The aim of the present study was to test the hypothesis that bodily maxillary molar distalization was not achievable in aligner orthodontics. Forty lateral cephalograms obtained from 20 non-growing subjects (9 male, 11 female; average age 29.73 years) (group S), who underwent bilateral distalization of their maxillary dentition with Invisalign aligners (Align Technology, Inc., San José, CA, USA), were considered for the study. Skeletal class I or class II malocclusion and a bilateral end-to-end class II molar relationship were the main inclusion criteria. Cephalograms were taken at two time points: (T0) pretreatment and (T2) post-treatment. Treatment changes were evaluated between the time points using 39 variables by means of paired t test. The level of significance was set at P < 0.05. Reproducibility of measurements was assessed by the intraclass correlation coefficient (ICC). The mean treatment time was 24.3 ± 4.2 months. At the post-treatment point, the first molar moved distally 2.25 mm without significant tipping (P = 0.27) and vertical movements (P = 0.43). The second molar distalization was 2.52 mm without significant tipping (P = 0.056) and vertical movements (P = 0.25). No significant movements were detected on the lower arch. SN^GoGn and SPP^GoGn angles showed no significant differences between pre- and post-treatment cephalograms (P = 0.22 and P = 0.85, respectively). Aligner therapy in association with composite attachments and class II elastics can distalize maxillary first molars by 2.25 mm without significant tipping and vertical movements of the crown. No changes to the facial height were revealed.

Root resorption (RR) is described as a permanent loss of tooth structure from the root apex. Many reports in the literature indicate that orthodontically treated patients are more likely to have severe apical root shortening, interesting mostly maxillary, followed by mandibular incisors. The aim of the study was to investigate the incidence and severity of RR in adult patients treated with aligners. The study group consisted of 71 class I adult healthy patients (mean age 32.8 ± 12.7) treated with aligners (Invisalign®, Align Technologies, Santa Clara, CA, USA). All incisors, canines, upper first premolars, and first molars were assessed. Root and crown lengths of 1083 teeth were measured in panoramic radiographs at the beginning (T0) and at the end (T1) of clear aligner therapy. Individual root-crown ratio (RCR) of each tooth and therefore the relative changes of RCR (rRCR) were determined. A decrease of rRCR was assessed as a reduction of the root length during treatment. All patients had a minimum of one teeth affected with a reduction of root length, on average 6.38 ± 2.28 teeth per patient. Forty one, 81% of the 1083, measured teeth presented a reduction of the pre-treatment root length. A reduction in percentage of >0% up to 10% was found in 25.94% (n = 281), a distinct reduction of >10% up to 20% in 12.18% (n = 132) of the sample. 3.69% (n = 40) of the teeth were affected with a considerable reduction (>20%). Orthodontic treatment with Invisalign® aligners could lead to RR. However, its incidence resulted to be very similar to that described for orthodontic light forces, with an average percentage of RR < 10% of the original root length.

Pathologic tooth migration (PTM) is a complication of Stage III and IV periodontitis. This pilot study aims to analyze the periodontal response to orthodontic aligner therapy in stage IV periodontitis patients, by perio charting and digital orthodontic data obtained from intraoral scans. Following periodontal treatment of 21 recruited patients, 11 underwent clear aligner treatment. Periodontal data (Probing Pocket Depth—PPD, Recession Index—REC, Clinical Attachment Loss—CAL) were collected at baseline (T0), after periodontal treatment (T1), and at the end of the orthodontic treatment (T2). Digital data obtained at T1 and T2 were processed with the 3D software Geomagic^® Control X™. Occlusograms obtained by the proximity sensors of the scans were converted into differently colored pixelated areas. These results were compared to highlight changes in clinical crown length or occlusal contact areas. The results showed a slight increase in the REC index and a statistically significant reduction of PPD and CAL at T1 and T2. Digital data showed a statistically significant decrease in terms of gingival recessions and clinical crowns at the end of orthodontic treatment. Hard occlusal contacts showed a statistically significant decrease by the end of the orthodontic treatment. The results are comparable to those reported in the scientific literature for fixed orthodontic treatment. Clear aligner treatment could be considered an option in patients with severe periodontitis, promoting final light occlusal contacts.