Evaluation of the effects on lower central incisors intrusion and lower first molar extrusion at different mixed dentition stages using clear aligners for deep overbite treatment: a retrospective study.

BACKGROUND

Deep overbite, a prevalent malocclusion, may cause oral-maxillofacial dysfunction if untreated during mixed dentition. This study evaluated clear aligner efficacy for deep overbite correction across developmental stages of lower central incisors, assessing the accuracy of incisors intrusion and first molar extrusion alongside root development and alveolar bone height changes.

METHODS

46 volunteers were selected as the Control groups. 38 patients were selected as the Treatment groups. The study analyzed changes in lower central incisors' intrusion amount, intrusion rate and labial inclination, lower first molars' extrusion amount, extrusion rate, bucco-lingual and mesial-distal inclination as well as the changes in root length, root apical foramen size and alveolar bone height before and after first batch of clear aligners.

RESULTS

Lower central incisors at stages F, G and H showed intrusion rates of 33.3%, 34.1% and 34.6%, while first molars at G, H-1 and H-2 demonstrated extrusion rates of 29.0%, 29.4% and 29.2%. Regardless of the root developmental stage, neither lower central incisors nor first molars exhibited statistically significant differences in root length, root apical foramen size, alveolar bone height compared to the Control groups (P > 0.05).

CONCLUSION

Clear aligners could produce an intrusion effect on lower central incisors while achieving a slight extrusion of lower first molars during mixed dentition. In addition, the developing roots continued their normal progression in the treatment process. And no significant changes were observed in developed roots. Regardless of the developmental stages of roots, there were also no obvious changes in the alveolar bone height.