# Lower Molar Distalization Using Clear Aligners: Bodily Movement or Uprighting? A Preliminary Study
## 2 Materials and Methods  
### Subjects  
A sample of 21 Caucasian subjects treated in Dental School, University of Turin (Italy) and in orthodontic private practice with Invisalign system were retrospectively recruited between November 2018 and October 2021.  
All the patients needed lower molar distalization and the met the following inclusion criteria: (1) adult age (confirmed by CVM method [25]); (2) Full Class III molar relationship at the beginning of the treatment (T0); (3) \(\geq\) 1.5 mm distalization movement programmed on the first Clincheck; (4) standardized treatment protocol; (5) absence of lower wisdom teeth; (6) good compliance; (7) good quality pre-treatment and post-treatment latero-lateral radiographs.  
Exclusion criteria were the following: (1) use of orthodontic auxiliaries to obtain the lower distalization or control the loss of anterior anchorage; (2) endodontic and/or prosthodonic therapy on lower molars; (3) periodontal disease; (4) signs or symptoms of Temporomandibular Disorders (TMDs) [26]; (5) bone metabolic disease.  
To avoid selection bias, all the patients were included in the study regardless of the final results.  
From the initial sample, 5 subjects were excluded according to the defined criteria: endodontic treatment on lower molars (1), prosthesis on lower molars (1), poor radiography quality (2), use of TADs (1). The final sample consisted of 16 adult patients (8 males, 8 females; mean age: 25.6 \(\pm\) 4.5 years).  
This study was performed in accordance with the Declaration of Helsinki; a signed informed consent was obtained from all patients before collecting the data, and researchers provided to protect the privacy.  
Thirty-two cephalograms in habitual occlusion were considered for the study. Radio-graphs were collected at the beginning (T0) and at the end (T1) of the Invisalign therapy.  
All the patients were treated using Invisalign System(r) by three board-certified orthodontists in Dental School--University of Turin (Italy) and orthodontic private practice.  
The standardized orthodontic protocol was represented by sequential lower molar and premolar distalization similar to the upper molar distalization one. The ClinCheck(r) (AlignTech, Santa Monica, CA, USA) is a software developed by Align Technology in order to provide the doctor a virtual 3-D simulation of the planned orthodontic treatment based on the patient's beginning situation and the doctor's pre-described treatment plan. Every treatment was planned with a 50% sequential distalization in order to obtain the movement of maximum two distalizing teeth at a time; the distalization starts with the lower second molar, and once the second molar is half of the way, then the lower first molar starts its movement, then premolars, and so on [27]. Third molars, if they were present, were extracted before CAT started, as near as possible to the starting time.  
No attachment was needed during the distalization movement on the involved teeth, while a buccal rectangular attachment is positioned on them at the end of their movement; the aim was exclusively to support the movement of the other teeth.  
The protocol comprised also intermaximillary Class III elastics [28] (1/4\" in. 4.5 oz, ORMCO Corp, Glendora, CA, USA) to counteract the proclination of lower incisors during the entire distalization phase. This protocol was adapted from the existing upper molar distalization protocol for Class II treatment.  
All the patients were asked to wear aligners and class III elastics at least 22 h per day as recommended by Align Technology with regular 4-week checks in office.