Factors related to microimplant-assisted rapid palatal expansion in teenagers and young adults: A cone-beam computed tomography study.

INTRODUCTION: For patients with maxillary transverse deficiency, selecting an appropriate therapeutic method is important for the treatment effect and prognosis. Our study aimed to explore factors related to microimplant-assisted rapid palatal expansion (MARPE) in teenagers and young adults using cone-beam computed tomography. METHODS: Twenty-five patients who underwent MARPE were included in this retrospective study from February 2014 to June 2019. Midpalatal suture density (MPSD) ratio, midpalatal suture maturation (MPSM), bone effect, dentoalveolar effect, and dental effect in maxillary first molar were evaluated using cone-beam computed tomography. Spearman correlation analysis was used to analyze the correlation between the MPSD ratio, MPSM, age, and the expansion amount generated by MARPE. RESULTS: Twenty-five patients (mean age, 19.84 ± 3.96 years; range, 15-29 years) with maxillary transverse deficiency were analyzed. Age was negatively correlated with bone expansion, alveolar expansion, and alveolar change (all P <0.05). There was a negative correlation between MPSM and nasal cavity variation, bone expansion, and alveolar change (all P <0.05). The bone expansion was negatively correlated with MPSD ratio 3 (r = -0.417; P <0.05) and MPSD ratio 4 (all P <0.05). CONCLUSIONS: Age, MPSM, and MPSD ratio were significantly related to the MARPE effect. Age, MPSM, and MPSD ratio should be considered when choosing MARPE.

[Efficiency of clear aligners in extrusion of posterior teeth evaluated by 3-dimensional model superimposition].

PURPOSE: To explore the efficiency of posterior teeth extrusion with clear aligners by 3-dimensional model superimposition, which provides a reference for the design of clinical programs. METHODS: We selected 24 patients with clear aligners whose posterior teeth were designed to extend more than 0.5 mm, and a total of 126 teeth were included. Digital models were obtained before and after treatment by intraoral scanning with iTero, named as "actual initial" and "achieved" digital models. Initial and final models from the ClinCheck, labeled as "virtual initial" and "predicted" models respectively. Initial, predicted, and achieved digital dental models were exported as stereolithography files and subsequently imported into Geomagic Studio. Extrusive measurements were made from the superimposition of the initial and predicted models (predicted movement) and from the superimposed initial and achieved models (achieved movement). Statistical analysis was performed with SPSS 23.0 and GraphPad Prism 5.0 software package. The extrusion efficiency of the posterior teeth was calculated, at the meanwhile the influencing factors were analyzed. RESULTS: The mean extrusion efficiency of posterior teeth during clear aligners treatment was 30.2%. The actual extrusion was linearly related to the expected(P<0.05), and the linear regression equation was y=0.305x-0.010. The difference between the actual and the predicted extrusion was positively correlated with the number of appliances(P<0.05), and also positively correlated with the predicted extrusion value(P<0.001). This difference was larger in low-angle patients than in patients with average angle (P<0.05). CONCLUSIONS: The extrusion rate of posterior teeth is relatively low during clear aligners treatment, and the average efficiency is 30.2%. Vertical growth pattern affects the extrusion efficiency. So more overcorrections can be designed for average angle patients.