Presurgical orthodontic decompensation with clear aligners

Historically, dental malocclusion was promptly treated with the help of analogue fixtures like fixed appliances. However, sometimes, the malocclusion would be so severe that it could not be corrected with orthodontics alone. As if on cue, orthognathic surgery made its way into orthodontic treatments, especially where indicated to enhance and alleviate malocclusion and dental crowding. One of the first published cases of orthognathic surgery was the one reported by Dr Simon P. Hullihen dating back to 1849.

Orthognathic surgery or corrective jaw surgery, as we know it today is a surgical treatment designated to correct deformities of the jaw and lower face related to skeletal disharmonies and orthodontic dental bite problems. The most successful outcomes in modern orthognathic surgery arise from the harmonious collaboration between the oral surgeon and the orthodontist across all stages of treatment, beginning from preoperative planning to the finalization of occlusion.

How is orthognathic surgery performed?

Typically performed via the mouth, orthognathic surgery is done when the jaws do not align correctly. In simpler words, it is performed by cutting the jaw bone, then moving and modifying it to realign with the correct or desired occlusion.

Once a patient is diagnosed with a dentofacial deformity and is confirmed to merit a surgical correction, a comprehensive evaluation is done by the surgeon and orthodontist. All available medical and dental records of the patient are examined and an appropriate treatment plan is put into place.

Contrary to popular belief, orthognathic surgery is not a single event. Instead, it is a process that includes orthodontic treatment to prepare teeth for surgery, the surgery itself, recovering from said surgery, and additional orthodontic treatment for up to a year after the surgery.

1. In the preoperative orthodontic phase, levelling and alignment of teeth are of primary importance. The dentist will focus on correcting dental compensation, establishing proper incisor inclination and transverse arch width, and maintaining the dental midline. By definition, presurgical orthodontic decompensation is the opposite movement of dentoalveolar compensation. The orthodontist by means of orthodontic treatment accentuates the patient’s deformity to place the teeth in the correct position so that the jaws will have aligned.
2. Next, the surgical portion of orthognathic surgery may include maxillary or mandibular surgery or both. Sometimes, conjunctive intranasal surgery with septoplasty and reduction of the inferior turbinate may be required to improve nasal airflow.
3. Postoperative orthodontic treatment begins soon after the surgery and the healing phase is complete. It typically starts 4 to 6 weeks after the operation. Any remaining detailing of occlusion will be completed by the orthodontist, which is then followed by a post-orthodontic retention phase.

All in all, the jaw surgery process can take between two and three years.

Now that we are caught up to a general overview of orthognathic surgery, we look into this study that evaluates the efficacy of clear aligners in the presurgical orthodontic phase of orthognathic surgery.

This study was published in the American Journal of Orthodontics.

Presurgical orthodontic decompensation with clear aligners.

Cong A, Ruellas ACO, Tai SK, Loh CT, Barkley M, Yatabe M, Caminiti M, Massaro C, Bianchi J, Deleat-Besson R, Le C, Prieto JC, Al Turkestani NN, Cevidanes L.

Am J Orthod Dentofacial Orthop. 2022 Oct;162(4):538-553. doi: 10.1016/j.ajodo.2021.12.019.

What they asked

They aimed:

“To evaluate the accuracy of tooth movements with clear aligners during presurgical orthodontics using novel 3-dimensional superimposition techniques.”

What they did

They included a sample with:

• Participants: 20 participants who had completed presurgical orthodontics using Invisalign® clear aligners.

They analysed initial (pretreatment) digital dental models, presurgical digital dental models, and ClinCheck prediction models. Presurgical models were superimposed onto initial ones using stable anatomic landmarks; ClinCheck models were superimposed onto presurgical models using surface best-fit superimposition.

A total of 545 teeth were measured for 3 angular movements (buccolingual torque, mesiodistal tip, and rotation) and 4 linear movements (buccolingual, mesiodistal, vertical, and total scalar displacement). They then compared the predicted tooth movement with the achieved amount for each movement and tooth, using both percentage accuracy and numerical difference.

What they found out

They acquired an average percentage accuracy (63.4% ± 11.5%) higher than in previously reported literature.

The most accurate tooth movements they found were buccal torque and mesial displacement as compared with lingual torque and distal displacement, particularly for mandibular posterior teeth.

They reported this finding: “Clinically significant inaccuracies were found for the buccal displacement of maxillary second molars, lingual displacement of all molars, intrusion of mandibular second molars, the distal tip of molars, second premolars, and mandibular first premolars, buccal torque of maxillary central and lateral incisors, and lingual torque of premolars and molars.”

What we can conclude

What we learn from this study is that superimposition techniques for presurgical orthodontic decompensation can be used to lay the groundwork for future studies, especially when analysing advanced clear aligner patients. Invisalign® clear aligners being a reliable orthodontic treatment modality may also be used for presurgical orthodontics where the tooth movements are highly accurate as compared to the simulated and clinically achieved movements.