BackgroundClear aligner treatment offers several advantages, but the available literature shows that some kind of tooth movements are unpredictable. In addition, the majority of the studies are focused on one clear aligner system, while different characteristics of various systems can provide different treatment outcomes. The aim of the present retrospective cohort study was to evaluate the predictability of Nuvola® aligner system in achieving torque movements of anterior teeth.MethodsThirty-nine adult patients, who were consecutively treated with clear aligners, were retrospectively selected, and digital models pre-treatment (T0), post-treatment (T1) and the digital setup models (TS) were collected. Only the first phase of treatment made of 12 aligners was considered for the present study. Torque of anterior teeth was measured as labiolingual inclination on digital models at T0, T1, and TS using VAM software. Any difference between the predicted and achieved torque movements was evaluated using Wilcoxon signed-rank test or paired sample t test. First-type error was set as p < 0.008.ResultsNo statistically significant difference was found for all the anterior teeth between predicted and achieved torque movements.ConclusionsThe studied clear aligner system was able to produce clinical outcomes comparable to the planning of the digital setup relative to torque movements of the anterior teeth.Electronic supplementary materialThe online version of this article (10.1186/s40510-018-0207-3) contains supplementary material, which is available to authorized users.

Class II high-angle patients tended to have narrower and higher palates, while Class II low-angle patients were related to wider and more shallow palates.

Summary Objective The objective of this study was to compare an expansion screw of the maxilla that generates moderate and continuous forces versus a conventional screw for rapid maxillary expansion (RME) on patient-reported outcome measure during the first 12 weeks of treatment. Trial design This is a superiority, multicenter, two-arm parallel balanced randomization trial. Methods Patients in the mixed dentition were included with a transverse discrepancy between the two arches of at least 3 mm. An expansion screw using moderate continuous forces (Leaf group, treated with an expansion screw with Ni–Ti springs) was compared to a conventional RME screw that generates intermittent heavy forces (RME group). The primary response variable was the visual analogue scale (VAS) on pain calculated in the first 12 weeks of therapy. The VAS on difficulty on speaking and oral hygiene, patient satisfaction, and complications were also evaluated. A computer-generated block randomization was used with allocation concealed in sequentially numbered opaque-sealed envelopes. Blinding was not applicable. Linear models were used for statistical analysis. Results Twenty-eight patients in the Leaf group and 28 patients in the RME group were randomized and included in the study. There were no dropouts. The mean of the VAS for pain was 0.3 ± 0.4 in the Leaf group and 0.6 ± 0.5 in the RME group. The difference was −0.3 (95 per cent CI from −0.5 to −0.0; P = 0.017) in favour of the Leaf group. The difference in pain was marked in the first week (Leaf group 2.2 ± 2.3; RME group 3.7 ± 2.6; difference −1.5; 95 per cent CI from −2.7 to −0.3; P = 0.019). Conclusions Patients in the Leaf group experienced a lower degree of pain, especially during the first week following the application of the expander. For the other variables, no significant differences were reported between the two treatments. Registration The study was registered in the ISRCTN register on 8 November 2016 with the number ISRCTN18263886.

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Objectives To evaluate tooth movements during maxillary arch expansion with clear aligner treatment. Materials and Methods The study group included 28 subjects (16 females, 12 males, mean age 31.9 ± 5.4 years) collected prospectively from January 2018 to May 2019. Inclusion criteria were European ancestry, posterior transverse discrepancy of 3–6 mm, permanent dentition stage, presence of second permanent molars, mild or moderate crowding, and good compliance with aligners. Treatment protocol included nonextraction strategies, application of Invisalign clear aligner system, and no auxiliaries other than Invisalign attachments. Linear and angular measurements were performed before treatment (T1), at the end of treatment (T2), and on final virtual models (T2 ClinCheck). A paired t-test was used to compare T2-T1 and T2-T2 ClinCheck changes. The level of significance was set at 5%. Results Statistically significant differences were found for all measurements, except for ones at the upper second molars. The greatest increase in maxillary width was detected at the upper first and second premolars: +3.5 mm for the first premolar and +3.8 mm for the second premolar at T2. Comparison of T2-T1 angular outcomes showed statistically significant changes in the inclinations of all teeth except for the second permanent molars. T2-T2 ClinCheck showed significant differences for both linear and angular measurements for maxillary canines, resulting in poor predictability. Conclusions Maxillary arch development revealed a progressive reduction of the expansion rate and buccal tipping in the anterior, lateral, and posterior regions, with the greatest net increase at the first and second premolars. Clinical attention should be paid to maxillary canine movements, and overcorrection should be planned for them during dentoalveolar expansion.

The absence of maxillary central incisors over the physiological age of eruption influenced the development of the palatal morphology compared with subjects without eruption anomalies.

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