of Facial Asymmetry Using Clear Aligners

Tarek El-Bialy, Donna Galante, Sam Daher

Faculty of Medicine and Dentistry 7-020D Katz Group Centre for Pharmacy and Health Research University of Alberta, Edmonton, Alberta T6G 2E, Canada

Abstract

There are many etiological factors that could be attributed to facial skeletal asymmetry, including but not limited to hemifacial microsomia, unilateral temporomandibular joint ankylosis especially in growing patients or hypertrophic condyle on one side due to local tumor. Functional facial asymmetry could be attributed to bilateral constricted maxilla and the patient shifts his/her mandible to one side to achieve a comfortable occlusion on one side, or it could be due to dental interference, which mainly occurs due to one tooth in cross bite, usually upper lateral incisor. In this case, treatment is recommended as soon as possible especially in growing subjects to eliminate dental interference or to expand the maxilla so that no possible remodeling can happen in both TMJ fossae and possible need for surgical intervention later in life to fix jaw asymmetry. This chapter will discuss in details careful diagnosis of a case with facial asymmetry to simplify treatment planning.

Keywords: CBCT, Chin deviation, Crossbite, Elastics, Facial symmetry, Functional shift, Root movement, Stability, Tipping, Tomogrms.


* Corresponding author Tarek El-Bialy: Faculty of Medicine and Dentistry 7-020D Katz Group Centre for Pharmacy and Health Research University of Alberta, Edmonton, Alberta T6G 2E, Canada; E-mail: telbialy@ualberta.ca.

Introduction

Lateral mandibular functional shift in the mixed dentition has been recommended to be treated as early as possible to eliminate possible permanent changes in the TMJ and fossa [19]. It has been reported that in growing children with lateral functional shift due to bilateral maxillary constriction or due to dental interference, treatment of unilateral cross bite can lead to self-correction of the lateral shift and this treatment and correction of condylar position in the glenoid fossa that may minimizing the need for orthognathic surgical correction in the future [4, 7, 8]. Tomograms confirm abnormal condylar position in both sides in cases with functional mandibular shift [4, 7, 8]. Another study showed that

unilateral posterior crossbite can lead to asymmetric mandibular ramus height [6]. This study however is questionable as they used panoramic radiograph in assessing ramal height. Panoramic radiographs are known to have measurement errors due to the inherited magnification errors. Tomograms seem to be the best method of confirming mandibular condylar position before and after treatment.

Treatment of unilateral posterior crossbite may be performed using palatal expansion appliances (either removable or fixed), full fixed appliances with coordinated upper and lower archwires and/or crossbite elastics [10]. This chapter will show that functional mandibular shift once diagnosed and confirmed, can be treated as simple as removable appliance may be used to treat similar cases.

Case Presentation

This is a 39 years old female who presented to our clinic with a chief complaint that her dentist is referring her for comprehensive orthodontic treatment and surgical correction of her facial asymmetry. History revealed that the patient had no medical concern and she was initially interested in Invisalign treatment as fixed orthodontic braces were too challenging for her. However, her dentist who is an Invisalign provider convinced her that she is not a candidate for Invisalign treatment due to the high likelihood of surgical intervention and she better have comprehensive orthodontic treatment by an orthodontist and jaw surgery by an oral and maxillofacial surgeon. Clinical records (Fig. 10.1) revealed that the patient had a balanced face with chin deviated to the patient’s right side. Intraoral photographs show that the patient has cross bite of upper right lateral incisor and right buccal segment. Usually, cases with unilateral posterior cross bites develop facial asymmetry especially when the unilateral cross bite leads to lateral mandibular shift. In growing children, it is believed that fixing unilateral cross bite would lead to self-correction of the lateral shift and the possibility of minimizing the potential for the need of surgical intervention when the patient grows up beyond adulthood.

To confirm if the patient had skeletal asymmetry or functional shift, tomograms would be required. The advantage of CBCT is that tomograms are simply generated. Evaluation of the patient’s initial CBCT generated tomograms (Fig. 10.2) confirmed the functional shift.

Fig. (10.1))
Initial clinical records of the patient with facial asymmetry. CBCT generated frontal cephalometric radiograph showing shift of the chin to the patient’s right side.

Fig. (10.2))
Initial tomograms showing functional shift as the right side condyle of the patient has a posterior shift, while left condyle showing forward shift. The shifts are confirmed by comparing anterior and posterior disk spaces on each side.

Lateral cephalometric analysis showed a balanced cephalometric values (Table 10.1) while frontal cephalometric analysis showed chin deviation to the patient’s right side. CBCT sagittal screen shows lingual tipping of the crowns as posterior teeth in cross bite and the roots are almost out of the buccal plate of bone.

Treatment Objectives

In order to correct the patient’s facial asymmetry, it would be easy to perform by fixing the unilateral posterior cross bite that would be needed to be corrected by uncontrolled tipping. Uncontrolled tipping is required in this case to move the crowns of the upper right posterior teeth buccally and the roots palatally. This palatal root movement is required to move the roots back into maxillary alveolar cancellous bone. It was hypothesized that eliminating dental interference due to the cross bite of the upper right lateral incisor would eliminate the functional shift and consequently correct the patient’s facial asymmetry.

Fig. (10.3))
Buttons were inserted for cross bite elastics and occlusal attachments on lower right first and second molars to eliminate occlusal interference can be seen (top right photo). It also can be seen that the patient’s midlines are now coordinated.

Treatment Plan

Treatment planning included clear aligners and cross bite elastics from lower first molar on the buccal surface to the palatal surface of the upper first molar and right premolars. In order to facilitate treatment, occlusal bite clearance attachments were prescribed on the lower right first and second molars (Fig. 10.3). Patient was fitted with 19 aligners. From day one, cross bite elastics (3/16” that produce 3.5 ounces of force) were recommended and the patient was instructed to wear these elastics every day all the time when the aligners were worn.

Treatment Progress

At stage 7 out of 19, patients midlines were already corrected, patient’s facial asymmetry was improved and patient’s right posterior cross bite was improved. Figure 64 compares before and stage 7 progresses. After 6 months, (total 19 trays with no refinement), the patient was completely finished treatment with cross bite improved and facial asymmetry improved (Fig. 10.4).

Fig. (10.4))
Comparison before and after stage 7/19.

Patient was informed by her dentist that upper right lateral incisor, although cross bite was improved, it doesn’t have adequate torque (Fig. 10.5). When the patient presented with this concern, the patient was informed that there is no enough labial bone to move the root of that lateral incisor labialy to provide adequate torque and option of bone graft was presented. Patient understood the option and declined periodontal surgery.

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May 6, 2017 | Posted by in Orthodontics | Comments Off on of Facial Asymmetry Using Clear Aligners
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