Treatment results
Overall treatment time was less than 1 year of active treatment. After 10 months of treatment, the treatment objectives had been successfully fulfilled. The treatment was completed in one phase with no additional refinement required. Forty-four aligners were used as planned by the ClinCheck, where 24 aligners were used for upper molars distalization and the other 20 aligners were used for incisor retraction and finishing. Post treatment records demonstrate satisfactory final results with all objectives achieved (Fig. 4) . Extraoral photos show an enhanced profile and improved lip competency. The smile of the patient was restored with optimal smile arc and decreased gum show. Intraoral examination reveals coincident upper and lower dental midlines, class I canines and molars bilaterally, adequate overjet and overbite and ovoid well aligned upper and lower arches. Post-treatment panoramic radiography showed good root parallelism, no signs of crestal bone height reduction and no evidence of apical root resorption. Cephalometric and digital model superimpositions highlight the distalisation of upper molars with no vertical movement and retraction of upper incisors. There was a mild extrusion of lower molar and proclination of the lower incisors due to the use of class II elastics which helped reduce the overjet and attain incised contact(Figs. 5 and 6) . The patient was very satisfied with the treatment results. For retention, the patient had Vivera removable retainers and follow up examination after 1 year of retention showed stable treatment results (Fig. 7) .
DISCUSSION
The aim of the present case report is to explain the management of a dental class II malocclusion case using CAT, where the patient was not willing to undergo fixed appliance therapy. CAT with intermaxillary elastics enabled resolution of the malocclusion within a treatment time comparable with that required for conventional fixed appliance therapy, providing the patient with comfortable, practical and an esthetically pleasing appliance. There were controversies over whether moderate to difficult malocclusions can be successfully accomplished with CAT.5, 7
The distalization of maxillary molars is frequently the treatment of choice required in class II non extraction patients. Distalization achieved in this case was 2.5mm with no observed vertical movement. These findings are in accordance with the mean reported distalization values by Ravera et al14on 20 non growing patients (2.52mm) and Simon et al15 on 30 adult patients (2.7mm), who reported the highest accuracy for bodily distal movement of molars of 87%. The authors further emphasized the greater accuracy when the movement was supported by the presence of attachments. In the present case, attachments were planned on most teeth to guide their movement and control their axes, resulting in higher predictability of movements. Different attachment angulations and geometries were planned, where vertical attachments were placed on the premolars and molars to prevent tipping and allow for bodily distalization. The attachments were located on the mesial side of the upper molars to prevent any mesial rotation of molars. Additionally, paired vertical root control attachments on the canines bilaterally were placed to help achieve bodily movement and control their long axes during distalization. Horizontal attachments were also planned on upper incisors for extra retention and firmer grip of the aligner. On the contrary, Saif et al 3stated that although distalization can be successfully attained in adult patients with a mean of 2.6mm, significant anchorage loss occurs and the use of attachments has no enhancement effect on distalization. This was further elaborated by a systematic review in 2019 concluding that attachment incorporation is not necessary when molar distalization is planned.10
Furthermore, Simon et al15 highlighted the importance of staging in increasing the predictability of distalization. This was also observed in our case, where sequential distalization was planned on 24 stages of aligner treatment, hence achieving the highest predictability of distalization.
The increased overjet was corrected by a combination of upper molars distalization, upper incisor teeth retraction and lower incisor proclination. This was facilitated by the use of class II elastics to augment the anchorage and aid in class II correction. However, short class II intermaxillary elastics were placed from upper premolars to lower molars, unlike the conventional attachment from upper canines to lower molars. The reason behind that protocol was that in this case, it is desirable to avoid the vertical reciprocal forces from elastics to act on the upper anterior teeth, leading to further bite deepening by the clockwise rotation of the upper anterior teeth. In contrast, Patterson et al in 2020 observed on a sample of 80 adult patients, that no significant class II correction or overjet reduction were achieved with class II elastics for an average of 7 months using ABO model grading system.16
To quantify the amount of tooth movements in the present case, two methods of superimpositions were utilized which were the ClinCheck software superimpositions and the 2D lateral cephalometric superimpositions.
In the present case report, the aligner change was performed every two weeks. Recently, Align Technology has indicated that weekly changes of aligners can be made. A study evaluating the effect of 7 days versus 14 days of aligner wear concluded that the 14 day changes revealed greater accuracy in posterior movements.17 Moreover, the tooth requires a period of adaptation for recovery to aid in stabilization and increase retention.18
The whole treatment objectives were accomplished in one phase with no additional refinements in 10 months. This is considered to be a great advantage for CAT where it was proved to result in a significantly shorter treatment duration than with braces.19 Patterson et al findings contradict our findings where they stated that additional refinements were necessary to address problems created during treatment.16
CONCLUSIONS
Combined use of aligners with appropriate attachment location and geometry is an efficacious means of resolving more complex orthodontic issues such as class II malocclusions within a time-frame comparable, if not less, to conventional fixed orthodontics, but with excellent esthetics, oral hygiene and quality of life. Proper planning and ideal case selection are essential for achieving the highest predictability of movements. Staging is crucial in molar distalization in CAT.
Consent for publication
Written informed consent was signed by the patient for the inclusion of her images for the purpose of publication.
Availability of supporting data
All data generated or analysed during this study are included in this article in the form of table and figures.
Competing financial and/or non-financial interests
The authors declare that they have no competing interests or other interests that might be perceived to influence the results and/or discussion reported in this paper.
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Table 1: Cephalometric analysis pre and post treatment