Perspective Chapter: Orthognathic Surgery with Clear Aligners

Abstract

Orthognathic surgery for dentofacial deformities typically requires orthodontic treatment before and after surgical treatment. Traditionally, the orthodontic-fixed appliance with arch wires aids to secure dentition to allow dental movement and stabilization. Many patients, especially those who require orthognathic surgery (OGS) to correct their dentofacial abnormalities, are requesting esthetic and metal-free treatment options. Clear aligners are also better camouflaged than traditional orthodontic brackets and wires, maintaining a more esthetic appearance. Because of the benefits of aligners, which include simplicity of use, esthetics, comfort, and hygiene, they are chosen over traditional braces. In this chapter, we focus on orthognathic surgery treatment with clear aligners.

1. Introduction

Orthognathic surgery (OGS) is indicated for patients whose orthodontic problems are so severe that neither growth modification nor camouflage provides a solution. Since its initial conception, it has seen remarkable improvements in its planning and technique [1]. Advance in digital technology has made the paradigm shift from 2-dimensional cephalometric radiographs to 3- dimensional virtual analysis and treatment planning using cone-beam computed tomography (CBCT) [2]. Fabrication of splints using computer-aided design and computer-aided manufacturing (CAD/CAM) technology also aids maxillofacial surgery in positioning the osteotomized maxillofacial complex [2, 3].

Traditionally, orthognathic surgery involved conventional fixed braces on all teeth with metal bands on the first and second molars. Orthodontic treatment in preparation for surgery would involve taking a series of plaster casts at various treatment intervals to assess tooth alignment, arch coordination, and access post-surgical occlusion. With the advent of digital treatment planning, it is now possible to plan the tooth alignment and coordinate the dental arches using software that will simulate the surgical phase to access postsurgical occlusion.

In 1946 Kesling first introduced the concept of clear orthodontic appliances to move misaligned teeth [4]. Due to increased patient demand for more esthetic and comfortable orthodontic appliances. In 1999, Align Technology Inc. (San Jose, CA, USA) launched the Invisalign system [5]. The initial cases were minor crowding or spacing. Skeletal deformities and other severe dentoalveolar problems were initially listed as a contraindication by the Food and Drug Administration (FDA) [2, 6]. As the technology improved, with the development of material and computer design of tooth movement, the indication of clear aligners has been able to treat mild to severe malocclusions. CAT was gradually used for more complex cases like orthognathic surgery later the FDA ultimately changed these contraindications to precautions [2]. Now more patients are even seeking orthognathic surgery in conjugation with clear aligner therapy. Removable aligners can be changed by the patient, and subsequent splints may be delivered to their residence. This eliminates the need for regular orthodontic treatment to adjust the appliance. Azaripur et al. Recently, it has been reported that patients are more satisfied with Invisalign compared to fixed orthodontic appliances [7]. Kankam et al compared the outcomes in orthognathic surgery using clear aligners and fixed appliances and demonstrated that complex multiple jaw orthognathic procedures can be successfully performed in Invisalign patients [8].

In the “surgery first” approach after intraoral scanning of both arches, treatment planning was performed using clincheck software this helps the clinician not only to plan treatment but also to decide whether a candidate is ideal for this approach for treatment. Once planning is done utilizing software and computer-aided design/computer-assisted manufacturing (CAD/CAM) technology, the STL files may be exported, and a surgical stent may be fabricated for positioning the occlusion during surgery.

Steps in clear aligner therapy with orthognathic surgery include

• Data acquisition

• Diagnosis and treatment planning.

• Virtual surgical planning

• The presurgical phase of orthodontic treatment with clear aligners.

• Splint fabrication.

• Orthognathic surgery with temporary anchorage devices (TADs) for maxillomandibular fixation.

• Additional aligners to detail and refine the postsurgical occlusion.

• Retention.

This paper aims to discuss the treatment consideration for pre-surgical, surgical, and post-surgical orthodontics using CAT.

2. Data acquisition, diagnosis, and treatment planning

Orthodontic records are recommended for the proper diagnosis and treatment planning of proposed dental and surgical goals. Records obtained include intra-oral and extra-oral photographs, panoramic radiographs, lateral and posteroanterior cephalograms, an intraoral optical impression, and a cone-beam computed tomography scan.

The orthodontist performs preliminary treatment planning using a proprietary treatment outcome planning software by Align Technology, USA called ClinCheck. The Clincheck software has tools like tooth movement table, Bolton analysis, overjet, overbite prediction, and Arch width table which makes it easier for clinicians to predict the most possible clinical outcome that can be achieved with postsurgical orthodontic treatment and today with recent advancements in Clincheck with CBCT integration helps to analyze final root positioning and possible root collision during active treatment. Initial ClinCheck aims to include decompensatory movements which are based on the orthodontists’ diagnosis of the malocclusion and esthetic treatment objectives and related surgical goals. This software enables clinicians to plan each phase of the treatment and visualize both the dental and surgical outcomes digitally, which allows for effective treatment planning. It is also used to carefully evaluate the asymmetry of the dental arches, the occlusion, the curve of Wilson, and the curve of Spee using different projections.

The surgical goal after decompensation is visually represented in ClinCheck as a single stage of instantaneous arch coordination referred to as a bite jump.9 The ClinCheck will then be reviewed with the oral surgeon to mutually agree upon the goals based on the two VSP meetings for any given patient.

2.1 Virtual surgical planning

Visualization of proposed jaw movements and resulting facial soft tissue changes is critical to successful surgical planning. Proposed surgical procedures are tested by a multidisciplinary team before fabrication of the appliance thus ensuring a more practical and beneficial execution of the proposed therapeutic goals.

The first VSP session includes the Maxillomandibular repositioning based on the facial and dental occlusal goals incorporating the proposed bite jump, cephalometric norms, facial balance, airway considerations, and surgical feasibility is also taken into consideration. For the VSP sessions, 3D Systems (Rock Hill, SC) has been used for the fabrication of 3D-printed surgical splints. During this preliminary session, only the goals and feasibility of the proposed movements are examined, and the surgeon confirms or adds comments to modify the plan. The movements such as extraction vs. interproximal reduction (IPR), restoration of excess space, 1 vs. 2 step expansions, etc are then either modified or accepted [9]. The careful preplanning during the preliminary process ensures a more predictable way to achieve optimal occlusion and facial esthetics and no compromise is suffered. Once the presurgical orthodontic preparation is performed to achieve decompensation, a clear understanding is achieved of programming the final digital treatment plan or ClinCheck for clear aligner fabrication. The superimposition tool in this software is useful in evaluating the type of movements that have been made. The occlusion should be evaluated one stage before the final surgical jump to ensure that the presurgical treatment objectives have been achieved (Figure 1).

Figure 1.

Clincheck software showing the initial setup and proposed treatment stimulation.

The advantage of digital treatment planning is that the presurgical tooth movements can be planned precisely and the post-surgical occlusion may be visualized through the surgical simulation.

3. Presurgical clear aligner therapy

Presurgical treatment objectives include the following:

• Level and align the dental arches.

• Position teeth over the basal bone.

• Remove existing dental compensations.

• Maximize skeletal correction through orthognathic surgery.

3.1 Removing existing dental compensations

Most skeletal jaw discrepancies have some dental compensations that often camouflage the true degree of the underlying skeletal discrepancy. These dental compensations need to be removed before surgery as part of the orthodontic preparation to maximize the amount of skeletal correction. For example, In Class II skeletal malocclusions the maxillary anterior retrocline compensates for maxillary prognathism, and the mandibular incisors procline compensates for mandibular retrognathism. While in class III skeletal malocclusion the proclined maxillary anterior compensates for maxillary retrognathism and the retroclined mandibular incisor compensates for mandibular prognathism. Failure to remove these anterior incisor compensations pre-surgically will limit the surgical correction, leading to compromised facial esthetics and occlusion. Extraction patterns for surgical corrections of Class II malocclusions, involving the upper second premolars and the lower first premolars, whereas Class III malocclusions correction, the upper first premolars, and the lower second premolars are suggested in moderate to severe crowding cases. Other extraction patterns involve mandibular premolar in Class II case and maxillary premolar in Class II case, which temporarily increase the overjet and thus allow the jaw to move further forward. Removing dental compensations will usually result in an increased overjet in Class II cases before surgery. Additionally, there could be other factors such as crowding, protrusion, and vertical discrepancies such as a deep bite or anterior open bite present in the malocclusion that will need to be resolved. The first set of aligners tries to achieve decompensation.

Orthognathic surgery relies on a close collaboration between the surgeon and the orthodontist across all stages of treatment, from preoperative planning to the finalization of occlusion. The digital treatment plan must not be considered as the outcome but as a representation of a force system that aims to achieve a proposed result or outcome. Sometimes, tooth movements depicted in the Clincheck may have poor clinical predictability and need to be evaluated by the orthodontist. The reason is CAD technicians not being a dentist would wholly be dependent on the Treat software to prepare the ClinCheck [9]. Hence, the onus lies with the orthodontist and surgeon to properly review the digital treatment plan for proper staging of tooth movements, modifying attachment design, plan intentional virtual overcorrection, or incorporating auxiliary features like TADS or elastics to augment where needed force system mechanics and thereby delivering a customized appliance to each patient with more predictable clinical outcome.

3.2 Arch coordination

Arch coordination refers to the coordination of arch widths such that there is a normal transverse relationship. Often, dental compensation is seen in transverse relations so expansion or contraction of the arch to coordinate the upper and the lower arches should be carried out before the surgical procedure. In Class II skeletal discrepancy, where the maxillary arch is narrow may require expansion for the dental arches before mandibular advancement to provide post-surgical stable occlusal. Poor arch coordination, particularly in the transverse or vertical plane, will restrict jaw movements at the time of surgery and compromise postsurgical stability. For maximum possible dental arch development, attachments on the buccal surface to provide a push surface for engagement of a counter moment to seat the buccal cusp occlusally need to be considered. This attachment is provided as a G8 feature in the Invisalign system [9]. Otherwise, the buccal cusps may intrude, causing a posterior open bite as a side effect of the forced arch development when posterior teeth are not properly anchored within the aligner leading to challenging finishing issues after surgery.

When planning a 3-piece maxillary surgery, attention should be paid to open space usually distal to the maxillary lateral incisors, and to diverge the roots of the canines and lateral incisors for osteotomy. Attachments specific for root movement (i.e., long vertical or twin attachments) should be placed to provide the proper push surfaces to facilitate the moments needed for the desired movement. Postsurgical detailing focuses should consider moving the roots back toward each other for parallel refinement [9].

3.3 Curve of Spee

The curve of Spee is frequently leveled before surgery when preparing a patient for orthognathic surgery with clear aligners. This enables software simulation to precisely depict the occlusion after surgery. In the postsurgical simulated occlusion, incomplete leveling of the Spee curve before surgery will result in premature incisor contact and a buccal open bite. Buttons and elastics for mandibular posterior extrusion may be added after surgery to complete leveling the curve of Spee. To level, the curve of Spee in deep overbites, movements should be overtreated virtually mostly due to inadequate clinical presentation of movements such as anterior intrusion in clear aligners. Postoperative Spee correction is considered more beneficial for some patients when there is a desire to increase the posterior height of the face [9, 10].

3.4 Dental midlines

When there is a dental midline discrepancy it is important to determine whether it is due to a skeletal or dental component or a reflection of maxillary or mandibular asymmetry. When dental midlines are not coincident in the presurgical occlusion, it is important to determine where the dental midlines are located in the facial midline. Often there is a component of skeletal asymmetry present. If the midline discrepancy is due to a dental component, it can be corrected orthodontically before surgery. whereas if the midline deviation is skeletal, it should be corrected surgically rather than through dental tooth movement.

3.5 Spacing

In cases like Class II malocclusion, if anterior Bolton discrepancy is present due to the peg lateral incisor this may be left unclosed before surgery. As these spaces allow the oral surgeon more flexibility in setting the mandible anteriorly and overcorrection, if necessary, thus eliminating tight anterior coupling in the postsurgical occlusion and permitting the occlusion to a cusp-to-fossa relationship after surgery [11]. To correct any further tooth size discrepancy, these spaces may be closed in the post-surgical using the extra aligner phase with or without concurrent interproximal reduction (IPR).

3.6 Class II Presurgical tooth movements

3.6.1 Maxillary arch

Clear aligners work well for maxillary incisor intrusion before orthognathic surgery in cases of vertical maxillary excess or excessive gingival display. If the maxillary incisor intrusion is successful in giving the patient a more esthetic smile by decreasing gingival display, this may eliminate the need for a maxillary jaw procedure. In the case of maxillary occlusal plane cant, the cant must be corrected surgically via a maxillary surgical procedure or dentally via selective anterior intrusion. TADs can be used to improve the anchorage for selective anterior intrusion. In Class II, division 2 cases where the maxillary incisors are retroclined, the power ridge feature can be used to procline incisors. This should also assist in correcting the deep bite before the simulated surgery.

The narrow maxillary arch will need to be expanded in the presurgical phase so that arch coordination can be achieved after the mandibular advancement. Adequate buccal root torque in the maxillary posterior molars to require to prevent contact of the lingual cusps of the maxillary molars with the mandibular molars. This issue should be considered in the clincheck planning stage by ensuring that the appropriate vestibular root moment is incorporated into the finishing occlusion on the first and second molars [11].

3.6.2 Mandibular arch

In Class II malocclusion mandibular incisors are usually proclined. The presurgical treatment goals will involve achieving normal incisor mandibular plane angle (IMPA) before surgery. Sometimes there may be concurrent mandibular arch crowding present, some mandibular IPR would be beneficial for crowding resolution as well as to achieve normal incisal inclination. If there is severe crowding in the mandibular arch, extractions may be considered.

Before surgery, the Curve of Spee in the mandibular arch should be flattened. This can be through either mandibular incisor intrusion with or without mandibular premolar extrusion. For patients with a brachyfacial skeletal pattern (i.e., a short face) with a low mandibular plane angle, to level the Curve of Spee it would be desirable to extrude mandibular premolar extrusion. The intrusion of the mandibular incisor is preferred to level the Curve of Spee in a dolichofacial skeletal pattern (i.e., a long face) with a steep mandibular plane angle, as posterior extrusion may be undesirable for this type of facial pattern [11].

3.7 Class III presurgical tooth movements

In Class III cases, maxillary incisor extrusion is often required to achieve adequate overbite in the postsurgical occlusion. The proclined maxillary incisors and retroclined mandibular incisors should be corrected. To correct the axial inclination of the mandibular incisor, the power ridge feature may be used to effect lingual root torque. As a result of removing dental compensations, the negative overjet in a Class III skeletal malocclusion will be increased before surgery. This maximizes the amount of skeletal correction achieved through surgery if there is crowding, it can be resolved IPR or extractions can be performed, and also the correct axial inclination of teeth. This assists in removing dental compensations before surgery. When there is a component of mandibular asymmetry with midline deviation, it is important to align the teeth and ensures that the asymmetry will be corrected surgically.

4. Post-presurgical decompensation

Using a passive aligner for at least two months before surgery is recommended. This is either a series of aligners created for the last active stage of the presurgical treatment plan or a stiffer retainer (0.040-in thermoformed retainer) ordered for this final stage [9]. Hence, the use of the word passive is misleading as there will be an expression of lag of many movements within the aligner. Prolonged use of these aligners allows for further expression of important decompensatory movements such as leveling of the curves of Wilson and Spee. This helps to reduce occlusal inferences when coordinating the arches at the time of surgery. Once proper decompensation has been achieved, the final presurgical VSP is then performed. This allows for the confirmation of surgical movements and the fabrication of 3D-printed surgical splints.

The preferred protocol post-surgery to prevent any challenge for the patient in removing the aligners due to the limited range of mouth opening is to remove attachments and in place of attachments place button cutouts for bonding buttons. This protocol allows for simplified bonding of buttons post-surgery as no intervention will be needed to remove the composite, which can be challenging with the limited range of mouth opening for most patients after surgery [9]. These elastic buttons are not bonded before surgery as it may lead to accidental breakage and loss of button at the time of surgery. Before surgery, the patient presents with no elastic buttons, brackets, wires, or hardware placed prior. During surgery two temporary anchorage devices are placed on each quadrant to be used for intermaxillary fixation of segments at the time of surgery for 6 weeks. It is recommended that the TSADs be placed mesial of the first molars and distal of the canines. Placing TSADs mesial to the canines increases the risk for gingival irritation from elastic wear after surgery as the elastics will cross the curvature of the arch-form and create tissue impingement.

5. Intraoperative management of osteotomies on patients with CAT

In absence of orthodontic brackets with surgical hooks, the ability to apply temporary maxillo-mandibular fixation (MMF) is difficult [12, 13].

The available options for temporary MMF include:

• Erich arch bars and Ivy loops.

• Screw-retained arch bars.

• Temporary orthodontic anchor devices (TADs).

• Maxillomandibular fixation (MMF) screws.

• Bonding prefabricated buttons to all or specific teeth (Figure 2).

• Bonding of full fixed orthodontic appliances one month before surgery.

• SMARTLock Hybrid Maxillomandibular Fixation System (Stryker, Kalamazoo, MI) [14].

• Clear Aligner Orthognathic Splint (CAOS).

Figure 2.

Elastics attached to bonded buttons.

The use of Erich arch bars or fixing screws is also not recommended because of gingival injury and the difficulties of maintaining good oral hygiene. The large MMF screws may cause severe mucosal irritations over 2–3 weeks. These are cumbersome and uncomfortable for patients to wear over periods [13].

The placement of orthodontic TADs is currently the most used approach and, at least 8 orthodontic TADs are inserted bilaterally, distributed equally per arch. (Figure 3) Smaller orthodontic TADs provide a better profile, are easier to clean, and are less irritating to mucous membranes. In addition, if TADs are damaged or loose during the perioperative period, they are simple to replace under local anesthesia. These TADs support not only perioperative fixation but also postoperative fixation of elastomers. Finally, bonding orthodontic brackets is a quick and easy way to create a temporary MMF.

Figure 3.

Temporary anchorage device.

Another approach involves bonding orthodontic brackets which is a quick and simple method for achieving temporary MMF. A minimum of 6 brackets should be bonded at the cementoenamel junction (CEJ) to the central incisors and canines and first molars of each arch [13]. The brackets placed at their ideal facial positions are more prone to breakage and this effect is minimized when the brackets or buttons are placed as apically as possible.

5.1 Clear aligner orthognathic splint (CAOS)

CAOS is intended to be used on patients without any fixed orthodontic brackets, bands, or buttons. Attachments must be removed from the dentition, and the tray’s design engages the dentition’s undercuts. It begins with the digitization of the patient’s dentition and skeletal structures using an intraoral scanner and CT or CBCT, respectively. The CAD/CAM manufacturer matches the digitized dentition’s occlusal surfaces to the CT or CBCT data. Then, virtual surgical planning is completed with the occlusion preferably digitally, although elastomeric or wax registration material also can be used. CAOS seats the full crown of all the teeth in each arch and the opposite arch can be positioned by seating into the tray on the underside of CAOS or positioned against intended cusps tips. At the end of virtual planning, the splints and guide determinations are reviewed. The design of the CAOS should include a full crown-covered acrylic shell for the dentition [2]. Benefits include accurate and precise dental seating, rigid IMF fixation for intraoperative placement, and easy fabrication with any digital planning manufacturer (Figure 4).

Figure 4.

Clear Aligner Orthognathic Splint.

CAOS does two things:

• Position the osteotomized jaw according to your virtual plan.

• Provide for maxillomandibular fixation.

6. Postoperative management of patients with CAT

Immediately after Orthognathic surgery is completed, post-operative oral maintenance can be difficult for the patient to manage because of the difficulty in removing the aligners as well as keeping adequate dental hygiene. Patients are seen by the orthodontist within two weeks to confirm the correct usage of TSAD elastics, and then every two to three weeks to continue to check healing and elastic use [8]. Because TSADs are generally inserted in the mucosa for surgical patients, the usage of elastics from TSADs is limited to 6 weeks only. This is due to the greater risk of patient pain from possible gingival irritation. Depending on the pre-surgical malocclusion, several interarch elastic configurations are employed, such as class II, class III, or box elastics (Figure 5).

Figure 5.

Class II interarch elastics attached to bonded buttons.

One month after surgery, physical treatment is started to relax the muscles and improve the mandibular range of motion. Usually, in the 8-week, a refinement scan is taken for the fabrication of additional aligners when needed for detailing postsurgical occlusion [9]. An alternative protocol would be to scan the patient before surgery after they have been fully decompensated. This ensures additional aligners are delivered as soon as possible after post-surgery to immediately facilitate any perceived needed finishing and detailing. In theory, this has the advantage of the initiated regional acceleratory phenomenon from surgery more readily. Refinement aligners are mandatory for segmental maxillary surgery cases due to inherent changes in the arch form. During the refinement scan appointment, the orthodontist and surgeon should undertake clinical virtual planning before the final aligners are supplied to the patient [13].

7. Retention and stability

When orthodontic treatment is completed, the patient will be placed into retention. Clear aligners can make for excellent retainers when worn properly with or without a mandibular lingual bonded retainer from canine to canine, depending on the initial malocclusion. However, with maxillary expansion, Hawley retainers, or clear vacuum formed retainer with full palatal coverage (Essix retainers), for more rigid retention of transverse correction.

When compared to traditional orthodontic appliances, clear aligners showed no significant change in stability or occlusal characteristics [15, 16]. When the combination of clear aligners and orthognathic surgery was evaluated for post-operative stability, the results were comparable to traditional surgery [16].

8. Conclusion

For individuals with cosmetic issues, orthognathic surgery with Clear aligners is an effective treatment choice. When clear aligners are used to aid in orthognathic surgical repair of skeletal malocclusions, there are several benefits for both the patient and the treating practitioner. Most adult patients, particularly those who have previously worn braces and who will need to wear permanent equipment throughout the process, will benefit from Orthognathic therapy. The introduction of Clear aligners as a treatment option has made this process more manageable. Furthermore, clear aligners make it easier to maintain good dental hygiene during treatment, especially just after surgery, than Fixed orthodontic appliances. Logistically, treating patients with clear aligners requires fewer appointments and less overall chair time, allowing for more convenience throughout the treatment process, particularly in COVID circumstances. Furthermore, because of the undetectable orthodontic treatment, patient satisfaction was extremely high, and his Furthermore, patient satisfaction was recorded as very high due to the invisible orthodontic treatment, and, above all, occlusion can be effectively restored.

Conflict of interest

“The authors declare no conflict of interest.

Acronyms and abbreviations

CAD/CAM

Computer-Aided Design and Computer-Aided Manufacturing

FDA

Food and Drug Administration

CAT

Clear Aligner Therapy

TADs

Temporary Anchorage Devices

OGS

Orthognathic Surgery

TSADs

Temporary Skeletal Anchorage Devices

MMF

Maxillomandibular Fixation

CAOS

Clear Aligner Orthognathic Splint

CT

Computerized Tomography

CBCT

Cone-Beam Computed Tomography