Condition category
Digestive System
Date applied
Date assigned
Last edited
Retrospectively registered
Overall trial status
Recruitment status
No longer recruiting
Publication status

Plain English Summary

Background and study aims
Malocclusion is a problem in the way the upper and lower teeth fit together when biting or chewing. Orthodontic treatment can be used to improve the appearance, position and function of the teeth. In the last few decades increasing numbers of adults have sought orthodontic treatment and expressed a desire for aesthetic and comfortable alternatives to conventional fixed braces. Clear aligners were introduced to answer this request. Cosmetically, invisible aligners are more appealing because they are difficult to notice, making them particularly popular among adults who wish to straighten their teeth without the use of traditional metal braces. Such aligners are also easily removed during eating and tooth brushing. However, little is known about the effects of clear aligners on the teeth and bones of adult patients treated to correct a forwarded position of the upper dental arch. The aim of this study is to find out whether it is possible to correct this type of malocclusion with clear aligners.

Who can participate?
Adult patients (over 18) treated with clear aligners for a forwarded upper dental arch

What does the study involve?
Participants undergo a profile x-ray of the head before and after their orthodontic treatment to assess the position of the teeth, jaws, skull and soft tissues.

What are the possible benefits and risks of participating?
Participants will benefit from the correction of their malocclusion with an aesthetic and comfortable appliance. There are no risks in participating in the study - a large number of patients have previously been treated with the clear aligners used in the study, and x-rays are always needed at the beginning and at the end of any orthodontic treatment.

Where is the study run from?
Two orthodontic private practices in Torino (Italy) and Vancouver (Canada), and the University of Torino (Italy).

When is the study starting and how long is it expected to run for?
March to September 2015

Who is funding the study?
Investigator initiated and funded

Who is the main contact?
Dr Tommaso Castroflorio (
Dr Andrea Deregibus (

Trial website

Contact information



Primary contact

Dr Tommaso Castroflorio


Contact details

Via Nizza 230
+39 (0)11 1950 7750



Additional contact

Dr Andrea Deregibus


Contact details

Via Nizza 230
+39 (0)11 633 1514

Additional identifiers

EudraCT number number

Protocol/serial number


Study information

Scientific title

Dentoskeletal effects of maxillary molars distalization with aligners in adult patients: a retrospective observational trial


Study hypothesis

The study was conducted in order to test the hypothesis that maxillary molar bodily distalization is not achievable with aligners.

Ethics approval

Ethics approval pending - to be submitted to the ethics board of the City of Health and Science of Torino, Italy in November 2015

Study design

Multicentre retrospective observational trial

Primary study design


Secondary study design

Case series

Trial setting

GP practices

Trial type


Patient information sheet

Not available in web format, please use the contact details below to request a patient information sheet


Skeletal Class I or Class II malocclusion and a bilateral end-to-end class II molar relationship


Orthodontic treatment with Invisalign aligners, composite attachments and class II inter maxillary elastics. Lateral cephalograms in habitual occlusion obtained before and after treatment of 20 Caucasian subjects were collected. For standardization purposes, the magnification was corrected to 8% for all cephalograms. The digital x-rays were stored in a computer, imported into commercial software ORISCEPH Rx3 (Elite Computer, Vimodrone, Italy), in order to perform landmark identifications and cephalometric tracings. These operations were randomly performed by one investigator blinded about the study, using a customized digitization set including 47 landmarks and 54 variables chosen from different existing and validated cephalometric analyses. The great number of variables was due to the number of analyzed teeth and to the number of analyzed crown and roots landmarks.

All the cephalograms were traced again after 3 weeks and then after 6 months. If there was a discrepancy between the three cephalograms, a new tracing was obtained by mutual agreement between the researchers involved in the protocol. Statistical analysis was performed using the R statistical package (version 3.0.1, R Core Team, Foundation for Statistical Computing, Vienna, Austria). The normality assumption of the data was evaluated with the Shapiro-Wilk test. According to this evaluation, the differences between before (T0) and after treatment (T1) were compared with the t-test. The level of significance was set at P<0.05.

Intervention type



Drug names

Primary outcome measure

Maxillary molars distalization movement: on the lateral cephalograms collected before (T0) and after treatment (T1) (mean treatment time was 24.3 ± 4.2 months) crown and roots landmark were identified in order to describe the mean distalization movements on the sagittal plane as well as the vertical and the angular movements. Crowns’ centers, obtained as the midpoint between the greatest mesial and distal convexity of the crown, as well as the axis passing through mesial cusps and mesio-vestibular roots’ apex were taken as reference points of the maxillary first and second molar as seen on the cephalograms. The movements of these points at T1 with respect to T0 were considered in relation to the reference axes represented by the palatal plane (x axis) and by a perpendicular line to the palatal plane passing through the Ricketts’ Pt point (y axis). The palatal plane was used to measure vertical and angular movements, while the y axis was used to measure sagittal movements of the second molar and of the first molar.
The overall craniofacial treatment changes were evaluated by superimposing on the stable structures of the anterior cranial base according to the Structural Method (Björk A. Guide to superimposition of profile radiographs by “The Structural Method” Superimpositions were conducted digitally.

Secondary outcome measures

Central incisor retraction movement: the incisal edge point, the root apex point and the crown centre point, the midpoint of the lateral projection of the circumference formed by the root and crown conjunction, were the landmarks considered on the lateral cephalograms to describe the movement of the maxillary central incisor with respect to the reference axes described above.
On the lateral headfilms, the palatal plane/mandibular plane (PP/MP) and the SN/mandibular plane angles were evaluated as indicators of skeletal posterior vertical dimension changes.The overall craniofacial treatment changes were evaluated by superimposing on the stable structures of the anterior cranial base according to the Structural Method (Björk A. Guide to superimposition of profile radiographs by “The Structural Method” Superimpositions were conducted digitally.

Overall trial start date


Overall trial end date


Reason abandoned (if study stopped)


Participant inclusion criteria

1. Age over 18 years old
2. Skeletal Class I or Class II malocclusion and a bilateral end-to-end class II molar relationship
3. Normodivergence on the vertical plane (SN/GoGn angle less than 37 degrees)
4. Mild crowding in the upper arch (≤ 4mm)
5. Standardized treatment protocol
6. Good compliance during the treatment (wearing aligners time: ≥20 hours per day)
7. Absence or previous extraction of the upper third molars
8. Good quality radiographs, with adequate landmark visualization and head rotation control

Participant type


Age group




Target number of participants


Participant exclusion criteria

1. Transversal dental or skeletal discrepancies
2. Vertical dental or skeletal discrepancies
3. Extraction treatment (except for third molars)
4. Unilateral distalization
5. Signs and/or symptoms of temporomandibular disorders (TMDs) accordingly to Diagnostic Criteria for TMDs
6. Periodontal disease
7. Endodontic treatments of the maxillary molars
8. Prosthodontics rehabilitations of the maxillary molars

Recruitment start date


Recruitment end date



Countries of recruitment

Canada, Italy

Trial participating centre

Daher Orthostyle
BC V7V 1H9

Trial participating centre

Studio Associato Icardi Castroflorio Odontoiatri

Trial participating centre

University of Torino
Orthodontics Department Lingotto Dental School

Sponsor information


University of Torino (Italy)

Sponsor details

CIR Lingotto Dental School
Via Nizza 230
+39 (0)11 633 1514

Sponsor type




Funder type


Funder name

Investigator initiated and funded

Alternative name(s)

Funding Body Type

Funding Body Subtype


Results and Publications

Publication and dissemination plan

We would like to publish a paper reporting the protocol and the results of the study in the first quarter of 2016. The dissemination of the results will be performed also with the presentation of scientific posters or oral communications during orthodontic Congresses in 2016.

Intention to publish date

Participant level data

Available on request

Basic results (scientific)

Publication list

2016 results in:

Publication citations

Additional files

Editorial Notes

18/04/2016: Publication reference added.