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@#In recent years, clear aligner technology has been maturing and is rapidly gaining popularity in the orthodontic market for its aesthetic and removable properties. However, despite the background of its large-scale clinical application, mechanical properties of clear aligners need to be studied in depth. This paper reviews the factors influencing mechanical properties of clear aligners and the current status of research to provide evidence-based guidance for clinical application.
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Objective @#To investigate the achieved intrusion amount of the maxillary incisors and the influencing factors in clear aligner cases treated with extraction of premolars. @*Methods @#This study has been reviewed and approved by the Ethics Committee, and informed consent has been obtained from patients. Thirty adult female patients who underwent extraction of the bilateral maxillary first premolars followed by clear aligner therapy were included. CBCT data before and after treatment were obtained, and three-dimensional reconstruction with registration alignment was performed. A spatial coordinate system was established, and the achieved intrusion amount was measured, followed by calculation of the intrusion efficacy. The factors related to the achieved intrusion amount were investigated through multiple linear regression analysis.@*Results @#The overall efficacy of maxillary incisor intrusion was 54%, with the maxillary central incisors (48%) lower than the lateral incisors (59%), which was statistically significant (P<0.001). Regression analysis showed that the designed intrusion amount and the stepwise intrusion design were positively correlated with the achieved intrusion amount. The designed retroclination amount and use of class Ⅱ intermaxillary elastics were negatively correlated with the achieved intrusion amount. The initial overbite, overjet, crowding, upper central incisor inclination, amount of the first series of aligners, canine attachment type, posterior teeth attachment type and bite ramps had no significant correlation with the achieved intrusion amount.@*Conclusion@# In maxillary first premolar extraction cases treated with clear aligners, the upper central incisors have lower efficacy of intrusion movement than the lateral incisors. The achieved intrusion amount of maxillary incisors was influenced by multiple factors, which should be considered comprehensively for better vertical control in such cases.
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Objective To explore the effect of attachment wear on tooth movement in clear Aligner treatment, and to provide references for improving the efficiency of orthodontic treatment. Methods The tooth cone bean computed tomography (CBCT) scanning data were obtained, and the tooth model was established and assembled with the worn and complete attachment, respectively. When the appliance applied 2° distal torsion, 0.25 mm distal displacement, 0.1 mm depression displacement and 0.1 mm elongation displacement to the teeth, the changes of tooth displacement, periodontal ligament stress and root equivalent stress in the worn and complete attachment groups were compared. Results When the clear Aligner was used to apply distal torsion and elongation displacement to the teeth, the maximum tooth displacement decreased significantly, and the worn attachment caused the teeth to move obliquely when the distal translation and elongation displacement occurred. When the tooth was subjected to distal torsion, distal translation, depression and elongation, the maximum principal stress of periodontal ligament and the equivalent stress of tooth root decreased when the worn attachment caused the tooth to be subjected to distal torsion, distal translation, depression and elongation. Conclusions Attachment wear will affect the efficiency of tooth rotation and elongation.When the attachments are obviously worn, they should be replaced in time to ensure normal function of the attachments.
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No matter what kind of therapies you choose, clear aligner treatment (CAT) or fixed orthodontic treatment (FOT), the therapy must be performed on the basis of periodontal health and follow the rule that the treatment cannot be harmful to the periodontal tissues. Doctors and patients prefer the clear aligner treatment because of its features, such as aesthetic, removable and comfortable. There are many studies which consider the influences of CAT on the periodontal health, and the conclusions are relatively consistent. The CAT is more beneficial for the plaque-control and maintaining the periodontal health. However, there are a few articles which are talking about applying the CAT to the patients with severe periodontitis. This article mainly reviews the effect of CAT towards the patients with periodontitis, and provides some reference when the patients with severe periodontitis need to choose a proper treatment.