMF retention. Solid IMF is then easily obtained by using IMF screws with 24-gauge wires. Lastly, increase comfort and ease to maintain postoperative oral hygiene has been observed due to the lack of arch bars or orthodontic brackets. Important to mention that at the beginning of our experience, the level of tightness (tolerance) of the splint had to be adjusted. CAOS that were too tight were difficult to remove and the ones that were loose made establishing IMF harder. Another disadvantage of this approach includes potential dental root damage with the placement of IMF screws if guides are not used; when used, IMF screw guides increase the planning and manufacturing time and cost. Another drawback is related to the common practice in orthognathic surgery that helps the surgeon determine if the condyles are properly seated and the mandible has been fixated in the right position. This is done by passively manipulating the mandible into the final splint once IMF has been released. This maneuver is unavailable while using CAOS due to its snap-on design. Further outcome studies are required to compare traditional versus clear aligner orthognathic splints.3Kankham H Madari S Sawh-Martinez R et al.Comparing outcomes in orthognathic surgery using clear aligners versus conventional fixed appliances.Traditional and virtually planned splints have been used with great success for the repositioning of the maxilla, with vertical position set intraoperatively on the basis of clinical assessment and, in some cases, external or internal reference points. The advent of custom maxillary fixation plates eliminates the need for intermediate splints and reference points and achieves a very accurate positioning of the maxilla especially in the vertical position. Another advantage of the custom maxillary fixation plates is the increased stability of the maxillary fixation which results from the 3D print fabrication of the plate without the need for intra-operative plate manipulation, and the placement of fixation screws in the areas of greatest bone stock. The increased stability and the high accuracy of transferring the treatment plan into reality afford the placement of the maxilla in unconventional positions that would prove difficult to achieve with traditional methods. As an example, custom maxillary fixation plates will make more feasible the inferior repositioning of the maxilla with counterclockwise rotation of the maxillomandibular complex (Fig 10). Similarly in segmental maxillary surgery the segments are more accurately positioned with increased fixation stability. This technique may also allow for reduced surgical time once the surgeon is familiar with the workflow.

FIGURE 10Virtual surgical planning for a case with inferior repositioning of the maxilla and counterclockwise rotation of the maxillomandibular complex that was completed using custom maxillary fixation plates.

The disadvantages of the technique include increased planning and manufacturing time, demands and cost. Intraoperatively we have encountered a couple of cases in which the maxillary cutting guide did not allowed for a 100% accurate placement. In those cases the guide was positioned with the best possible fit and no predrilling was done in the holes where the guide was not properly seated. The custom maxillary fixation plate was then passively positioned in the predicted holes. Once the plate was secured, the residual holes were drilled with no further issues. Although one of the premises of this technique is the splintless placement of the maxilla, to have an intermediate splint is always a good back up in case the custom maxillary fixation plate does not fit properly. An intermediate splint was necessary in a 2-piece Le Fort I case in which after placing the custom maxillary fixation plates, the segments were malpositioned resulting in malalignment of the central incisors. One of the plates was removed from the native maxilla, then the entire tooth-bearing maxilla was placed on the intermediate clear aligner orthognathic splint. A lag screw was placed in the area of the anterior nasal spine to ensure the proper alignment of the incisors and new holes were drilled in the native maxilla with no further clinical complications.

In conclusion, the workflow presented above represents the successful experience of our institution using the novel approach of clear aligner orthognathic splints in combination with custom maxillary fixation plates for surgery-first or surgery-only cases. They serve as examples of the exciting innovations we are witnessing in the evolution of orthognathic surgery in the digital era. Further research is required to fully appreciate the true benefits and shortcomings associated with integrating these technologies into routine patient care.

ReferencesHeufelder M Wilde F Pietzka S et al.

Clinical accuracy of waferless maxillary positioning using custom surgical guides and patient specific osteosynthesis in bimaxillary orthognathic surgery.

J Craniofac Surg. 45: 1578-1585

Clear aligner orthognathic splints.

J Oral Maxillofac Surg. 77 (): 1071Kankham H Madari S Sawh-Martinez R et al.

Comparing outcomes in orthognathic surgery using clear aligners versus conventional fixed appliances.

J Craniofac Surg. 30: 1488-1491Article InfoPublication History

Accepted: March 26, 2021

Received: March 26, 2021

Footnotes

Conflict of Interest Disclosures: None of the authors have any relevant financial relationship(s) with a commercial interest.

Identification

DOI: https://doi.org/10.1016/j.joms.2021.03.023

Copyright

© 2021 The American Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved.

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