17: Surgery first with aligner therapy
Flavio Uribe, Ravindra Nanda
Historic background
The treatment of moderate to severe dentofacial deformity is usually addressed by means of orthognathic surgery. The objectives of orthognathic surgery are to accomplish adequate facial esthetics while achieving a functional occlusion. The occlusal relationship serves as a guide for the skeletal movements and therefore is an important element in orthognathic surgery. Fixed orthodontic appliances in the presurgical phase have historically been used to prepare the dentition for the skeletal movements and to fine-tune the occlusion after orthognathic surgery. Specifically, labial fixed appliances in the presurgical phase eliminate dental compensations and prepare the arches for surgery. Bonded orthodontic brackets on the labial surfaces of the teeth and wires are the orthodontic appliances of choice by clinicians in orthognathic surgery as treatment complexity is high in these patients.
Clear aligner therapy (CAT), with Invisalign (Align Technologies, San Jose, CA, USA) at the forefront, has become a treatment modality in orthodontics that has gained acceptance by practitioners after the significant improvements in the appliance over the last few years. More complex malocclusions have been able to be treated with this appliance with the addition of attachments that optimize tooth movements. An example of more complex approaches with the Invisalign appliance is evident in its use in tandem with orthognathic surgery instead of the conventional labial fixed appliances.
Orthognathic surgery in conjunction with the Invisalign appliance is well accepted by patients with dentofacial deformity for two main reasons. First, most of these patients are usually adults who understandably favor the inconspicuousness of clear aligners over fixed labial appliances. Second, often patients undergoing orthognathic surgery have received orthodontic treatment with fixed appliances during their early teenage years. This treatment has usually been long as the orthodontic therapy may have tried to camouflage the effects of abnormal growth. The net effect is a burnout of the patient who does not want to receive any more orthodontic therapy.
Orthognathic surgery has three specific stages, which include a presurgical orthodontic phase, the surgical procedure, and a postsurgical orthodontic finishing phase. The incorporation of Invisalign in orthognathic surgery can be accomplished in different ways, depending on which stage of treatment it will be used and the type surgical approach (surgery first or conventional approach). For example, one of the approaches is to limit the Invisalign appliance to the presurgical phase. Typically this phase is the longest in orthognathic surgery, lasting approximately from 12 to 25 months.1,2 Therefore if patients receive CAT on the presurgical phase, fixed appliances will be only used for a short period of time during the postsurgical phase. This approach is often preferred since the labial fixed appliances used in the postsurgical phase typically have better finishing control of the occlusion. The labial orthodontic appliances are placed just before surgery, thereby facilitating the conventional approach during surgery that ties the interocclusal surgical splint to the orthodontic bonded appliances, required for fixation of the proximal and distal bone segments after the osteotomies. The second approach uses the Invisalign system for both pre- and postsurgical phases, with no fixed labial appliances, which has the challenge of limited areas available to securely tie the surgical splint for maxillary and mandibular fixation.
Although clinicians are using Invisalign in conjunction with orthognathic surgery, no studies have been conducted evaluating the outcomes with this approach. In fact, most of the published literature has been in the form of case reports. The first report of this approach was published in 2005 using Invisalign in combination to orthognathic surgery.3 The treatment of two patients was described in which Invisalign was used for the presurgical phase of aligning and leveling the arches. Segmental fixed appliances were also used as adjuncts to the clear aligners to derotate some teeth, since at that point in time the Invisalign appliance had not developed the optimized attachments that facilitated these corrections. Fixed appliances were placed just before the surgical procedure and maintained through the postsurgical detailing phase. The total treatment time for one patient was 44 months (20 months for the presurgical phase with Invisalign) and 31 months for the other (27 months for the presurgical phase with Invisalign). The reason for one of the patients having undergone almost 4 years of treatment was attributed to insurance approval and scheduling the surgery date. Additionally, the patients were changing aligners every 2 weeks. Finally, the author suggested that in patients with single jaw surgery, fixed appliances would not be necessary, being managed fully with the Invisalign appliance.
In 2008, Womack and Day4 reported on another patient treated with Invisalign and orthognathic surgery who had class II malocclusion and sleep apnea. In this report, bimaxillary advancement with a two-piece-maxilla for transverse correction was executed. Both the pre- and postsurgical phases were completed with the Invisalign appliance. The duration of the presurgical phase was 8 months for this patient. The fixation during surgery of the maxilla and the mandible after the osteotomies was achieved by means of archbars tied to the splint. Since the maxilla was split for transverse expansion, a soft tissue splint was placed during surgery and left for 6 weeks for stabilization of the two maxillary halves. After the surgical procedure, polyvinyl siloxane (PVS) impressions were taken for refinement of the occlusion, which took another 6 months of treatment. The total treatment time was 22 months, which included a period in which the patient was not seen due to unavailability related to a work schedule. During this finishing phase, buttons were bonded to the posterior teeth to settle the occlusion with elastics.
Mancuzzi et al.5 in 2010 reported on the treatment of a patient who had multiple missing teeth and class III malocclusion who underwent orthognathic surgery with Invisalign. Both pre- and postsurgical phases were performed with the Invisalign appliance. The presurgical phase lasted 6 months. For the fixation of the maxilla and mandible into their new positions, buttons were bonded to the labial surfaces of the majority of the posterior teeth. The authors maintained the patient on the splint for 4 weeks after surgery and then delivered a dynamic functional positioner for 3 months. Some ceramic brackets were bonded to help with the seating of the occlusion. The total treatment time was 10 months.
Pagani et al.6 in 2016 reported on another patient with a class III malocclusion treated with Invisalign in the pre- and postsurgical phases. A total of 10 months was the duration of the presurgical alignment phase. The day before surgery, fixed appliances were bonded, which were removed 1 month after surgery. The total duration of treatment was 12 months.
Splint-aided maxillary and mandibular fixation without labial fixed appliances
When labial fixed orthodontic appliances are not present, the stabilization of the surgical splint after the osteotomies can be troublesome. The maxilla and mandible need to be securely tied to the surgical splint to ensure proper referencing the jaws to each other to achieve the planned outcome after surgery. The surgical splint transfers the information of the virtual three-dimensional (3D) plan to guide the free osteotomized segment to a stable reference skeletal region. The splint must be tied to the dentition or denture bases to reference maxilla and mandible to each other. The connection of the splint to the teeth is usually facilitated when orthodontic appliances are bonded to the labial surfaces of the teeth. With Invisalign there are no labial appliances to enable this connection (Fig. 17.1). Different approaches have been described in the literature to overcome this problem.7 Archbars used for maxillary and mandibular fracture fixation are one of the earliest adopted approaches. The problem with this approach is it is time consuming, thereby extending the duration of time the patient is under anesthesia, which increases the risks of the surgical procedure. Another approach is to bond multiple buttons on the labial surfaces of teeth, specifically to be used for the surgical procedure. This was reported by Hong et al.8 when using lingual orthodontic appliances in orthognathic surgery. However, since no archwires are present connecting the bonded buttons, bonding failure could occur during the operation while the jaws are being tractioned to seat them into the splint. Furthermore, the breakage of one of these attached buttons may end up entrapped in the mucoperiosteal flaps, causing a significant complication to the surgical procedure.
With the advent of miniscrews in orthodontics, the connection of the dentition to the surgical splint has been facilitated. This was reported by Paik et al.9 who added two miniscrews in each of the quadrants, mesial to the first molars and premolars. These miniscrews are used to secure the splint tightly to the teeth and can be used after surgery to support the use of intermaxillary elastics to keep the teeth in the postsurgical planned occlusion. A more complex setup that connects the miniscrews through a bar framework is commercially available.7 The Smartlock hybrid MMF from Stryker (Kalamazoo, MI, USA) and the MatrixWAVE MMF from Depuy Synthes Craniomaxillofacial (West Chester, PA, USA) are similar bone-supported archbars to be used during surgery. This framework is secured to the labial alveolar bone of the dentition through four to six miniscrews per arch. The main advantage of these two products over an approach that uses only the miniscrews is that more locations are available to connect the surgical splint to the maxilla and mandible through ligatures. This may facilitate more tight adaptation of the osteotomized segments into the surgical splint. Typically, the mesh (including the miniscrews) is removed after the osteotomized maxilla and mandible are secured with hardware, which has the drawback that intermaxillary elastic wear in the postsurgical stage will require to be delivered from the teeth, which could have an unfavorable extrusive effect on the specific teeth from which the elastics are being worn.
Transitioning into and out of surgery with clear aligners
As mentioned, the major difference in the execution of surgery in patients with CAT is the absence of labial fixed orthodontic appliances typically necessary for securing the surgical splint. These patients are typically wearing a series of sequential aligners as part of the presurgical phase and will transition to the aligners in the postsurgical phase to complete orthodontic treatment. If the patient is wearing aligners in the presurgical phase, the surgical plan will consist of maxillomandibular movements that will achieve a result close to the final idealized occlusion. Prior to surgery, a scan or impression is taken to plan the tooth movements after surgery to detail the occlusion, which will be used for fabrication of the aligners. An alternative is to take this scan or PVS impression after surgery. However, the acquisition of a scan or impression after surgery is somewhat difficult due the limited mouth opening observed during the first 2 months after surgery. Therefore taking the scan prior to surgery may be advocated to be able to start wearing the aligners soon after surgery (approximately 2 weeks after). Although this approach may expedite treatment there still may be a slight unpredictability in the planned occlusion, and the actual postsurgical occlusion if different may require different movements than originally planned. However, since the teeth would be usually well aligned after the presurgical phase, any inaccuracies between the planned and the obtained occlusion can be managed with intermaxillary elastics.
On the other hand, the predictability of the planned final occlusal outcome for the fabrication of the postsurgical aligners could be more difficult in patients where the maxilla will require segmentation in two or more pieces. In these situations it is still possible that the presurgical dental models could be segmented to the planned outcome, and a scan of this model could be used for the fabrication of the surgical splint and the postsurgical aligners. However, it is better recommended to take the scan or impressions after the surgery to ensure a more precise fit of the aligners, especially if the segmentation is more that two pieces.
Another important consideration when segmenting the maxilla is that the patient typically will have to maintain the splint after surgery for 4 to 6 weeks prior to resuming orthodontic movements. A splint covering the incisal and occlusal surfaces of the teeth is bulky and cumbersome for a patient in recovery after surgery. A splint not covering the occlusal surfaces is typically recommended for the postsurgical phase prior to resuming the new aligners (Fig. 17.2).
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