Orthodontic Treatment Using Invisalign First® in Pediatric Patients with Mild Skeletal Malocclusion: Case Reports
Article information
Trans Abstract
This case report explores the orthodontic treatment of pediatric patients with mild skeletal malocclusion using Invisalign First®. Two cases are presented: (1) a patient with upper incisor protrusion, deep bite, and skeletal Class II malocclusion; and (2) a patient with dental crowding and skeletal Class III malocclusion. Their treatment demonstrated the efficacy of Invisalign First® in achieving arch expansion, tooth alignment, space creation for erupting teeth, and skeletal malocclusion correction. The overall results were satisfactory; however, limitations in rotational and intrusive movements, as well as skeletal improvements, were observed. Careful treatment planning, including overcorrection and patient selection, is essential for achieving optimal outcomes.
Introduction
In the treatment of skeletal malocclusion in pediatric patients, Class III malocclusions have traditionally been managed using rapid palatal expanders, facemasks, Frankel appliances, and others [1,2]. These devices are effective in controlling skeletal growth but can be uncomfortable to wear and may cause inconvenience in daily life [3,4]. Similarly, appliances such as Hotz and headgear have been used for Class II malocclusions, which can cause significant discomfort and make it challenging to align individual teeth during use [5,6].
In recent decades, with advancements in orthodontic technology and materials, clear aligners have gained considerable attention, particularly as an aesthetically pleasing and comfortable treatment option [7]. The use of clear aligners has been increasing among mixed dentition and a growing number of patients, largely because patients and guardians increasingly prefer non-invasive and aesthetically superior treatment options [8,9]. Clear aligners have primarily been used to manage mild to moderate dental malocclusions; however, their efficacy in treating skeletal malocclusions remains debatable [10].
Clear aligners offer aesthetic benefits, improved maintenance of oral hygiene, and better comfort than fixed appliances [11,12]. However, research on their ability to induce skeletal changes is limited. Therefore, it is important to assess the effectiveness of clear aligners in the management of skeletal malocclusion in growing patients.
This case report describes the treatment of two pediatric patients with mild skeletal malocclusions using clear aligners. It evaluates the impact of clear aligners on dental alignment and skeletal improvement, as well as the overall effects on facial aesthetics and patient satisfaction. Through this analysis, we aimed to identify the advantages and limitations of clear aligners for the treatment of skeletal malocclusion in pediatric patients.
Case Reports
The publication of these case reports and any additional photographs received approval through written consent from the patients’ legal guardians.
1. Case 1
A 10-year-old boy presented with a protrusion of the maxillary anterior teeth. Upon clinical intraoral examination and model analysis, he exhibited a significant vertical and horizontal overbite (overbite [OB] 5.0 mm, overjet [OJ] 6.5 mm), with a proclined maxillary and mandibular anterior segment (Fig. 1). He presented with a right Class II and left Class I molar relationship, with the maxillary midline shifted 1.0 mm to the left. The facial profile had a convex appearance.
Pre-treatment intraoral photographs for Case 1. Deep bite, large overjet, and proclination of the upper and lower incisors were observed.
Cephalometric analysis revealed a skeletal Class II tendency (SNA 76.9, SNB 72.3, ANB 4.6, APDI 79.2, Wits -0.5, facial angle 83.8), deep bite (ODI 81.9), proclination of the maxillary and mandibular anterior teeth (U1 to SN 112.0°, IMPA 100.7°), and protrusion of the lips (UL to EL 2.2 mm, LL to EL 2.3 mm, Table 1, Fig. 2).
Pre- and post-treatment cephalometric measurements for Case 1
Pre-treatment radiographs for Case 1. (A) Panoramic radiograph of the patient at age 10. (B) Lateral cephalogram of the patient at age 10. Proclination of the upper and lower anterior teeth and a convex profile were observed.
All plans were conducted using ClinCheck, a software that visualizes and simulates tooth movements in 3D. To improve the deep bite, an overbite reduction of 2 – 3 mm was planned for the anterior maxillary and mandibular teeth. The patient exhibited dental exposure in a repose state and presented with a gummy smile. Furthermore, the maxillary anterior teeth were noted to be over-erupted in relation to the functional occlusal plane, indicating the need for planned intrusion of the maxillary anterior teeth. A crown-lingual torque between 3° and 10° was planned for the proclined maxillary anterior teeth, and the maxillary right central incisor (#21) was retracted 1.6 mm lingually. In addition, a 5.0-mm maxillary arch expansion was planned. To correct for the Class II molar relationship, precision cuts were made on the maxillary canine regions of the aligner, and buttons were attached to the mandibular first molars using bilateral Class II elastics (1/4”, 3.5 oz, Fig. 3). The treatment was planned in 30 steps for both arches, with each aligner worn for one week, estimating the first set to take 7.5 months.
Precision cuts on the maxillary canines and buttons of the mandibular first molars for bilateral class II elastics (1/4’’, 3.5 oz).
The aligners did not fit well by the 17th step, particularly on the left maxillary side. When the treatment plan was superimposed on the scan data at that time, the buccal movement of the maxillary molars was not progressing as expected. This issue may be attributed to insufficient wear time, the presence of unerupted teeth, and the mobility of primary teeth. In the first set, teeth #14 and #24 were configured for eruption compensation and therefore did not have attachments. Additionally, mobility was observed in teeth #63 and #65, which may have compromised the retention of the aligner. Consequently, a re-scan was performed.
The second set consisted of 20 steps for both the upper and lower arches. After 11 months, the patient completed the second set of 20 steps and continued wearing the final stage aligner until the eruption of the permanent teeth.
After 6 months of retention, a re-scan was performed for the third set, which was also planned for 20 steps for both arches. Overbite reduction was achieved by increasing the intrusion of the maxillary anterior teeth by 1.7 – 2.2 mm and the mandibular anterior teeth by 1.2 – 2.1 mm. A precision bite ramp was added to the palatal surface of the aligner on the maxillary anterior teeth, and horizontal rectangular attachments were placed on all canines to assist with the intrusion. Bilateral Class II elastics were used continuously.
Over a period of 2 years, including 1 year and 6 months of active treatment and 6 months of retention, the patient wore three sets of 57 aligner steps (17 + 20 + 20). The OB decreased from 5.0 mm to 3.0 mm, and the OJ was reduced from 6.5 mm to 3.0 mm (Table 2, Fig. 4, 5). The scan superimposition revealed an expansion of the maxillary and mandibular posterior regions, accompanied by a palatal movement of the maxillary anterior teeth (Fig. 6).
Comparison of the pre-treatment, planned, and post-treatment measurements in Case 1
Post-treatment intraoral photographs for Case 1. The overbite and overjet were reduced, and the protrusion of the upper and lower incisors was corrected.
(A) Pre- and (B) Post-treatment overjet and overbite photographs of Case 1. The overbite decreased from 5.0 mm to 3.0 mm, and the overjet was reduced from 6.5 mm to 3.0 mm.
Superimposition of (A) the maxillary and (B) mandibular occlusal views of the pre-treatment (blue) and post-treatment (white) scans of Case 1. The scan superimposition revealed an expansion of the maxillary and mandibular posterior regions, accompanied by a palatal movement of the maxillary anterior teeth.
Cephalometric superimposition showed that the previously proclined maxillary and mandibular anterior teeth had moved lingually (U1 to SN from 112.0° to 97.3°, IMPA from 100.7° to 96.2°), and the lip protrusion improved (UL to EL from 2.2 mm to 0.8 mm, LL to EL from 2.3 mm to 0.7 mm, Table 1, Fig. 7, 8). Additionally, Wits decreased from -0.5 mm to -2.4 mm, ANB decreased from 4.6° to 4.1°, and ODI decreased from 81.9° to 78.9°, with both Wits and ODI remaining above average.
Post-treatment radiographs for Case 1. (A) Panoramic radiograph of the patient at age 12. (B) Lateral cephalogram of the patient at age 12. The protrusion of the anterior teeth was successfully corrected, leading to the establishment of a straight facial prof ile.
Cephalometric superimposition between the pre- (black) and post-treatment (red) of Case 1. The previously proclined maxillary and mandibular anterior teeth had moved lingually, and the lip protrusion improved.
Following treatment, the patient was given a clear retainer, Vivera® (Align Technology, Santa Clara, CA, USA), as a retention appliance. To prevent relapse of the deep bite, a bite ramp was added to the palatal surface of the maxillary anterior segment of the Vivera® retainer (Fig. 9).
Clear retainer Vivera® (Align Technology, Santa Clara, CA, USA) with a bite ramp on the palatal side of the maxillary incisors, designed to prevent relapse of deep bite.
2. Case 2
A 9-year-old girl presented with upper and lower anterior crowding. Upon clinical intraoral examination and model analysis, she exhibited a narrow maxillary intercanine width (25.9 mm), bilateral crossbite of the primary canines, and anterior crowding in both the maxilla and mandible (maxillary ALD +7.2 mm, mandibular ALD +0.7 mm, Fig. 10). The mandibular midline shifted 2.5 mm to the left, with a right Class I and left Class II molar relationship. The facial profile had a concave appearance.
Pre-treatment intraoral photographs and radiographs for Case 2. Narrow maxillary arch, crowding in both the upper and lower anterior segments, and crossbite of the primary canine were observed.
Cephalometric analysis showed skeletal Class III malocclusion with reduced maxillary growth (SNA 77.1, SNB 76.1, ANB 1.0, APDI 86.7, Wits -5.9, Table 3) and a clockwise growth pattern (PFH/AFH 60.6%, Sum 401.5). In addition, the maxillary and mandibular anterior teeth were retroclined (U1 to SN 98.8°, U1 to NA 21.7°, L1 to NB 18.7°, IMPA 84.1°, Fig. 11).
Pre- and post-treatment cephalometric measurements for Case 2
Pre-treatment intraoral photographs and radiographs for Case 2. (A) Panoramic radiograph of the patient at age 9. (B) Lateral cephalogram of the patient at age 9. Retrusion of the upper and lower incisors and a concave profile were observed.
All plans were conducted using ClinCheck software. To address the anterior crowding in the maxilla, maxillary arch expansion and sequential distalization of the molars were planned. The maxillary intercanine width was to be expanded by 9.1 mm, and the intermolar width by 2.6 mm, with distalization of the maxillary right first molar by 0.5 mm and the left first molar by 1.4 mm. To address mandibular crowding, mandibular arch expansion was planned with an expected expansion of 2.3 mm in intercanine width and 1.2 mm in intermolar width, with distalization of the mandibular right first molar by 0.4 mm. Treatment was planned in 29 steps for the maxilla and 25 steps for the mandible, with each aligner worn for one week, estimating the first set to take 7 months.
After 7 months, both the maxillary and mandibular arches were successfully expanded and crowding improved. Compared to the initial visit, the maxillary intercanine width increased from 25.9 mm to 33.2 mm, a 7.3-mm increase. The mesial rotations of #12 and #22 improved, but to a lesser extent than planned.
After completing the first set, the patient had a 4-month retention period while awaiting the eruption of the first premolars. After 4 months, the crowns of the first premolars on both sides were still short, and the remaining primary molars had not yet been exchanged for premolars. Therefore, no attachments were placed, and the space was left open for eruption compensation. Further arch expansion was planned to create space for the canines. The maxillary intercanine width expanded from 33.2 mm to 37.9 mm, a 4.7-mm increase. The second set consisted of 17 steps for the maxilla and 14 steps for the mandible.
After 6 steps in the second set, the patient declined cooperation, causing the aligners to fit well no longer. A re-scan was performed, and a third set was planned to focus on further arch expansion and mesial rotation of the maxillary anterior teeth. This third set involved 22 steps for both arches over a period of 6 months.
The total treatment period was 1 year and 2 months, including 4 months of retention, resulting in a total duration of 1 year and 6 months, during which the patient wore three sets of aligners with 57 steps in the maxilla (29 + 6 + 22) and 54 steps in the mandible (25 + 6 + 22). Arch expansion was achieved, and crowding improved (Fig. 12, 13). Compared to the initial visit, the maxillary intercanine width increased from 25.9 mm to 36.2 mm (10.3-mm increase, Table 4), and the maxillary intermolar width increased from 47.2 mm to 51.8 mm (4.6-mm increase).
Post-treatment intraoral photographs for Case 2. The maxillary arch was expanded, and crowding in both the upper and lower arches was corrected.
Superimposition of (A) the maxillary and (B) mandibular occlusal views of the pre-treatment (blue) and post-treatment (white) scans of Case 2.
Comparison of the pre-treatment, planned, and post-treatment measurements in Case 2
Cephalometric analysis showed an increase in ANB from 1.0° to 2.9° and a decrease in APDI from 86.7° to 84.4°, whereas Wits improved from -5.9 mm to -3.0 mm, indicating significant improvement (Table 3, Fig. 14). Cephalometric superimposition showed that the retroclined anterior teeth improved to within the normal range (Fig. 15).
Post-treatment radiographs for Case 2. (A) Panoramic radiograph of the patient at age 11. (B) Lateral cephalogram of the patient at age 11.
Cephalometric superimposition between the pre- (black) and post-treatment (red) of Case 2. The retroclination of the anterior teeth was successfully corrected. The B point has moved posteriorly after treatment.
The anterior crowding, which was the primary concern, was successfully resolved, and both the patient and guardian were satisfied. However, the newly erupted maxillary second premolar was mesially rotated. Therefore, an additional phase of treatment using Invisalign Phase 2 was planned to correct this rotation.
Discussion
In 1997, Zia Chishiti and Kelsey Wirth founded Align Technology and developed the ‘Invisalign’ product by applying 3D computer image graphic technology to orthodontics [13]. This was the first orthodontic device to use computer-aided design (CAD) and computer-aided manufacturing (CAM). In 2013, a new elastic material called SmartTrack was developed, which significantly increased the elasticity compared to the previously used single-layer EX30 material, allowing the device to exert a consistent force in the mouth for over 14 days without distortion [14].
The attachments are affixed to the teeth using either optimized or conventional attachments. Optimized attachments have an active surface where the orthodontic force is directly applied, and the convex space for attachment on the device is larger than the attachment itself on the tooth. When force is applied to the active surface, it moves the tooth through the space between the attachment and the device on the opposite side. The angle between the active surface of the attachment and device is called the activation angle, and the orthodontic force is delivered according to the activation angle. Conventional attachments lack active surfaces and provide only retention. When this attachment and the device are combined, the tooth moves because of its elasticity [13].
In 2018, Invisalign First® was launched for children and adolescents and introduced in Korea in June 2020. Compared to Invisalign Comprehensive®, which can be used for 5 years, Invisalign First® has a shorter usage period of 1 year and 8 months, but with a cost that is half as low, making it less burdensome for pediatric patients. According to the conditions set by Align Technology for using Invisalign First®, the first molars must be erupted, and at least 2/3 of the incisors must be erupted, or at least two stable deciduous incisors must be present. Additionally, at least two deciduous teeth (C, D, or E) or two unerupted permanent teeth (teeth 3, 4, or 5) were present in each of at least three quadrants [15]. Based on these conditions, pediatric patients at our clinic typically begin Invisalign First® treatment between the ages of 8 and 10 years.
In pediatric patients, the use of clear aligners offers the advantage of simultaneously achieving arch expansion, creating space for the eruption of permanent teeth, and aligning the anterior teeth, differentiating them from conventional removable devices [11,16]. However, achieving the exact planned expansion is challenging. According to a systematic review published by Gonçalves et al. [17] in 2023, Invisalign First® was able to achieve approximately 62.6% of the predicted maxillary expansion. In this case report, for the second case, after the first set of aligners, the predicted increase in maxillary intercanine width was 9.1 mm, and the predicted increase in maxillary intermolar width was 2.6 mm. However, the re-scan results showed that the maxillary intercanine width increased by 7.3 mm (80.2% of the predicted increase), whereas the intermolar width increased by 1.1 mm (42.3% of the predicted expansion). These results indicate that approximately 60% of the planned expansion may be clinically achievable.
In the first case, correction was planned owing to the presence of an overbite. The goal was to achieve an overjet of 1.4 mm and an overbite of 1.0 mm, but the final outcome resulted in an overjet of 3.0 mm and an overbite of 3.0 mm. According to a study by Al-Balaa et al. [18], the average accuracy of anterior tooth intrusion using Invisalign was 51.19%, with an average correction of 48.81%. To reduce the frequency of additional corrections, auxiliary methods such as bite ramps may be necessary for anterior intrusion. In contrast, in the first case, the adjustment of the labiolingual inclination of the anterior teeth was effectively achieved. In the second case, the retroclined anterior teeth moved toward a more normal labial inclination. According to a study by Haouili et al. [19], the average accuracy of all tooth movements was 50%, with the labiolingual inclination movement showing the highest accuracy at 56%.
In the same study, the most inaccurate tooth movement was rotation (46%), particularly in canines, premolars, and molars [19]. Similar findings were reported by Simon et al. [20] and Charalampakis et al. [21]. In this case report, the effect of distal rotation of the maxillary second premolars in the first patient was not as significant, while in the second case, the maxillary lateral incisors rotated distally to some extent, but not as much as planned. In our clinic, when premolar rotation is required, attachments are placed on both the buccal and lingual sides of the tooth to enhance retention. If this method proves ineffective, the aligner is cut on either the buccal or lingual side, and buttons are attached to the tooth requiring rotation as well as the adjacent teeth. These are then retracted using a power chain to facilitate individualized rotation.
In the first case, which exhibited a skeletal Class II tendency, a decrease in both ANB and Wits values was observed; however, the overall changes in skeletal cephalometric measurements were minimal. Patient compliance with elastic wear was insufficient, and additional patient education is required to improve compliance. Additionally, if mandibular advancement (MA) [22] using a precision wing brace, similar in function to the twin-block appliance, had been incorporated, it could have further helped in resolving skeletal Class II malocclusion. In contrast, in the second case, which was a skeletal Class III malocclusion, significant skeletal changes were observed, with an increase in both the SNA and ANB values, and the APDI and Wits values improved to the normal range.
In the Invisalign First® system, which has a treatment period of 1 year and 8 months, the first patient completed treatment with permanent tooth alignment by the end of the period, whereas in the second patient, the newly erupted second premolar was mesially rotated when the treatment period expired, necessitating additional phase 2 treatment. Therefore, when planning treatment, it is essential to carefully consider the timing of tooth exchange and inform the patient that additional treatment may be required depending on the position and rotation of the newly erupted teeth.
In both patients, 3 sets of aligners were utilized. In the first patient, a re-scan for the second set was performed midway through the first set due to a fitting issue. This was attributed not only to insufficient wear time but also to a lack of retention resulting from the eruption compensation for the maxillary premolars and the mobility of primary teeth. After completing the second set, it was necessary to wait for the eruption of the premolars before transitioning to the third set. In the second patient, a waiting period for premolar eruption occurred after the completion of the first set. In the second set, both maxillary canines and the second premolars ‒ 4 teeth in total ‒ were configured for eruption compensation, which led to inadequate retention. Additionally, insufficient wear time contributed to a poor fit, necessitating a re-scan before proceeding to the third set.
As such, patients starting Invisalign First are in a mixed dentition phase. Consequently, when primary teeth are exfoliated or if the crowns of the premolars are still short, attachments may not be placed, resulting in diminished retention. Furthermore, a waiting period may be required for the eruption of premolars. It is important to inform both patients and guardians in advance that treatment may need to adapt based on the eruption of newly erupting premolars, and that scans may need to be performed multiple times.
In the first case, a Vivera® clear retainer was used after the completion of treatment. According to research conducted by Raj et al. [23], Essix retainers (clear retainers) demonstrated lower stability compared to bonded lingual retainers and Hawley retainers. Additionally, the study by Ali et al. [24] indicated that the Essix retainer exhibited inferior occlusal settling compared to bonded retainers and Hawley retainers. However, Demir et al. [25] reported that the retention characteristics of both Essix and Hawley retainers are similar, with Essix retainers being more effective in maintaining mandibular incisor positions during the retention phase. Furthermore, the research by Saleh et al. [26] noted that clear retainers were associated with less embarrassment and were more acceptable to patients compared to Hawley retainers.
The choice of the Vivera® retainer was primarily based on its ability to provide a more comfortable fit and aesthetic appeal compared to traditional retainers. Pratt et al. [27] predicted a significant shift in preferred retainer types among orthodontists in the United States, moving from Hawley retainers to clear retainers, due to higher patient compliance with invisible retainers. In our clinic, patients are given the option to choose between Hawley retainers and clear retainers after treatment completion; to date, all patients who have undergone clear aligner treatment have opted for clear retainers.
The issue of oral care is a crucial consideration when using Invisalign in children, as illustrated by the plaque accumulation observed in Fig. 10. While Invisalign aligners are generally easier to maintain in terms of oral hygiene compared to traditional fixed appliances [28], neglecting to brush teeth or clean the aligners can lead to an increase in cariogenic bacteria on the inner surface of the aligners [29]. This can accelerate plaque accumulation, threatening both dental and periodontal health, and may also result in staining of the attachments, thereby compromising the aesthetic qualities of Invisalign. It is essential that aligners are worn only after ensuring that teeth are thoroughly brushed. During the brushing process, the aligners themselves should also be cleaned. Furthermore, patients should be instructed to avoid consuming any beverages or foods other than water while wearing the aligners.
Invisalign First® offers the advantages of simultaneous management of arch expansion, space for tooth eruption, and tooth alignment in patients with mixed dentition [11,16]. Additionally, it is more convenient for maintaining oral hygiene and is aesthetically superior to traditional bracket devices, which increases patient compliance [28]. However, there are limitations to tooth movement, such as rotation and extrusion, and the actual clinical results may not meet planned tooth movements [18-21]. Therefore, when developing a treatment plan using ClinCheck, overcorrection should be planned, and additional auxiliary devices or strategies should be considered to overcome potential clinical limitations.
Furthermore, although minor improvements in skeletal cephalometric values and dental changes were observed with Invisalign First®, for severe skeletal malocclusions or complex dental issues, sufficient results may be difficult to achieve with clear aligners alone. In such cases, the use of auxiliary devices should be considered, and proper patient selection through orthodontic diagnostic testing is critical.
Summary
Satisfactory outcomes were achieved in the treatment of patients with anterior dental protrusion, overbite, crowding, and mild skeletal malocclusions using the clear aligner system Invisalign First® in mixed dentition patients. Invisalign First® allows for simultaneous arch expansion, space management for tooth eruption, and alignment of teeth in patients with mixed dentition, while offering advantages in oral hygiene management compared to traditional bracket systems. However, depending on the position and rotation of newly erupted teeth, additional orthodontic treatment may be required. Therefore, careful consideration of the timing of tooth exchange is essential when planning treatment. Given the limitations in treating skeletal malocclusions and tooth movements, overcorrection and the use of additional auxiliary devices and treatment strategies should be considered.
Notes
Conflicts of Interest
The authors have no potential conflicts of interest to disclose.