Postural changes in orthodontic patients treated with clear aligners: A rasterstereographic study.

BACKGROUND: Correlation between malocclusions and body posture has been discussed in the last decades, but there is still a lack of consensus in existing literature. Rasterstereography allows tridimensional reconstruction of the spine, starting from the back surface analysis. So far studies which tested modifications of rasterstereographic parameters during orthodontic treatment, comparing with those obtained from untreated control group, are not available. Clear aligner treatment produces alteration of vertical height due to the occlusal coverage and, subsequently, a stimulation of periodontal receptors which causes an inhibition of the jaw closing muscles and, hypothetically, changes in mandibular posture. OBJECTIVES: Evaluate possible correlations between orthodontic treatment and posture. MATERIALS AND METHODS: Rasterstereographic values of 15 untreated patients and of 15 patients treated with clear aligners were compared at baseline, after 1, 3 and 6 months. Rasterstereographic parameters considered were the following: the kyphotic angle, the lordotic angle, the upper thoracic inclination, and the pelvic inclination. RESULTS: Correlations between Kyphosis Angle, Upper Toracic Inclination and Pelvic Inclination and body posture were found after 6 months of treatment with clear aligners. CONCLUSIONS: Occlusal coverage caused by aligners could influence body posture not only for upper spine sections but also lower spine sections.

Root resorption during orthodontic treatment with Invisalign®: a radiometric study.

BACKGROUND: 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. RESULTS: 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%). CONCLUSIONS: 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.

Maxillary molar distalization with aligners in adult patients: a multicenter retrospective study.

BACKGROUND: The aim of the present study was to test the hypothesis that bodily maxillary molar distalization was not achievable in aligner orthodontics. METHODS: 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). RESULTS: 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). CONCLUSIONS: 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.